./ J\l^^ Columbia WLnibtt&ity in tfce Cttp of i&eto §9orfc &cf)ool of Bental anb <®ta\ gmrgerp Reference Htbrarp ELEMENTARY AND DENTAL RADIOGRAPHY BY HOWARD RILEY RAPER, D.D.S. Professor or Roentgenology, Operative Tecnnic, Materia Medica ana Therapeutics at the Indiana Dental College, Indianapolis. Past Dental Surgeon to the Indiana School tor the Feeble-Minded Youth. Mem- ber Institute or Dental Pedagogics, local, etate and national dental societies. Associate member A. M. A., Section or Stomatology. WITH 354 ILLUSTRATIONS FIRST EDITION Adopted as a Text-Book by the National Association of Dental Faculties NEW YORK : Consolidated Dental Mfg, Co. LONDON : Claudius Ash. Sons & Co., Ltd. 1913 ' Copyright. 1913 By HOWARD R. RAPER Copyright. 191.3. in the United KinRdom By CLAUDIUS ASH. SONS & CO.. LTD.. LONDON One of ' his boys, the •writer, grasps this opportunity to show his Jove ana respect for GEORGE EDWIN HUNT, M.D., D.D.S. by dedicating this book to him. Digitized by the Internet Archive in 2010 with funding from Columbia University Libraries http://www.archive.org/details/elementarydentalOOrape PREFACE. The object of this book is to teach, first, the elementary principles of radiography; second, special dental radiography. Tlic first part of the book is written on the presumption that the reader knows nothing about electricity, photography, or the X-rays, and might therefore be used by anyone who wishes to take up radiographic work, whether a dentist or a physician In dealing with the preliminary subjects mentioned, an earnest effort has been made to avoid useless, impractical and confus- ing elaboration. The second part of the book is devoted to dental radiog- raphy, and is consequently of interest mainly to dentists and specialists in radiography who do work referred to them by dentists. It gives in detail the special technic involved in the practice of dental radiography, also a chapter with one hundred and eighty-three halftone illustrations, demonstrating sixty- four different uses to which the radiograph may be put in the practice of dentistry. The use of the radiograph in the practice of modern dentistry is not a mere fad; it is a necessity, if one wishes to render the best dental service. Nothing but great good can come from its more frequent use. To the end of bringing about a more extensive use of the radiograph by dentists this work is pub- lished. At present it is the only work of its kind on the book market. So many people have helped me in the compilation of this ■volume that I refrain from naming and thanking any particular individual. A publication of this kind, of necessity, represents the work of many. June 5, 1913. H. R. R. CONTENTS CHAPTER PAGE elementary Radiography I. Electricity T II. X-Ray Machines 14 III. X-Ray Tubes and the X-Rays 41 !V. Making Radiographs 65 Dental Radiography V. Making Dental Radiographs . . . . • . . 85 VI. Reading Radiographs 136 VII. The Uses of the Radiograph in Dentistry . . . .146 VIII. The Dangers of the X-Ray 273 IX. Purchasing a Radiograph Outfit 292 X. Stereoscopic Radiography 297 elementary and Dental Radiography. CHAPTER I. electricity. Dental radiography is the science and art of making pictures of the teeth and contiguous parts with the X-rays. Its place and value in the practice of modern dentistry will be dealt with later. Before we can produce X-rays we must have at our disposal that something called electricity. Electricity is a form of energy closely related Electricity. to motion, light and heat. We know it is closely related to motion, light and heat because these forms of energy can be made to produce electricity, and electricity conversely can be made to produce them. Electricity is discernible to but one of the special senses, namely, feeling. It cannot be seen, heard, smelled or tasted. Victims of severe shocks have noted a peculiar taste, which they call the taste of the electricity, but it is my opinion, neither proved nor disproved as yet, that this taste is due to the presence of new chemical bodies formed in the saliva by electrolysis. In other words, the passage of the current of electricity through the saliva causes chemical changes to occur, resulting in the formation of new chemical bodies, and it is these new bodies, not the electricity, that produce a taste. When electricity passes from one place to an- Conductors. other the substance through which it passes is said to be a conductor. A substance through which electricity passes with great difficulty, when at all, is said to be a non- conductor. Metals are the best conductors of electricity. Silver is the best, then copper. Copper wire is the most used of any conductor of electricity. German silver carries electricity very reluctantly, and bis- muth is the poorest conductor of the metals. It was formerly thought that electricity traveled on the surface of a conductor, but if this were true a round wire could be made to carry more current by simply flat- tening it and so making the surface greater: while, as a matter of fact, 2 ELEMENTARY RADIOGRAPHY the flattened wire would carry less, because of the condensation of the metal incident to flattening. The human body is a conductor. Wood. glass and vulcanite are examples of non-conductors. \\ hen electricity passes from one place to another through a con- ductor, what is known as the electric current is established. There are four kinds of electric currents: (i) Currents. The continuous, constant, or direct current, commonly designated D.C. ; (2) the pulsating; (3) the inter- rupted; 14) the alternating or oscillating, designated A.C. The direct current is one in which the electricity is presumed to flow through the conductor in one direction at a uniform rate of pressure. The pulsating current is one in which the electricty flows through the conductor in one direction, but at variable pressure. The interrupted current is one in which the electricity flows through the conductor in one direction while in motion, but which is completely arrested in its flow at frequently recurrent intervals. The alternating current is one in which the electricity Hows through the conductor first in one direction, then in the other. When the current, tli. wing in a given direction, reverses, flows in the opposite direction, and then resumes its original direction of flow, it is said to have completed a cycle. The number of cycles occurring in a second determines the fre- quency of the current. We thus have, for example, a 60-cycle frequency current, making sixty complete alternations per second. Electricity travels from one place to another be- Potcntial. cause of a difference in potential. The term poten- tial means latent, inactive, or stored-up energy. Take lightning as an example of traveling electricity. Why does it occur? < Ine cloud ha- a potential, figuratively speaking, of say 30, another of 20. These cloud- approach close enough to one another so that electricity can jump the atmospheric gap between them, which it does, passing from the one with a potential of 30 to the one with a potential of 20 and equalizing the potential of each to 25. The lighl of lightning is caused b\ the resistance of tin- atmosphere to the passage ol electricity. If such a thing were possible and an electric conductor stretched from the one cloud to the other, the potentials would be equalized as just described, but without the occurrence of the phenomenon called lightning, because lectricity would unostentatiously flow through the conductor instead of through the highly resistive atmosphere. All electricity-producing machines then, simplv create a compara- tively high potential, so that when a path is afforded—;, e., when con- ductor- are attached to the machine— the electric'ty leave-, in i'- eft it uali/e pi tential. ELECTRICITY 3 Electricity travels at an inconceivably rapid rate UdOCity. °f speed, instantaneous results being obtained hun- dreds of miles distant on pressure of a button. It is stated that the velocity of electricity is about the same as light, which latter travels about 186,000 miles per second. To comprehend this great speed compare it to the velocity of sound, which travels only 1,090 feet per second. In dentistry and medicine the terms used can often be translated literally into their meaning. For example, "odontalgia" is a combination of two Greek words meaning tooth and pain; "tonsilectomy" is a com- bination of a Latin and a Greek word meaning tonsil and excision. Elec- trical terms are. however, derived principally from proper names. For example, volt, the unit of measurement of electric pressure, has no literal meaning at all, but is so called in honor of Alexander Yolta, a great elec- trician. And so with the terms ohm, watt and ampere. When electricity leaves the electricity-produc- UOlt. ing, or, if you choose, potential-creating, machine, it passes into the conductors at a given pressure. This pressure is measured in volts, just as pressure in a water-pipe is measured in pounds. The volt, then, is the unit of measurement of pressure of electricity. Just what is a "unit of measurement"? Take, for example, the unit of linear measurement; it is called the "meter." and and is one-ten-millionth of the distance from the equator to one of the earth's poles. The unit of linear measurement, then, the meter, is a definite name applied to a definite distance. So the volt is a definite name applied to a definite degree of electric pressure, or. which means the same as electric pressure, electromotive force, designated E.M.F. This force is sufficient to maintain a current of electricity of one ampere ( the unit of measurement of volume of electricity) through a resistance of one ohm (the unit of measurement of resistance to the flow of current offered by an electric conductor). Let us then fix this firmly in our minds. The volt is the unit of measurement of electromotive force, or pressure. Though it is not commonly used, the writer much prefers the word "pressure" to "force," believing it to more clearly express the meaning. Xo conductor carries electricity without ofifer- Obm. ing a certain amount of resistance to its Mow. This; resistance, which might be compared to the friction offered by the sides of a pipe to the flow of water, is measured in ohms. The ohm. then, is the unit of measurement of resistance offered to the flow of electricity by a conductor, and is equivalent of the resistance afforded by a column of mercury having a cross-section of one square millimeter and a length of t 06.28 centimeters, at a temperature of o° C. 4 ELEMENTARY RADIOGRAPHY We have considered pressure and resistance. flmpcrc. Now we come to the energy itself, which may be compared to the water in a water-pipe, and is meas- ured in amperes. The ampere capacity of an electric conductor cor- responds to the cross-section of a water-pipe, which latter is measured in square inches. Thus the larger the pipe, which means, of course, more square inches in its cross-section, the more water it will carry ; and so the larger the electric conductor of a given material the greater its ampere capacity, and the more electricity it will carry. d^L FIG. The analogy between the water in the water-pipe and the electricity in the conductor is not perfect, however. A given-sized pipe will carry a column of water of a given cross-section and no more, because water is practicallv non-compressive. When the flow of the water is opposed to gravity, as when drawing water from a faucet, this complete cross-sec- tion must be obtained, too — that is, the pipe must be full — before any pressure will establish a current through the pipe. Not so with electricity in a conductor. A wire which has a normal capacity of say 30 amperes will carry a current of 10, and it can be made to carry 40 or 50 by in- creasing the pressure, because electricity is compressible. Amperage, or the volume of electricity carried in a conductor, de- pends "ii two things — the pressure of the current and the resistance of the conductor. Hence Ohm's law, which is that the volume of the current can be obtained by dividing the pressure by the resistance. In other words, the amperage can be obtained by dividing the volts by the ohms. Problem: An electromotive pressure of 100 volts is acting against a resistance of 50 ohms. What is the ampere strength of the current? ilution: 100 volts divided by 50 ohms equals 2 amperes. To give the exact amount of electricity represented by the ampere, it i- that amount which, when passed through a standard solution of sil- ver nitrate in distilled water, will cause a deposition of metallic silver at the r;it<- of i.uS milligrams per second. ELECTRICITY Electromotive power (not electromotive pres- Ulatt. sure or force; note the word "power"), or the ability of a current to do work, depends on two things — the pressure measured in volts and the volume measured in amperes. This is also true in hydraulics. The amount of work a stream of water will do depends on pressure and volume. The watt is the unit of meas- Fig. Fig. :;. Fig. 2. Arrows A represent the direction of flow of electric current. Arrows B represent the direction of flow of magnetic flux in the magnet. Fig. 3. Bar magnet with polarity indicated. urement of electromotive power, and the wattage of a current is obtained by multiplying the volts by the amperes. Thus, if we had a current of one ampere under a pressure of one volt, one watt would be operative. When i.ooo watts are active for an hour — that is, when a current i,ooo watts strong has been in motion, the current turned on, for one hour — the electrometer will register one kilowatt-hour. So bills for elec- tricity are made out for so many kilowatt-hours. Magnetism is a form of kinetic energy very magnetism. closely related in its nature to electricity. Mag- netism produces electricity, and vice versa. 6 ELEMENTARY RADIOGRAPHY The substance in which this energy, or property, magnetism, resides is called a magnet. 1 f a bar of magnetized steel be dropped into iron filings, and then raised, the fillings will adhere to the ends of the bar, but not to the center. (Fig. i.) The ends of the bar represent, respectively, the north, or positive, and the south, or negative, poles of the magnet. If, now, this bar be broken at its exact center, instead of having a half magnet all north pole and another half magnet all south pole, we have two magnets with two poles each. If one of these magnets be broken at its center the same thine occurs, namelv, two magnets, each one-half as large as the first, Fig. i. When poles are arranged as in A repulsion exist- between the magnets. When poles an- arranged as in I', the magnets are attracted t<> one another with the magnetic flux <>f each north pole flowing into the south pole of the other magnet. are made.-. This redivision can he repeated down to the molecule, which would have a north and a SOUth pole. Magnets are of two kinds — the natural magnet, or "loadstone," and the artificial magnet-. '[lie earth may he considered a large magnet, the poles of this mag- net being near the north and south poles of the earth. The natural mag- net is iron ore, found in nature with all the properties of the magnet, and representing a portion of the great magnet, the earth. Artificial magnets are of four kinds— the electro-magnet, the perma- nent magnet and the induced magnet. ELECTR1CI1 Y If a bar of soft iron be wrapped with insulated wire (wire covered with a nonconductor) and a current of electricity b"e sent through the wire, the iron bar becomes magnetized while the current passes through the conductor, but loses its magnetism when the current ceases to flow. Such a magnet is called an electro-magnet. (Fig. 2.) If the current be sent through the conductor in the opposite direction to that shown in the diagram, polarity of the magnet will be changed: the north pole will become the south pole and the south pole the north pole. Fig. 5. Fig. 6. If hard steel, instead of soft iron, be used as the core and wrapped with insulated wire and a current of electricity be sent through the wire for a great length of time, then the current shut off and the wire removed, it will be found that the steel retains its magnetism and will continue to retain it over a number of years. Such a magnet is called a permanent magnet ( Figs. 1 and 4, for example ) , though it is not actually permanent and will lose its magnetism in time. The permanent magnet in greatest general use is the "horseshoe" magnet (Figs 4 and 5), which is simply the bar magnet (Figs. 1 and 3) bent into horseshoe or staple shape. Instead of using the electric current, a permanent magnet can be made by rubbing hard steel with another magnet. Fig. 3 shows a magnet holding three nails. As long as the magnet 8 ELEMENTARY RADIOGRAPHY remains in contact with the first nail it will hold the second nail, and the second will hold the third. But remove the magnet and no attraction exists between the nails. While the magnet touches the first nail each nail is an induced magnet, with a north and south pole, as shown in the figure. While either the north or south pole of a magnet will attract a piece of unmagnetized iron or steel, only unlike poles of two magnets will be attracted to one another. Thus, if two north or two south poles of mag- nets he brought in close proximity repulsion instead of attraction exists between them ( Fie. 4. ) Fig. 7. Magneto-Dynamo. A. the magnets or field. B, casting surrounding revolving con- ductor or armature. <'. appliance for outlet "t' electricity from armature. An alternating cur- rent i- generated bj this machine. In 183] Faraday discovered that when an electric conductor is set in motion so as to cut the lines of force of the magnet at right angles, an electric current is induced in the conductor. Fig. 5 shows the lines of force of a horseshoe magnet passing from the north to the south pole. Imagine now a spool wrapped with copper wire, not as thread is wound around a spool, but lengthwise oi the spool, the wire passing over it- end-. Place this spool between the poles of the magnet, revoke it on its axis, and the copper wire— that is, the electric conductor — is made to cut the force of the magnet at right angles and an alternating current of electricity will be produced in the wire (Fig. 6), the current flowing in opposite directions as the different poles are passed. ELECTRICITY 9 Add to this arrangement a means for carrying the current away from the apparatus and we have the magneto-dynamo, now very extensively used in automobiles. (Fig. 7.) Dynamos may be divided into two classes : the Dynamos. magneto-dynamo, just described, and the electro- dvnamo. Fig. 8. A Direct Current Generator or Electro-Dynamc All dynamos consist of three cardinal parts, to wit : the field, or mag- nets ; the armature, or revolving conductor, and the rings, or appliance for carrying off the electricity. If the current sent out is direct instead of alternating, a commutator instead of rings must be used. A commu- tator is an appliance which changes the alternating current induced in the armature into a direct current as it leaves the dynamo. The electro-dynamo, an example of which is shown in Fig. 8, dif- fers in principle from the magneto-dynamo only in the kind of magnets used. Permanent magnets are used in the magneto-dynamo whereas electro-magnets are used in the electro-dynamo. Immense electro-dynamos, or generators, as they are called, make io ELEMENTARY RADIOGRAPHY our commercial currents, steam power being used to revolve their arma- tures. By commercial current is meant the electric current supplied to us by the electric light and power companies. Let us trace a current of electricity through what is known as the electric circuit. When the armature is revolved the potential at C, of Six Pole Direct Current Generator, parts disassembled. E, electro-magnets with poles of differenl denominations directly opposite one another -the field. Large alternating current tors have as many as 10 poles in the field which revolves, the armature remaining ionary. A. armature. (', commutator. Fig. 7. rises. The potential of the positive wire attached to binding post — (which post is connected to C) is instantly raised to thai of C, and the current ceases to flow, potential being equalized between the arma- ture and tbe positive wire. If now the positive wire ot the high poten- tial be brought in contact with the negative wire, which is of low poten- tial the current flow- into the latter. Tbe negative wire is attached to the negative binding post, which is connected to the magnets themselves. Thus tb«- current passes through the negative wire into the magnets. which have a low potential. Tbe current will continue to flow, making a circuit from C, out through the positive wire, back through the nega- tive wire, into the magnet^ until their (the magnets') potential is raised ELECTRICITY i r to that of C. If an incandescent light bulb be connected to the positive and negative wires the current will pass from the positive wire, through the bulb, and into the negative wire. As the electricity passes through the bulb it heats the filament of carbon to incandescence, producing light and some heat. Most of the electricity is used up in the production of the light and heat — this is true if the circuit is what is called "well bal- anced" — but what is not, travels in the negative wire toward the magnet, equalizing potential until it dissipates itself in the effort. C- Fig. 10. Diagram of a step-down transformer. Commercial circuits supply either a D.C. (direct current) or an A.C. ( alternating current ) . The wiring from the D.C. dynamo to the consumer is an intricate problem, difficult to understand. It is enough for us to know that the D.C. is supplied, as a rule, only to downtown districts of cities, by a circuit giving no volts pressure, or a special three-wire cir- cuit, which supplies either no or 220 volts, according to the manner of the connections made to the mains. The amperage depends on the size of the wires ; the more amperage desired the larger the wires connecting to the mains must be. The A.C. leaves the generator at a voltage of from 1,000 to 3,000 and flows in the mains at this pressure. Such great pressure is both danger- ous and uselessly high for ordinary uses, such as lighting, running motors, operating X-ray machines and the like. So, by means of a transformer, the voltage is reduced to any desired strength, usually from 100 to 125 volts. The commercial A.C. is either 60 or 133-cycle. usually 60. Since the principle involved in the transformer is quite similar to the one met with in X-ray machines a description of it would not be out of place in this work. Fig. 10 shows the plan of construction of a transformer. A represents an iron core, around which is wrapped insu- lated wire. This is the primary winding through which passes the pri- mary current at the high voltage of from 1.000 to 3,000. As always, the amperage depends on the size of the wire. B represents another iron 12 ELEMEXTARY RADIOGRAPHY core, around which is also wrapped insulated wire. This is the secondary winding, through which the secondary current passes. "C shows soft iron connections between the two cores. When the electric current is established in the primary winding a current is set up or induced in the secondary winding. Bear in mind there is no electric connection between primary and secondary windings. Fig. II. A Transformer. The primary current enter-, and leaves unaltered except for a slight loss in amperage, but in its passage it induces a current in the secondary. If the wire used in the secondary winding be of the same length and size as that used in the primary winding, the induced secondary current will be of practically the same voltage and amperage as the primary cur- rent. But if the wir.- in the secondary be shorter and larger, the induced current will be lower in voltage and higher in amperage. < >r it the wire of the secondary winding be longer and smaller than the wire in the primary winding, the induced secondary current will be higher in voltage and lower in amperage than the primary current. The wattages of the primary and secondary currents remain practically the same. For example, suppose the voltage of the primary current is [,000, the am- perage 5. the wattage would be 5.000. Suppose now. by means of the ELECTRICITY 13 transformer, the voltage is lowered to 100; there would he a raise in am- perage to 50. Notice the wattage remains the same, 5,000. The figures do not represent what actually happens, since they do not take into ac- count the loss of current due to the internal or intrinsic resistance of the transformer, hut they do represent roughly the general principle of the action of the transformer. A transformer which lowers voltage — the kind used on A.C. cir- cuits between mains and consumer — is known as step-down transformer; one which raises voltage is a step-up transformer. The transformer does not alter the nature of the current. That is, the secondary is an alternating current, the same as the primary, the change being only in voltage and amperage. Transformers cannot be used on a direct current. The foregoing is calculated to give the reader a speaking acquaint- ance with electricity, the wonderful force which produces X-rays. Fur- ther treatises of the subject will be made as necessity demands. It will be noted that but one source of electricity has been considered, namely, dynamo electricity — that furnished by light and power companies. Be it known, however, that electricity can be produced by means other than the dynamo — by friction and chemical change, for examples. We have con- sidered only the source of electricity which is used to operate the X-ray coils. CHAPTER IT. X-Ray machines. It was stated in Chapter I that an electric current is necessary to produce X-rays, but nothing was said concerning the strength of the current required. It takes a current very high in voltage, varying from 30.000 to 300,000 or more volts, and low in amperage, the amperage being measured in milliamperes. The ordinary commercial circuit for lighting purposes is almost in- variably either D.C.. 1 10 volts, or A.C., 60-cycle, 100 to 125 volts. The amperage varies according to the amount of electromotive power needed, ranging from 4 to 5 to over 100 amperes. The commercial current, as supplied, is therefore useless. However it will operate a machine which will give the desired current. X-ray machines are of two classes: Those that X.Ray generate their own electricity without any external machines. electric supply, and those that depend on a commer- cial current or storage batteries to excite them. There i> but one of the first class, namely, the static machine ( Fig. 12). and of the second class there are three — the Ruhmkorff coil ( Fig. 13), the high frequency or Tesla coil I Fig. 14). and the "interrupterless" coil I Fig. [5). All of the latter class are literally induction coils, just as the transformer, described in Chapter I is an induction coil, but when the term induction coil is used we may assume that it is the Ruhmkorff coil that is referred to. We shall follow the precedent and call the Ruhm- korff coil the induction coil, though it is no more an induction coil than the high-frequency or "interrupterless" coils. The static machine is so much inferior to the induction coil for pic- ture work, and so large and difficull to Operate, compared with any coil, thai the only reas< n for using it would be the lack of a commercial cur- rent with which to operate a coil. Even in such an event— the lack of a commercial current — I would advise the use ol an induction coil operated by storage batteries I Fig. 16) in preference to the static machine 14 X-RAY MACHINES *5 The induction coil is the most popular ap- TlldUCtion paratus for giving the electric current necessary €oil. for X-ray picture work. It is a step-up trans- former to this extent, namely, its primary current is of comparatively low voltage and high amperage, while the secondary is very high in voltage and low in amperage. It differs from the trans- former in mechanical construction, and also in that the primary current must be an interrupted current and the secondary, induced current is Fig. 12. A static machine. practically a uni-directional one. It will be recalled that the primary and secondary currents of the transformer are both alternating. Let us trace a current of electricity from the Installation. mains through an induction coil and auxiliary appli- ance leading to it. (Fig. 17.) Wiring from the mains to the coil should always he done by a com- petent electrician. A wire of a given size will carry only a certain am- perage without heating. If this amperage be exceeded greatly the wire i6 ELEMENTARY RADIOGRAPHY may become hot enough to set fire to surrounding building material of a combustible nature. There are, therefore, laws governing the size of wires to be used to carry different amperages. Coils are rated by their manufacturers to consume a certain number of amperes, and wiring Fig. 13. Induction or Ruhmkorfl coil. should be done according to this rating. The amount of amperage neces- • to operate a coil varies directly according to the size of the coil — the larger the coil the more amperes it takes. Assuming tin- coil to be of a medium large size, the lead wires used to conned it t<> the mains should be capable of carrying at least 30 amperes without heating! B) "lead wire>" I mean the win- leading to the machine — not lead (the metal ) wires. The wires arc copper. X-RAY MACHINES 17 Somewhere near where the wires enter the fuses. building, and also at the coil itself, will be found fuses. (Fig. 18.) A fuse is a wire, an alloy of lead, of a given size, and fusing point capable of carrying only a limited amperage without melting. Thus if more than 30 amperes be sent through a 30-ampere fuse, the wire is heated to its fusing point, it melts, the circuit is broken, and the flow of electricity is stopped. A fuse is a Fig. 14. High-frequency coil. sort of safety valve. About 30 ampere fuses should be used for a medium large induction coil. This information, however, will always be given by the manufacturers of the coil. Somewhere near where the wires enter the build- SwitChCS. ing, and also at the coil, are placed switches. An electric switch (Fig. 19) is an appliance for throw- ing the electric current into, and out, of an extended or auxiliary circuit. Assuming that the current at our disposal is D.C.. it must first be passed through an interrupter. An interrupter is an electric apparatus by means Interrupters. of which a constant current is converted into an in- terrupted one. Interrupters are of three kinds : ( 1 ) The electrolytic. Fig. 20; (2) the mercury turbine. Fig. 21, and (3) the mechanical or vibrator. Fig. 22. For picture work, in connection with the induction coil, the elec- trolytic, or, as it is sometimes called in honor of the inventor, the YVeh- nelt interrupter, is quite the best. With it the constant current may be . The platinum is covered with a porcelain sheath, C except for its point, which projects into the electrolyte. Little or much of the poinl may be exposed in the acid by the regulating arm, I). \\ «• have two wires now leading from the mains to our apparatus. X-RAY MACHINES 19 ( >f these one is the positive wire which brings the electric current, and the other is the negative or return wire. The positive wire must be at- tached to the binding post of the platinum electrode, marked -f-. (Fig Fig. 10. Induction coil for use with storage cells. 20.) But how can we tell which is the positive wire? Cut some of the insulation off the ends of the wires, immerse them in a glass of water, and bubbles will be given off from the negative wire. When making this test, care should be taken not to touch one wire to the other, so making a short circuit. The term (short circuit) almost explains itself. The desired circuit in this instance is from the positive wire, through the water, which is highly resistive to the flow of electricity, into the negative wire and back to the mains. Suppose that the wires come in contact 20 ELEMENTARY RADIOGRAPHY (that portion of the wires from which the insulation has been removed), the current no longer passes through the water, but takes the shorter path of less resistance, passing directly from positive to negative wire. All the amperage formerly used and choked back by the resistive water flows through the wires, heating them rapidly. Fuses Switch Shdin$ Rods io regulate length Of spark gap ■Secondary K Terminals Interrupter Rheostat Fijy. 11 Coil The course of the electric current, through the electrolytic inter- rupter. i-> from platinum through the acid electrolyte, and on through the lead electrode. As the current flows through the acid solution, a chemical change occurs and a gas is formed. This gas accumulates in the form of a bubble around the exposed platinum point, and momentarily stops the flow of the current. Then the bubble bursts and the current is tablished onl) to be stopped again in the manner just described, and so on. The more platinum exposed in the solution the slower the inter- ruptions and the more amperage will pass through the interrupter. In order that the amperage may be increased without producing a corre- sponding decrease in the number of interruptions per minute, interrupters arc made with several platinum points. I Fig. 23. ) Thus with a multi- point interrupter, when more amperage is desired, more points are thrown into tin- circuil by means of small switches for the purpose. A two-point X-RAY MACHINES 21 interrupter will draw enough amperage, and give sufficiently rapid in- terruptions, for dental radiographic work. The current is sometimes stopped altogether by the interrupter. This may be due to the accumulation of a large bubble of gas, on the platinum point, which will not burst. By moving the point — or points if the inter- Fig. IS. Patent fuses or cutouts. rupter is multipointed — up and down several times by means of lever D, Fig. 20, the bubble will be broken and the current re-established. On a D.C.. no-volt circuit the electrolyte should be 15 to 20 per cent, acid; on a D.C.. 220-volt circuit, from 5 to 8 per cent, is strong enough. The jar should be one-half or three-quarters full. As the solu- tion stands, some of the water evaporates, so raising the per cent, of acid in tbe electrolyte. As this occurs, more water should be added. The strength of the solution can be easily and accurately determined by means of a special hydrometer. (Fig. 24.) As the water evaporates, and the solution gets stronger, its specific gravity raises. The hydrometer is sensitive to this change of specific gravity, and shows by a special marking the exact per cent, of the solution. As the current passes through the interrupter, heat is produced. Hence the glass jar is placed in a metal-lined box and the box filled with water. (Fig. 23.) Even with this means for cooling, when used con- tinuously for fifteen minutes or longer, the electrolyte becomes so heated that the interrupter no longer works properly. In dental picture work., though, the time of operation is a matter of seconds. Tt. therefore, will be understood that no trouble ever occurs due to heating of the elec- trolvte. 22 ELEMENTARY RADIOGRAPHY u i* Diagrammatic illustration showing ihi an electric switch. The single .it we shall call (not knowing :i bettei name) the original The double arrows mark an extended circuit. The drawing shows the switch if the double 1- > closed. With the ^wi tcli open the current could no) i ;t-s through the extended circuit X-RAY MACHINES 23 When the X-rays are used for their therapeutic value, long ex- posures are made; so long that undue heating of the electrolytic inter- rupter would be sure to occur. Hence, for this work the mercury turbine interrupter (Fig. 21) is best. In principle the mercury turbine is a mechanical interrupter, depending on no chemical change for its action, being operated by means of a.i electric motor. We shall not consider it Fig. ^n. Non-water cooled one-point electrolytic interrupter. further, for it should not be used for picture work, except in the absence of an electrolytic interrupter. The mechanical interrupter, or vibrator (Fig. 22), is used only on the smallest coils. The principle on which it operates is the one involved in the construction of electric bells ; Fig. 25 illustrates the principle. A is a movable arm with fulcrum at B. When the current travels, the path marked with arrows, the electro-magnet, C. draws the movable arm A, over to it, breaking the circuit at D. When the circuit is broken the electro-magnet loses its magnetism and the spring, E. draws the movable arm back, re-establishing the circuit. The rapidity of interruptions may be regulated by altering the strength of the spring. A popular form of vibrator is the ribbon vibrator illustrated in Fig. 26. 24 ELEMENTARY RADIOGRAPHY In tracing the current directly from the supply Rectifier. wire into the interrupter, we have assumed, as stated, that we are receiving our supply from a D.C. circuit Suppose however, that the only current at our disposal is A.C., as is often the case. It is necessary to send the alternating current through a rectifier | Fig. 2~ I before allowing it to enter the interrupter. A rectifier is an electrical apparatus by means of which an alter- nating current is converted into a uni-directional. pulsating current, and Fig. 21. Mercury turbine interrupter. consists of a glass jar containing an electrolyte, a solution of ammonium phosphate usually, in which is immersed a steel electrode and an alumi- num electrode. The jar, the electrolyte and the two electrodes consti- tute one cell. Fig. 27 shows a one-cell rectifier. With the direct current, we are able to test and determine which of the two lead wires is positive. This is impossible with the alternating current, because polarity changes at each alternation. Either of the lead wires ma\ therefore In- attached to the steel electrode, and a wire con- nected from the aluminum electrode to the platinum of the interrupter. A- long as tin- aluminum remains the negative electrode of the rectifier, the current flows in m steel to aluminum and on, but when the current and starts to flow from aluminum to steel, a chemical change occurs in the aluminum, making it a non-conductor and choking off tin- flow. Thus a current of 60-cycle frequency, after passing through a one- cell rectifier becomes practically (there i~ a slighl inverse current) a X-RAY MACHINES 25 uni-dircctional current with 30 interruptions per second. If, after passing through the rectifier, as just described, the current is an interrupted one, the questions arise : Why send it through an interrupter? Why not directly on to the coil ? Because the interruptions are not sharp and complete enough. The current is pulsating rather than interruupted. By connecting three or four rectifier cells in a certain way (Fig. 28), we are able to obtain practically a uni-directional, constant current. If the supply current is 60-cycle, as is usually the case, the electrolyte in the interrupter remains the same as for a D.C., no-volt circuit namely, Fig. 22. Vibrator or mechanical interrupter. about 20 per cent., but if the A.C. supply is 133-cycle, the solution should be stronger — about 30 per cent. From the interrupter the current passes into the rheostat, as per Fig. 17. A rheostat (Fig. 29) is an apparatus by the use Rheostat. of which we are enabled to regulate the quantity of electricity entering an electric machine. The rheostat does not have much effect on voltage. Fig. 30 illustrates the rheostat. A represents coils of wire, often German silver, offering great resistance to the flow of electricity. When the arm, B, is on button 1, the current must pass through all the re- sistive wire on its way to the electric machine, induction coil, motor, or what not. This resistive wire chokes back amperage. On button, 2, there is less resistance ; on button, 3 still less, until on the last button the current passes directly into the machine. The rheostat illustrated acts -' ELEMENTARY RADIOGRAPHY also as a switch, completely breaking the current when the arm, B, is on button, o. From the rheostat the current passes into the coil proper, follows the wire of the primary winding, and passes back through the negative lead wire to the mains. <2** Fig. -'::. Seven-point electrolytic interrupter, water-cooled. A different method of wiring to that shown in Fig. 17 is illustrate- 1 in Fig. 31. At first glance it seems that the primary current is not inter- rupted, the interrupter being on the negative wire with the current pass- through it after passing through the coil. But since the current can- not enter the coil any faster than it leaves the manner of its exit will govern it- entrance, and hence the current of the primary is interrupted just the same, whether the interrupter be placd On the positive or nega- tive lead wire. X-RAY MACHIXES 27 The coil consists of a soft iron, cylindrical core, gOll # around which is wrapped insulated copper wire, the primary winding. (Fig. 32.) (The necessity for good insulation will be appreciated it we stop to consider what would si w= Fig. -'4. Acid hydrometer. happen if the core were wound with uninsulated wire. If this were done the current would not follow the windings of the wire at all. but would choose the shorter path of less resistance, passing along the iron core, making a short circuit. ) ( )ver the primary winding is placed a heavy insulation of mica or vulcanite, and around this is wound more insulated wire the secondary winding. (Figs. 32 and 33.) There is positively no electric connection between the primary and secondary windings. The primary current passes through the primary 2S ELEMEXTARY RADIOGRAPHY winding and into the negative lead wire. But in its passage it has in- duced or created a secondary current in the secondary winding. Coils are rated and designated according to the maximum num- ber of inches of atmosphere the secondary current can be made to jump. As the current jumps from one terminal to the other of the secondary winding, a spark occurs, due to the resistance of the atmosphere to the P n t 4- B Fig. 25. Fig. 26. Fig. 25. A. movable arm with fulcrum at B. C, electro-magnet. D, break. E, spring. Fig. 26. A, piece of ribbon steel. B, point where circuit is broken. C, electro-magnet. flow of the current. When we speak of a coil as, say a 12-inch coil, we mean that the spark gap of that coil is twelve inches long; that its sec- ondary current can be made to jump twelve inches of atmosphere. The larger the coil the longer the spark gap. From 6-inch to as high as 40- inch coils are manufactured. From 8-inch to about 18-inch coils are the sizes generally used. The wire of the primary winding is from \ 2- to 8-gauge; of the sec- ondary from 34- to 29-gaUge. The length of the windings varies accord- ing to the size of the coil, of course. The wire in the primary of a [2-inch coil is about 100 feet long, in the secondary about 28 miles long. The win- in the primary of an [8-inch coil is about [40 feet, and in the sec- ondary 38 miles long. X-RAY MACHIXES 29 Fig. 27. One-cell rectifier. - S8 Three-cell rectirk 3° ELEMENTARY RADIOGRAPHY At each "make" and "break" of the circuit of the primary current, a current is induced in the secondary. The secondary current induced ai ;he break of the primary Hows in the same direction as the current in the primary, while the current induced at the make flows in the opposite direction. Thus the secondary is an alternating current; but the current oi the make is SO much weaker than the current of the break that, for practical purpose, the secondary may be considered a uni-directional, pul- Fig. 39. Twenty-nine button rheostat. sating current. The current of the make is what is known as the inverse current, and it is the effort of all coil manufacturers to make a coil giving a> little inverse current as possible. The voltage of the secondary current cannot lie determined ac- curately. Authorities differ very greatly in their estimate of the number of volts required to jump one inch of atmosphere, giving the figure as low a- kkxx), and as high as 6o,000. What voltage is required to jump each succeeding inch after the fust, j^ also a question shrouded in very greal uncertainty. Estimating each inch of atmosphere at 10,000 volts, which perhaps tting a- near the truth a- possible ai the present time, the voltage X-RAY MACHINES 31 furnished by any size coil can easily be determined. Figuring on this basis, an 8-inch coil in full operation supplies a current with a potential of 80,000 volts; a 20-inch coil, 200,000 volts. The amperage, or, to be more exact, the milliamperage of the sec- ondary current of an induction coil varies according to the resistance Fig. 30. Diagram of rheostat. through which the current is forced. Thus, allowing the rheostat to re- main on the same button, the milliamperage is increased or decreased accordingly as the spark gap (Fig. 17) is shortened or lengthened. With the spark gap at its maximum length, the milliamperage is least. As the sliding rods are pushed closer to one another, so lessening the length of the spark gap, milliamperage increases. Different coils are capable of forcing different milliamperages through their maximum length of spark gap. Thus one 10-inch coil may be able to force twenty milliamperes 32 ELEMENTARY RADIOGRAPHY through ten inches of atmosphere, while another could send only two milliamperes through such a resistance. All coils give a high milliam- perage on a short spark gap, the amount running into hundreds of mil- liamperes. Instead of the sliding rods, some coils have an arrangement, as per Fig. 34. for regulating the length of spark gap. The milliamperage strength can he estimated roughly by the ap- pearance of the spark. A thin, blue spark indicates low amperage. A Mains Y Inierrupter Coil Fig. 31. fat, fuzzy spark, the caterpillar spark, indicates high milliamperage. To do rapid dental radiographic work a coil should give at least six inches of the fat, fuzzy spark. Amperemeters and milliamperemeters are used on the primary and secondary current-, respectively, to measure their volume. (Fig. 13.) While these meters may be considered luxuries rather than necessities, they are certainly ver\ useful luxuries. How dangerous are the currents of an induction Colli coil? is a question often asked. Both primary and Dangerous. ondary currents of an induction coil are danger- ous. The larger the- coil the greater the danger. Tf one should come in contact with a terminal of the coil, he would receive '•re. painful shock. It would he much more severe and painful if X-RAY MACHINES 33 the victim happened to be standing on a conductor, for then the current would pass entirely through the body into the conductor. If one should come in contact with both terminals of a large coil, so that the entire current would pass through the body, the accident might result fatally. Fig. ss: A, iron core. B. iron core with primary winding. C, iron core, primary winding and insulation. D, iron core, primary winding, insulation and secondary winding. Now let us consider the high-frequency coil. fiifllvTrequency (Figs. 14 and 35.) In mechanical construction the Coil. high-frequency coil may be considered a kind of double coil with the secondary of the first coil act- ing as the primary of the second coil. The primary current of the first coil should be A.C. 3 .; ELEMENTARY RADIOGRAPHY From the supply wire the current passes through the primary wind- ing of a step-up transformer | first coil ) at the usual commercial ioo to 125 volts, no-cycle. (Fig. 35.) An alternating current of the same frequency as the primary, but higher in voltage and lower in amperage is generated in the secondary of the transformer, and passes into the condenser, which acts as a reservoir. As the current leaves the condenser ami jumps the regulating spark gap. it is oscillating at a frequency of Fig. 33 Cross-section diagram of induction coil. A, iron core. B, primary winding. C, insulation. D, secondary winding. from 10.000 to more than a million. It passes through the primary wind- ing of the Tesla coil, inducing a secondary current of the same high frequency. This Tesla coil is the same as an induction coil ( Figs. 32 and 33), except that some inert substance, instead of soft iron, is used for the core. The secondary current of the second coil is the one supplied by the machine, the one to be used to generate X-rays. Like the current of the Kuhmkortl. or induction coil, this current is high in voltage and low in amperage. The current 1 f the induction coil is, however, practically a uni-directional one. while the current supplied by the high-frequency coil is alternating at the inconceivably high frequency of tens of thousands or million-. Hence the term "high frequency," which is applied to the current and the coil producing it. The frequency is governed by the size of the condenser; the smallet the condenser the higher the frequency. Tims most "high-frequency and X-ray machine-" are equipped with a switch, by means of which all, or X-RAY MACHINES 35 a part, of the condenser may be used. When using the coil for X-ray work, this switch should be turned to "low frequency," so that all of the condenser is used. When using the coil for "high-frequency" treatments — using the current as a therapeutic agent — the switch should be on "high frequency," so that only a part of the condenser is used. By means of the regulating spark gap, we can control to an extent the secondary current of the second coil — the current supplied by the Fig. 84. machine for use. Widening the gap increases voltage at the expense of the amperage; narrowing the gap increases amperage at the expense of the voltage. The wattage remains the same. For X-ray work the gap should be as short as possible, without reducing the voltage to a point where the current will not pass through the X-ray tube. The ideal current for exciting an X-ray tube ( in other words, pro- ducing X-rays) is a uni-directional one. Compared with that of the high-frequency coil the current of the induction coil more nearly ap- proaches this ideal. Because of this, the writer advises the use of the induction coil in preference to the high-frequency coil, unless a very small machine is desired. We thus eliminate large high-frequency coils from further consideration. The small, portable, suitcase, high-frequency coils called "X-ray and high-frequency coils," may be used where the lack of space makes the installment of a larger machine impossible or undesirable, when a transportable coil is wanted, and when the purchaser wishes to make the minimum cash investment. 36 ELEMENTARY RADIOGRAPHY As stated, the primary, or supply, current of a coil, built on the high- frequency plan illustrated, should be A.C. When attaching the portable coil (Fig. 14) on an A.C. circuit, therefore, all that needs to be done is to screw the attachment into a lamp socket. Terminal Spark Cap (Aoi rejulatinj spark <}ap) z n J Coil m Tesla Coil Regalatinf Spdrk (sap Condenser 11' Coil or Step - Up Transformer secondary 71717771717^ Primzjy JeconcLa-riy Pr-ifna.ry r.//. / / ' /vv -K=> Fig. 35. When the supply current is D.C., a rotary cori- Rotary verter should be used. A rotary converter I Fig. 36) Converter. consists of an electric motor set in motion by the supply current, which motor in turn revolves the armature of an A.C. dynamo, which generates the electricity that is sent into the coil. Instead of having the D.C. motor and the A..C. generator eparate machines connected by a common shaft so that movement of armature of one machine revolves the armature of the other, the rotary converter can be made si > as n 1 be end' ised in one casing. ( Fig. 1 5. 1 Tracing the current, as per Fig. 37« coming through the fuse and !:. the current passes through the positive wire to the starting box X-RAY MA CHINES V or rheostat. it leaves the starting box through two wires, passing through one to the field of the motor marked S.F., through the other to the armature of the motor, marked ARM, and out of the motor through the negative lead wire. A new circuit is formed from the generator side of the converter marked A.C., passing through the coil. It may be well to state just here that an electric motor is. in con- struction, practically the same as a dynamo or generator. In fact, taking Fig. 36. Rotary converter, or motor-dynamo. a given machine, it may be used as either a dynamo or a motor. If its armature is revolved by some power, it will generate electricity, and it is then a dynamo ; if a current of electricity is sent into its field and armature, the armature revolves ; and it is then an electric motor. Motors are made to be operated by both D.C. and A.C. circuits ; that is, we have D.C. motors which can be run only by a direct current, and A.C. motors which can be excited only by an alternating current. Instead of a rotary converter, some machines are equipped with a mechanical vibrator (Fig. 22), which interrupts the current as it enters the coil. This is not so efficacious as the converter. Machines with the mechanical interrupter are advertised to operate on either A.C. or D.C. circuits. The length of the spark gaps of portable machines varies from four to ten inches. They are seldom able to give a fat, fuzzy spark longer than half the length of the spark gap. The full-length spark is almost alwavs thin and blue. 38 ELEMENTARY RADIOGRAPHY As a general proposition the alternating is the Danger of most dangerous of electric currents. Mysterious and Currents. surprising as it is, however, high-frequency currents, such as high-frequency coils produce, are much less dangerous than the current of an induction coil. If one should touch a Line, J 10 Direct Current Portable Coil. converter Fig. 37. terminal of a high-frequencj coil a spark would jump to the hand just as it came within sparking distance of the terminal. This spark might make a blister, hut if the experimenter had been standing on a non-con- ductor, no further discomfort would he felt. Indeed, one may take a small steel bar ami. standing on a non-conductor, touch a terminal of oil and -o take into the body enough current to cause great injury, if it were of the nature of the induction coil, without receiving any sen- sation at all. If he should stand on a conductor, however, the shock would he painful. If he should grasp both terminals, so that the entire current passed through the- body, the result would be severe pain and probably injury. Tin- larger the coil the more dangerous the current. 'The primary current of the portable high- frequency coils is not as dangerous as the primary current of the stationary induction coils, he- X-RAY MACHINES 39 cause they draw cnly from three to ten amperes, while the induction coils seldom draw less than twenty and as high as sixty amperes. The "interrupterless" coil, or transformer, as it TnlcrruptcrlCSS is often called (Fig. 15). is the newest and perhaps Coil. the most powerful X-ray machine made. On the market these coils are known by such trade names as "The Snook Roentgen Apparatus," "The Peerless Roentgen Appa- ratus," "The Solace Interrupterless." Fig. 38. Interrupterless coil, showing switch and rheostat, rotary convtrtcr, transformer and rectifying switch. The interrupterless coil consists of a rotary converter, a step-up transformer, and a rectifier switch. (Fig. 38.) The step-up transformer may he of the closed magnetic circuit core type (Fig. 10), or the open core type (Fig. 32). These machines are of two kinds: Those built to be operated on a D.C. circuit, and those designed for the A.C. circuit. Let us consider the former first : The converter is set in motion by the commercial direct current. It generates an alternating current which is sent through the primary of the transformer. The induced current in the secondary is of the proper voltage and amperage for X-ray work, but it is alternating. It should be direct. It is made so by means of the rectifying switch, and is then an ideal current for X-ray work. The rectifying switch is a revolving mechanical device similar to a commu- tator in principle. 40 ELEMENTARY RADIOGRAPHY The A.C. machine is similar to the D.C. machine, the principal difference being the addition of an A.C. motor. An alternating cur- rent motor transmits mechanical power to the "rotary converter," which, in this case, becomes simply an A.C. generator, not. strictly speak- ing, a rotary converter, though it is usually so called. Since the supply current is alternating, and it is an alternating cur- rent that must be sent into the primary of the coil, one may logically ask, \\ h\ not send the commercial current directly into the primary, instead of operating an A.C. motor, which, in turn, revolves the armature of an A.C. generator, which produces the current which is sent into the coil ? The answer is that the rectifier switch must work in synchronism with the generator, which supplies the current to the coil. In other words, the rectifier switch must be on the same shaft, and revolve in unison with the generator in order to rectify the alternating current induced in the sec- ondary winding of the coil. The interrupterless coils are rated according to the amount of "energy" they create, not according to their spark gap length. The spark gap is usually ten or twelve inches long. The machines are rated to have a capacity of so many kilowatts. Take a "4 kilowatt" machine, for ex- ample. Its primary current, we will say, is 100 volts, 40 amperes (4,000 watts), the secondary current something like 100,000 volts, 40 milliam- peres (4,000 watts). This system of rating is being adopted by manu- facturers of induction coils also. CHAPTER III. X-Fay tubes and the X-Rays. Thus far we have considered only the electric phase of the subject. We shall now describe the apparatus through which the electricity is passed, and which generates the X-rays, namely the X-ray tube. An X-ray tube is a bulbular glass tube, from which the atmosphere has been exhausted to quite a high degree of vacuum — about 1/1,000,000 part of an atmosphere. It should be remembered that there is a some- thing which occupies all space, even vacuua, and that something is known as ether. There is, of course, ether in the X-ray tube. X-ray tubes are often called Crooke's tubes, but they resemble the tube made by Pro- fessor Crooke only in having a high degree of vacuum. In mechanical construction they are quite different. Tubes may be divided into two classes : those designed to be used on an induction coil or interrupterless coil, and those made to be used on a high-frequency coil. We shall describe the former first. Sealed in the X-ray tube are the anode. Fig. Simple 39, A (also called anti-cathode and target), and the Cubes. cathode, B. The anode is usually flat, placed at an angle of 45 degrees to the long axis of the tube, and made of some high-fusing metal, such as platinum, iridio-platinum or tantalum. The cathode is concave, saucer shape, and usually made of aluminum. Since, in connecting the tube to the coil, it is necessary to attach the connecting terminal tape or wire from the positive side of the coil to the target end of the tube, we must be able to determine which is the positive terminal of the coil. This may be done on an induction coil, as follows : Cut out the resistance of the rheostat, adjust the sliding rods to about one-half the distance of the maximum spark gap, and throw on the switch. The spark will jump the gap so quickly that it is impossible to learn by simple observation in which direction it is traveling. By watch- 41 4- ELEMENT. IRY RADIOGRAPHY ing the large disc terminal, however, this can be determined. If on throwing the switch on and off the spark is noticed to cling to the edge of the disc always, then the current is passing from the disc. If, how- ever, the spark occurs from the surface of the disc just as the current is turned on ( it may then seek the edges), the current is traveling from the small bulb to the disc. (Fig. 40.) With the tube properly connected to the coil as per Fig. 41. the current is shunted (Fig. 42) through the tube, instead of jumping the + «fc A B '. A. anode. B. cathode. C, point at which the atmosphere was pumped from the tube. spark gap, passing from anode to cathode. Whether the current will choose the path through the tube or jump the spark gap depends on which offers the less resistance. A current of electricity always travels the path 1 >f least resistance. Tubes are designated according to the degree of their vacuum. Thus we have the high or hard tube, in which the vacuum is well-nigh com- plete; the medium tube in which the vacuum is less complete, and the -.ft or low tube, in which the vacuum is least complete. High tube- offer the greatest resistance to the passage of the electric current through them, then comes the medium, while the low vacuum tube oilers the least resistance. For dental picture work a tube should be high or medium. preferably high. The operator may determine whether a tube is bard, medium or -oft. ; t , follow-: Conned tin- tube to the coil. (Fig. 41.1 Separate the sliding ro.l- to give a spark gap of two or three inches and turn on the current. I Inless the tube is very low indeed, the current will jump the soark gap instead of passing through the tube. Let us suppose the cur- X-RAY TUBES AND THE X-RAYS 43 rent does jump the spark gap. Now widen the gap a little; turn on the current, and it passes through the tube. The tube will, therefore, be rated as one of low vacuum, offering a resistance slightly greater than two or three inches of atmosphere. When the current jumps the spark- gap instead of passing through the tube, the tube is said to have "backed up" so many inches — the number of inches of the gap — of ''parallel spark." Thus a low tube will hack up two or three inches of parallel A + A <- -*m A + P ^ — > Fig. 40. spark ; a medium tube will back up four or live inches of spark ; a high tube will back up six or seven inches of spark, and a very high tube will back up eight or nine inches of spark. Aery high tubes offer so much resistance that only the largest coils are able to force sufficient milliam- perage through them to generate a sufficient number of X-rays for picture work. A tube that will back up more than nine inches of spark is too high to be useful ; it is impossible to force enough milliamperage through it. From the foregoing it will be seen that any coil smaller than one with an eight-inch spark gap could not well excite a high tube, and that at least a ten-inch coil is necessary to light a very high tube. It seems, too, that any coil with a spark gap wider than eight or ten inches is need- lessly large. The coils with the long spark gaps are, however, seldom able to throw a fat, fuzzy spark farther than eight or ten inches. The throwing of a thin, blue spark a greater distance is simply incidental and 44 ELEUEXTARY RADIOGRAPHY without practical usefulness. Thus an eight or ten-inch coil may be as powerful as one with an eighteen or thirty-inch spark gap; that is, capable of forcing as high a milliamperage through a high tube. If. however, a coil can force any kind of a spark at all through from eighteen t<> thirty inches of atmosphere, we may be sure it will send a high milliam- perage through a good radiographic tube, or, what is the tube's equivalent Fig. 41. The X-ray tube connected with the induction coil. in resistance, six or eight inches of atmosphere. It is so well understood to-day that the coil with the very wide spark gap is not necessarily more powerful, that manufacturers arc making practically all of their coils witb from an eight to a twelve-inch spark gap, then rating them ac- cording to the milliamperage they can force through this resistance. To light a tube well a coil should be capable of giving a fat. fu/.zy spark, tin' distance of the parallel spark which the tube backs up. The tube thus far described is the simplesl form of X-ray tube. Xext in simplicity is the bi-anodal tube | Fig. 43.) When the two anodes are connected, as in Fig. Bi-anodal 43- the positive terminal may be attached to either Cubes. anode or assistanl anode, preferably the anode. The advantage of tin- assistanl anode is a matter on which authorities have widely different opinions. < >ne manufacturer, a man X-RAY TUBUS AND THE X-RAYS 45 who is making one of the very best tubes on the market, tells me that he puts the assistant anode in his tubes because some of his customers de- mand it. and he is able to do so without impairing their efficiency; that his tubes would be just as good with but one anode. Remember the vacuum of an X-ray tube is not perfect ; there are some gases in the tube. The function of the assistant anode is to draw these gases back of it away from between anode and cathode. Thus, if the removable wire W^- RESISTANCE vVWVAAAAAA m- m- THE SHUNT Fig. 42. The arrows show the current flowing through the shunt. connecting the anode and assistant anode (Fig. 43) be removed and the tube hitched to the coil, the positive terminal being attached to the anode, the tube will work with a slightly lower vacuum, because the assistant anode does not draw gases back of it. Tubes with assistant anodes are supposed to be capable of transmitting a greater milliamperage. We have divided X-ray tubes into two grand classes : those designed to operate on an induction coil or interrupterless coil, and those designed to operate on a high-frequency coil. Each of these classes may be sub- divided into tubes with a means for regulating their vacuum (Fig. 44), and tubes without a means for regulating their vacuum (Figs. 39 and 43). Tubes without regulators are no longer in general use. because, with use. they soon become too hard and must be sent back to the manufac- turers to be opened and repumped. This is expensive and annoying. A tube too high for use will sometimes drop in vacuum and regain its former usefulness if allowed to rest — remain unused — for a month or so. There are different methods of regulating the methods Of vacuum of X-ray tubes. The most popular and effi- Rcqulanna cient is the one we shall new consider. Uacuum. The vacuum is governed by means of a movable arm, which increases or decreases the distance be- 4" ELEMEXTARY RADIOGR. iPHY tween A and B, Fig. 44. This distance we shall call the tube-regulating spark gap. The shorter the gap the lower the vacuum can be made; that is. the shorter the gap the less perfect the vacuum can he made. The current enters the tube and, let us imagine, tries to pass from anode to cathode. The vacuum in the center of the tube is more perfect REMOVABLE WIRE A5SISTANT "ANODE > CATHODE ANODE Fig. 43. A Bi-Anodal X-ray tube. REGULATING CHAMBER Fig. 11. X-ray tube with vacuum regulator. than around the walls. I knee the path of least resistance is through the regulating chamber, through the movable arm. through the tube-regu- lating -park gap. into the negative terminal tape; unless of course, the lating -park gap is very wide. X-RAY TUBES AND THE X-RAYS 47 F!g. 4-"). Showing the manner of connecting the third terminal on the coil with the regulating chaml er. The regulating chamber contains asbestos impregnated with some chemical, sodium or potassium hydrate, for examples. When the current passes through the regulating chamber, heat is create '. which causes the chemical to give off gases. These gases lower the vacuum of the tube so that the current may pass directly from anode to cathode. When the 4* ELEMENTARY RADIOGRAPHY tube cools thoroughly — in the course of fifteen to thirty minutes — these gases are taken up again by the chemicals in the regulating chamber, and the vacuum rises again. Thus the vacuum of the tube is always too high when the tube is not in use, but can be lowered to the desired degree. For rapid picture work, the tube-regulating spark gap should be three CATHODE STREAM Fig. 46. Showing the direct X-ray and the cathode stream. to five inches. As the tube gets old the tube-regulating spark gap must be made shorter to obtain the same condition of tube. When the tube is properly hitched to the coil and the movable arm :or a high vacuum — to give a regulating spark gap of about four inches— and the current turned on, practically all the current will at first pass through the regulating chamber and jump the tube-regulating spark gap. As explained, this lowers the vacuum, ami in a few seconds the currenl i- passing from anode to cathode. All of the current ma) pass directly through the tube now for a few seconds, hut the passage of the current from anode t<» cathode raises the vacuum and presently some current will he seen to jump the gap for a while. And so mi, just as the vacuum raises ;i little, it is immediately lowered by some of the current sing through the regulating chamber. X-RAY TUBUS AND THE X-RAYS 49 Instead of the movable arm, a terminal tape and a third terminal on the coil may be used. (Fig. 45.) Thus the tube-regulating spark is transferred from the tube to the coil. The hitching of a tube to a coil with a third terminal is very simple. Hitch the positive terminal to the anode, or assistant anode if desired, and the negative terminal to the cathode as usual ; and the third terminal to the regulating chamber. The advantages of the third terminal over the movable arm are that the spark- ing is taken awa\ from the tube and so away from the patient (in radio- graphic work the tube is always near the patient), and. on some coils. Fig. 13 for example, the gap may be regulated from the end of the coil where the rheostat and switches are located, so making it unnecessary for the operator to move from his position to change the tube-regulating spark gap. When the current passes from anode to cathode, the cathode stream (Fig. 46) is given off from the cathode. The cathode stream is a form of vibratory motion of the ether. Leaving the concave surface of the cathode, the cathode stream is focused to strike the anode or target at a point. X-rays are given off from this point (Fig. 46). The cathode stream can be seen in a tube of very low vacuum, appearing blue. Great heat is generated at the point on the target where the cathode stream strikes it. Hence the necessity of making the target of some very high fusing metal. A small hole may be burned superficially into the target without spoiling the tube. The tube in Fig. 47 has a long sheath of metal connected with the target to take up the heat. Tubes are made with a means for cooling with water. These are intended for treatment rather than picture work, though they may be used for the latter. X-rays were discovered by William Conrad Roentgen, professor of physics at the Royal University of Wurzburg, Germany, in the summer of 1895. Roentgen applied the name X-rays because he did not know just what he had discovered; X. the algebraic symbol for the unknown, being adopted to signify this ignorance. They were not called X-rays because the rays cross, forming an X, as is popularly supposed. The Roentgen Congress, in Berlin, 1905, adopted a uniform set of technical terms in which the word Roentgen always occurred. Thus we have the phrase Roentgen ray for X-ray and such words as Roentgen- ology, Roentgenologists, Roentgenogram, etc., etc. While approving of a move for a uniform nomenclature, many of the new words are long and unwieldy and the writer shall, in this work, use many of the old and better-known terms. X-ravs are invisible, vibratorv waves of or in the ether. The most So ELEMENTARY RADIOGRAPHY popular theory is that they are light waves with an inconceivably rapid rate of vibration. Red light rays vibrate at the rate of four hundred billion per second; violet rays vibrate at the rate of seven hundred and l'"ig. 17. X-iay tube properly lit up ; ray tube with the current passing through it in the wrong dii i fifty billion ],f the target, similar to those shown in Fig. 4K, may he seen. 'Phis X-RAY TUBES AND THE X-RAYS 53 signifies that the coil is generating considerable inverse current. Recall that, while the current generated by the induction coil is practically a unidirectional one, there is an inverse current which is sometimes strong enough to manifest itself as just mentioned, especially when the vacuum of the tube is low. Fig. 51. A triple valve tube. There are several ways to keep this inverse cur- Cuttirtfl Out rent f rom passing through the tube. The simplest Tnpersc way is to make a spark gap between the coil and Current. terminal tape, which gap, for want of a better name, I shall call the inverse spark gap, since it is used to cut out the inverse current. ( Fig. 49. ) This gap may be made at either the positive or negative terminal, or both, as is found necessary. It cuts out the inverse current because this current is comparatively weak, not strong enough to jump the gap and pass through the tube. The main current jumps the gap easily. Unless inverse current is observed in the tube there should be no inverse spark gap — the little sliding rods should touch the binding posts of the terminal tapes. (Fig. 49.) Series spark gaps (Fig. 50) may be used between the coil and terminal tape to cut out the "inverse." The current passes easily from point to disc, but reluctantly from disc to point. Thus the series spark gap may be used to cut out inverse current from a tube, with the points toward the positive terminal tape and the points away from the negative terminal tape. Fig. 50 shows the points toward the positive terminal tape. They should be turned in the opposite direction at the negative terminal — away from the tape. 54 ELEMENTARY RADIOGRAI'l 1) The third, last, and the most efficient means of cutting the inverse current out of an X-ray tube is by means of a valve tube. ( Fig. 51.) The valve, <o>itive terminal tape of the coil, and, by means of a piece of conducting tape, or wire, the spiral end connected with the target side of the tube. Or the disc end of the valve may be attached, with a piece of conducting tape, to the cathode side of the tube and the spiral end of the valve to the negative terminal tape of the coil. (Fig. 52.) It is claimed by some that the valve tube acts only as an additional tance t<- the flow of the inverse current, cutting it out of the X-ray tube in the same manner that the inverse and multiple spark gaps do. The oscillimeter, <>r oscilloscope ( Fig. 53) is a Oscillimeter. ' Teissier vacuum tube with two straight aluminum electrodes. When a unidirectional current passes through it a violet light accurs at tin- negative electrode. When an X-RAY TUBES AND THE X-RAYS 55 alternating current passes through it the light occurs at both electrodes. When the current sent through it is stronger in one direction than in the other the electrodes light unevenly, the brighter electrode representing the negative of the stronger current. The oscillimeter is made to be used between the coil and the tube, Fig. 54. The Meyer penetrometer. Fig. 55. A fluoroscope. when the latter is covered, to detect inverse current. I have never felt the need of it, though I use an opaque shield over my tube. As has been stated, the X-rays are not discernible Demonstration to an ^ * tne s P ec ' a l senses. Their existence, how- Of X-Rays. ever, can be demonstrated as follows : Place an X-ray tube in a wooden box so that when the current is sent through it no fluorescence can be seen. Excite 56 ELEMENTARY RADIOGRAPHY the tube in a dark room and approach it with some object coated with calcium tungstate or platino-barium cyanide, and the object will be seen to fluoresce or glow something like phosphorus. This fluorescence is due to the action of the X-rays (which penetrate the wood of the box easily) on the calcium tungstate or platino-barium cyanide. Hence the closer the object to the tube the more and stronger the X-rays which strike it. and the brighter the fluorescence. X-rays from different tubes differ in length and Power Of power of penetration. A low tube gives the shortest Penetration and least penetrating X-rays ; then comes the medium Of X-Rays. tube, while the X-rays from a high tube are longest and most penetrating. The degree of penetration may be determined by means of a pene- trometer. (Fig. 54.) This particular kind of a penetrometer consists of two small flat pieces of wood fastened together, with a sheet of lead be- tween them. Holes are made through both wood and lead. Into these holes are placed thin metal discs which just fit the holes. The different holes receive different numbers of discs. To use this style of penetrometer we must have a fluoroscope. A fluoroscope (Fig. 55) consists of a light proof box,' tapered and made to fit over the eyes at one end, and covered at the other end with pasteboard coated with calcium tungstate or platino-barium cyanide. If one should look into the fluoroscope holding it toward ordinary light nothing could be seen — one would look into perfect darkness. But if the fluoroscope should be held so that the X-ray struck its screen — i. e., the pastboard covered with calcium tungstate or platino-barium cyanide — it would be seen to fluoresce, or glow, or light up. If now the penetrometer is held between the fluoroscope and the source of the X-rays a shadow will be seen on the screen, because the lead in the penetrometer is opaque to X-rays. Whether the X-rays will penetrate the metal in the holes depends on how much metal there is to penetrate and how penetrating the X-rays are. Thus the more penetrat- ing the rays the more holes can be seen. There are a great many different kinds of penetrometers. I shall not describe them here, but will give the scale of the two most popular, the Benoist and the Walter, together with that of the Meyer ( Fig. 54). Benoist. Walter. Meyei Soft, or low tube 1 — 2 t i — 2 Medium 3 — 5 2 — 3 3 — 4 Hard or high 6 — 12 4 — 6 5 — IO X-RAY TUBES AND THE X-RAYS 57 While the penetrometer is a very valuable appliance, it is far from being a necessity in the practice of dental radiography. As X-rays pass through the glass of the tube Secondary more X-rays are generated. These are known as Ray$. "secondary rays." They are short and feeble and do not travel parallel with the direct X-rays, but pass Fig. 56. High-frequency X-ray tube. Fig. 57. High-frequency X-ray tube. out from the tube in every direction intersecting the direct rays. Second- ary rays are also given off from any object which X-rays strike. Thus, direct rays will strike a wall ; secondary rays are given off from the wall and strike the other walls, the Moor, and the ceiling, whereupon a new set of X-rays, tertiary rays, are produced. When the tertiary rays strike an object still another set of X-rays are generated, and so on, each new set of rays being much shorter and weaker than the former. So a room in which an X-ray tube is excited is filled with X-rays — not with the direct rays, but with the comparatively feeble and inconsequential sec- ondarv, tertiary and other subordinate rays. 58 ELEMENTARY RADIOGRAPHY X-ray tubes are of different sizes. The bulb X-Ray Cubes. varies in diameter from five to eight inches. Thus we have the five-inch tube, six-inch tube, and so on. The six-inch tube is about right for dental work. With use the glass of the active hemisphere of the tube discolors to a purplish color. This does not materially affect the tube. The fatal injury to most tubes is a puncture. One means of guard- ing against punctures is to keep the tube clean. "A fruitful cause of Fig. 58. Tube rack for tubes when not in use. puncture is the discharging of the current from the tube into the rack on which the tube is kept when not in use. The tube may have been dis- charged by the operator touching the terminals before putting the tube away, but if the tubes are stored in the same room where high-frequency and other coil discharges are taking place, they will recharge themselves from the atmosphere and discharge onto the rack, no matter of what material the- rack may be made. A safe way of putting away tubes is to connect the anode and cathode terminals together 1>\ a wire during the time the tube is at rest." The general principle- of construction of the high-frequency X-ray tube | Figs. 56 and 57) arc those already given in the description of the tube-, built to be operated by a unidirectional current. The chief differ- X-RAY TUBES AND THE X-RAYS 59 ence between the high-frequency tubes and those already described lies in the different mean resorted to in the former to dispose of one direction or wave of the alternating current, or, to speak more definitely, one cathode stream. ^4w Fig- 59. Fig. 60. Fig. 59. Plain X-ray tube stand. Fig. 60. Tube stand, with a lead glass protection shield and a compression diaphragm. Either end of a high-frequency X-ray tube may be connected with either terminal tape of a high-frequency coil. While this is theoretically true, it will sometimes be found in practice that the tube works better hitched up one way than the other. When the tube is hitched up the current oscillates through it and two cathode streams are generated. One of the streams is focussed against the target and X-rays are given off from the focal point, while 6o ELEMENTARY RADIOGRAPHY the other is focused into a funnel in the back of the target. (Fig. 56.) X-rays cannot be given off from this funnel ; hence the tube lights up in the active hemisphere as illustrated in Fig. 47. This funnel scheme is Fig. 61. A pedestal, with a lead glass protection shield, compression diaphragm and plate holder. one way of taking care of one cathode stream while the other is being used for X-ray production. Another scheme is to move one cathode back so far that the cathode stream focuses before reaching the back of the target. (Fig. 17.) The high-frequency tube ma) be used to advantage on an induction coil which is generating a great deal of inverse current. One may wonder why a valve (Fig. 51) or a rectifier (Fig. 27) could nol be used to CUt OUl the flow of current in one direction, and a tube like the one in Fig. 44. for example, used on a high-frequency coil. Xeitbcr the valve nor the rectifier is capable of cutting out one X-RAY TUBES AND THE X-RAYS 61 direction of flow of a current of such high potential (voltage). The valve is able to cut out the inverse current of an induction coil because it (the inverse current) is comparatively weak; and the rectifier can cut out one wave of the commercial A.C., because the voltage is only a little over a hundred. The voltage of the high-frequency coil is perhaps a hundred thousand. Fig. 62. Table, with a lead glass protection shield and compression diaphragm. To avoid "straining" a tube, it should not be again used, after hav- ing been used till hot, until it has cooled thoroughly. Overheating the tube will destroy the gases in it, and so raise the vacuum to such a degree as to make it impossible to force a sufficient milliamperage through it to produce a sufficient number of X-rays. Sending a very strong current through a tube of low vacuum will also destroy the gases of the tube and spoil — strain — it. Fig. 58 is a tube rack for holding the tube when not in use. It is obvious that there must be some kind of a device for holding the tube when in use. This may be either a plain tube stand (Fig. 59), or a tube stand with a lead glass, protection shield and a compression 62 ELEMEN T. IRY RADIOGRAPH ) ' X-RAY TUBES JXD THE X-RAYS 63 diaphragm 1 Fig. 60). or a pedestal with a lead glass protection shield, compression diaphragm, and plate holder (Fig. 61), or a table with a lead glass, protection shield and compression diaphragm. (Fig. 62.) Dr. Blum, of New York, uses a wall bracket fixture to support a lead glass, protection shield and o ■mpression diaphragm. The tube, one of the water-cooled type, is seen fitting into the lead glass shield. Fig. 6i. A Protection Shield. (Fig. 63.) This would be, I imagine, a very adaptable and satisfactory apparatus. A tube stand should be heavy enough to be firm and not allow any vibration of the tube while in use. The parts coming in contact with the tube must be made of an electric non-conducting material ; otherwise the current would pass from the tube into them, so puncturing the tube. The uses of the compression diaphragm are : To hold the patient immovable ; to compress the soft parts as when making a picture of the kidney, for example ; to aid the operator in directing the rays through a part at the proper angle and to cut out the secondary rays given off from the tube. A protection shield, often called a Friedlander's shield (Fig. 64), which is opaque to X-rays except for the window or opening in it, and which is used to cover X-ray tubes, also cuts out some, but not all. second - arv ravs given off from the glass of the tube. Thus if the Xravs from an 64 ELEMENTARY RADIOGRAPHY X-ray tube are directed on a part through a diaphragm, only the direct rays strike the part, as in the diagram study shown in Fig. 65. While, with the Friedlander shield, some of the secondary rays might strike the part also. (Fig. 66.) Fig. 65. D U O, direct ray. S S. secondary ray. 1' I', part. Fig. 66. I> i> l». direct ray-. S S. secondary rays. P P. part. When there i> inverse current passing through a tube supplemental X-rays are produced thereby. It is desirable thai these rays should not strike the plate when making a picture. Either a compression diaphragm, or a protection shield will cut out these rays -or at least most of them. CHAPTER IV. making Radiographs. The X-ray picture is variously called radiograph, skiagraph. Roent- genograph, radiogram, skiagram and Roentgenogram. The word radi- ograph is a combination of a Latin and Greek word meaning ray and urite or record. The word skiagraph (spelled also sciagraph) is a com- bination of two Greek words meaning sliade or shadozu and write or re- cord. The word Roentgenograph is a combination of a proper name, Roentgen, and the Greek word meaning write or record. The terminal gram occurring in the words radiogram, skiagram and Roentgenogram — as well as the more common words such as telegram, program, epi- gram, and others — is of Greek origin and denotes that which is written or marked. The use of the X-rays for radiographic work depends on two prop- erties of the rays. First, they penetrate substances in direct proportion to the density of the substance, and second, they affect the photographic plate or film the same as white light does. A photographic plate is a piece of transparent Photographic plate glass about an eighth of an inch thick, one Plates, side of which is coated with an emulsion of a silver salt, usually gilver bromide, and gela- tine, albumen, or collodion. The use of the gelatine, albumen or collodion is simply to stick the salt to the glass. When a thin coating of this emulsion has dried on the glass we have what is called the photographic "dry plate." In appearance it is similar to trans- lucent greenish-white glass, but on close inspection one is able to de- tect that one side is a little less glossy than the other. The less glossy is the coated side, also called the sensitive, the film, or the emulsion side of the plate. The term "dry plate" is to-day an almost superfluous one, practically all the plates used being dry plates. There is, however, a photographic plate known as the "wet plate," but, since it is never used in radiography, I shall not describe it. 66 ELEMENTARY RADIOGRAPHY The dry plate is made in the absence of white light, put up in light- proof packages, and so supplied to consumers. These packages must not be opened except in a dark room, for the slightest exposure to a white light will spoil them. The difference between the photographic dry plate and the photo- graphic film is only that the plate is a piece of glass coated with a silver salt, while the film is a thin sheet of transparent celluloid coated with a silver salt. As with the plate, the sensitive side of the film is a little less glossy than the uncoated side. The film curls slightly toward the coated side, unless it is of the "non-curling" variety, when it is straight, or may even curl slightly away from the coated side. X-ray pictures may be taken on ordinary photo- Special graphic plates or films made to be used in cameras. X-ray Plates While this may be done, the results obtained are not and Tilms, nearly so good as when special X-ray plates and films are used. The special X-ray plates and films dif- fer from the ordinary plates and films in that a thicker coating of the emulsion is put on them. This is sometimes accomplished by coating the celluloid or glass two or three times, one coat on another. When this is done the film or plate is said to be multi-coated. X-ray films and plates should not only be thickly coated, but, which is more important, should also be extremely sensitive — that is, easily acted upon by light — for, though the X-rays have a wonderful power of penetration, their action on the silver emulsion is feeble compared to the white light of day. The following manufacturers make X-ray plates of any desired size: The Eastman Kodak Company, Rochester, N. Y. ; Cramer Dry Plate Company, New York City; Hammer Dry Plate Company, St. Louis, Mo. ; The Lumiere X. A. Company, Burlington, Vt. ; and the Ilford Mfg. Co.. flford, London, England (American agents for Ilford goods, E. 15. Mey- rowitz, 104 East 23d Street. New York City). But two manufacturers, the Ilford M ig. Co., London, England the Eastman Kodak Co., Rochester. X. Y., make special X-ray films. I wish here to advise against buying large quantities of either plates or films at a time. They deteriorate in a few months. The making of a radiograph of the hand is one technic of °* tne s ' m P^ est operations in radiography, and for making that reason it will be described to teach elementary Radiographs. principles. The following technic of making a radio- graph will, of necessity, be much broken into by descriptions of materials and appliances used. A 5 x 7-inch plate i- about the righl size to make a radiograph of MAKING RADIOGRAPHS 67 the hand. Plates are supplied by the manufacturer packed in light-proof boxes, holding usually one dozen plates, with the warning on the box. "Open only in a dark room." The "dark room" is simply what the name states — a room from which light is excluded. A closet without a window makes a good dark room, except that there is seldom running water in it. It is not absolutely necessary to have running water in the dark room, but it is very convenient. If a closet cannot be utilized a room, light- Fig. 67. To left, window ready for frame. When frame is in position the metal catches arc turned to hold it. The frame fits inside of the strip on the sill. Figure to right shows frame in position. proof except for one window, may be made dark by covering the window with a frame on which is tacked some material such as the leather or rubber used for side and storm curtains in buggies. If this material does not completely turn the light, it should be painted with thick black paint. The frame should be made to fit over, not into, the window casing. (Fig. 67.) With the frame so placed, if a little light comes in around it. it does not come directly into the room, but is reflected to the side. The more perfect the darkness of the room the better, but the very little light oS ELEMENTARY RADIOGRAPHY which can enter through a window with the blind drawn down, and with a well-made frame over it will not cause any trouble. If the door to the room permits light to leak in around it. such light should also be shut out. It would be impossible, of course, to work to any advantage in a perfectly dark room, for we could not see what we were doing. Hence' the necessity of having a dark room lantern (Fig. 68). which will give sufficient light to guide us in our work, without being of such nature as to have any act inn on plates or films. The term "developing light" — the Fig. 68. Dark room lantern. ligbt given by the dark room lantern — may mislead one to believe that the light in some way aids in developing a plate by its action on it. But such is not the case. The light is of value only because it enables the worker to sec. The light may be a candle, a coal nil lamp, or an incan- descent electric light shining through red glass. While such a lantern can easily he made, the writer warns against it, for. though the light of a home-made lantern may appear the same to the eye as the light of the lanterns manufactured by photographic supply manufacturers, its action mi a plate or film may he disastrously different. The lantern shown in Fig. 68 consists of ;i [6-candle power incandescent lighl with a frosted glass hulh. in a light-proof tin box, the front of which is of removable glass. The light shines first through the frosted .^lass of the hulh, then an orange-colored j^lass, then a ruby glass. In the dark room, with only the light of the dark room lantern we M.IK IXC RADIOGRAPHS 69 open our box of plates,* take out one, carefully close the box, and place the plate in an envelope of black, light-proof paper just large enough to receive it. Now place plate, black envelope, ct 2 ounces 960 c.c. To Develop, take No. 1, 6 ounces (180 c.c.) ; No. 2, 4 ounces (120 c.c.) ; 10 per cent, solution Bromide of Potassium, 3 to 10 drops. Mix the developers in the order given, and use cold. 500 c.c. IV2 grammes 2 grammes 7 grammes 13 40 grammes drops *M — Q stands for "metal — quinol." In photography the word "quinol" is used as an abbreviation for "hydroquinol." This is unfortunate, because quinol and hydroquinol are different substances. There are several words and different spell- ings of the same word used to designate the substance — hydroquinol. They are : hydroquinon (spelled also hydroquinone) ; hydrochinol (spelled also hydrokinol) ; hydrochinon (spelled also hydrochinone, hydrokinon, and hydrokinone). 76 ELEMENTARY RADIOGRAPHY Pyro Developing Formula Pyrogallic Acid Solution "A" Avoirdupois Metric System Pyrogallic Acid i ounce 30 grammes Sulphuric Acid 20 minims I c.c. Water 28 ounces 840 c.c. Soda Solution iidh Avoirdupois Metric System *Carbonate of Soda (Anhydrous) 2 ounces 60 grammes *Sulphite of Soda (Anhydrous) 3 ounces 90 grammes Water 28 ounces 840 c.c. To Develop, take "A." 1 ounce (30 c.c.) ; "B," 1 ounce (30 c.c.) ; Water, 8 ounces (240 c.c). This developer will then contain 1.56 grains Pyro per ounce. The developer may be made and kept in stock solutions as above, if desired. A better plan is to buy the prepared developing powders. They may be purchased at any photographic supply store. The chemicals come in glass tubes or packages mixed in the proper proportions, and all that is necessary to make the solution is to dissolve them in the quantity of water (distilled or tap water either) suggested on the package. The package or tube usually contains a sufficient quantity to make 4 to 8 ounces of developing solution. The advantages of this over mixing the chemicals yourself are : First, the convenience and saving of time, and second, only small quantities being made at one time, the developer is used immediately, and is therefore always fresh when used. A developing bath does not keep well in stock solution unless the bottles are full and well corked. Even then discoloration and disintegra- tion occur in the course of a month or so. It is always advisable to use as fresh a solution as possible. Packed in the box with the plates will always be found a formula for a developer recommended by the manu- facturer of the plates. It is not at all necessary to use the particular developer recommended. During the hot summer months it is necessary temperature. to use ice in the developer, ice water to make the solution, or place the tray containing the developer in another larger tray with ice water in it. If the developer is too warm it will soften the emulsion, cause frilling at the edges, blistering and fogging of the negative. The developer should be between 60 and 75 degrees F. It" too cold, development takes place slowly, and the negative, when finished, is pale and thin. I use tap water in the winter and have no trouble due to improper temperature. In the summer, though, even using ice water and ice, the work is often discouraging. If possible dur- ing the hottest weather defer development until the cool of the evening. *If crystal^ arc used, double the quantity. MAKING RADIOGRAPHS 77 When development is complete, remove the fixing. plate, dip it in clear water, then immerse it in the fixing bath. The fixing bath is a solution of chem- icals which dissolves out the unaffected silver. Leave the plate in the fixer for two or three minutes after the milky appearance of the glass side of the plate has disappeared. A plate must be removed promptly from the developer as soon as development is complete, or the negative will be overdeveloped, spoiled, but it may be left in the fixing bath for hours longer than necessary without danger of spoiling the negative. Fig. 73. Titubator. It will not injure the plate to remove and replace it in the baths at any time during developing or fixing. The actual time required for fixing varies from 5 to 20 or 30 min- utes. The thicker the emulsion the longer time it requires for fixing. Movement of the fixing solution over the surface of the plate will hasten 78 ELEMENTARY RADIOGRAPHY fixing. A titubator (Fig. y^ ls a machine on which the fixing bath tray may be set, and the bath kept in constant movement over the plate. When several negatives are being made at the same time, it is well to n>e a fixing box (Fig. 74) instead of a tray. If the plates were piled one on another in the tray, they would probably stick to one another and, when pulled apart, the emulsion would be scarred. The plates stand on end in the fixing box, fitting into grooves. Hyposulphite of soda is the standard fixer. There are not a great number of fixers, as there are of developers, to choose from. Hypo- sulphite of soda and water alone will fix plates, but is not so efficacious as when other chemicals are added to harden the emulsion. Acid-Fixixg Bath Avoirdupois Metric System Water (34 ounces 2 liters Hyposulphite of Soda 1<5 ounces 450 grammes Sulphite of Soda ( Anhydrous) 24 ounce 20 grammes When fully dissolved, add the following hardener : Powdered Alum Y 2 ounce 15 grammes Citric Acid V2 ounce 15 grammes A -tock solution may be made as given in the foregoing formula, or the prepared fixing powder purchased, and the fixing bath made by sim- ply dissolving the powder in a stated quantity of water. There is nothing secret about the formulas of the prepared fixing powders. They are all practically the same as the formula given. The advantage in using them lies in the saving of time and energy that would otherwise be spent weighing chemicals. If prepared developing and fixing powders are used, it will not be necessary to have a pair of scales for this work. A grad- uated glass for measuring liquids will be all that is needed. During the hot months, it is expedient — not necessary — to use a freshly mixed fixer. If this is done the negative is less likely to frill or blister. Unlike the developing bath, however, the fixing bath will keep without disintegra- tion for months. If scum or sediment appears after standing for some time, this may be removed by filtering the solution through filter paper or cotton. The temperature of the fixer should he at least as low as that of the developer, and better lower. sa\ about 50 degrees I'. When fixed, if the plate is held up to the light (any light for the plate i- no longer sensitive to light), the shadow of the bones of the hand will appear as transparencies; the flesh shows a little less transparent than the hone, and the balance of the plate will he opaque and black. Thus the shadows show 1 i j^l it . and where no shadow was thrown the plate i- dark. Hence the name negative which is applied to this picture on the plate. The making of the positive picture on paper, the print, as h MAK1XG RADIOGRAPHS 79 is usually called, from the negative will be described presently. The plate is no longer sensitive to white light, and may therefore be exposed to it any time after having been in the fixer a minute or so. Great care must be exercised not to get any of the fixing bath into the developer. A very little "hypo" will spoil the developer. It is well to label the trays so that the tray used to hold the fixer one time will not be used for the developer another. Or. instead of labeling the trays, a black one may bt used for the developer and a white tray for the fixer. Fig. 74. Fixing box. Fig. 75. Plate, or negative, rack. When fixing is completed the negative must be UlasMng. washed in clear water to remove all '"hypo" from it. If the negative be placed in a tray, the tray in a basin or sink and the tap turned up. or. in other, words, if the negative be washed in running water it requires 15 to 30 minutes to thoroughly wash it. Where running water cannot be had.* and sometimes during hot weather when tap water is too warm, the negative may be placed in a larger vessel of water and left for about an hour, changing water sev- eral times. A tray of water used on a titubator is efficient. The water must be changed often, and the time required is about three-quarters of an hour or longer. When several negatives are being made, it is ad- visable to use a washing box similar to the fixing box. ( Fig. 74.) * "Running water*' is much to be preferred, as the friction or movement of the water is a great factor in cleansing the plate. After a few months, if plates show cloudiness, or a metallic luster is observed, this means that the plates were not thoroughly washed. It is even advisable, after washing, to rub the surface of the film side with clean, wet cotton, holding the plate under a faucet during the act. 8.) ELEMENTARY RADIOGRAPHY The next and the last step in the making of the Drying. negative, is to dry it. The plate should be set on edge. Drying should take place in a clean atmos- phere, so that no dust or soot will fall on and stick to the coated surface of the negative. Plate racks (Fig. j=> ) may be used, but are not a neces- sity. The plate may he set on edge at an angle of about 95 degrees by simply leaning it up against some perpendicular wall. ( Fig. j6. ) Dry- Fig. 70. Negatives leaning against perpendicular wall, drying. ing requires several hours. It may he hastened by placing the negative in a breeze. By immersing the negative in a mixture of formalin and alcohol, then placing it in the breeze of an electric fan. drying will be very materially hastened. The use of the formalin and alcohol some- time- causes spotting and blurring of the negative. If all the salts "t the fixer are not well washed out of the emulsion, it will not dry prompt- ly, but will become rough and sticky, and. when finally dry. it will be fill! of little holes. Summarizing the making of the negative, it consists of exposing developing ( washing — mere dipping in water), fixing, washing, and dry- ing. If tlie negative when finished i- very dark. SO dark that parts of the image are lost, the plate was either overexposed, or overdeveloped, or MAKING RADIOGRAPHS 81 both. I prefer usually to say that it was overdeveloped, for even if it had been exposed unnecessarily long, this mistake might have been corrected by leaving it in the developer a shorter length of time. If the negative is almost entirely transparent and the image can hardly be seen, it is due to underexposure, or underdevelopment, or both. The mistake of overexposure or overdevelop- RcdUCCrS. ment can be corrected to an extent by the use of a "reducer." The following solution is a reducer: *A. Water 16 ounces (480 c.c.) Hyposulphite of Soda 1 ounce (30 grammes) B. Water 16 ounces (480 c.c.) Potassium Ferricyanide 1 ounce (30 grammes) Mix 8 parts of solution "A" and one part of solution "B," and use in subdued light. The negative can be placed in this solution directly after fixing, without washing. Or it may be washed- — it makes little or no difference. If a dry negative is to be reduced, it must be soaked in water for at least half an hour before placing it in the reducer. When sufficiently reduced, wash thoroughly for about three-quarters of an hour, then dry. The work of reducing may be done in any light. When not in use keep solution "B" protected from the action of light. Remember that this solution is one of the most powerful poisons known. Handle it with extreme caution. The mistake of underexposure cannot be cor- Tntcnsifier. rected to an appreciable extent by any means. The mistake of an underdevelopment can be corrected to an extent by the use of an "intensifier." After having fixed the negative, wash it well in running water for about thirty minutes or longer, then place in the, following solution : Mercuric Bichloride 200 grains (13.3 grammes) Potassium Bromide 120 grains (S.O grammes) Water §y 2 ounces (195 c.c.) Keep the plate in this solution a short time, when it will be observed to be bleached uniformly white (the longer the negative is bleached the denser it will ultimately become). Remove from the bleaching solution. wash in running water for a few minutes, then blacken in the following solution : Sodium Sulphite 1 ounce (30 grammes) Water 4 ounces (120 grammes ) Or Ammonia 20 minims (1 c.c.) W r ater 1 ounce * "Electro-Therapeutics and Roentgen Rays," Kassaban. $2 ELEMENTARY RADIOGRAPHY It is now being blackened, tbe negative is again washed, then dried. Intensifying should be done in a subdued light — not in bright daylight. An old negative, one which has been made for some time, may be intensified by first soaking in water, then following the technic given. Prepared reducers and intensifiers, with directions for their use, may be purchased at any photographic supply house. Fig. 77. Showing how the printing frame is held Up to the light to expose the photographic paper. Also showing the back of the printing frame, the frame half open, and the photographic paper in position. While reducers and intensifiers have their place in dental radiog- raphy, they are used only to correct mistakes, and they do not entirely correct the mistakes. It is usually expedient to make a new negative ratber than to attempt to reduce or intensify a faulty one. Round transparent spots on the negative are caused by air bubbles, or air "bells," as they are called, attaching themselves to the emulsion side of the plate while in the developer. Spots of irregular size and character appearing on a negative are due often to the use of an old developer. In radiographic work, where the appearance of a spot may determine a diagnosis, it is to be hoped that fresh developer will always be used. By fresh developer I mean de- veloper not, at most, over a month or so old, having been kept while in Stock in a filled, tightly stoppered bottle, and free from all scum rind sediment. A developer containing pyrogallic acid disintegrates so rap- idly that it must be used immediately after mixing — it will not keep at all. "Pyro" developers stain the hands badly. MAKING RADIOGRAPHS 83 When the negative is dry we are ready to make Pwittoe the positive pictures. The pictures are made on Prints, sensitized paper, a very fine grade of white paper, one side of which is coated with a silver salt some- what as plates and films are coated. These papers sell under such vari- ous names as Velox, Cyko. Artura, and Azo, and may be purchased in any size, put up in light-proof packages. Papers are not as sensitive as plates and films, and an orange instead of a ruby light may be used in the dark room. Place the negative, emulsion side up, in the printing frame (Fig. Jj). Place a sheet of paper, sensitive side down, over the negative, and close printing frame. The sensitive side of the paper may be determined by observing that the paper curls slightly toward it ; or by biting a cornet of the paper, when the sensitive side will stick slightly to the teeth. To make the exposure now, either artificial or daylight may be util- ized. Before making the exposure be sure that the balance of the paper in the package is well protected against the light. Hold the printing frame so the light will shine through the negative and strike the paper. (Fig. J J.) It is not necessary to hold the printing frame immovable during exposure. The time of exposure varies greatly according to the density of the negative ; the denser the negative the longer the exposure must be. Some idea of the time of exposure necessary may be learned from the directions enclosed with the paper. To make the print for Fig. 71, a 16 c.p. electric light was used, holding the printing frame about 8 inches from the light and exposing the paper — Azo — 3 minutes. With the 16 c.p. light turned off, in the orange Development light, the paper is now removed from the frame. As Of Prints, with the plate there is not the, slightest change in the appearance of the paper after exposure, but the image is there, it is latent, it needs only to be developed. The developing formulae for papers are, broadly speaking, the same as for plates. It is very important that the developer for paper be freshly mixed, for the slightest discoloration of the bath will soil the paper. It is not desirable to save the developer used to make the negative and use it again for the paper. It is too liable to cause discoloration of the print. "Pyro" is a very poor developer for paper. Immerse the paper quickly, sensitive side up, gently passing the tips of the fingers over the surface, to hasten development by agitating the developer, and to keep the paper submerged. As soon as the image ap- pears as desired, transfer it to clean water, then quickly into the fixeiv (It is kept in the water but a moment or so.) If, when placed in the developer, the image comes up so quickly that it gets too dark before it s: ELEMENTARY RADIOGRAPHY can be transferred to water and fixer, it has probably been overexposed. Shorten the time of exposure, and if the image still comes up too quickly, dilute the developer. It the whites of the prints come up gray, add a few drops of a to per cent, solution of bromide of potassium to the developer. Any number of prints — pictures — may be made from a negative. The fixing bath for prints is the same as for plates, but the bath used to make the negative should not be saved and used again for prints. It might discolor them. Allow prints to remain in the fixer 15 to 20 minutes. This dissolves out the unaffected silver. Next wash print in running water for an hour. No visible change occurs in the print from the time it leaves the developer. Fixing and washing are done to make it permanent. The temperature of the de- veloper, fixer, and water should be the same as for plates, to' obtain the best results. When thoroughly washed remove the prints from the wash water and place on a piece of clean glass face down one on the other, and press out the water. Then lay them out separately on a frame, covered with cheese cloth. The cheese cloth being very thin, allows the prints t>: dry on the side next the cloth as well as the upper side. When dry the prints may he mounted on cardboard. Dental Radiography. CHAPTER V. making Dental Radiographs. In the foregoing chapter we dealt with the general elementary prin- ciples of radiography. We shall now take up a more concrete considera- tion of dental radiography. The first radiograph of the teeth was exhibited by Prof. K to the Society of Physics at Frankfort-on-Main. Germany, in February, 189(3 — only a few months after the discovery of the X-ray. Five months later an article appeared in Dental Cosmos by Morton, entitled "X-Rays in Dentistry." Since then there have been scores of articles written on the subject and published in various dental, medical, and Roentgeno- graphic journals. Most dental radiographs are made on films held in the mouth dur- ing their exposure to the X-rays, the patient being seated in the dental chair. Ordinary films, as stated in Chapter IV, are not efficacious. As stated previously, but two manufacturers, the Spec) Hford Co. and the Eastman Co.. supply special XRay films. FF 3 F X-ray films. The Ilford film, being a foreign product, cannot be delivered with desired promptness. It is. however, the best X-ray film on the market, and may be obtained from the American agent for Ilford goods, E. B. Meyrowitz, 104 West 23d St.. Xew York City. Ilford films of prac- tically any size — 4x5 in., jxj in., Sxio in., etc. — can be purchased in packages, one dozen films to the package. Ilford films are also supplied just ready for dental use in sizes of about i3sxi? s in-, one film to the packet, wrapped in black paper and covered with a rubber-like, moisture-proof material, such as tailors use to- mend clothes. For the past several years the Eastman Kodak Mfg. Co., of Roches- ter, X. Y., have supplied films for radiographic work. These films are covered with the same emulsion that is used to make cinematograph ( moving picture) films. There are two kinds of cinematograph films, the positive and the negative. The positive films yield very satisfactory radiographic results, but the negative films are little or no better than 85 86 DENTAL RADIOGRAPHY ordinary films for cameras. This explains why some of the films hereto- fore supplied by the Eastman Company have proved satisfactory, while others have not, for both the negative and positive films have been sold under the label "X-ray films." I have been in communication with the Eastman Kodak Mfg. Co., and have informed them of the failure of their negative cinematograph films to meet the requirements of a good X-ray film, but to guard against a possible mistake it would be well when ordering to state that the positive film is wanted. The negative film is a little faster than the positive, but sufficiently contrasty results cannot be obtained with it. E. 1 Fig. 78. A. rubber-dam stretched out and fastened to a board with pins. B, the rubber covered with cement and the film packet on it. C, pins removed from one end and the rubber lapped over packet. D, all pins removed. E, excess rubber trimmed off. The Eastman Company will supply films in any size to order; or in little black paper packets, ready for dental use, two films about i^xi^ in., to the packet, the sensitive side of the films presenting toward the black side of the packet. The special 4x5 in. X-ray film, formerly manufactured by the Seed Dry Plate Mfg. Co., of St. Louis, is now made by the Eastman Kodak Co., of Rochester, successors of the Seed Dry Plate Co. The old Seed film was not a non-curling film. The "Seed Positive Film." now manu- factured by the Eastman Co., however, has a coating of gelatin on the back of the film to keep it from curling. With the film thus coated on both sides it is impossible to tell by observation which is the sensitive side. The way to determine this is by the manner in which the films are packed in the envelopes. Of the twelve films in the package, eleven have the sensitive surface presenting away from the seam of the enclosing envelope. The twelfth film — the one farthest from the seam — has the sensitive surface presenting inward the seam. Because it is efficacious and is furnished promptly and at a reasonable cost, the most popular dental X-ray film is the Eastman film supplied in -mall packets. The black paper of the packet is thick enough to pro- tect the film against moisture when taking pictures of the upper teeth, but additional protection is needed when making radiographs of the lower M.IK IXC DENTAL RADIOGRAPHS 87 teeth. This protection may be given by covering the packet with rubber clam. The rubber dam is staked out with pins to prevent curling, and covered with ordinary rubber cement, such as is used to repair the inner tubes of bicycles and automobile tires. Allow the cement to dry a minute or so. Place the packet on one end of the rubber, remove the pins at said end, and fold the rubber ; so covering the packet. Trim off the excess rubber. (Fig. 78.) Fig. 79. Illustrating method of covering a more or less circular film with black paper. This method of protecting the film against moisture is so much better — easier, quicker, more efficient, and less expensive — than the usual method of covering the film with unvulcanized plate rubber that a description of the latter will not be given. Lately I have adopted a method of covering film packets to protect them against moisture, that is just as efficacious and much more con- venient and less expensive than the one just described. Take a piece of mending tissue, such as is used by tailors to mend clothing, of such size that when folded over the film packet (Fig. 78, C and D) it will extend beyond the packet on the three open slides, about one-half inch. Warm the edges of the tissue slightly by passing over the flame of an alcohol lamp or Bunsen burner, and pinch them together. Then warm them ( the edges) to stickiness again and turn them back and stick them to the tissue covering the back — ;'. c, the nonsensitive side of the film packet. If the large II ford or Eastman films are used the operator may cut the original large film into any size or shape, and cover with two thicknesses of black, lightproof paper. This must, of course, be done in a dark room. A pair of scissors, with long, sharp cutting blades, will be found especially suitable for this work. Cover the film so the sensitive 88 DENTAL RADIOGRAPHY will be the smooth side of the packet. Fig. 79 illustrates a method of wrapping up more or less circular or oval films. By unwrapping an Eastman film packet one can learn how best to cover a square or rectangu- lar film. If the films are to be used to radiograph the lower jaw or teeth the packet should be cohered with rubber dam as described. Two films may be put in a packet if desired. The advantages of this are as follows : If one negative is spoiled, or spotted during development, possibly the other will not be. If the patient be referred from another dentist or physician, one negative may be given to the man referring the case and the other retained and filed away. Instead of wrapping the film in black paper, as suggested above, one may have little black paper envelopes of the desired size made and use them. Instead of using rubber dam, one may have small oiled paper envelopes made and protect the films against moisture by enclosing the packet in them. With the films ready for use we may now proceed as follows : Be it understood that some of the steps in the technic for technic* given hereinafter are for the beginner, and Dental may be eliminated after the operator is acquainted Radiographs. with his coil, tubes, films, etc. First test the coil and see that it gives a fat, fuzzy spark, at least 6 or 7 inches long. This almost invariably neces- sitates cutting out all the resistance of the rheostat. I cut out all the resistance of the rheostat on my 18-in. induction coil and obtain a fat, fuzzy spark 10 inches long. Some of the most modern induction coils are made with "multiple inductance." With this equipment, by changing a plug or switch, the induced current is made stronger or weaker in milliamperage. The higher the milliamperage sent through a tube the greater the number of X-rays produced. Thus the more rapid the work to be done the higher the inductance should be. Some of the very largest induction coils on their highest inductance, and the interrnpterless coils, can force 30 or 40 milliamperes through a high vacuum X-ray tube. With such a current dental radiographs can be made instantaneously. A tube will not stand such a current without injury for longer than about fifteen seconds at most. Some induction coils, nol yet on the market, but under construction, *There are some special steps in technic when using a high-frequency coil d of an induction coil <>r transformer. These stcp^ arc not mentioned here, hut will be found immediatelj following tin- summary of the conditions under which the negative for Fig, L15 was made. MAKING DENTAL RADIOGRAPHS 89 will be, if we are to believe the men who are making them, able to force from 80 to 200 milliamperes through a hard tube. A tube could not stand such a current longer than a second or so, if so long. After testing the coil, throw off the switch and hitch up the tube. Have the terminal tapes tight, so they will not come unhooked from the tube while it is in operation. When a terminal becomes disconnected from the tube while the current is passing through it a puncture of the tube sometimes results. Fig. 80. Position of the film in the mouth for making radiographs of the upper bicuspid and first molar region. Set the tube-regulating arm to give a tube-regulating spark gap of 4 inches. This is not an invariable rule. Perhaps the gap should be 5 inches when a tube is new and reduced to 3 or 2 inches when the tube is old. And so with many statements following — they are subject to variation ; they are calculated only to give a beginner something tangible to start with. When the tube is hitched to the coil, separate the sliding rods the entire distance of the maximum spark gap. See to it that the terminal tapes or the tube are not near any conductor, or the current may jump to it — the conductor. If this occurred from the tube it might be punctured. Turn on the switch just for a moment, then off, then on, then off, and so on, slightly lengthening the time the current is left on until it is observed to pass through the tube without a spark at the tube-regu- DENTAL RADIOGRAPHY lating spark gap. This warms the tube gradually. In cold weather it is well to warm it slightly over a register before sending the current through it. Sometimes no spark will occur at the tube-regulating spark gap at all. This simply means that the vacuum of the tube is such that it does not need lowering.* Turn the current on now for a few moments and see that the tube lights up properly. In order to observe the fluorescence the room should be either dark or semi-dark. Turn off the current, shorten the spark gap, turn on the current again, and observe whether it passes through the tube or jumps the spark gap. Repeat this until the current jumps the gap. This tells us the condition of the tube by showing how many inches of parallel spark it will back up. The tube should back up about 6 inches of spark. After the operator is well acquainted with his tube and coil this test of the vacuum of the tube will not be necessary. The operator will be able to judge the vacuum fairly well by the fluorescence of the tube and the length of the tube-regulating spark gap. We are now ready to pose the patient. As we do this we must constantly bear in mind that we are simply throwing a shadow on the film, and that, like all shadows, this one is liable to be distorted unless the tube, the part to be radiographed, and the film are in their proper relative positions. The ideal position would be so that the X-rays would strike the part to be radiographed and the film at right angles, as in Fig. 70. But this is quite impossible when radiographing the upper teeth. With the film in the mouth, as per Fig. 80, the Position of Tilm common mistake will be to have the tube too low and Direction (Fig. 81 ). The result of this is shown in the radio- Of Ray$. graph in Fig. 81, and the reason for it in the dia- gram (Fig. 82) in which the angle of the rays, the object, and the film are in about the same relative positions as in Fig. 81. The proper position and the radiograph made from this pose are shown in Fig. 83. Fig. 84 diagrammatically illustrates the pose in Fig. 83. 'Instead of setting the tube regulating spark gap at a certain distance and leav- ing it there while the exposure is being made, as T have suggested and will continue j-cst, it i- th<- common practice for radiographers to make the tuhe-regulating -park gap short — i. c. about two or three inches — turn on the current for a second or a fraction thereof, until the tube lights up properly, then widen the gap to its maximum length, then turn on the current again foi a moment to see that the tube lights np properly with the gap so widened, and, if so, make the exposure with the Hap it> maximum width, a distance too greal for sparking to occur. If, after low- r- ing the vacuum, inverse current is seen in the tube it means thai the vacuum has been lowered too much, \llow the tube to cool MAKING DENTAL RADIOGRAPHS 9i Fig. 81. The tube too low, and the resulting radiograph. Fig. S5. Diagrammatic illustration of the X-rays striking the tooth and film at such an angle as to cause a lengthening of the shadow cast on the film. (For this idea of diagrammatic illustration the writer is indebted to Dr. Price.) DENTAL RADIOGRAPHY Fig. 83. The proper pose for making radiographs of the upper bicuspid and molar region, and the radiograph which was made from this pose. 34. Diagrammatic illustration "f the raya striking the tooth and film at such an angle as i» avoid cither lengthening or shortening the shadow cast on the film. MAKING DENTAL RADIOGRAPHS 93 ^k C ■ i rV> Fig. 85. The tube too high, and the resulting radiograph. Film Fig. 86. Diagrammatic illustration of the rays striking the tooth and film at such an angle as to cause a shortening of the shadow cast on the film. • DENTAL RADIOGRAPHY If the tube be placed too high the teeth on the radiograph will be shorter than the teeth themselves, somewhat distorted and blurred (Fig. Fig. 86 diagrammatically illustrates the pose in Fig. 85. A study of Figs. 82, 84 and 86 will show that in order to make a radiograph which will not picture the teeth too long nor too short the X-rays should strike the film almost, but not quite, at right angles to its surface. The angle of the film in Figs. 82, 84 and 86 is what it would Film Fig. 87. be in the average mouth. Suppose, however, the vault is very flat. In such an event the angle of the X-rays as illustrated in Fig. 84 to be cor- rect would cause a marked lengthening of the shadow, as illustrated by the dotted lines and drawing in Fig. 87. The angle of the X-rays should be as in Fig. 86 to avoid, as nearly as possible, any distortion. (Notice in Fig- 87 that the bending of the film would cause a lengthening of the shadow.) Just in proportion as the vault becomes more flat the film departs from the vertical and the tube must be at a different and higher angle. And so, inversely, as the vault is higher the film may be placed more nearly parallel with the teeth and the tube may be lowered. From the foregoing it will be understood why we can never be sure that our radiograph gives the exact length of Upper teeth. MAKING DENTAL RADIOGRAPHS 95 Owing to the fact that it causes distortion, bending of the film should be avoided as much as possible. Fig. 83 shows the proper pose for making a radiograph of the bicus- pid region. The slight changes of this pose necessary to make radio- graphs of the anterior and extreme posterior teeth are apparent. When making radiographs of the posterior upper teeth the mistake at first will probably be that the X-rays will not be directed at a point far enough back on the face and pictures of the bicuspids will be made when the operator desired to picture the molars. Fig. 88. As a film is placed in the mouth for the pose and radiograph shown in Fig. 89. Instead of placing the film in the mouth, as in Fig. 80, a larger film may be used and placed as in Fig. 88, the sensitive side toward the upper teeth. With the film in this position the patient is instructed to close the mouth, so holding the film firmly in position. With the film in such a position either the tube must be placed higher and the rays directed more nearly straight down ; or the head must be tipped down- ward toward the tube, which accomplishes the same result, viz., causes the rays to strike the film more nearly at right angles. (Fig. 89.) The radiograph made on a film held in this position is very likely to be dis- torted. (Fig. 89.) The usual position of the film for taking pictures of the lower teeth is illustrated in Fig. 90. With the film in this position it should be covered with rubber or oil paper to protect it against moisture. Fig. 91 shows the proper pose for taking pictures of the lower bicus- pid and molar region. If the radiograph does not show the apices of DEXTAL RADIOGRAPHY Pig, -■'. The pose with the film in the mouth, a- in Fig. 88, ami the radiograph made from this pose. the roots it is because the film was not pressed down far enough, or the tube was not low enough. The slight differences in the poses to make radiographs of the anterior teeth and the third molars from the pose shown in Fig. 91 are apparent. With the film placed in the mouth as in Fig. 89. except with the sensitive side of the film presenting toward the lower instead of the upper teeth, and a pose as per Fig. 92, radiographs of the lower teeth may be made. MAKING DENTAL RADIOGRAPHS 97 The distance the tube is placed from the film Distance Between is about 12 to 20 inches, measurements taken from Cube and Patient. the target of the tube. A good rule to follow is to place the tube so that there is a distance of about 8 inches between the glass of the tube and the patient's face. If. as is almost invariably the case, a 6-inch tube is used, this makes the distance between the target and him about 12 to 13 inches.* 1 never have the glass of the Fig. 90. Position of the film in the mouth for making radiographs of the lower molar and bicuspid region. tube closer than 6 inches from the face. A tube of medium vacuum must be brought a little nearer to the film than one of high vacuum if the same length of exposure is to be made, because the X-rays from it are not so penetrating. The advantage in having the tube as far away as possi- ble lies in the fact that both the patient and film are then more nearly out of range of the soft, secondary rays. These rays may burn the pa- tient (set up a dermatitis) and fog the film. In most works on radiography the writers advise 18 inches as the proper distance between target and film. I believe this to be needlessly *Eight inches between the glass of the tube and the patient's face, plus three inches the distance from the glass of the tube to the target, plus one to two inches the thickness of the maxilla and overlying parts, equals twelve to thirteen inches the distance between the target and the film. DENTAL RADIOGRAPHY long. As 1 have just stated. 1 bring my tube much closer, and I have never had any trouble from dermatitis or fogging of the radiograph. By bringing the tube as close as I do 1 am able to get a clearer, better pic- ture in about one-half the time of exposure that would be required if the distance between the target and the film were l8 inches. Before placing the film in the mouth, after the tube and the patient are in their proper positions it is well to turn on the current for a mo- ment, that the patient may become accustomed to the sound and light. Otherwise the patient would probably be startled, move involuntarily and spoil the picture. 1 f the films have been in the same room while Protection we have been testing the tube, or even if they have Of Tilm$. been in a room immediately adjoining the operating room, they must have been kept in an X-ray proof, lead-lined box. the lead of which should be about % inch thick ( Fig. 93). All films, plates or papers must be kept in such a box if they are to remain in the same room, or even an adjoining room, while the tube is lit, to keep them from becoming fogged. If the position of the film is as per Fig. 88, methods of whh the mouth closed, the problem of holding the fiolding Tilms film while making the exposure is solved. If, as in the lllouth. in Figs. 80 or 90, however, the film must be held immovable by either patient, assistant, or operator. The patient can hold the film, and it is best that he should. If the oper- ator or assistant holds it he or she should wear X-ray proof gloves to protect the hands. Otherwise the repeated exposure of the hands to the rays might prove disastrous. See chapter on "Dangers of the X-Rays." Dr. Tousey, of New York, and Dr. Ketcham, of Denver, have de- signed little devices, film holders, for holding the film in the mouth during it- exposure. It has been recommended that a modeling composition impression of the mouth may be made, a place cut out for the film, which is placed therein and the impression reinserted in the mouth. This method of holding films I consider extremely impracticable, because of the time consumed in unnecessary work and the considerable bending of the film. When using square or rectangular film packets bend the sharp cor- ners to keep them from digging into the tissues of the month. When making radiographs of the lower teeth with the film in the month, as per Fig. 90, the patient should be warned not to swallow during the exposure. Movemenl of the tongue in swallowing would move the film. MAKING DliXTAL RADIOGRAPHS 99 Fig. 91. Proper pose for making radiographs of the lower molar and bicuspid region, and the radiograph made from this pose. As stated in Chapter IV, the length of time of time Of exposure depends on several things. With the coil Exposure. capable of giving a fat, fuzzy spark 10 inches long, the tube backing up 7 inches of parallel spark and the distance of the target from the film about 12 inches, the time of ex- posure for an Eastman film will be between 5 and 10 seconds. I have seen tables giving the exact time of exposure for the differ- ent teeth — upper molar teeth so many seconds, upper anterior teeth so manv seconds, lower molar teeth so many seconds, and so on — but such tables are utterly useless. No fixed rules for the length of time of exposure can be made and adhered to. For example, I had been making 10-second exposures. I purchased a new tube — the same make tube I IOO / CENTAL RADIOGRAPHY Fig. 92. Pose for making radiographs of the lower anterior teeth, and the radiograph made from this pose. The lack of detail in this radiograph is due to the fact that a negative cinematograph film was used. When a terminal of the tuhe is brought as close to the patient as is shown in this picture it is necessary to place a piece of wood or glass, or some other non-conductor, between the terminal and the patient — in this case over the patient's breast — to prevent the current "sparking" into the patient. had been using — and found that with it pictures could be made in half the time, g seconds. Then after using the tube a few weeks it became necessary to again increase my time of exposure to 10 seconds. As to a longer exposure being required for some teeth than for others, very little need be said. The time of exposure for radiograph- ing third molars is slightly longer than for any other teeth oi the same mouth. Age increases the density of hone, and so the time of exposure neces- MAKING DENTAL RADIOGRAPHS 101 sary to make radiographs will be somewhat proportionate to the age of the patient. The time of exposure can be shortened from (ISC of one-half to four-fifths by using an intensifying Intensifying Screen. screen. An intensifying screen is a piece of paper, or cardboard covered with calcium tungstate, or platino-barium cyanide. The coated side of an intensifying screen is placed against the coated Fig. 93. Lead-lined, X-ray-proof box. side of the film or plate, and both screen and film are placed in the light- proof packet as usual. Thus we get a double action on the film when it is exposed, the action of the X-rays themselves and the action due to the fluorescence of the intensifying screen. When using an intensifying screen the uncoated side of the film should present toward the object being radiographed. This is contrary to the rule that to obtain the best results the coated side of the plate or film should present toward the object to be radiographed. The advantages of the intensifying screen are: (i) Just in propor- tion as it reduces the time of exposure it protects both patient and oper- ator against any ill-effects of the X-rays. (2) By shortening the time of exposure the life of the tube is lengthened. From a financial standpoint [02 DENTAL RADIOGRAPHY this is of importance. (3) By using an intensifying screen one is able to do tolerably rapid work even with a very small coil. The disadvantages of the intensifying screen are: (1) It causes a granular appearance of the negative, blotting out detail. (2) It is liable to spot the negative, due to unequal fluorescence of its surface. (3) It fluoresces for a minute or so after exposure, and if the plate and screen do not maintain their exact relation to one another blurring of the nega : tive results. (4) Unless one owns several screens, so that a number of packets may be made at a time, their use necessitates the making of a film packet before each exposure, which is discommoding. Such grosser lesions as an impacted tooth, for example, can be radio- graphed satisfactorily with the intensifying screen, but when we wish to obtain detail, such as is necessary to observe pulp stones or a necrotic condition, for example, the use of the intensifying" screen is contraindi- cated. An intensifying screen disintegrates with use. Because, as I have said, the intensifying screen fluoresces for some time after the the exposure has been made it has been the practice of radiographers to lay the plate and screen aside for some time before dis- turbing their relation to one another. Dr. Sidney Lange, however, be- lieving that the continued fluorescence will cause blurring .of the negative even though the relation of the screen to the plate be not disturbed. removes the plate from the screen immediately after exposure. His re- sults from this practice are excellent. After the film has been exposed we are ready to Development develop it — to make the negative. Of negative. The trays for the developer and fixer should be about 4x5 inches, or smaller. The author uses little white enamel soap dishes, about 3x4 inches. If. owing to the particular developer or film used, development re- quires a ci 'ii>iderable length of time, say, perhaps 20 minutes, and one does not wish to remain all this time in the dark room, the tray containing the developer and developing negative may be covered with a heavy board on the down side of which is tacked or glued thick felt or plush, and the operator may then leave and return to the dark room at will, the film hem- protected against the lighl from the opening of the dark room door. Whal developer shall we use? I obtained the Choice of formula^ for the developers used by twelve different Developer. radiographers, and they were all different! From this we may conclude that any clean, properly mixed developer will do the work. The writer uses a prepared developer which may be purchased at MAKING DENTAL RADIOGRAPHS 103 almost any photographic supply store, the Eastman M. O. developer, the formula for which is given in Chapter IV. This developer is sold for developing photographic paper, but it develops films and plates perfectly. The lahel on the tube containing the chemicals directs that they be mixed with 4 ozs. of water for one kind of photographic paper, '"Regular Ve- 1<>\." and 8 ozs. for two others, "Azo" and "Special Yelox." 1 use 6 ozs. of water. After the powder is dissolved in the water in my graduate I put 3 ozs. of the solution in the tray for immediate use and 3 ozs. in a 3-oz. amber glass bottle. In this bottle, tightly corked, the developer will keep as long as a month. Even if it does discolor slightly it can Fig. 94. Films hung up to dry still be used for negatives, though it might stain paper. When the nega- tives are developed — one or many may be developed — the developer in the tray is thrown away. I never try to save developer that has been used, with the idea of using it again in the future. Since writing the foregoing I have been using another prepared de- veloper, rodinal. My limited experience with it teaches me to believe that it is as good as the M. O. developer. My chief reason for using it, how- ever, is because it is so extremely convenient to handle. It is a liquid. When I wish to develop a film I take 2^/2 ozs. of tap water to 2 drams of rodinal. This makes a 1-10 solution. The water and the rodinal are simply placed in the tray together, and the developer is ready for use ; one does not need to wait for powders to dissolve. When conditions and length of exposure are as given above, the time the film remains in the developer is usually about 5 minutes ; the high lights come up in about 15 seconds and the image can be seen tolerably well in 30 seconds. 104 DEXTAL RADIOGRAPHY The time in the fixer varies according to the fixing and film used. The Eastman film requires about 5 min- Wasbing. utes; the Ilford film, because it is so much thicker, 15 or 20 minutes. The writer uses a prepared acid fixing powder, mixing about a pint at a time. The solution will keep indefinitely. As with the de- veloper, no attempt is ever made to save for future use any of the solu- tion once used. The negative should be washed in running water for 15 to 30 min- utes, then hung up to dry. (Fig. 94.) Instead of washing the negative in water for 15 to 30 minutes it may be soaked in Thioxydant, a '"hypo eliminator," for about five min- utes. This dissolves out all the "hypo," and so accomplishes the object of washing. Thioxydant is a proprietary preparation made by the Lu- miere Dry Plate Mfg. Co. The advantage in using it lies chiefly in the saving of time. It may also be used in the summer to advantage, when tap water is so warm that it softens the emulsion and washing is fraught with the liability of spoiling the negative. It may be used for photo- graphic paper as well as for plates and films. Drying requires several hours, unless the negatives are placed in the breeze of an electric fan as suggested in Chapter IV. It requires a longer time for the Ilford negative to dry than for the Eastman product, because the emulsion on it is thicker. When the negative is dry we may then make making as many prints therefrom as desired, immediately Prints. or years after. The technic for making prints was given in the preceding chapter. The negative is laid on the glass in the printing frame, film side up, and the paper placed over it sensitive side down, and so on as given. The best prints can be made on glossy, contrasted paper. Using glossy, contrast}- Azo paper, the time of exposure to a 16-candle power electric light at a distance of about a foot is from 1 to 10 minutes. When the negative is badly overexposed or overdeveloped, and it is therefore verv dark, the time of exposure to a 16-candle power electric light may be as long as 20 to 30 minutes. If the exposure be made to sunlight instead of the electric light tlii- time may be reduced to a couple of seconds. I use M. Q. developer to make my prints. Lately 1 have used, with a moderate degree of satisfaction, a sunlight photographic paper made by the Eastman Kodak Company and sold under the trade names of "Solio" ami "Kresko." Unlike the photographic papers thus far described, this paper is not affected, except alter pro- MAKING DENTAL RADIOGRAPHS 105 longed exposure, by ordinary daylight. So the room in which it is used need be neither dark nor semi-dark. The exposure must be made to sunlight, and, for the average cellu- loid, dental negative is about one hour long. At the end of this time the picture is printed. It can be seen, and needs no developing to bring it out as other photographic papers do. At this stage the picture looks like and in fact is a "proof," the like of which photographers submit to their patrons. It will "fade"' or, to speak more accurately, become dark and so blot out the picture, as all proofs do, unless the unacted-upon silver salt is dissolved out. This may be accomplished and the print made per- Fig. 95. A roller. manent by placing it in an ordinary fixing solution for about eight min- utes. Then it is transferred to running water" and washed for about an hour. Instead of using the ordinary fixing bath much better results may be obtained by placing the print in "Solio Toning Solution," a preparation made by the Eastman Kodak Company. This solution not only fixes the print by dissolving the unacted-upon silver salt, but, because it contains gold chloride, changes the color from a reddish-brown to a rich choco- late, and so makes a better-looking print. A printing frame the back of which is in two pieces joined with a hinge (Fig. jj) is necessary for this work. By releasing only part of the back and raising it on its hinges, we may look at the print from time to time in the course of its development, without altering the relative positions of the negative and paper. The greatest disadvantage in using this paper lies in the fact that we must have sunlight for our exposures. In this climate (Indiana) many days pass without any sunshine and, during such a period, sunlight paper cannot be used successfully. The directions given for the use of "Solio Toning Solution'* advise io6 DENTAL RA1UOCKAPHY placing the print in a solution of sodium chloride, for five minutes, after mova] from the toning solution, before placing it in the wash water. This step is not imperative. Prints may be made more glossy and altogether more beautiful by placing them on a ferrotype, or squeegee board. The ferrotype is a sheet of metal on one side of which is baked black enamel. After the prints are washed they are laid face down on the enamel side of the ferrotype, rolled with a roller (Fig. 95), covered with a lintless blotter and rolled Fig. 9';. Film packet held against the cheek with adhesive tape. again with a roller. The ferrotype is now set on end, and as the prints dry they fall off. Before placing the prints on the ferrotype the enamel surface should be polished with ferrotype polish. Ferrotype polish is a solution of paraffin in benzine. It is put on the ferrotype, allowed to dry for a few minutes, then the enamel surface polished with chamois skin. If the prints do not come off the ferrotype as they should, but stick tightly, mor,- paraffin should be added to the polishing solution. The most common cause for prints sticking to the squeegee board, however, is the failure to allow them to dry thoroughly. In all the poses thus far described the film has Placina films been placed inside the mouth. Though it is not of ten Outside the expedient to do so, because of the longer exposure Ittoutb. necessarv, it i- nevertheless sometimes advisable to place the film outside the mouth. (Fig. 96.) The MAKING DENTAL RADIOGRAPHS 107 film packet may be held, sensitive side toward the cheek, with adhesive tape. With the film placed as in Fig. 96, the pose should be as in Fig. 97. The time of exposure for this pose is about six times as long Fig. 07. Pose for making a radiograph of the lower molar region with the film outside of the mouth, as in Fig. !*fi. and the radiograph made from this pose. as it would be if the film were placed inside of the mouth and the same field radiographed. The increase in time exposure necessary is due to three things : First, the increased distance between the target and the film. Second, the great thickness of tissue to be penetrated. Third, the increased distance between the teeth and the film; the closer the object to be radiographed is to the film or plate the better and more quickly it can be radiographed. ro8 DENTAL RADIOGRAPHY Owing to the curvature of the dental arch it is often extremely diffi- cult to obtain a good picture of the lower incisors with the film placed to the lingual and parallel to the long axis of the teeth. This is because FiK. !)-. Pose for making a radiograph of the lower incisors, and the antra. the film cannot be placed in this position without bending it considerably, and the bending results in distortion and blurring of the radiograph. A film may be placed in the mouth as in Fig. 92, or a plate or large film, 4x5 inches or larger, may be placed on a stand, sensitive side up, and the patient posed as in Fig. 98. It is usually necessary to have the patient remove the collar for this pose. Fig. 98, because of its lack of per- spective, is perhaps a little misleading. The rays are not directed straighl through the neck, as the picture seems to show. The tube is a MAKING DENTAL RADIOGRAPHS 109 Fig. 99. Radiograph made from the pose shown in Fig. 9S. Notice how clearly the antra show little to one side. Fig. 99 is the radiograph made from the pose Fig. 98. Notice how clearly the antra of Highmore show in this picture. I be- lieve that in posing my patient as just described to make radiographs of the lower incisors I have by accident stumbled on to the best pose for making pictures of the antra. Except Fig. 98, all of the poses so far described have been with the patient in the dental chair, and films have been used. no DENTAL RADIOGRAPHY Poses for targe Plate Radiographs. To make the radiograph shown in Fig. ioo the pose was as in Fig. 101 and the radiograph was made on a 5x7 plate. Fig. 101 illustrates the principle of posing for large plate radiographs. Modifications of this pose pig, Radiograph made from the pose similar to Fig. 101, The arrow points to an impacted upper third molar. Th< lack of detail in this, and all radiographs made from a similar pose, i- due to a superimposition of shadows the shadow of one side of (lie jaw is mingled with the shadow of the other. (Radiograph by A. M. Cole and Raper.) are of course necessary, according to whal particular region is to be pictured. The objection to this pose as illustrated is that the part being radio- MAKING DENTAL RADIOGRAPHS 1 1 1 graphed is not close enough to the plate. With the apparatus used the patient could not be posed lying on the side, because the shoulder would have been in such a position that the tube could not have been brought close enough to the part. The pose would have been better had the patient been lying on the stomach with the head turned to one side and the cheek resting firmly against a plate placed on a book about three or four inches thick ( Fig. 330). Fig. 101. Pose for the radiograph shown in Fig. ion. Note that the patient is covered with rubber matting such as is used in halls and on stairways. This serves as an insulator to keep the current from jumping to the patient's body. In case the current did jump to the body of the patient a blister would probably be made at the point of entrance and the shock would be more or less painful, but not dangerous. The tube is of course insulated from the metal of the compression diaphragm. An additional precaution to guard the patient against shock is to hook a chain — any conductor, in fact — to the metal of the compres- sion diaphragm and adjusting apparatus and fasten the other end to a chandelier, gas pipe or water pipe. With this arrangement, if any cur- rent passes into the compression diaphragm or metal adjusting- apparatus it will follow the chain into the gas or water pipe, and on to where the 112 DEXTAL RADIOGRAPHY pipe may lead, until it dissipates itself, eventually reaching the earth, possibly. This is called "grounding- the current." While it is always host to have the patient in a recumbent position to make a radiograph such as Fig. ioo. it is not necessary to use a special Fig. 102. Pose for the radiograph shown in Fig. 103. cause they are less expensive and just as well adapted for the work. Plates could not be used satisfactorily inside the mouth, because they will not permit the slightest bending. Large plate radiographs are sadly lacking in detail compared to those made on films held in the mouth. radiographic table and compression diagram as is shown in Fig. 101. The patient may recline on the ordinary couch, and a plain tube stand used to hold the tube. Though it is hardly practical, because the position is 50 awkward, it is nevertheless possible to take radiographs similar to Fig. ioo without having the patient assume the recumbent position. the patient on a -to..l or chair and have him lay the head on the plate, which i- placed on a stand (Fig. [02). Fig. 103 is a radiograph made from a pose similar to Fig. [02. Fig. 100 was made on a 5\7-inch plate. Fig. 103 on an Xxio-inch M.IK IXC DENTAL RADIOGRAPHS "3 plate. Plates are used instead of films for these large radiographs be- This loss of detail is due, not to the fact that a plate instead of a film is used, but to the greater distance between the teeth and the photographic emulsipn, and a superimposition of shadows. The most popular pose for taking a radiograph of the antra of Highmore is shown in Fig. 104, and the radiograph made from this pose Fig. 103. Radiograph made from the pose shown in Fig. 102. The arrows point to unerupted upper and lower third molars. in Figs. 105 and 106. This radiograph shows also the frontal sinuses and the ethmoidal cells. To obtain the best results when making such a picture a diaphragm should be used. To avoid unnecessary straining of the tube it is well to use an intensifying screen. Instead of using the radiographic table and having the patient posed as in Fig. 104. the patient may assume a pose similar to Fig. 98. A picture of one of the antra, or a part of it. may be made on a film 1 l-l DEXTAL RADIOGRAPHY held in the mouth, the pose being quite similar to Fig. 85. A picture of one antrum can also be made on a plate by a modification of the pose, shown in Figs. 101 and 102. (Fig. 107.) Fig. 104. Pose for making radiograph of the antra of Highmore. The advantages of the small dental radiographs fldcantafles made on films held in the mouth over the large plate of film radiographs are: (i) There is no superimpositiorj Radiographs. of shadows, and therefore a clearer, better radio- graph can he made on the small film. (2) The patient may 1>< seated in the dental chair while the exposure is made when small films are used. (3) The time of exposure is shorter for the small films. (4) Small machines with which it is necessary to make an MAKING DliXTAL RADIOGRAPHS i'5 Fig. 105. Radiograph made from the pose shown in Fig. 104. A, B, frontal sinuses. C, D, orbits. E, F, ethmoidal cells. F does not show as well as E because the cells of this side are full of pus. G, H, antra of Highmore. I. J. nasal cavity. As an aid in reading this radiograph observe Fig. 106. (Radiograph by A. M. Cole, of Indianapolis.) exposure of one minute or longer for large plate radiograph will make a good dental radiograph on a film held in the mouth in 10 to 30 seconds. (5) A compression diaphragm, though always a valuable appliance, is not so essential when small films are used as it is when large plates are used. (6) The negative on celluloid cannot be broken. The great advantage of the large plates over the small films is that a larger field can be pictured. DENTAL RADIOGRAPH Fig. 106. - 16. A, frontal sinuses. B, orbits. < . ethmoidal cells. I), antra. E, nasal cavities. Instead of using a photographic plate or film a Radiographs radiograph may be made directly on photographic made on Paper. paper. This paper should be the most sensitive made, so that the exposure will be as short as possi- ]>]<■. Glossy "bromide" paper is the hest. Fig. [08 illustrates a radio- graph of the hand made directly on bromide paper. (Reduced one-half.) When cutting the films as desired and covering them with black paper — in other words, when making the film packet — a piece of bromide MAKING DENTAL RADIOGRAPHS 117 paper may be cut the same size and shape and wrapped up with the film. The paper will then, of course, be exposed at the same time the film is, and may be developed also at the same time. (Figs. 109 and no.) After making a radiograph as shown in Fig. 89, it may be trimmed Fig. 107. The more or less oval shadow at which the arrows point is a piece of tooth root in the antrum. (Radiograph by Carman, of St. Louis, Mo.) to a more symmetrical form. In other words, the film or bromide paper. as wrapped up in the film packet, may be left an indefinite unsymmetrical lorm and trimmed to a more pleasing outline after the picture is made. The length of exposures when making a radiograph directly on bromide paper is slightly longer than when using a film or plate. Unlike the other sensitized papers — Azo. Yelox, or Cyko — the bromide paper must not be exposed to the orange light. The light must be the same as for films and US DENTAL RADIOGRAPHY plates, a ruby light. The radiograph made directly on paper lacks good detail. Prints from negatives may be made on bromide paper. The advan- tage in using it is that less time is taken up in making exposures, and the disadvantage is that, since the work must be done in the comparatively weak ruby light instead of the orange light, it is difficult to tell just when development is complete. Fig. 108. Radiograph made on bromide paper. The conditions for making this radiograph were exactly the same as those given in Chapter IV for the negative of Fig. 71, except tin- time in 'lie de- veloper, which was about 100 seconds. Fig. 109. Dental radiograph made directly on bromide paper. Fig. 110. The negative for this radiograph was made at the same lime with Fig. 109, the film being enclosed in the same packet with the bromide paper. Lantern slides may easily be made from a good Lantern negative. A lantern slide plate is a photographic Slide*. plate 31/4x4 inches, manufactured especially for the purpose. Like all other photographic plates, it should be "worked" in the ruby, never the orange, light. The negative is placed in the printing frame, sensitive side up. and the slide laid over it, sensitive NOTE.— Fig, no appears to he reversed. This is due to the fact that it is a print from tin- film. In tin- film itself the teeth would appear in same positions as in Fig. 109. — Ed. MAKING DENTAL RADIOGRAPHS 119 side down. The average celluloid, dental, radiographic negative is of such density that the time of exposure of the plate to a 16-C. P. electric light, at a distance of two feet, is between one and two seconds. Allow the slides to remain in the developer a few seconds after the radiograph shows best, until it shows a little too dark. Wash in water quickly and transfer to the fixing bath, where it should remain until the picture shows clearly as desired. The writer uses Seed's lantern slide plates and Seed's pre- pared metol-hydrochinone developer. After fixing, the slide is washed and dried the same as any photographic plate. When dry a piece of transparent glass, the same size as the slide, is laid on the film side of the slide and the two stuck together at their edges with binding tape, such as is used for passe-partout work. The piece of clear glass is used to protect the emulsion of the slide against scratching. If the negative from which the slide is to be made is larger than the slide, as is always the case when the negative is on glass, the work had better be turned over to a professional slide-maker. Dr. Kells makes lantern slides of, instead of from, his celluloid den- tal negatives. This is accomplished as follows : On a clear glass S l A x 4 inches place a piece of black paper the same size, with a hole in the centre large enough to show all of the negative that the operator wishes to exhibit. Place the negative directly over this hole in the paper. Place another piece of glass 3/4x4 inches over the whole and bind the two pieces of glass together at their edges with bind- ing strips. The advantage of this method, over making photographic slides are : The ease and dispatch with which they may be made — a dark room and equipment is not necessary — and, since we are using the negative itself, there is no loss of detail such as might occur when the other method is employed and a new picture is made on the photo- graphic slide. The disadvantage is that the negatives with good detail are usually so dark that the light from the lantern is not strong enough to penetrate them. That the student of dental radiography may learn the different con- ditions under which radiographs of the teeth and jaws are made, I give the following summaries in which are recorded the important factors. The summaries, in the order in which they follow, to and including Fig. 115, represent some experimental work done by the writer. These reports, like most reports, make very dry reading, but they contain some information of importance. A study of the summaries for Figs. 81. in, 97, 99 and 103, will give a tolerably good idea of what can be done with an induction coil. A study of the summaries for Figs. 112, 113 114 and 115 will give an idea of what can be accomplished with a small, suitcase, high-frequency coil. 120 DENTAL RADIOGRAPHY A careful reading of the "comment" at the close of some of the summaries is especially advised, because therein will be found some valuable pointers. To make the negative of the radiograph shown Tig. 81. in Fig. 81 the conditions were as follows: I. Machine used: A Scheidel, 18-inch, induction coil with 2-point, electrolytic interrupter, operating on a no-volt D. C. circuit. All the resistance of the rheostat cut out. Fig. 111. The two circular shadows in the corners are due to small paper clips used to hold the intensifying screen and film together. 2. Strength of current : Xo meters on machine. A rough guess would be 26 amperes in the primary, about 13 milliamperes sent through the tube. Ten ( 10) inches of fat, fuzzy, yellow spark obtainable. 3. Make and condition of tube used: Green and Bauer, "Clover- leaf," 6-inch tube. Length of tube-regulating spark gap, 3^ inches. Tube backs up 7 inches parallel spark. The tube vacuum is therefore high, and the X-rays produced penetrating. Xo penetration guide used. 4. Distance of target from film: Between 12 and 13 indies. Distance of glass of tube from face, about 8 inches. 5. Thickness of part : That of superior maxillary bone and over- lying tissues, about i l / 2 inches. 6. Density of part: That of superior maxillary bone and overlying tissues. ( Density varies slightly with age, growing denser.) 7. Film used: Eastman f positive cinematographic) X-ray film. 8. Time of exposure: Eight (8) seconds. <). Time in the developer, and developer used: Five (5) minutes in Eastman's "M. O." prepared developer. MAKING DENTAL RADIOGRAPHS 121 Comment: When using an Ilford film the exposure can be reduced one-half, *. c, to 4 seconds, and the time in the developer remains 5 min- utes. The negative of Fig. 83 was made on an Ilford film, exposure 4 seconds. It will not be amiss here to give my readers some idea of how T "guessed" at the amperage and milliamperage, respectively, of my pri- mary and secondary currents. The fuses just in front of my coil are 30 ampere fuses. I know, therefore, that I am drawing something less than 30 amperes. I know also that I must be drawing almost 30 amperes with all the resistance of the rheostat out, and I make a rough guess of 26, leaving a margin of 4 amperes between the current I am using and one which would "blow" (burn) the fuses. Having guessed at the am- perage, I calculate that the average induction coil is capable of forcing one-half as many milliamperes through a high vacuum tube as it draws amperes in its primary. Thus, if the coil draws 26 amperes the milliam- perage output through a high vacuum tube is 13. A high frequency coil is capable of forcing two-thirds as many mil- liamperes through a high tube as it draws amperes in its primary, and the interrupterless coil can force about four-fifths as many milliamperes through a high tube as it draws amperes into its primary. This is only an estimate, not a mathematical fact. To make the negatives of the radiagraph shown fig. 111. in Fig. 1 1 1 the conditions were as follows : 1. Machine used: Same as for Fig. 81. 2. Strength of current: Same as for Fig. 81. 3. Make and condition of tube: Same as for Fig. 81. 4. Distance of target from film: About 13 inches. Distance from glass of tube to patient's face, about 8 inches. Pose as in Fig. 89. 5. Thickness of part: Same as in Fig. 81. 6. Density of part: Same as in Fig. 81. 7. Film used : Ilford film, with a Kny-Scheerer intensifying screen. (I wish to thank the Kny-Scheerer Mfg. Co. for their kindness in making a dental intensifying screen after my instructions, and furnishing me with samples for experimental purposes.) 8. Time of exposure : One ( 1 ) second. 9. Time in the developer, and developer used: Four (4) minutes in the Eastman "M. Q." developer. Comment: Had the intensifying screen not been used, the time of exposure would have been about four (4) seconds. Thus the use of the screen shortened the time of exposure necessary three-fourths (^4). To make the negatives of Fig. 97 the conditions Tifl. 97. were as follows : 1. Machine used: Same as for Figf. 81. 122 DENTAL RADIOGRAPHY 2. Strength of current: Same as for Fig. 81. 3. Make and condition of tube: Same as for Fig. 81. 4. Distance of target from film: About 14 inches. Distance of glass of tube from face, about 8 inches. Pose as in Fig. 97. 5. Thickness of part: Tissues of neck, mandible and overlying parts — about 3 inches. 6. Density of part : That of tissues of neck, mandible and overlying parts. 7. Film used : Ilford film. 8. Time of exposure : Thirty-five (35) seconds. 9. Time in the developer, and developer used: Five (5) minutes in Eastman "M. O." developer. To make the negative of the radiograph shown fig. $9. in Fig. 99 the conditions were as follows : 1. Machine used: Same as for Fig. 81. 2. Strength of current: Same as for Fig. 81. 3. Make and condition of tube: Same as for Fig. 81. 4. Distance of target from film: About 16 inches. Distance of glass of tube from patient's neck, about 8 inches. Pose as in Fig. 98. 5. Thickness of part: That of the tissues of the neck, the mandible and overlying parts — about 5 inches. 6. Density of part : That of the tissues of the neck, mandible and overlying tissues. 7. Film used : Lumiere, "Sigma," double-coated, 5x7~inch X-ray plate. 8. Time of exposure: Thirty-five (35) seconds. 9. Time in developer, and developer used: Fifteen (15) minutes in Eastman "M. Q." developer. To make the negative of the radiograph shown fig. 103. in Fig. 103 the conditions were as follows: I. Machine used: Same as for Fig. 81. 2. Strength of current: Same as for Fig. 81. 3. Make and condition of tube: Same as for Fig. 81. 4. Distance of target from plate: Between 12 and 13 inches. Dis- tance of glass of tube from patient's face and neck, about 6 inches. I This is bringing the tube about as close to the patient as it can be placed with safety.) Pose similar to Fig. 102. 5. Thickness of part : That of the tissues of the neck, the mandible and overlying tissues for the lower jaw, and the cheek, the superior maxillary bone and overlying tissues for the upper jaw — 3 to 4 inches. 6. Density of part: As above, under "thickness of part." MAKING DENTAL RADIOGRAPHS 123 7. Plate used: Lumiere, "Sigma," double-coated, 8xio-inch X-ray plate. 8. Time of exposure : Forty-five (45) seconds. 9. Time in the developer, and developer used: Ten (10) minutes in the Eastman "M. Q." developer. Comment: After such an exposure the tube would be very warm, and should be allowed to cool thoroughly before using again. The rule to allow the film or plate to remain in the developer twenty times as long as it takes the high lights to show up well is often inap- plicable when developing these large pictures on plates. It is sometimes necessary to leave the plate in the developer thirty or forty times as long as it takes the high lights to appear. Allow the plate to remain in the developer until almost all black — not jet black, but darkened well. It is difficult to the point of being impossible, usually, to see the image while the plate is in the developer ; only an obscure suggestion of the radiograph can be seen. Had the negative for Fig. 103 been left in the developer but 5 or 6 minutes instead of 10, or had the exposure been made slightly shorter, say 40 seconds, then the outline of the mandible would not be lost, as it is. To make the negative of the radiograph shown Tifl. 100. in Fig. 100 the conditions were as follows : 1. Machine used: Kelly-Koett, "Grosse- Flamme," induction coil on third inductance, with 7-point electrolytic in- terrupter, operating on a no- volt D. C. circuit. 2. Strength of current: Primary about 40 amperes. Milliamper- age sent through tube, about 20. Fat, fuzzy spark obtainable full length of spark gap, 12 inches. 3. Make and condition of tube: Green and Bauer, "Cloverleaf" 6-inch tube. Length of tube regulating spark gap, about 4^ inches. Tube backs up 7 or 8 inches of parallel spark. 4. Distance of target from plate: About 16 inches. 5. Thickness of part: See Fig. 101. 6. Density of part : That of tissues of the neck, mandible and over- lying parts for the lower jaw, and superior maxillary bone and overlying parts of the upper jaw. 7. Plate used : Lumiere, X-ray plate, 5x7 inches. 8. Time of exposure: Ten (10) seconds. 9. Time in developer, and developer used: Five (5) minutes in "M. Q." prepared developer. Comment : The Kelly-Koett, Gross-Flamme, coil is one of the most powerful induction coils made. 124 DENTAL RADIOGRAPHY To make the negative of the radiograph shown fig. ios. in Fig. 105 the conditions were as follows: 1. Machine used: Kelly-Koett, "Gross-Flamme"' induction coil on inductance four, with 7-point electrolyte interrupter, operating on 110-volt D. C. circuit. 2. Strength of current: Primary, 50 amperes. Milliamperes sent through tube, about 25. 3. Make and condition of tube: Green and Bauer, "Cloverleaf" 6- inch tube. Length of tube regulating spark gap, 5 inches. Tube backs up 8 inches of parallel spark. Fig. 112. 4. Distance of target from plate: About 19 inches. 5. Thickness of part: That of the cranium coverings and con- tents, about 8 inches. (Fig. 104.) 6. Density of parts: That of the cranium, coverings and contents. 7. Plate used: Cramer X-ray plate, 8x10 inches, with intensifying screen. 8. Time of exposure: Three (3) seconds. 9. Time in developer, and developer used: Seven (7) minutes in water, 32 oz. ; soda sulphite, 12 dr.; hydrochinone, 2 dr.; edinol, 75 gr. ; potassium bromide, 90 gr. ; potassium carbonate, 2 oz. Comment: Had an intensifying screen not been used, the time of exposure would have been about ten (10) seconds. To make the negative of the radiograph shown Tig. 112. in Fig. 112 the conditions were as follows: I. Machine used: Scheidel-Western, portable high-frequency, 6-inch coil, operating on [04-volt A. C. circuit. ( [' wish to acknowledge my indebtedness and express my sincere thanks to the Scheidel-Western X-ray Coil Mfg. Co., who furnished me with their coil for experimental work.) MAKING DENTAL RADIOGRAPHS I2 5 Fig. 113. Arrow A points to an impacted lower third molar. Arrow B points to the temporo- mandibular articulation, which shows very clearly in this picture. IJt. DENTAL RADIOGRAPHY 2. Strength of current: No meters. A rough guess, 12 amperes in primary. Milliamperage sent through tube, about 8. Fat, fuzzy spark 6 inches long obtainable. 3. Make and condition of tube: Green and Bauer, 6-inch, high-fre- quency tube. Tube-regulating spark gap, 5 inches. (In my limited ex- perience I have found that the tube-regulating spark gap must be longer for higl -frequency tubes to obtain the same condition of vacuum.) Tube backs up 6 inches of parallel spark. Fig. 114. 4. Distance of target from film: Between 11 and 12 inches. Dis- tance between glass of tube and patient's face, about 7 inches. 5. Thickness of part : That of superior maxillary bone and overly- ing tissues. 6. Density of part : That of superior maxillary bone and overlying tissues. 7. Film used: Ilford X-ray film. 8. Time of exposure: Ten (10) seconds. 9. Time in developer: Five (5) minutes in "M. Q." developer. Comment : Flow can a tube backing up 6 inches of parallel spark be operated by a coil the terminals of which are only 6 inches apart? is a natural and fair question. This is accomplished by placing an up- right piece of plate-glass between the terminals of the coil, which pre- vents sparking between them. With conditions as above, an exposure of about 20 seconds is neces- sary when Eastman films are used. Be it understood that [O seconds for Ilford films and 20 seconds for Eastman films do not represent the minimum exposures for the making of dental radiographs under the conditions as above. For example, I MAKING DENTAL RADIOGRAPHS 127 rig. 115. Arrow A points to an unerupted lower third molar. Arrow B points to the temporo- mandibular articulation, which shows very clearly in this radiograph. The triangular spot marked C is the result of not completely covering the plate immediately when it was placed in the developer. I2 8 DENTAL RADIOGRAPHY was able to obtain a tolerably good radiograph after a io-seconds ex- posure on an Eastman film by leaving it in the developer 14 minutes. To obtain the best pictures, however, the exposure should be 10 seconds for Ilford film- and 20 seconds for Eastman films. To make the negative of the radiograph shown fig. 113. in Fig. 113 the conditions were as follows: 1. Machine used: Same as for Fig. 112. 2. Strength of current: Same as for Fig. 112. 3. Make and condition of tube: Same as for Fig. 112. 4. Distance of target from plate: Between 12 and 13 inches. Dis- tance of glass of tube from patient's face and neck, 6 inches. Pose similar to Fig. 102. 5. Thickness of part : That of tissues of the neck, mandible and overlying parts for the lower jaw, and the superior maxillary bone and overlying parts for the upper jaw — 3 to 4 inches. 6. Density of part : As above under "thickness of part." 7. Plate used: Lumiere, "Sigma/' double-coated, 8xio-inch X-ray plate. 8. Time of exposure: Sixty (60) seconds. 9. Time in the developer and developer used: Seven (7) minutes in Eastman "M. Q." developer. Comment : The tube-regulating spark gap was set at a distance of 5 inches, or perhaps a little longer, and at no time did the current jump the gap. Theoretically, as the current passes through the tube the vacuum becomes higher. I was considerably surprised, therefore, to ob- serve after the current had been passing through the tube for about 50 seconds that the blue cathode stream could be seen, indicating a very low vacuum. My friend, Mr. Darling, a designer of coils, informs me that this lowering of the vacuum is due to heating of the tube. The milli- amperage sent through it heats the entire tube, which means, of course, that the regulating chamber and its contents are heated, gases from the regulating chamber are liberated, and so the vacuum is lowered, without at any time a spark occurring at the tube-regulating spark gap. It is well to mention here, perhaps, that there is very often a blue color bark of the target in high-frequency tubes, which does not signify a low vacuum. However, when a blue cathode stream can be seen, or when there are areas of blue in any part of the active hemisphere, it sig- nifies a vacuum too low for good picture work. To make the negative of the radiograph shown fig. )|4. in Fig. 114 the conditions were as follows: 1. Machine used: Scheidel-Western, portable high-frequency, 6-inch coil, operating on a 70-volt A. C. circuit generated MAKING DENTAL RADIOGRAPHS 129 by a rotary converter. The rotary converter being set in motion by the commercial no-volt D. C. 2. Strength of current: The primary current furnished by the con- verter, about 5 amperes. Milliamperage sent through tube, 3 or a little over. A tolerably fat, fuzzy spark four (4) inches long obtainable. The spark, instead of being white or yellow as when the milliamperage is high, is of a blue or purplish color. Fig. 116. Diagram of portable, high-frequency coil. Six (6) minutes in 3. Make and condition of tube: Same as for Fig. 112. 4. Distance of target from plate: Same as for Fig. 112. 5. Thickness of part: Same as for Fig.- 112. 6. Density of part: Same as for Fig. 112. 7. Film used : Ilford X-ray film. 8. Time of exposure: Fifteen (15) seconds. 9. Time in the developer and developer used : the Eastman "M. Q." developer. Comment : Because of the considerable difference in the milliam- perage sent through the tube it might be expected that there would be an increase in the time of exposure necessary when operating the high- frequency coil from a rotary converter. Using the same coil, the time of exposure when the coil is excited by the rotary converter should be, to obtain the same results, about one-half longer than when the coil is operating from the commercial 104-volt A. C. To make the negatives of the radiograph shown fig. us. in Fig. 115 the conditions were as follows: 1. Machine used: Same as for Fig. 112. 2. Strength of current: Same as for Fig. 112. 3. Make and condition of tube: Same as for Fig. 112. 4. Distance of target from plate: Between 12 and 13 inches. Dis- i 3 o DENTAL RADIOGRAPHY tance of glass of tube from patient's face, about 6 inches. Pose similar to Fig. 102. 5. Thickness of part : That of the tissues of the neck, the mandible and overlying parts for the lower jaw, and the superior maxillary bones and overlying parts for the upper jaw. 6. Density of part : As given under "thickness of part." 7. Plate used: Lumiere, "Sigma," double-coated, 8xio-inch X-ray plate. 8. Time of exposure: Seventy-two (72) seconds. 9. Time in the developer, and developer used : Fourteen (14) min- utes in the Eastman "M. O." developer. Comment : When the time of exposure is so long, 72 seconds, as in this case, the matter of a couple of seconds or so makes little or no difference. That is to say, the time of exposure might have been, say, 70 or 75 seconds, and the same results obtained as with an exposure of J2 seconds ; and this without altering the time in the developer. When developing an especially sensitive plate, such as the one used in this case, the Lumiere "Sigma" plate, for a considerable length of time it is not expedient to keep it constantly exposed to the ruby light. Fogging might result. It will be noticed that to make this negative the time of exposure was only one-fifth longer than to make the negative for Fig. 113. Ac- cording to my remarks under the heading "Comment" in the summary of the conditions under which Fig. 114 was made, the exposure should have been "about one-half longer to obtain the same results." But notice, please, that it was necessary to leave the plate for Fig. 115 in the developer twice as long as for Fig. 113. Therefore, I did not get the same results when I increased my exposure only one-fifth. There are two or three special and important technic for points concerning the operation of a high-frequency Use Of High- coil that I shall mention here : frequency Coil. First, move the lever at the back of the coil onto the button marked "low frequency" (sometimes "X-rays") — off of the button marked "high frequency." (Fig. 116.) By doing this all of the condenser of the coil is used, and so the rate of frequency lessened. For high-frequency treatment work only a part of Lhe condenser i- used, with the lever arm on the button marked "high frequency." md, <-ut out all the resistance of the rheostat, separate the sliding rod or rod- to the maximum spark gap — usually about 6 inches — and turn on the current. Third, widen and narrow the "regulating spark gap" until the cur- M.IK IXC DENTAL K. IDIOGR. WHS 131 rent is as high in milliamperage as it can be and still jump the terminal spark gap. It will be remembered that widening the regulating spark gap (up to a certain point) increases the voltage of the output current at the expense of the milliamperage, and that narrowing it increases the milliamperage at the expense of the voltage. Alter the regulating spark gap to get as heavy a spark as possible. It should require but a few sec- onds to accomplish this regulation. Sometimes it is impossible to obtain as fuzzy a spark as you know the machine is capable of giving. This is due to the fact that the little approximating metal studs at the regulating Fig. 117. Radiograph by Peabody, of South Orange. X. J. spark gap are dirty. Place a piece of emery cloth between the studs, screw them together until they hold the cloth loosely, then draw the cloth back and forth over the face of the stijd. Clean both studs in this way. Fourth, place a piece of plate glass between the terminals in order that a high vacuum tube, one with a resistance equivalent to 6 or more inches of parallel spark, may be used. Fifth, connect the tube to the coil, set the tube-regulating spark for about 5 inches, turn on the current and see that the tube lights up O. K. I recall and shall here set forth an experience J\ti Instructive I had while making a radiograph on a large plate Experience. with a small, high-frequency coil. I had followed the technic given above, posed my patient, and turned on the current for a one-minute exposure. For the first thirty- five seconds the tube maintained a good light. Then suddenly the cur- rent ceased to pass through it. At first I thought I had burned out a fuse. (I was using 15-ampere fuses on the supply wires to protect the coil.) But by turning the switch on and off I learned that in this surmise I was wrong, for when the switch was on there was a humming sound in the coil, and as I turned it off a spark occurred as the circuit was broken. I shortened the tube-regulating spark gap, thinking perhaps the 132 DENTAL RADIOGRAPHY vacuum in the tube had suddenly and mysteriously become so high that the current could not pass through it, but when the current was turned on, the only evidence of the fact was a slight humming inside the coil. I disconnected the tube, removed the plate glass from between the ter- minals and turned on the current, but no spark jumped the gap. Not un- til then did I realize that the trouble was at the regulating spark gap. I changed the adjustment of the gap slightly and immediately a spark jumped the terminal spark gap. The metal at the regulating spark gap had gotten warm and expanded, thus altering the width of the gap and shutting off the current. With two exceptions, all the summaries of conditions under which radiographs are made have been records of my own work. (These two exceptions are Fig. ioo, made by Dr. A. M. Cole and myself, and Fig. 105, made by Dr. Cole.) That my readers may have some idea of the govern- ing circumstances under which other men make radiographs, I print the following summaries. For the report and radiographs we are indebted to the men whose names appear beneath the radiographs. To make the negative of the radiograph shown Usinq an m ^ig- 1: 7 tne conditions were as follows: Tnterrupterless I- Machine used: Kny-Scheerer interrupterless Coil. coil. Four and one-half kilowatts. Eleven-inch spark gap. Operating on 104-volt A. C. circuit. 2. Strength of current: Primary, 50 amperes. Milliamperage sent through tube, 40. Fat, fuzzy spark obtainable full length of spark gap, II inches. 3. Make and condition of tube: Machlett tube, Excelsion brand. Tube backs up about 6 or 7 inches of parallel spark. Penetration of X-rays, 8 Wehnelt, which is the same as 6 Walter. Very penetrating. 4. Distance of target from film: About 12 inches. 5. Thickness of part : That of superior maxillary and overlying tissues. 6. Density of part : That of superior maxillary and overlying tissues. 7. Make of film: Eastern X-ray film. 8. Time of exposure : One ( 1 ) second. 9. Time in developer and developer used: Five (5) minutes. For- mula not given. Comment: "Four and one-half killowatts" expresses the rating of the machine. < haptcr 1 1. Had an [lford film been used instead of an Eastman, the time of exposure would have been one-quarter second. It will be noticed that MAKING DENTAL RADIOGRAPHS 133 Dr. Peabody considers the Ilford film four times as fast as the Eastman, while my own experience leads me to believe that it is only about twice as sensitive. When making exposures that necessitate the splitting of seconds, an automatic switch timer may be used to advantage. To make the negative of the radiograph shown ffg. ii$ in Fig. 118 the conditions were as follows: 1. Machine used: A Ritchie, 10-inch induction coil, with i-point electrolytic interrupter, operating on a uo-volt D. C. circuit. 2. Strength of current: Fat, fuzzy spark 10 inches long obtainable. Fig. 118. By Lodge, of Cleveland, O. 3. Make and condition of tube : Hartford, 7-inch tube. Length of tube-regulating spark gap, 3^ inches. The tube backs up four (4) inches of parallel spark. 4. Distance of target from film : Ten ( 10) inches. 5. Thickness of part : That of superior maxillary and overlying tissues. 6. Density of part : That of superior maxillary and overlying tis- sues. Patient 12 years old. 7. Film used : Eastman dental film. 8. Time of exposure. Six (6) seconds. 9. Time in the developer and developer used : Ten minutes in : Solution A, Water, 64 oz. ; metol, 120 grs. ; hydrochinon, 120 grs. ; Seed's sulphite of soda, 2 oz. Solution B, water, 16 oz. ; Seed's carbonate of soda, 2 oz. For use take of A, 4 oz. ; of B, 1 oz., and of water, 4 oz. To make the negative of the radiograph shown fig. 119. in Fig. 119 the conditions were as follows: 1. Machine used: Scheidel- Western, 12-inch induction coil, with electrolytic interrupter, operating on a uo-volt D. C. circuit. *34 DENTAL RADIOGRAPHY 2. Strength of current: Eighteen (18) or twenty (20) milliamperes sent through tube. 3. .Make and condition of tube: Green and Bauer "Cloverleaf." Length of tube-regulating spark gap : 2 l / 2 inches. 4. Distance from target to him: About 18 inches. 5. Thickness of part: That of the body of the mandible and over- lying tissues. 6. Density of part That of the body of the mandible and overlying tissues. 7. Film used : Seed's special X-ray film. 8. Time of exposure : About 6 seconds. Fig. 119. By Ketcham, of Denver, Colo. Fig. 120. By Blum, of New York. 9. Time in developer and developer used : About 20 minutes in : Sodium sulphite, 3 oz. ; potassium carbonate, 2 oz. ; eikogen, 2 oz. ; water, 2 quarts. Dissolve in boiling water and filter when cool. Take one part of the developer to three parts of water for use. To make the negative of the radiograph shown Tig. 120. in Fig. 120 the conditions were as follows: 1. Machine used: A Wrappler 12-inch induction coil, with 2-point, electrolytic interrupter, operating on a 1 10-volt D. C. current. 2. Strength of current: Twenty-five 12^) amperes in the primary. About 9 inches of fat, fuzzy spark obtainable. 3. Make and condition of tube: Muller, water-cooled. Penetration about 7 Benoist. Length of tube-regulating spark gap. 3^ inches. Tube • 6 i" 7 inches of parallel spark. 4. Distance of target from film: About 14 inches. 5. Thickness of part: Thai of superior maxillary bone and over- lying 6. Densit) of part: That of superior maxillary bone and overlying MAKING DENTAL RADIOGRAPHS 135 7. Film used: Eastman positive cinematograph film, sold for dental radiographic purposes. 8. Time of exposure: About 10 seconds. 9. Time in developer and developer used: About 8 minutes in: Water, 10 oz. ; sulphite of soda (crystals), 4 oz. ; carbonate of potash, 3 oz. ; adurol, y 2 oz. From the concentrated solution take 2 oz. to 6 oz. of distilled water, and to this mixture add 15 drops of 10% solution of potassium bromide. To make the negative of the radiograph shown fig. i2i t in Fig. 121 the conditions were as follows: 1. Machine used: A Scheidel 12-inch induction coil, with i-point. electrolytic interrupter, operating on a no-volt D. C. circuit. All of the resistance of rheostat cut out. Fig. 121. By (.". Edmund Kelts, Jr., of New Orleans, La. 2. Strength of current: Thirty (30) amperes in primary. Twelve (12) inches of fat, fuzzy spark obtainable. 3. Make and condition of tube : "Cloverleaf " 6-inch tube. Length of tube-regulating spark gap, 4 inches. Tube backs up 10^2 inches of parallel spark. 4. Distance of target from film: Eight (8) inches. 5. Thickness of part: That of lower jaw and overlying parts. 6. Density of part: That of lower jaw and overlying parts. 7. Film used : Eastman's positive cinematograph emulsion. 8. Time of exposure: One (1) second. 9. Time in the developer and developer used: (Time not given.) Developing started in metol-hydroquinone and finished in hvdroquinone. Comment : Notice that the distance between the target and the film is 8 inches. Therefore, the distance between the glass of the tube and the patient's face is only about 4 inches. With the tube this close a "filter" (Chap. VIII) should be used to protect the patient. An alumi- num filter was used in this case. CHAPTER VI. Reading Radiographs. Seeing things is truly a mental effort. Though an object or shadow be reflected on the retina of the eye, it is not "seen" unless it has an effect upon the brain. When we say, "train the eye" to see such and such a thing, we mean really, train the mind — the brain. To correctly read a radiograph, to see all there is in it to be seen, and to understand it to mean what it stands for, requires experience and an intimate knowledge of the anatomy and pathology of the parts under observation. Experience is an important factor. Upon looking over old negatives, I see many things of interest in them now which I did not observe a year ago. It is always advisable to study the negative in Illuminating preference to the print. Some of the finest details BOXCS. are lost in the print. The negative may be held up to a window or an artificial light, or it may be placed in an illuminating box (Fig. 122) for observation. While the illuminating boxes on the market are suitable for studying large plate or film negatives, they are needlessly large and poorly adapted for studying the small, dental, film negatives. A small illuminating box can easily be made. A light-proof box, with a window of frosted glass and a light inside, may constitute the illuminating box. It is well to paint the inside of the box white, so increasing the power and uniformity of il- lumination. With the negative held against the frosted glass of the window on the outside and the light lit inside, one is able to study the negative to great advantage. Little spring steel clips, similar to the ones used to hold a slide or a microscope, may be used to hold the negative against the frosted glass window. The use of a reading glass in connection with an illuminating box will enable one to observe the negative to the best possible advantage. The denser the part, the deeper will be the the Relative shadow thrown on the film, and, consequently, the Ualues of Dense more transparent the negative in that region. Thus Areas in negatives, in the negative, metal fillings, posts and metal crowns appear as transparent areas ; gutta-percha, cement, 136 READING RADIOGRAPHS *37 enamel and porcelain a little less transparent ; then in the order of their respective densities, dentin, bone, gum tissue, and, last, the cheek appears — when it is shown in the negative at all — as the least transparent part, except that part of the negative on which the X-Rays have fallen directly without anything intervening except the black paper of the packet. The contrast between tooth and bone tissue is very marked. Unfilled canals and pulp chambers appear as dark streaks and areas in the teeth. Filled canals and pulp chambers appear light. Pulp stones appear as lighter Fig. 122. An Illuminating Box. spots in the dark of the pulp canal or chamber. Abscess cavities appear as dark areas. It is easy to distinguish enamel from dentin, and the peri- dental membrane can clearly be seen as a dark streak following the out- line of roots. A bit of calculus in the peridental membrane will appear as a light spot. This calculus must be on either the mesial or distal side of a root to be seen. It could not be radiographed if it occurred on the buccal, or labial, or lingual. All the foregoing may be seen in good negatives, negatives Prints but a ^ tms cann °t be seen in prints and half-tones. and fjalf-tone I recall distinctly having read an article on Dental Reproductions. Radiography in which the writer printed a half-tone and told his readers to "observe the enamel, the den- tin and the peridental membrane." The writer of this article wrote his [38 DENTAL RADIOGRAPHY paper with either a negative or a good print before him, and assumed that all he saw there would be reproduced in the half-tone. It was not. The half-tone was so dark that all detail of the picture was lost, and the best that could be done was to distinguish between bone and tooth struc- ture. Let us stop to consider the steps in the making of a half-tone pic- ture and the chance for the loss of detail is apparent. From the negative a new picture is made on photograph paper, the print. From this another picture is made on a half-tone plate, and from this the half-tone picture is printed on paper with ink. The finest details of a negative cannot be shown in a half-tone, and, though I have seen many prints that seemed to have fully as much detail as the negative, there is usually at least a slight loss of minute detail even in well made prints. I have stated, that in order to make a half-tone picture it is neces- sary first to make a photographic print or picture from the negative, then, from this, to make the half-tone picture. Thanks to the efforts of Dr. Ot- tolengui and his co-workers, I am able to print half-tones made directly from negatives. The difference in the appearance of a half-tone made from a negative and one made from a photographic print is shown in Fig. 123 (made directly from the negative) and Fig. 124 (made from the photographic print, but reversed in the process for easier comparison). Densities — deep shadows — we have seen appear Relative Ualues as transparencies in the negative. The print, or posi- Of Shadows in tive, is the opposite of the negative. Hence, in Prints. prints, and half-tones made from them, we see the deep shadows of metal fillings, crowns and posts ap- pearing very dark, gutta-percha, cement, enamel and porcelain a little less dark, and so on. On the print, filled canals appear dark, unfilled ones light, abscesses appear as light areas, and so on, always the opposite of the negative. In order to avoid confusion of the right and left sides when studying a negative, bear the following in mind : When looking at the negative from its film side it is as though you observed the part radiographed from the position occupied by the tube during the exposure. When look- ing at the negative with the film side presenting towards the light, away from the eye, it is as though you observed the part from the position of the film during exposure. This is the case, granting that the sensitive side of the film presented toward the object radiographed at the time of exposure, a condition that should always obtain excerjt when an intensify- ing screen is used. If the techjiic previously given is followed, and the sensitive side of the film or plate be placed so as to present toward the part to be radio- 1\I'..U >1 .\ (, K. -IUIULi K. II I I $ 139 140 / >/;'.Y TAL RADIO GRAPH ) ' READING RADIOGRAPHS 141 graphed, and then the negative placed in the printing frame with the sensitive side up (this must be done, or there will be a loss of detail) when observing prints, it is as though one looked at the part from the position of the film or plate during exposure. When observing half-tones made from photographic prints it is the same as when observing the prints themselves, unless special steps have been taken in the process of making the half-tones to reverse the sides, as was dmie in Fig. 124. When observing half-tones made from negn- tives it is the same as observing negatives from the film side. When looking at radiographs made directly on paper, it is as though you observed the part from the position of the tube during exposure. How to mark negatives is a subject that has marking caused the use of a great deal of perfectly good paper negatives. and ink. After trying several methods, I no longer attempt to mark my negatives, but place them in envelopes and mark the envelopes as desired. The Lumiere Dry Plate Co. print the following outline on the backs of their envelopes : No Name Address Date Case Tube used Exposure Distance of Tube from Plate .» Developer Referred by Doctor Remarks I have lately heard of an "X-Ray ink" for marking negatives, but have been unable to procure any. The desired markings are placed on the envelopes or black paper covering the plate or film, the marking being done on the side of the envelope or black paper presenting toward the sensitive side of the plate or film, so that when the exposure is made the ink markings are between the source of the rays and the sensitive side of the plate or film. This ink must, I think, contain some salt of lead or bismuth, for the X-Rays penetrate it very poorly, and consequently there is a shadow cast on the negative. My objections to marking small dental films in this manner is that occasionally the shadow of the markings will occur in such a place in the radiograph as to spoil the picture. The older methods of placing wires bent to form the figures or letters for marking, or a stencil of sheet metal, between the source of rays and the plate, is highly unsatisfactory, so far as their application to the marking of small dental radiographs is con- 142 DEXTAL RADIOGRAPHY cerned. After the negative is made, markings may be scratched in the film. But, as I said before, no system of marking the negative itself is as satisfactory as marking the envelope in which it is kept. One of the most unfortunate limitations of the Perspective. radiograph is that it lacks perspective. For example, though we are able to observe the exact mesio-distal Fig. 125. (Reduced one-half.) position of an impacted tooth, we are unable to determine its bucco- or labio-lingual position, with any degree of accuracy. The closer the object, which is being radiographed, is to the film during exposure, the clearer the resulting shadow will be. Thus, for example, if an impacted cuspid lay lingually to the other teeth, and the film were held inside the mouth as usual, the detail in the picture of the cuspid would be a little greater than the detail in the other teeth. If the cuspid lay to the labial, — farther away from the film, — detail in it would be less than in the other teeth. Hut, on the whole, this method of deter- mining bucco- or labio-lingual location i^ unreliable. RliADLXG RADIOGRAPHS 143 While I agree with Dr. C. H. Abbot, of Berlin, who has done some writing and experimental work to prove that radiographs are not totally lacking in perspective, yet I do declare, from the standpoint of their prac- tical application to dentistry, that they are simply shadow pictures. And let me here warn you that like all shadows, X-Ray pictures are often ex- tremely misleading; one might say, for the word seems to fit so well, treacherous. To eliminate the chance of misreading, because of distor- tion of the radiograph, it is often expedient to make several pictures of the same part or field, changing the pose. Even this, however, does not Fig. 126. A dental fluoroscope. Fig. 127. Shadows of teeth cast on the fluoroscope. preclude the possibility of misinterpretation. To correctly read radio- graphs, a man must be, not only a student of radiography, anatomy, his- tology and pathology, but he must have and use that gift of the gods — common sense. He must not jump at conclusions, and he should ever regard the radiograph as a shadow picture, liable to all the apparent mis- representations of shadows. A study of Fig. 125 will convince anyone of the lack of perspec- tive in at least some radiographs. One is unable to determine, from observing this radiograph, whether the coin pictured is in the flesh of the hand, on the back of the hand, or in the palm of the hand. Likewise, from simple observation, it is impossible to tell whether the needle is in, on, or under the hand. By deduction, we may come to this conclusion : The coin was nearer the plate, during its exposure, than the needle, be- cause the outline of the coin is much clearer than that of the needle, and other things remaining equal, the closer the object being radiographed is to the plate, the clearer its shadow will be. Still we cannot determine M4 DENTAL RADIOGRAPHY the exact location of either needle or coin. We know only that the coin was somewhat closer to the plate, during its exposure, than the needle. That is all. The coin lay under the hand on the envelope holding the plate, the needle on the back of the hand, when the exposure for Fig. 125 was made. To overcome the fault of the lack of perspective Stereoscopic and. to some extent, the distortion in radiographs, Radiography. one must resort to stereoscopic radiography. Stereoscope radiography is the science and art of making radiographs, which, when observed through a stereoscope, have perspective. The technic of making stereoscopic radiographs, together with a discussion of their value and efficiency, will be dealt with at some length in a subsequent chapter. A work of this kind would be incomplete with- Dental out some mention of the dental fluoroscope. The fluoroscope. simplest and most efficient dental fluoroscope has been designed by Dr. Tousey (Fig. 126). Like all fluoroscopes, this one depends on calcium tungstate, or platino-barium cyanide, for its action. A disc of cardboard, coated on both sides with either of the above named chemicals, is placed between two discs of transparent glass, and the glasses and cardboard (or fluorescent screen, for the cardboard becomes a fluorescent screen when it is coated with calcium tungstate or platino-barium cyanide) held together by means of a circular band of metal. A handle now, and we have a dental fluoro- scope, the screen protected against moisture, and either side of it may be used. To use the fluoroscope, the operating room should be dark. It is best that the operator remain in this darkened room for some time until his eyes become accustomed to the darkness before making the exposure. Hold the fluoroscope inside of the mouth, and have the tube placed so that the X-ravs will pass through the part to be observed, and strike the fluoroscope. Fig. 127 shows the fluoroscope and a shadow of the teeth thrown on it. The disadvantages of the fluoroscope are: r. The operator must expose himself to the actions of the X-rays. 2. Either the time for observation must he made very short, or both operator and patient must he exposed to the rays unnecessarily and dangerously long. 3. The picture on the fluoroscope lacks detail. 4. Xo record of the case, other than a mental picture, can he kept; READING RADIOGRAPHS 145 while a negative may he referred to as often as expediency or neces- sity demands. 5. From an educational standpoint, the fact that prints, lantern slides and half-tones can be made from negatives is a great advantage. To learn to eat olives, one must eat them, so I am told. To learn to read radiographs, one must read them, and so we pass to the next chapter, wherein we shall study, in a practical way, the reading of radio- graphs. CHAPTER VII. the Uses of the Radiograph in Dentistry. The use of the radiograph in the practice of modern dentistry is almost limitless. Some of the cases hereinafter mentioned are such as the general practitioner of dentistry might not be called upon to diagnose or treat oftener than once or twice in a lifetime, if at all. But by far the greater number of them are such as are met repeatedly in the prac- tice of dentistry. The radiograph may be used in the following cases: (i) In cases of delayed eruption, to determine the presence or absence of the un- erupted teeth. (2) In cases where deciduous teeth are retained long alter the time when they should have been shed, to learn if the succe- daneous teeth be present. (3) To learn if the roots of children's teeth be fully formed. (4) To determine whether a tooth be one of the pri- mary or secondary set. (5) To determine when to extract temporary teeth. (6) To show the orthodontist when he may move the coming permanent teeth by moving the deciduous teeth. (7) To observe moving teeth. 18) In cases of supernumerary teeth. (9) In cases of impacted teeth as an aid in extraction. (10) To determine the number of canals in some teeth. (11) As an aid in filling the canals of teeth with large apical foramina. (12) To learn if canals are open and enlarged to the apex before filling and to observe the canal filling after the operation. (13) To determine whether an opening leading from a pulp chamber be a canal or a perforation. (14) In cases of pulp stones (nodules). (15) In cases of secondary dentine being deposited and pinching the pulp. V16) To learn if the filling in the crown encroaches on the pulp. (17) In cases of teeth with large metal fillings or shell crowns which do not re-pond to the cold test, to learn if the canals are filled. (18) To learn if apical sensitiveness is due to a large apical foramen or an unremoved, undevitalized remnant of pulp. (19*) In cases of chronic pericementitis ("lame tooth"). (20) In cases of alveolar abscess to de- termine which tooth is responsible for the abscess. (21 )i In cases of alveolar abscess to determine the extent of the destruction of tissue — bony and tooth. (22) In cases of alveolar abscess to learn how many teeth are involved. (23) In cases of abscess of multi-rooted teeth to learn at the apex of which root the abscess exists. (24) In cases of 146 THE USES OF THE RADIOGRAPH IN DENTISTRY 147 abscesses of crowned teeth to learn whether the canals are properly filled. ( 2^') As an aid in differential diagnosis between chronic alveolar abscess and pyorrhea alveolaris. (26) To observe destruction of tissue , due to pyorrhea alveolaris. (2J) In cases of pericemental abscess. (28) In cases of persistent suppuration which does not yield to the usual treat- ment. (In fact in all cases that do not yield promptly to the usual course of treatment.) (29) To observe the course of a fistulous tract. (30) To observe the field of operation before and after apicoectomy. (31) To locate foreign bodies, such as a broach in the pulp canal or tissues at the apex of a tooth ; a piece of wooden toothpick in the peri- dental membrane, etc. (32) To determine the presence or absence of a bit of root imbedded in the gum tissue. (33)\ To diagnose fracture of a root. (34) To observe the size and shape of the roots of teeth to be used in crown and bridge work. (35) As an aid and safeguard when enlarging canals for posts. (36) To examine bridges about which there is an inflammation. (37) To observe the field before constructing a bridge. (38) To observe planted teeth. (39) In cases of cementoma. (40) In cases of bone "whorls." (41) To locate stones (calculi) in the salivary ducts or glands. (42) In cases of bone cysts. (43) In cases of dentigerous cysts. (44) In cases of tumor, benign or malignant. (45) To observe anomalous conditions, such as the fusion of the roots of two teeth for example. (46) To observe the location and extent of a necrotic or carious condition of bone. (47) To diagnose antral empyema. (48) To observe size, shape and location of the antrum as an aid in opening into it. (49) To locate foreign bodies, such as tooth roots or broaches, in the antrum. (50) To observe cases of luxation. (51) In cases of fracture of the jaw before and after reduction. (52) In cases of anky- losis of the temporo-mandibular articulation or the joint formed by the tooth in the jaw. (53) To observe the field of operation before and after resection of the mandible. (54) In all cases of facial neuralgia with an obscure etiology. (55) To observe the inferior dental canal. (56) In cases of Ludwig's angina. (57) In cases of insomnia, neurasthenia, insanity* and kindred nervous disorders. (58):- In cases of periodic headaches. (59 V 1 In cases of facial gesticulatory tic (spasmodic twitch- ing of a set of the facial muscles). (60) To allay the fears of a hypochondriac. (61) In cases where the patient cannot open the mouth wide enough for an ocular examination. (62) In research work to study osteology, the development of teeth, action of bismuth paste, bone production and destruction, changes occurring in the temporo-mandibular articulation when jumping the bite, blood supply to parts, resorption of *Dr. Upson — Cleveland. i 4 8 DENTAL RADIOGRAPHY teeth and the causes for it, etc. (63) As a record of work done. (64) In cases of hidden dental caries. It is with a mingled feeling of enthusiasm and misgiving that I now attempt to illustrate the above named uses of the radiograph. It is not reasonable to hope that half-tones will show all that can be seen in negatives. As a result, things may be mentioned in the text that cannot be observed in the half-tones ; but, be assured, all clinical factors mentioned in the text were observable in the original radiographs. Thanks to the help rendered by the many radiographers, whose names appear beneath the half-tones, and the practitioners, whose names are mentioned in the text. I will be able to illustrate almost all of the above enumerated uses. I have tried to make this collection of radio- graphs representative — that is, to have it represent the work of Ameri- cans in the field of dental radiography. In describing cases which have not come under direct personal ob- servation there is, of course, considerable liability to mistakes. I ask my readers to bear this in mind. It shall be my policy to print as few radiographs as possible to fully demonstrate the different uses. For example, I could print hundreds of different radiographs illustrating the use "in cases of delayed eruption to determine the presence or absence of the unerupted teeth." But only a few will be used, because that is all that is necessary to demonstrate the value of the radiograph in such cases, and to use more would be superfluous in a work of this kind. 1. In Gases of Delayed eruption to Determine the Presence or Absence of the Unerupted teeth. Upper, permanent laterals missing in the mouth Tig. 128. of a girl, eighteen years of age. Spaces between the centrals, and the centrals and cuspids. In this case the deformity seemed particularly distressing because, save for the spaces between her teeth, the young lady was positively beautiful. A radiograph (Fig. 128) was made and shows that the laterals are not impacted in the upper maxilla. It therefore became necessary to move the centrak together and construct a bridge. Had the laterals been present in the maxilla, and space made for them by moving the centrals together, they would probably have erupted into their places. Had they not erupted after space had been made for them the tissues covering them could have been dissected away, holes drilled into the teeth, little hooks cemented into these holes and the teeth elevated or- thodontically. THE USES OF THE RADIOGRAPH IN DENTISTRY 149 When there seems to be a congenital absence of fig. 129. a tooth from the jaw it is expedient — which is ex- pressing it mildly — to use the radiograph before constructing and setting a bridge. Failure to do this might result in what Fig. 128. Congenital absence of the upper lateral incisors. Age of patient, eighteen years- Fig. 129. Fig. 130. Fig. 129. Bridge from central to first bicuspid. Unerupted cuspid. The arrow points to a bit of tooth root. (Radiograph by Ream of Chicago.) Fig. 130. An upper cuspid in the place of the lateral. A temporary cuspid in the place which should be occupied by permanent cuspid. The lateral missing from the jaw. is shown in Fig. 129 — an unerupted cuspid covered with a bridge. Such a condition as this may or may not cause local inflammation, neuralgia, or any of a series of inflammatory and nerve disorders. In this case the bridge covers not only an unerupted cuspid, but also a bit of tooth root. In a case presented to me an upper permanent fig. 130. cuspid was seen occupying the place of the lateral incisor, and a temporary cuspid was in the space I^O DEXTAL RADIOGRAPHY Fig. 131. Fig. 132. Fig. 131. Congenital absence of the upper second bicuspid. Observe the orthodontia appliance in position. (Radiograph by Lewis of Chicago.) Fig. 132. Delayed eruption of an upper second bicuspid. The orthodontia appliance in position is being used to make space in the arch for the delayed tooth. (Radiograph by Lewis of Chicago.) \ bad! impacted ' d bicuspid, with no span- aj .'ill for it in the dental arch. (Radiograph by Pancoast of Philadelphia.) THE USES OF THE RADIOGRAPH IN DENTISTRY 151 which should have been occupied by the permanent cuspid. A radio- graph was made 1 Fig. 130) to locate the missing lateral. It was not present in the jaw. Though I am not absolutely sure of this, I never- theless feel quite certain that the permanent lateral was mistaken for a Fig. A. Odontoma in patient eight years old. (Radiograph by Schamberg, of New York.) temporary tooth and extracted when the patient was about seven or eight years old — a mistake which could not have happened had the dentist used radiographs. Fig. 131 proves the absence of a second bicus- Tigs. 131 and 132. pid and shows that bridgework must be resorted to, to fill the space. Fig. 132 discloses the presence of a second bicuspid and shows that it will not be necessary to make a bridge. As they appeared before radiographs were taken the cases, from which Figs. 131 and 132 were made, were similar. Fig. 133, a case of Dr. Oyer's, shows a Tig. 133. badly impacted lower second bicuspid with no space at all for it in the dental arch. i ;_' DENTAL RADIOGRAPHY With the exception of the third molars no teeth fig, i34, are so liable to be delayed in their eruption as the upper cuspids. For this reason, when making a radiograph to determine the presence or absence of an unerupted cuspid Fig. b. Same patient. n]<\ .,-ii. side of jaw. ( Radiograph 1 >y Sclianiberg, of New York.) or a third molar, 1 feel tolerably sure, before I make the picture, that the tooth will be found somewhere in the jaw. When the missing tooth is a central, lateral, bicuspid, or lower cuspid, I am in doubt as to what to expect. My experience teaches me that when these teeth are missing they are just as likely to be entirely absent from the jaw as present in it. and simply unerupted. So far, I have never seen either long delayed eruption or congenital absence of the first <>r second molars. Since the tir-t publication of the above. Dr. Ottolengui has reported two interesting cases (Items of Interest, February [9, [913), from which record I quote in part, as follows: THE US US OF THE RADIOGRAPH IN DENTISTRY [53 "Very shortly after Dr. Raper had published the missing quoted statement, that up to that time he had not first molar. seen a case wherein first or second molars were con- genially absent, a little girl patient of mine came in for her periodical examination, and I noted that since her previous visit Fig. c. Patient aged 13. Right side. Two upper and one lower molar absent. Geo. M. McKee, of New York.) (Radiograph by she had erupted three first permanent molars, but the fourth had not appeared. I immediately began to wonder whether or not 1 was about to discover an authentic case of congenital absence of a first molar. I say authentic, because in records of this kind it is not always that one may be sure that the history is authentic. But in this particular case there can be no doubt. The child was the sister of another girl in my care and had been under my observation since she was four years of age. I have casts of her mouth at the age of five, which show the primary denture complete. I may add also that there never had nor has been any caries, and consequently there was no possibility that a molar had been extracted, a suspicion always warranted when we find a first molar absent from the 154 DEXTAL KADlOCR.ll'IIY mouth of an adult. An ordinary small mouth radiograph was made, and while it did not disclose the shadow of a molar, neither did it satisfac- torily show what really existed. I therefore determined to have a large radiograph made, so that we might have a picture of the entire bone. Fig. D. atient. Left side. Same molars absent. (Radiograph by McKce, of New York.) "The patient was sent to Dr. M. I. Schamberg. who made radiographs of both sides of the mandible, that we might compare them. The radio- giaphs are reproduced in bigs. A and 15. My surprise may be imagined when I found that in the region which should have been occupied by the second bicuspid and the first molar, there was a well-defined com- posite odontoma. And perhaps even more astonishing is the position of the molar lying distally of the tumor. Whether this tooth, which is seen lying horizontally in the bone, is the first molar or the second molar, is a question that has been raised by an orthodontist of national reputa- tion, a man of keen judgmenl and well informed as to tooth forms. While 1 am willing to admit that this looks more like a first than a second molar ially when we compare with the normal side (Fig- B), still THE USES OF THE RADIOGRAPH IN DENTISTRY 155 I very much doubt that it is the first molar. The odontoma is more apt to be a composite of the bicuspid and first molar. But in any event, interesting as this case is. it cannot be entered in the literature as a record of congenital absence of a first permanent molar, because that tooth is either in the bone or else is included in the odontoma, whereas by "con- genital absence" I understand to be meant complete non-existence. "The second case which I am permitted to report Itlissing is from the practice of Dr. Thaddeus P. Hyat, and Second molars, is in the hands also of Dr. George B. Palmer for orthodontic treatment. The patient is a boy of fourteen, and we are assured that no permanent teeth have been ex- tracted, yet no less than thirteen permanent teeth are missing. In the upper jaw the absent teeth are: both lateral incisors, three bicuspids, both second molars and both third molars, a total of nine teeth (note that both upper laterals are absent, while both upper cuspids are pres- ent). In the lower jaw the following teeth are absent: the first bicuspid and the third molar on the right side and the second bicuspid and the third molar on the left side. "Figs. C and D are radiographs of the two sides of the head. In the upper the first molars are easily distinguished, but there are no evidences of the second and third molars. In the mandible the third molars are absent, but the other four molars are present, though in one case the crown has been lost by caries. Considering 4he boy's age, this seems to be an authentic record of congenital absence of two second upper molars, and of all four third molars, as the extraction of any of these teeth could not have been forgotten. "Dr. Hyat has kindly asked another patient of missing first ms to ca ^ a * m y °^ ce tna t: I might examine a very Second and similar case. In this instance the patient is a woman third molars. about thirty-five years of age. She is a highly cultured person engaged in the editorial department of one of our leading magazines. She is quite positive that the only tooth she ever had extracted was one lower first molar. If this be true she has fourteen teeth congenitally absent as follows : In the upper jaw the missing teeth are the two lateral incisors, the first, second and third molars on the left side, and the second and third molars on the right side. In the lower jaw the missing teeth are the second bicuspid and all three molars on the right side, and both bicuspids and the third molar on the left side. Again we have the upper laterals missing, and the upper cuspids present. r 5 6 DENTAL RADIOGRAPHY "In this mouth we have the strange anomaly of three molars missing from the upper jaw on the right side, and three molars missing from the lower jaw on the left side. Enumerated in full the absent molars were all four of the third molars, three of the second molars and two of tlu* first molars." Fig. 134 is representative of a class of delayed eruption that is most common. I could print as many as forty or more radiographs of such cases. Fig. 123 was a beautiful example. The age of the patient Fig 134. Age of patient, fourteen. An unerupted malposed cuspid. No room for it in the dental arch. Obser\e the tipping of the lateral, which is probably due to the pressure of the cuspid against the apex of its root. in this particular case (Fig. 134) was some months over fourteen. The radiograph was made for an orthodontist who was just beginning treat- ment of the case. There was no evidence of the presence of the cuspid and no room for it to erupt. When the arch was broadened and space made for it the cuspid erupted. It required some mechanical guidance to make it come into its exactly proper position. The mere making of space for them in the arch will usually result in the eruption of unerupted teeth, unless they are badly malposed. If, after space is made, the tooth does not move, the gum and process over it should be slit surgically. If this does not suffice to induce eruption, the soft parts and process must be cut away, and sometimes it may be necessary to resort to the use of orthodontia appliances to assist erup- tion, as formerly suggested. THE USES OE THE RADIOGRAPH IN DENTISTRY 157 2. Tn Cases Where Deciduous teeth are Retained Cong After the time When they Should fiave Been Shed, to Cearn if the Succedaneous teeth be Present. Case — Girl, age seventeen, large cavity in fig. 135. upper, second, deciduous molar. Whether to fill this tooth or extract it depended on whether there was a second bicuspid to take its place in case of extraction. It was not at all loosened and there was no visible evidence of the presence of the suc- Fig. 135. Fig. 136. Fig. 135. Age of patient, seventeen. Retained upper, second, temporary molar. The radiograph shows that the second bicuspid is present in the jaw. Fig. 136. Age of patient, twenty-one. Retained lower, second, temporary molar with a large cavity in the crown of the tooth and the roots almost entirely resorbed, despite the fact that there is no oncoming second rTicuspid. ceeding bicuspid. Fig. 135, however, shows the bicuspid to be present. The half-tone may not do so, but the negative now before me has per- spective enough for me to see that the bicuspid is being deflected toward the lingual. The deciduous tooth was extracted and the bicuspid erupted promptly. Case — young man, age twenty-one, lower, sec- Tig. 136. ond, deciduous molar with pulp exposed. Question : Should the tooth be treated, filled and retained in the mouth, or extracted to make room for the second bicuspid? Fig. 136 demonstrates the futility of attempting to treat the tooth — its roots are almost entirely resorbed despite the fact that there is no succedaneous tooth in the jaw — and shows also that there is no bicuspid to take its place. Extraction and bridgework are indicated. Fig. 137 shows two retained temporary up- Tifl. 137. P er cuspids with the permanent cuspids impacted and malposed. 158 DENTAL RADIOGRAPHY Fig. 138 shows two retained, primary, lower Tig. 13$. central incisors with no sign of the permanent cen- trals. Age of patient, seventeen. Case — a young man, age twenty-two; with a Tigs. 139 and 140. retained, temporary, lower, second molar. The tem- porary tooth was too short to reach its antagonists in occlusion. For this reason the patient, a dental student, wished to have it crowned. Before making the crown, a radiograph was taken (Fig. Fig. 137. Fig. 138. Fig. 187. Two retained temporary cuspids, with the permanent cuspids impacted and malposed. (Radiograph by Lewis, of Chicago.) Fig. 138. Two retained temporary, lower, central incisors. No permanent centrals present. Age of patient, seventeen. (Radiograph by Blum, of New York City.) [39) after the development of which it was seen that the making of a crown was not indicated. From the appearance of the radiograph one might suppose that the temporary tooth was loose — its roots being almost entirely resorbed. But such was not the case. Fig, 140 is a radiograph of the same case one month after the extraction of the temporary molar. Notice how rapidly the bicuspid is erupting into its place. The force of eruption, which had been held in abeyance for about eleven years, became promptly active upon removal of the abating object. Case — young man, age twenty-one. A retained, Tigs. 141 and 142. temporary, upper cuspid with no observable sign of the sun cdancous cuspid. A radiograph was made (Fig. 141 ), but, being a poor one, it failed to show the looked-for tooth. Yet from the reading of this radiograph I was able to state with a mod- erate degree of certainty that the cuspid was present in the jaw. If the THE USES OF THE RADIOGRAPH IN DENTISTRY 159 tooth itself cannot be seen, what is there in the picture to lead one to believe that the permanent cuspid is present? The arrow points to the upper end of a dark line. The dark line represents dense bone and such a line almost always is to be noted in radiographs of impacted teeth. Fig. 139. Fig. 140. Fig. 139. Retained temporary, lower, second molar, with the succedaneous tooth beneath it. Age of patient, twenty-two. The dark spots in the temporary tooth and two permanent molars are metal fillings. All of the mesial root and some of the distal root of the temporary tooth resorbed. Fig. 140. The same as Fig. 139 one month after extraction of the temporary tooth. Observe how rapidly the bicuspid is erupting. When this picture was made it could be seen in the mouth. Fig. 141. Fig. 142. Fig. 141. Age of patient, twenty-one. A retained temporary upper cuspid. The arrow points to a dark line following along the side of the impacted cuspid. The impacted tooth itself cannot be seen. Fig. 142. The same as Fig. 141, but taken at a different angle and showing the permanent cuspid. To verify or disprove my deductions another radiograph was made (Fig. 142), which shows the impacted cuspid clearly. The question arises naturally. What operative procedure should be 160 DENTAL RADIOGRAPHY resorted to in such cases as the one just described? Had the patient been younger, or had the root of the temporary cuspid been much resorbed, or had the pressure of the impacted tooth been causing resorption of the permanent lateral root, or central root, or had the patient been suf- fering from neuralgia, periodic headaches, or any nervous disorder — had any of these conditions existed the temporary tooth should have been extracted immediately, space made in the arch for the permanent tooth and such orthodontic assistance given as might prove necessary to cause it (the permanent cuspid) to erupt into its proper place. As none of Fig 143. The roots of a lower, first, permanent molar not quite fully funned. Age of patient, eight years and four months. Only the crowns of the second bicuspid and second molar are formed. these conditions did exist, and as the patient expressed a definite disin- clination to have anything done unless absolutely and imperatively neces- sary, the case was dismissed with the understanding that the condition should be kept under rigid observation. The man may go through life without trouble, or inside of a year he may be suffering almost any nervous disorder from simple neuralgia to insanity* ; or he may lose the temporary cuspid as a result of the resorption of its roots, or he may even lose the lateral or central as a result of absorption of their roots, or suppuration may occur. 3. Co Cearn if the Roots of Children's Ceetb arc fully formed. Case — patient, eight years and four months old. Til. 143. A large "cavity in a lower first, permanent molar. To remove absolutely all of the decalcified dentin meant extensive exposure of the pulp, and, therefore, pulp devitaliza- tion, extirpation and canal filling. But should we practice pulp devitali- zation in such a case? If the roots of the tooth are fully formed, yes; •Dr. Upson THE USES OF THE RADIOGRAPH IN DENTISTRY 161 if the roots are not fully formed, no. A radiograph (Fig. 143) was made and shows that the roots of the tooth are not quite fully formed. Accordingly exposure of the pulp was avoided, the unremoved, decalcified dentin painted with silver nitrate, a paste of zinc oxide and oil of cloves placed in the bottom of the cavity and the tooth filled with cement, the object of this treatment being to conserve the pulp in the tooth at least until the roots are fully formed. Often a child meets with some accident which breaks off the angle of a central or lateral incisor. To restore the angle sometimes necessi- Fig 144. Post-collar crown on a temporary cuspid root. The permanent cuspid erupted down to the post of the crown. The dark shadows in the region of the temporary cuspid crown are numbers used to mark the negative. (Radiograph by Kells, of New Orleans.) tates the removal of the pulp and the placing of a post in the canal. The question should always be raised, "is the tooth's root fully formed?" If it is, we may proceed with the devitalization, but if not, some tem- porary restoration should be made and the pulp conserved until it has fulfilled its function of root development. Whether the root is fully formed or not can be determined only by the use of the X-rays. In a child's mouth we occasionally find an anterior tooth so badly decayed that crowning is indicated. Again we are confronted with the question, "is the root fully formed?" And whether we should devitalize and crown the tooth or keep it patched with cement for a year or so depends entirely upon the answer which the radiograph may make to this question. 4. to Determine UPbetber a tooth be One of the Primary or Secondary Set. What treatment we give a tooth depends very largely on whether it be of the permanent or deciduous set. If a man knows his dental anatomy as well as he should it is usually easy for him to determine whether a tooth be a primary or secondary one. Occasionally, how- ever, we find a tooth (usually an upper lateral incisor) that looks as ]'._> DENTAL RADIOGRAPHY much like a member of one set as the other and the radiograph must be used to arrive at a definite conclusion. To mistake a permanent tooth for a deciduous one and extract it (Fig. 130) is an inexcusable and dis- astrous blunder. Sometimes a tooth is so badly decayed (the crown may be entirely destroyed) that it is impossible to determine by simple ocular observa- tion whether it be a temporary or a permanent one. The radiograph can be used to great advantage in such cases. If the carious tooth be one of the temporary set, with the succedaneous tooth ready to take its place, it should be extracted. If the carious tooth be a permanent one s the radiograph shows the size and condition of its roots. Case — a post-collar cuspid crown became loose. Tig. 144. A radiograph (Fig. 144) was made and shows that the crown is placed on a temporary cuspid root. Part of the root of the temporary tooth is resorbed and the permanent cuspid has erupted down to the end of the post of the crown. The very dark shadows in the region of the temporary cuspid crown are caused by lead numbers placed against the film packet to mark the negative. 5. to Determine Ulben to extract temporary teeth. The best rule ever formulated for the extrac- f jg. 145. tion of deciduous teeth reads, "Extract a deciduous tooth only when its successor is ready to take its place." There are many cases where the operator is able to detect the presence of the succedaneous teeth by ocular and digital examination. In about as many cases, however, the only way to determine the presence of such teeth is by the use of the radiograph. Thus the rule just quoted is one which, when followed, necessitates the use of the radiograph. Fig. 145 is of a case where extraction of the temporary first molar is indicated, and extraction of the temporary second molar is contraindicated. The temporary second molar should not be removed for a year or so — not until the second bicuspid is just ready to take its place. Often in practice we are confronted with abscessed temporary teeth. The age of the patient is such that we cannot decide whether the tieeth are loose as a result of the abscessed condition, or because of resorption of the roots and the presence of the succedaneous teeth. A radiograph of the case will enable us to decide, and our treatment will be governed accordingly. Not only will the radiograph show the operator when de- ciduous teeth should be removed, but will aid him in their removal — especially in cases where the temporary teeth are badly decayed — by -bowing the exact size and location of the temporary teeth's roots and the position of the succedaneous teeth. THE USES OE THE RADIOGRAPH IN DENTISTRY 163 6. Co Show the Orthodontist Ulhen Re may move the Coming Permanent teeth by moving the Deciduous teeth. It impressed me very much when I first heard of radiographically observing, and then regulating, teeth before their eruption. I heard of this in a lecture by Dr. Ottolengui. I quote Dr. Ottolengui : "One of the difficult operations which confronts fig. 14&. the orthodontist at times is the bodily movement of the bicuspids buccally. Very often in the past at- Fig. 145. This picture shows that the temporary first molar should be extracted. The tem- porary second molar should not be extracted for a year or so, when the second bicuspid will be just ready to take its place. (Radiograph by Lewis, of Chicago.) tempts to widen the arch, after the eruption of the bicuspids, has resulted in tipping the crowns buccally, the apices of roots remaining in the orig- inal apical arch. Hence, one of the chief advantages of early orthodontic interference lies in the fact that the temporary molars may be moved buccally, carrying with them the underlying bicuspids, and this advantage is made more clear if it be recalled that at this period the bicuspid roots are but partly formed. Even when the roots of the temporary molars are already considerably absorbed, still enough may be left to serve to deflect the oncoming bicuspids in the direction desired. "This slide (Fig. 146), from the collection of Dr. Matthew Oyer (radiograph by Pancoast, of Philadelphia), shows nicely the usual rela- tion of the erupting bicuspids to their predecessors, the temporary molars. It will be noted that the apices of the bicuspids are still unformed, and it is clear that if these teeth can be led into proper positions during eruption r the formation of the apices afterward affords the most permanent 'reten- tion.' A casual glance at the upper temporary molars might create a doubt as to the probability of moving the unerupted bicuspids, but there is an easily overlooked factor, viz., the palatal roots of these molars do i&l DENTAL RADIOGRAPHY not show in radiographs of this region at this period, because they lie be- hind the crowns of the bicuspids ; that is to say 'behind,' in relation to the source of light, the X-ray tube." Fig. n<;, Radiograph made to show relation of temporary molar roots to advancing bicuspids. (Collection of Dr. Cryer. Radiograph by Pancoast, of Philadelphia.) 7. to Obscroe mooing teeth. Fig. 147 demonstrates the congenital absence of Tifl$- 147, 148 and 149. the upper lateral incisors. The orthodontic appliance, seen in the radiograph, is being used to draw the centrals together. It was highly important in this case that the teeth be THE USES OF THE RADIOGRAPH IN DENTISTRY 165 moved through the alveolar process en masse, and not tipped. The movement desired was one which would make the roots parallel when the crowns of the teeth came together, so that posts could be set in the canals of the central incisors, and a bridge made to restore the lost lat- erals. Fig. 148 was taken about a month after Fig. 147. It shows that the teeth had been moved together, but there was too much tipping of the Fig. 147. Fig. 148. Fig. 149. Fig. 147. Congenital absence of upper lateral incisors. The orthodontic appliance seen is being used to draw the central incisors together. Fig. 148. This radiograph was made one month after Fig. 147. It will be seen that there has been considerable movement of the teeth. The left central is tipped considerably. Fig. 149. Made one month after Fig. 148. The central incisors are together and their roots almost parallel. left incisor — not enough movement of the tooth at the apex of the root, compared to the movement of the crown. It, therefore, became necessary to modify the force which was being used. This was done, and Fig. 149 shows the teeth together and the roots almost parallel. A case in the practice of Dr. C. Edmund Kells, TiflS. ISO, 151 and 152. Jr., and reported by him in the May number of Items of Interest, 191 i. Fig. 150 shows a mal- posed permanent cuspid above the temporary cuspid, the root of which is somewhat resorbed. Age of patient, eleven years. Fig. 151 was made one year and seven months after Fig. 150. "Compare this pic- ture with Fig. 150, and it will be seen that the permanent cuspid has migrated in a line with its long axis," causing resorption of the perma- nent lateral root. The temporary cuspid was extracted, but the perma- nent tooth did not erupt into its position in the arch. It was, therefore, concluded that the tooth "would have to be brought down by some mechanical means." Accordingly, the gum tissue and overlving process were "slit down to the cuspid and then gently spread apart, and the 1 66 DENTAL RADIOGRAPHY cuspid was exposed to view." A piece of iridio-platinmn wire was then shaped, as shown in Fig. 152, and the hook was worked supposedly under the mesial prominence of the cuspid, and a rubber ring attached to the loop on the other end, and secured to a lug on the molar band, all as shown in Fig. 152. which is a skiagraph of the case with the appliance Fig. 150. Fig. 151. Fig. 150. Malposed, permanent cuspid above the temporary cuspid, the root of the latter somewhat resc-bed. Fig. 1"il. Same as Fig. 150 one year and seven months latT. Observe that the cuspid has migrated in the line of its long axis. The permanent lateral root is badly resorbed. Pig, 152. Same as I igs. 150 an. I ] :. l after removal of the temporary cuspid. The wire hooked the cusp of the tootb was thought to be placed over the mesial prominence until the radiograph was made. in position. Imagine my surprise to find by this picture that the hook nol anywhere near where I had thought I put it. [nstead <>f being well up under the medal prominence, it was merely caught under the point of tin- tooth, and, «>f course, it slipped off shortly after the patient left the office. Upon her return a hook -\x of an inch longer was fitted in place, and this time, with a radiograph as a guide, there was no mis- take about its placement. The appliance was worn for several weeks, at THE I'SES OF THE RADIOGRAPH IN DENTISTRY 167 the end of which time the point of the cuspid having been brought to the surface of the gum, it was removed and the tooth allowed to erupt by its own volition. Despite the great destruction of its root the lateral re- mains firm and apparently healthy. Tig. is3. 8. Tn Cases of Supernumerary Ceetb. A case in the practice of Dr. B. S. Partridge, Chicago. Patient's age, twelve years. The teeth were being regulated, and the radiograph. Fig. 151, Fig. 153. . Fig. 154. Fig. 153. A and B, supernumerary tooth bodies. C, the crown of the temporary cuspid. D, the permanent cuspid. (Radiograph by Lewis, of Chicago.) Fig. 154. A and B are supernumerary teeth. (Radiograph by Lewis, of Chicago.) was taken to determine the presence or absence of the permanent lower cuspid. A little supernumerary tooth (A) could be seen in the mouth occupying a part of the space which should have been occupied by the permanent cuspid. The two shadows marked "B" are two more super- numerary tooth bodies. The larger shadow marked "C" is the crown of the temporary cuspid, which had never erupted. The large shadow to the left, marked "D," is the permanent cuspid pressing against the side of the lateral at the apex of its root. The three supernumerary bodies and the crown of the temporary cuspid (the root was resorbed) were removed, allowing the permanent cuspid to erupt. Just lingually to each central incisor is a super- Tig. 154. numerary tooth. One (A) could be seen in the mouth, but there was no evidence of the other. Neither central nor lateral incisor roots are as yet fully formed, and the 108 DENTAL RADIOGRAPHY laterals have not yet erupted. Indeed, before the picture was made, it seemed that a peg-shaped lateral was erupting just lingually to the cen- tral. The radiograph shows this tooth to be supernumerary. Dr. T. W. Brophv. of Chicago, reports a case of insistent suppura- tion due to an impacted supernumerary tooth, which was found by the use of the radiograph. Dr. Brophv calls attention to the fact that a cor- rect and definite diagnosis could not have been made by any means at our command except the X-rays. The case recovered promptly upon removal of the supernumerary tooth. I regret that I have been unable to obtain radiographs of this case. Tig. 155. An impacted upper fourth molar. Fig. 155. Fig. 156. Fig. 155. An impacted upper fourth molar. Fig. 150. A supernumerary tooth in the canal of a cuspid tooth. (Radiograph by Clarence Van Woert, of New York City.) To me this is a most remarkable case — a super- Tig. 156. numerary tooth in the canal of a cuspid tooth — a tooth inside of a tooth. The supernumerary tooth has a root canal, and the crown is covered with enamel. There is no doubt of the fact stated, because Dr. Van Woert, after radiographing the case, drilled into the permanent cuspid and found the enamel-covered supernumerary within. The radiograph is not as good as I wish it were. The upper two-thirds of the roots of the teeth shows fairly well but tbere is a confusion of shadows in the lower third and m the crown. 9. Tn eases of Impacted teeth as an Aid in extraction. Impacted, lower, third molar tipped to the Tig. 157. mesial. The picture shows that in this case a knife- edge stone in the dental engine could he used to ad- vantage, rutting away the mesio-OCClusal portion of the third molar, and THE USES OF THE RADIOGRAPH IN DENTISTRY 169 so greatly facilitating the removal of the tooth. Observe the absorption of the distal surface of the second molar (the light area), due to pressure against it; and the large abscessed cavity (light area) between the sec- ond and third molars, extending down to the apex of the second molar. This radiograph is of particular interest, because it shows so clearly an abscess caused by impaction. That the pressure of an impacted tooth may Tigs. 158 and 159. cau?e a b SO rption of the tooth against which the pressure is brought to bear, is further illustrated in Figs. 158 and 159. Fig. 157. Fig. 158. Fig. 157. An impacted lower third molar. The light area between the second and third molars represents a destruction of bony tissue, arrow A. Arrow B points to a light area, which repre- sents the absorption of the second molar. (Radiograph by Blum, of New York City.) Fig. 158. An impacted upper third molar. The arrow points to a light area representing absorption of the upper second molar. Notice the very poor filling encroaching on the pulp of the first molar and filling the interproximal space between the first and second molar. (Radio- graph by Ream, of Chicago.) In Fig. 158 the arrow points to a light area representing absorption of the upper second molar, due to the pressure of the third molar against it. A study of this radiograph gives the dental surgeon a good idea of how he should apply his force in extraction. Fig. 159 is a case of Dr. Oyer's. I quote Dr. Oyer: Fig. 159 "shows an impacted, lower, third molar resting against the posterior root of the second molar. It will be seen that the root of the second molar is much absorbed, which caused considerable trouble. Removal of the sec- ond molar gave relief to the patient. . . . The upper third molar is in an awkward position." Figs. 160 and 161 show impacted upper third TlflS. 160 and 161. molars. The value of these radiographs to the ope- rator, about to extract, is apparent. This radiograph (Fig. 162) shows the surgeon fig. |^2. just how much bone must be dissected away before the malposed tooth can be removed. Patients seldom lyo DENTAL RADIOGRAPHY know that the removal of a tooth is not always a simple operation. They are therefore inclined to blame the operator if the tooth is not quickly removed, instead of crediting him with working dexterously on a difficult operation. They are likewise unwilling to pay a fee in proportion to the ■ 1 uppei and lower third molar. Absorption of the distal root of the lower second molar. (Radiograph by I'ancoast, of Philadelphia.) difficult) "i the operation, as compared t<> other operations. The removal oT the third molar, shown in Fig. 162, is a more difficult operation than t lie removal of a vermiform appendix. By showing patients radiographs of such cases the dentist will gain their earnest, intelligent co-operation. They will know just what is done for them, and for the first time in their THE USES OF THE RADIOGRAPH IN DENTISTRY 171 lives they will understand that the extraction of a tooth may be a serious, difficult and expensive operation. The following report of this case is by Dr. F. K. Tig. 163. Ream, of Chicago. "Patient's age, seventy-two years. Symptoms: Swelling near symphysis thought to be the result of wearing an artificial denture. Considerable pain. Diagnosed Fig. 160. Fig. 161. Fig. 160. Impacted upper third molar. (Radiograph by Lewis, of Chicago.) Fig. 161. Impacted upper third molar. Notice the difference in the position of the impacted tooth shown in this case and in Fig. 160. (Radiograph by Blum, of New York City.) Fig. 162. Fig. 163. Fig. 162. Impacted lower third molar with its occlusal surface presenting mesially. The radiograph shows the dental surgeon how much bone must be burred away before the tooth can be removed. (Radiograph by Ream, of Chicago.) Fig. 163. Impacted bicuspid in an otherwise edentulous mouth. Age of patient, 72 years. (Radiograph by Ream, of Chicago.) cancerous by surgeons, and patient advised to go to the hospital for opera- tion. The radiograph (Fig. 163) shows an impacted bicuspid in the otherwise edentulous jaw. Operation : Alveolar process burred away and tooth removed. Result: Immediate and complete recovery." I--' DENTAL RADIOGRAPHY tig. 104 is a case of Dr. Oyer's. I quote Dr. Tig. it>4. Cryer: Fig. 1(4 "shows a lower third molar passing under the second molar and becoming lodged be- tween the first and second molar, the crown of the third molar pushing against the root of the first molar. The first molar was extracted, which cleared up the neuralgia, and the third molar pushed up into the place 1 'f the first molar." Fig. 104. Lower third molar lodged between the first and second molars. (Radiograph by Pancoast, of Philadelphia.) Fig. 165 is also a case of Dr. Oyer's. The fig. its. radiograph shows an impacted upper third molar, with the occlusal surface presenting upwards. Dr. Oyer's remarks concerning this case are interesting. I quote Dr. Cryer: [65 "shows the occluding surface of the upper third molar pointing upward towards the posterior portion of the orbit. The patient had been suffering from disturbance of the eye for a long time. Considerable improvement took place in the eye soon after extraction of the inverted tooth." 10. Co Determine the number of Canals in Some teeth. It will be noticed thai I say "to determine the number of canals in tome teeth." Of course, it i> not necessary to use the radiograph each THE USES OF THE RADIOGRAPH IN DENTISTRY 173 time we open into a tooth to learn how many canals that tooth may have. But occasionally I do find it necessary or expedient to use the radiograph to verify or disprove the existence of some unusual condition suspected. Fig. i«; Impacted upper third molar with the occlusal surface pointing upward. (Radiograph by Pancoast, of Philadelphia.) Case : An upper first molar in which but one Tifl. 166. small canal could be found. After searching for the other two canals for a few minutes, the one canal was filled with gutta-percha, and a radiograph made (Fig. 166) ; this shows that the tooth had but one canal. In this case the radiograph saved considerable work and worry on the part of the operator. I have known second and third molars to have only one canal, but this is the only case I have ever encountered in which a first molar had but one canal. This case was in the hands of one of the most Tig. 167. expert operators in Indianapolis. The lower first bicuspid had been devitalized, and the pulp removed, 174 DENTAL RADIOGRAPHY but the tooth remained sore. Radiography was resorted to to learn, if possible, the cause of the persistent pericementitis. A piece of ligature wire, such as is used by orthodontists, was placed in the canal and radio- graph Fig. 167 made. The wire follows the enlarged canal. But this particular tooth happens to have two canals. The unopened canal is seen to the distal of the wire. If a man, having the skill of the operator who handled this case, misses a canal, as this man did, then I firmly believe that the mistake is one that anv man, however skillful, is liable to make. Fig. 166. Fig. 167. Fig. 1GG. Upper first molar with but one canal which is filled. Fig. 1G7. The dark streak in the first bicuspid is a wire passing into the canal. This tooth has another canal, which can be seen as a light streak distal! j' to the wire. The more or less oval dark spot at the neck of the first bicuspid is a buccal cervical filling. The cavity in the crown of the tooth is stopped up with gutta-percha. Let me say here that a lower bicuspid, or cuspid with two canals, is not such an unusual occurrence, as it is generally believed to be. Men have shown me such teeth, and spoken of them as though they were rare anomalies. As a teacher of operative technic, I devote a part of my time to the dissection of teeth. In this work I handle thousands of disasso- ciated human teeth. In my work of last year, for example, I estimate that I observed six to eight thousand teeth. And among these I noticed not less than seven lower cuspids and five lower bicuspids with two canals each. Without printing the radiograph, which is not a very good one, I quote the legend which appears beneath it in the last edition of Buckley's "Modern Dental Materia Medica, Pharmacology and Therapeutics." "In this case the author desires to insert a bridge. On opening into the third molar an. The skiagraph not only shows the involvemenl of both teethi but also that the roots are properly filled. The treatment here is purely surgical, and means the curettement of the affected area." Had the radiograph not been used the operator would, in all probability, have made the laborious and foolish mistake of removing the crowns on the assumption that tlie canals were not properly filled. THE USES OF THE RADIOGRAPH IN DENTISTRY 193 25. Hs an Hid in Differential Diagnosis Between Chronic Alveolar Abscess and Pyorrhea Alveolaris. When a chronic alveolar abscess discharges about the neck of a tooth the case so closely simulates calcic pyorrhea alveolaris that, without using the radiograph or opening into the affected tooth, the operator cannot make a definite diagnosis. Fig. 203 Fig. 204 Fig. 203. Absorption of the bone around the molar due to pyorrhea alveolaris. The tooth ha* no bony attachment at all. (Radiograph by Ream, of Chicago.) Fig. 204. Absorption of the bony tissue due to pyorrhea alveolaris. The distortion (elongation) enables us to observe clearly little spiculae of diseased bone. The central has no bony attachment, except at the extreme apex. This is a case from the practice of Dr. M. L. Tig. 201. Rhein, of New York City. Dr. Rhein says: "This is a typical example of a chronic alveolar abscess, which for years had been erroneously treated for pyorrhea." Fig. 202 represents another case from the Tig. 202. practice of Dr. Rhein, which had been wrongly diagnosticated as pyorrhea. The lateral incisor was supposed to be affected by pyorrhea, but after making a radiograph. Fig. 202 it was seen that the real trouble was an apical abscess, the infection arising from the death of the pulp. 26. Co Observe Destruction of tissue Due to Pyorrhea Alveolaris. Other factors being equal, our chances of curing Tig. 203. pyorrhea alveolaris vary inversely according to the amount of destruction of alveolar process surround- ing the affected teeth. Fig. 203 demonstrates the futility of treating and attempting to conserve the molar tooth. All of the bone immediately surrounding the tooth is destroyed. 194 DENTAL RADIOGRAPHY A central incisor affected with pyorrhea. The fig. 204. tooth has no bony attachment except at its extreme apex. Extraction is indicated. The distortion — the elongation — in this picture enables us to observe the diseased bone to the Fig. 205 Fig 200 Fig. 205. The distal root of the first molar has practically no bony attachment and is badly roughened. It was extracted. The arrow points to an absorbed notch in the distal root. . . '.. The arrow points to bit of calculus on t lie distal of a second bicuspid. The lighl area above the calculus denotes the destruction of bone and represents a pyorrhea pocket. left of the central unusually well. In the negative now before me I can see clearly the soft tissue between the centrals. Looking to the mesial and distal, I can distinguish also the enamel of the central. The lingual enamel in the incisal region has been worn away ; hence the lighter shadow of the tooth in this region. A lower first molar affected with pyorrhea. Tig. 20S. The distal root appears roughened, due to a necrotic condition of its surface and the presence of calculus on it. It has no attachment to bone except at its extreme apex. The alveolar process to the mesial of the mesial root is comparatively healthy. The tissues to the distal of the mesial root are not as healthy as those to - the mesial, but not so badly diseased that they cannot regain a healthy vitality. The treatment of this case should be begun with extraction of the distal root. This was done, and the mesial root successfully con- served. A pyorrhea pocket on the distal of an upper Tifl. 20t>. second bicuspid. There is but slight destruction of bone. The most remarkable thing about this picture is that it shows a bit of calculus on the distal of the second bicuspid. THE USES OF THE RADIOGRAPH IN DENTISTRY 195 27. Tn Cases of Pericemental Abscess. "Pericemental abscesses have been described by numerous writers, one of the best papers on the subject being that by Dr. E. C. Kirk, published in the Dental Cosmos for November, 1900. There are various views as to the etiology of this condition, but the main point of interest lies in the fact that pericemental abscess occurs on the root of a tooth in which the Fig. 207 Fig. 208 Fig. 207. Pericemental abscess at apex of upper cuspid. The crowned first bicuspid was sus- pected, but the radiograph shows an abscess at apex of the cuspid, which was sound and alive. Fig. 208. The light area to which the arrow points is a pericemental abscess. pulp is still alive, a fact which renders a true diagnosis sometimes quite complex. For example, a patient might present with a well defined fis- tula appearing between the roots of two teeth, one of which may be perfectly sound, whereas the other might be just as certainly pulpless. It would be quite reasonable for the operator to conclude that an abscess originated from infection coming from the root of the pulpless tooth, and to treat such a tooth, it might be necessary to remove important and well constructed work, such as an inlay or a bridge abutment. A radiograph, however, will disclose that the abscess involves the pericementum of the living tooth, and thus the dentist would be saved the mortification of un- necessarily destroying the inlay or abutment attached to the pulpless tooth, and the patient would be saved the annoyance and expense involved in such a misconstruction of symptoms. "From the practice of Dr. M. L. Rhein is a case Tifl. 207. °f tn is character. The bicuspid is crowned and might have been suspected as the cause of the ab- scess, especially as in the radiograph only one root canal filling is seen, but the history of the case made this impossible. The tooth was treated i,,.. DENTAL RADIOGRAPHY twelve years ago for an abscess, and both canals were perfectly filled, as can be seen in other radiographs of the case in the possession of Dr. Rhein. these radiographs being taken at a slightly different angle. The tooth having remained perfectly comfortable during all of these years. the well defined abscess disclosed at the apex of the cuspid tooth was diagnosed as a pericemental abscess. The tooth in question was abso- lutely sound, having no tilling or cavity of any kind, and when opened the pulp was found to be alive. Also there was no taint of pyorrhea in this mouth. This diagnosis was confirmed by the fact that the removal of the pulp from the cuspid and subsequent treatment through the canal effected a perfect cure.*" Case : A sinus discharging near the apex of an Tig. 20$. upper cuspid. The cuspid had no carious cavity in its crown, and responded to the cold test. A radio- graph i Fig. 208) was made and shows a pericemental abscess on the distal side near the apex of the cuspid, but not involving the apex, and hence was not involving the pulp. It would have been a mistake to remove the pulp from the cuspid because it was not involved. An incision was made through the external alveolar plate, the pus sinus was thoroughly curetted and then filled with bismuth paste. The result was a prompt and complete cure. Buckley, in his last edition of his Modern Dental Materia Mediea, Pharmacology and Therapeutics, prints a radiograph similar to Fig. 208. Before the radiograph was used, in the case reported by Dr. Buckley, the pericemental abscess was diagnosed as an alveolar abscess, due to a dead pulp. The tooth thought to contain a dead pulp was opened, and a vital pulp found. The operators who handled the case experienced a great deal of difficulty in removing the pulp, nitrous oxygen anesthesia being re- sorted to finally to accomplish it. After removal of the pulp "the tooth (a central incisor) became dark blue in color." In concluding the report of this case, Dr. Buckley says: "The patient in this instance was a lady. and when we recall that the tooth involved was an anterior one. the »f the mistaken diagnosis becomes all the more apparent." Compared to die occurrence of alveolar abscesses, as caused by in- fection from dead pulps, pericemental abscesses are rare. 2$. Tn eases of Persistent Suppuration Which Do not Yield to the Usual treatment. Case: Girl eighteen years old. had had a lower j\q 209. '""1 molar extracted two months previous to the time when she presented to me for treatment. The socket from which the second molar had been extracted was an open Dr. R. Ottolengui. THE USES OF THE RADIOGRAPH IN DENTISTRY 197 suppurating sure. The patient was poor, and, wishing to spare her the expense of having a radiograph made, a diagnosis was made to the best of my ability by other means — by symptoms and instrumental examina- tion. The diagnosis was infection by some particularly virulent pyo- genic organisms and a slight caries of the bone. I was unable to locate any unremoved piece of tooth root. The socket was vigorously curetted and cauterized with phenolsulphonic acid, a mouth-wash prescribed, and the patient instructed to return in three days. When next seen there was Fig, 809 Fig. 210 Fig. 209. An unerupted third molar which caused sufficient irritation to sustain a suppurating wound from where a second molar was extracted. Fig. 210. A case of persistent suppuration of several years' standing. The radiograph shows the cause — an impacted, malposed upper cuspid. (Radiograph by Lewis, of Chicago.) but slight improvement in the objective symptoms, and the patient re- ported that there had been no abatement in pain and soreness. The lesion was washed thoroughly with an antiseptic solution, and the patient in- structed to return in three days. When seen again there was no improve- ment over what had existed before the operation. Wishing to get a more complete and reliable history of the case, I consulted with the patient's physician. He had treated the oral lesion before the case came to me, and was of the opinion that it was tubercular. He suggested the tuber- culin treatment. A radiograph (Fig. 209) was made to make sure that there was not a piece of the second molar still in the jaw. As can be seen, there is no piece of tooth root present, but what we do see is an erupting third molar. Perhaps I should have thought of the third molar as a cause for the trouble. But I did not until the radiograph was before me. Believing this tooth, in its effort to erupt, to be responsible for a slight irritation and the consequent suppuration, the soft tissues and the 198 DEXTAL RADIOGRAPHY bone covering it were dissected away. The result was immediate im- provement. I regret that I cannot definitely report a complete recovery, but I am sure it occurred. The patient left the city about a week after the last operation, and I have not seen nor heard from her since. I have already referred to a case of persistent fig. 210. suppuration, reported by Dr. T. W. Brophy, which did not yield to treatment until a radiograph dis- closed the presence of a supernumerary tooth, and it was removed. In answer to a letter of mine, asking for a radiograph of the case, Dr. Brophy Fig. 211 Fig. 212 Fig. 211. Abscess at the apex of the shell-crowned, second bicuspid. It is very difficult to observe either the abscess or the unfilled canal in the bicuspid in the print, though both show clearly in the negative. The arrow A points to the abscess at the apex of the tooth. The arrow B points to an abscess on the side of the root, caused by the ill-fitting shell-crown. Fig. 212. Same case as Fig. 211. The dark shadow is bismuth paste. It passes from the apex of the upper second bicuspid downward and towards the second molar. informed me that it could not be found, and enclosed Fig. 210, saying it was a similar case, i.e., a case of persistent suppuration, which did not yield to treatment until the radiograph showed the exciting cause, and it was removed. The history of the case, illustrated in Fig. 210, is about as follows : The upper lateral became abscessed. It was treated, and the canals rilled. Pus continued to flow from a fistulous opening on the labial. The abscess was treated through the alveolar plate, but without success. A radiograph was made. I quote Dr. Brophy. "It (the radiograph) exhibits a cavity in the bone, absorption of the apex of the root of the lateral, as well as the apex of the root of the adjacent central tooth. Above is an impacted cuspid lying in a nearly horizontal position. To cure a case of this character calls for most careful study, deliberation and action. The course to pursue is largely dependent upon the condition of the other teeth forming the upper denture. In a young person, the removal of the lateral incisor root, which is crownless and diseased, and the gradual moving downward into its place of the cuspid would be the desirable procedure. If the patient is in middle life, and the teeth THE USES OF THE RADIOGRAPH IN DENTISTRY 199 badly diseased and loose, as the teeth here represented are, I would rec- ommend the removal of the diseased teeth, diseased bone, and impacted tooth. The history of this case, with suppuration extending over a period of several years, so beautifully and clearly illustrated by the use of the Roentgen photograph, impresses us with the inestimable value of this means of reaching a diagnosis." 29. to Observe the Course of the fistulous tract. Dr. Emil Beck, of Chicago, was the first to use bismuth paste* in radiography. The paste is opaque to X-rays. Thus Dr. Beck would inject a fistula and abscess cavity, then, with the paste injected, make a Fig. 213. Bismuth paste injected into fistulous opening just above the first bicuspid dummy and nearly filling a very large abscess cavity. (Radiograph by Ream, of Chicago.) radiograph. Deep shadows would be cast onto the film or plate by the subnitrate of bismuth, showing distinctly the course of the fistula and the extent of the abscess cavity. The curative property of bismuth paste was discovered truly by acci- dent. After using the paste to enable him to make better radiographs, Dr. Beck noticed that some bad pus cases recovered. "Cargentos," a colloidal silver oxid, made by Mulford & Company, can be used as bismuth paste is used, for either radiographic purposes or as a remedy. When the use "to observe the course of a fistulous tract" suggested itself to me, I had in mind a case which I treated some years ago. It was a case in which a fistula pointed externally at the symphysis. Without going into a detailed history of the case, let it suffice to say that a sound and not very badly impacted lower third molar was finally extracted and the case recovered. Probing to the seat of the trouble was impossible, but had the fistula been injected with bismuth paste and a radiograph made, the connection between the third molar and the fistulous opening *Bismuth subnitrate, vaseline, paraffine and white wax. 200 DENTAL RADIOGRAPHY at the symphysis would have been clearly shown. 1 regret that I have not been able to obtain a radiograph of such a case. I have not, however, and must, therefore, content myself with a report of the only case I have in which bismuth paste was used to trace a fistulous tract. Case : A fistulous opening on the buccal near Tigs, 211 and 212. the apex of an upper second bicuspid ; the first molar missing. Another fistulous opening on the buccal just above the gingival line of the second molar. A probe entering the fistula above the bicuspid led to its apex. A probe entering the fistula of the molar seemed to lead to the bifurcation of the roots of the molar. Having at a previous date treated the molar, and so knowing the condi- tion of the canals, I was reluctant to believe that the tooth was abscessed. Fig. 214 Fig. 215 Fig. 214. Before apicoectomy. Notice the considerable canal filling forced through the apical foramen. (Radiograph by Blum, of New York City.) Fig. 215. Same case as Fig. 214. After apicoectomy. (Radiograph by Ilium, of New York City.) I entertained the belief thai both fistulous openings led to an abscess at the apex of the bicuspid, but 1 could not verify this belief by probing. A radiograph (Fig. 21 1) shows the canals unfilled, and an abscess at the apex of the bicuspid. It shows also that there is no abscess at the apex of the molar roots. But it does not show a fistula leading from the bi- cuspid to the molar. The shell-crown on the bicuspid was removed and phenolsulphonic acid pumped through the tooth and out of the fistula over the bicuspid, but the acid could not be forced through the bicuspid and out at the opening over the molar. The tooth and both fistulous openings were injected with bismuth paste and a radiograph made. (Fig. 212.1 I was then able to see that, as I bad suspected, the seat of the trouble was at the apex of the bicuspid. The molar did not need treat- I be phenolsulphonic acid could not be forced through the bicus- pid and out at the molar fistulous opening, because it traveled the path of least resistance out the nearer opening. The fistulous tract could not be THE USES OF THE RADIOGRAPH IN DENTISTRY 201 seen without injection with bismuth paste, because there was so little bone destruction. Throughout most of its course the fistula traveled be- tween bone and periosteum. A large abscess arising at the apex of the sec- Tig. 213. onc l bicuspid, and discharging above the artificial first bicuspid. Bismuth paste injected into the fistulous tract. Perhaps the cuspid is involved also. It should be tested for vital- ity of its pulp. Fig. 216 Fig. 217 Fig. 218 Fig. 216. The apex of the lateral was cut off, then lost. The radiograph shows its location, so aiding materially in its removal. (Radiograph by Ream, of Chicago.) Fig. 217. A chronic abscess at the apex of an upper central incisor. The tooth carries a post- porcelain crown and the canal is filled almost to the apex. (Radiograph by Lewis, of Chicago.) Fig. 21S. The same as Fig. 217 four days after the amputation of the apex of the central and curettement of the pus sinus. (Radiograph by Lewis, of Chicago.) 30. Co Observe the Tield of Operation Before and After flpicoectomy (Root Amputation). When a tooth fails to respond to less radical Tigs. 214 and 215. treatment, and it is deemed necessary to amputate a portion of the apex of the root, the question nat- urally arises, how much of the root shall be cut off? A good radiograph will answer this question. Fig. 214 shows that but little of the root heed be amputated. Observe that a great amount of canal filling pene- trates the apical foramen. Fig. 215 is of the same case illustrated in Fig. 214 immediately after the operation. In his work on Materia Mcdica and Therapcit- Tig. 216. tics, Dr. Buckley reports an interesting case of apico- ectomy, in which the apex was amputated, then lost. A radiograph was made. (Fig. 216.) Dr. Buckley says: "This radio- graph aided materially, as it verified the presence of the root-end and its location." 2 _ DENTAL RADIOGRAPHY Radiographs from Dr. Buckley's Modern Den- Tigs. 217 and 21$. tal Materia Me die a, Pharmacology and Therapeutics. They are exceptionally good pictures taken before and after amputation of the apex. 31. to Locate foreign Bodies, Such as a Broach in the Pulp Canal or tissue at the flpcx of a tooth; J\ Piece of Wooden toothpick in the Peridental membrane, etc. Case : A young lady about twenty-five years of Tig. 219. age. Abscess pointing near the apex of an upper central incisor carrying a post porcelain crown. I suspected that the canal of the central was not filled properly, and made a Fig. 219 Fig. 220 Fig. 221 Fig. 21&. Cement and gutta-percha — mostly cement — in an abscess cavity at the apex of a post- porcelain crowned central incisor. Fig. 220. Same as Fig. 219, after what was thought to be all of the cement and gutta-percha was removed. The radiograph shows both some cement (the larger shadow) and some gutta- percha (the small shadow) still remaining in the abscess cavity. Fig. 221. The same as Fig. 219, showing the abscess cavity clear of all foreign bodies. radiograph (Fig. 219) to learn if in this surmise I was correct. The radiograph shows the canal filled. At the apex of the root can be seen a large abscess cavity, with foreign bodies of some nature in it. An incision was made on the labial aspect, and fig. 220. what was thought to be afl of the foreign material, which proved to be cement and gutta-percha — mostly cement — was removed through the external alveolar plate. A radiograph ' Fig. 220 ) was marie, and shows some cement (the larger shadow) and some gutta-percha (the small shadow; still in the abscess cavity. These bodies were removed and another radio- fig. 221. graph (Fig. 221) made to prove that no foreign irri- tating body remained in the abscess cavity. THE USES OE THE RADIOGRAPH IN DENTISTRY 203 The pus sinus was then curetted, washed, cau- Tifl. 222. terized, injected with bismuth paste, and another radiograph (Fig. 222) made. All of this work was done at one sitting, and consumed about two hours' time. The radiograph (Fig. 222) shows that the bismuth paste does not entirely fill the abscess sinus. It has been my experience that the most vigorous and earnest efforts often fail to "completely fill" an abscess cavity with bismuth paste. The manufacturers of the paste tell us that "every crevice" must be filled Fig. S22 Fig. 223 Fig. 222. Same as Fig. 219. The abscess cavity filled with bismuth subnitrate paste. Fig. 223. Same as Fig. 219, three and one-half months after the operation. The abscess cavity is entirely filled with new bone. The new bone is as yet not quite as dense as the surrounding bone? or -the paste will not have the desired curative effect. Every crevice that can be filled should be, I concede. But I am showing you a case now in which the sinus was not quite filled, and, as we shall see presently, the results obtained were ideal. Three days after the operation another in- jection of bismuth paste was made. At this sitting the paste was not in- jected under as much force as the previous injection, for I did not wish to break up and destroy any granulation tissue that had formed along the walls of the sinus. Another injection under even less pressure than the second was made at the end of four days. The patient returned one week after the third injection with no symptoms of her former trouble. Three and one-half months after the operation Tig. 223. Fig. 223 was made. It shows a most remarkable and gratifying condition. The abscess cavity is entirely filled with new bone. This new bone is as yet not quite as dense as the Case: Man of middle age had suffered obscure Tig. 224. neuralgic pams for about a month. None of the teeth on the affected side were tender to percussion -'-'4 DENTAL RADIOGRAPHY or pressure. A radiograph (Fig. 224) was made to learn whether or not the canals of the upper second molar were filled, There was a very large amalgam filling in this tooth. The radiograph does not show the roots of the molar well, hut it does show a dark shadow between the second and third molars just above the cervical margin of the filling in the distal of the second molar. On Inquiry it was learned that the patient was in the Fig. 221 Fig. 225 Fig. 224. The arrow points into a piece of wooden toothpick between the second and third molars. Fig. 225. The upper arrow points to a piece of broach in the canal of the upper first bicuspid. The lower arrow points to a piece of gutta-percha passing through a perforation to the distal. habit of using wooden toothpicks. Suspecting the shadow to be a piece oi t'Xrthpick, an attempt was made to remove it with explorers, canal pluggers and silk floss. The effort met with failure, but, feeling sure that my diagnosis was correct, the third molar was extracted. The piece of toothpick adhered to the extracted tooth. There was an immediate and complete recovery from pain.* 'Immediately after Fig. 224 appeared in the May. L912, issue of Items of [n- terest, Dr. ( . Edmund Kells. Jr., wrote to me saying there must be some mistake, that wood was "absolutely transparent" to the X-rays, and that according to the halftone, Fig. 224, the piece of toothpick casl a denser shadow than the amalgam filling in the molar tooth. I replied, insisting thai wood was not "absolutely trans- parent" to X-rays, explaining that it had been necessary to retouch the prim to make the shadow of the pick show at all in the- halftone, and enclosing the original nega- 1 the case. I then received two disassociated molar teeth stuck together, side by side, with pink paraffin and wax. and a piece of toothpick in the wax. parallel to the long axis ..f the teeth. Also a radiographic negative of the teeth and a letter from l>r. Kells, saying he had tried to make a radiograph of the pick and had failed. 1 glanced at the negative and could sec only the teeth neither the wax nor the piece of pick between them, I made a radiograph of the tesl specimen Dr. Kells had senl me and succeeded in showing both the wax and thai part of the ends of the pieci oi toothpick which extended beyond the wax. Thai pari of the pick covered with paraffin and wax could not he seen. I was talking of the experimenl and showing my own radiographs to a dental studenl The student asked to see Dr. Kells' negative, he examined it and said. "Why. I ran see the same thing in this that I see in your picture." \nd so he could. When examined close!} Dr. Kells' negative showed the ends of the piece of toothpick extending beyond tin- wax. I had no) examined it carefull) enough before — neither had Dr. Kells. I appreciate tlie interest Dr. Kells takes in my work, and I thank him mosl earnestly for calling mj attention to what seemed to be a mistake, hut having radio- graphed a piece of toothpick experimentally, I shall nol retracl anything said re- garding Fig. 224. THE USES OF THE RADIOGRAPH IN DENTISTRY 205 Case: Young woman, had been in the hands of Tig. 225. an incompetent dentist, who had treated an upper first bicuspid for several weeks, and had finally ad- vised its extraction, whereupon the patient left him, presenting to me, and asking if the tooth could not he saved. A radiograph (Fig. 225) was made, and shows a piece of broach in the canal and a perforation to the distal through which passes a gutta-percha point. About the end of the point is an ahscess. Owing to the position of the tube, which was placed Fig. 226 Fig. 227 Fig. 226. Unremoved mesial root of a lower second molar. Fig. 227. The radiograph proves the absence of an unremoved root of the lower first molar. too high, the teeth in the picture are too short, and the perforation, which was well above the gum line — too far to be. detected — seems to be just at the neck of the tooth. I agreed with the "incompetent dentist" that the tooth could not be saved. The condition revealed by the radiograph could not have been learned by any other means save extraction and dissection of the tooth. 32. to Determine the Presence or Absence of a Bit of Root Imbedded in the Gum tissue. After the extraction of a great number of teeth, or after having been operated upon by some other dentist, a patient will present with the gum tissue highly inflamed and. pointing to the inflamed area, say, "Isn't there a piece of tooth there yet?" Unless the X-rays are used it is necessary to anesthetize the parts and dissect away some of the soft tissues to de- termine whether the inflammation may be due to an unremoved bit of tooth root, an unresorbed spicula of process, or a bit of process fractured from the jaw. This requires a great deal of time and work, and causes the patient unnecessary pain. The radiograph should be used. Case : Much swelling of the face on the affected Tig. 22b. side. The patient was unable to open the mouth to any extent without considerable pain. Two weeks _'l II I DENTAL RADIOGRAPHY Fig. 228. This radiograph is of a dry subject. Pictures of dry bones show clearly because tbere are no soft tissues to penetrate. The third molar is badly impacted in the ramus. (Radiograph by Oyer, of Philadelphia.) previously the lower second molar on the affected side had been extract- ed i ?) by a quack dentist. The question naturally arose, "Has all of the second molar been removed?" A radiograph (Fig. 226) was made, and -hows that the mesial root still remains. It was taken out, and the case recovered promptly. The advantages derived from using the radiograph in thi> case were as follows: It saved the patient the pain of opening the mouth for a prolonged instrumental and ocular examination; and also the pain caused by lancing, dissecting, and probing incident to such an examination. It saved both the patient and the operator time. It showed clearly and exactly how much of the tooth was left, and illustrated its THE USES OF THE RADIOGRAPH IN DENTISTRY 207 exact location. It made the extraction of the piece of root decidedly easier for both patient and operator. Fig. 22~ is of a case similar In that shown in Tigs. 227 and 22$. Fig. 226. In this case, however, the second molar had been extracted a year previously, and the radio- graph shows no unremoved bit of tooth root. The radiograph fails to disclose a cause for the clinical signs. But let me impress you with this fact : it does show that an unremoved bit of tooth root is not the cause, and so aids us very greatly in a diagnosis by elimination. The patient did Fig. 229. A piece of tooth root and an impacted cuspid in* an otherwise edentulous upper jaw. (Radiograph by Lewis, of Chicago.) not return after his first visit, so the case was never diagnosed. There may have been a third molar impacted in the ramus. (See Fig. 228.) No one can deny the possibility. We took only the first step toward diag- nosis — we eliminated a possible cause. Though I have been unable to obtain a definite Tig. 229. history of this case, it is, in all probability, about as follows : After the extraction of the upper teeth the patient returned with a localized inflammation of the gum tissue in the cuspid region. A radiograph was made to learn if this inflammation was caused by an unresorbed bit of process or a piece of tooth root. The picture shows not only a piece of tooth root, but also an impacted cuspid tooth. It is not unlikely that this patient suffered from obscure neuralgic pains, headache, or other nerve affections. Notice the bit of root imbedded in the process. My chief reason for exhibiting this picture is because it shows so clearly the gum tissue overlying the process. Tig. 230. _ 8 DENTAL RADIOGRAPHY A piece of root, one end of which rests on the fig. 231. edge of an ill-titling shell crown, the other against the cuspid tooth. The inflammation caused by this root extends up to the apex and to the mesial of the cuspid. In such a position the root could never have dropped down to where it could be seen in the month. Fig. 230 Fig. 231 Fig. 2:w. The arrow points to a bit of tooth root. Notice how clearly the gum tissue shows in this radiograph. (Radiograph by Ream, of Chicago.) Fig. 231. A bit of tooth root, one end resting on the edge of an ill-fitting shell crown, the other against the cuspid. The abscess caused by this piece of root extends to the apex and to the mesial of the cuspid. (Radiograph by Blum, of New York City.) 33. Co Diagnose fracture of a Root. Within the same week two cases in which the Tigs. 232 and 233. upper anterior teeth had sustained a severe blow pre- sented at the college clinic for treatment. In one case a lateral incisor (Fig. 232), and in the other case both centrals (Fig. 233) \\ei\- very loose. Radiograph Fig. 232 shows the root of the lateral fractured. Extraction is indicated. Radiograph Fig. 2^^ shows that the roots of the centrals are not fractured. Extraction is contraindicated. 1 As can be seen in the radiograph, both central crowns are broken off, and one lateral is knocked out completely.) It will be appreciated that the radiographic findings in these cases governed completely our course of treatment. I would suggest it as a most rational expedient that radio- graphs be taken in all cases of traumatism, before treatment is begun. Case: Young lady fell on dance hall floor strik- ?i(j. 234. ing the upper centrals and loosening them. Her den- tisl treated both teeth, removing inflamed pulps. One tooth progressed promptly to recovery, but the other remained loose and Vfter several week- of treatment the patient presented to Dr. F. B. Moorehead, of Chicago, who had a radiograph made before commencing treatment. The radiograph shows the root of the loose tooth fractured THE USES OE THE RADIOC K. U'/I IN DENTISTRY 209 near the apex. Dr. Moorehead removed the apex of the root through the external alveolar plate, smoothed the end of the broken root, and the case recovered promptly. It is almost superfluous to do so, yet I want to call your attention to the fact that this case, like very many others I have re- ported, could not have been diagnosed and treated properly without using the radiograph. Fig. 233 Fig. 234 Fig. 232. Fractured upper lateral incisor. Because of the location of the break extraction is indicated. Fig. 233. It was thought that the roots of the centrals were fractured. The radiograph shows they are not. • Fig. 234. Left central fractured near the apex. The case had been treated for alveolar ab- scess without success for several weeks. The removal of the piece of fractured root-end through the external alveolar plate effected a cuic. (Radiograph by Lewis, of Chicago.) 34. Co Observe the Size and Shape of Roots of teeth to be Used in Grown and Bridgework. Malformed upper laterals — "peg laterals" — Tig. 235. occur quite frequently. Their appearance is bad, and, for esthetic reasons, we often crown them. The porcelain jacket crown is difficult to construct and, at best, fragile. If the root of the peg lateral is long enough a post porcelain crown of some kind is indicated in preference to the porcelain jacket. Fig. 235 shows a peg-shaped lateral. In this case the root is long enough to permit of the introduction of a post into the canal a sufficient distance to insure stability of a post crown. The root is somewhat tortuous, but, with the radiograph to guide, the operator should be able to enlarge the canal suffi- ciently, without clanger of making a perforation into the pericemental membrane. 210 DEXTAL RADIOGRAPHY Before using teeth as abutments for large Tig. 23fr. bridges, it would not be unwise to make radiographs to note the size of the roots. It would be a mistake, I believe, to use such a tooth as the malformed one shown in Fig. 236 as an abutment for a bridge of any extent. It should be borne in mind that unless the pose is exactly right — and we seldom have it so — the teeth, as they appear on the radiograph, do not represent definitely the exact length of the teeth themselves. Nevertheless, the radiograph does give us a fairly definite idea of the relative length of the teeth. Fig. 235 Fig. 230 Fig. 235. A peg lateral, the root of which is somewhat tortuous. (Radiograph by Blum, of New York City.) Fig. 23G. A malformed cuspid tooth. It would be a mistake to use such a tooth as an abutment for a large bridge. 35. fls an Aid and Safeguard Ulbcn enlarging Canals for Posts. There are times while enlarging canals for posts when we lose the course of the canal and are much disturbed to know if we are making our enlargement in the proper direction. Place a wire in the canal and make a radiograph. If the enlargement is being made to the mesial or distal, with danger of a perforation, this can be seen in the picture. One might completely penetrate the side of the root towards the labial, or buccal, or lingual, without being warned of the danger by a radiograph, but, bear in mind, perforations made through the side of a root are, with rare excep- tions, either to the mesial or distal. In Fig. 237, observe the central carrying a fig. 237. Post porcelain crown. The post does not follow the canal. Had the enlargement for it continued in the same direction as was started, the dentist would have penetrated the side of the root. A radiograph of this case would have enabled the operator to see his mistake and correct it. THE USES OF THE RADIOGRAPH IN DENTISTRY 211 This radiograph shows a perforation through the Tifl. 23$. side of the root, to the distal, in an upper second bi- cuspid. The perforation was made when enlarging the canal for a post. A probe passes through the side of the root, up into an abscess cavity at the apex of the tooth. The radiograph is an aid not only when we are enlarging canals for posts, but also when we are removing posts from canals. It shows us how long the post is, and how much tissue we can cut away from the sides of it in safetv. Fig. 237 Fig. 238 Fig. 237. The post in the post-porcelain crowned central does not follow the canal. It almost penetrates the side of the root. (Radiograph by Graham, of Detroit.) Fig. 238. Perforation through the side of the root of a» upper second bicuspid. A probe passes through the perforation. (Radiograph by Graham, of Detroit.) 36. to Examine Bridges About Which there Ts Jin Inflammation. At best fixed bridges are not sanitary. For this Tigs. 239 and 240. reason we often find an intense inflammation about them. Thorough depletion by scarifying and the use of an astringent, antiseptic mouthwash will usually give prompt relief. There may be causes for the inflammation other than the simple fact that the bridge is a foreign body in the mouth, making thorough cleanliness impossible. Observe Figs. 129, 239 and 240 as examples. It would be extremely difficult to remove the bit of root shown beneath the bridge in Fig. 239 without removing the bridge. The piece of root shown in Fig. 240 can easily be removed through the external alveolar plate without removing the bridge. I have recently heard of a case in which a very severe inflammation existed about a bridge which had only been set for about a week. The case was treated for several days, and finally the bridge removed when it was seen that, at the time the bridge was set, a considerable quantity of 212 DENTAL RADIOGRAPHY cement had been forced into the tissues near a shell crown abutment. Re- moval of this cement effected a prompt cure. Had a radiograph been made, the cause of the trouble would have been seen immediately, and, depending on the exact location of the cement, removal of the bridge may have been avoided. Fig. 239 Fig. 240 Fig. 239. A piece of tooth root in the tissues beneath a bridge. (Radiograph by Lewis, of Chicago.) Fig. 240. A piece of tooth root in the tissues above a very large bridge. It would be easily possible to remove it through the external alveolar plate without removing the bridge. (Radio- graph by Lewis, of Chicago.) 37. Co Observe the field Before Constructing a Bridge. Tin's use of the radiograph has already been illustrated — Figs. 129, 239, and 240. The radiograph will not only disclose the presence of un- erupted teeth, and unremoved pieces of tooth roots, but, as has been sug- gested under another heading, it will also show the operator the size, shape and health of the roots of the teeth he is using for abutments. 38. Co Observe Planted Ceetb. Case: One in the practice of Dr. C. Edmund Tigs. 241 and 242. Kells, Jr.. Fig. 241, shows a fracture of the root of a lateral, the result of a fall. After the two pieces of the lateral were extracted they were united and held together with an iridio-platinum -crew set in cement, and the repaired rout then replanted. The radiograph | li.L, r . 242) was made immediately after the operation. A gold splint i-> seen covering the crown of the cuspid, lateral and both cen- trals. THE USES OF THE RADIOGRAPH IN DENTISTRY 213 A case of replantation of a lower second bicus- Tig. 243. pi«l two years and four months after the operation. The root is almost entirely absorbed. Notice how plainly the pericemental membrane can be seen about the roots of the first bicuspid and first molar, appearing as a light line. Notice also the ab- sence of this line about the remaining portion of the root of the replanted tooth. The theory of the attachment of planted teeth is as follows : The roots of the planted teeth are absorbed at different points, and bone Fig. 241. Fig. 242. Fig. 241. Fracture of upper lateral incisor. ( Radiograph by Kells, of New Orleans.) Fig. 242. Same as Fig. 241 after the removal of the lateral and its replantation. Radiograph by Kells, of New Orleans.) immediately fills into these places, so holding the tooth. Hence, planted teeth do not have a pericemental membrane. Radiographic findings bear out this theory. ,-,. , . , , . . .-, rig. 244 shows an implanted porcelain root. Ob- fig. 244. serve that the root has practically no bony attachment at all, and would drop out save for the manner in which it is splinted to the other central. Dr. E. G. Greenfield. Wichita, Kas.. has designed Tig. 245. and manufactured a sort of cage-like root of iridio- platinum wire to be used for implantation. So far all forms of artificial roots for teeth have proven failures, but this one bids fair to be a success. Whether it will be a success or not depends on whether or not bony tissue will build in and about the wires. The radio- graph (Fig. 245) is introduced more for the purpose of showing the arti- ficial roots than for any other reason. The radiograph has not been made in such a way as to enable us to see whether there is an osseous deposit within the wires or not. 214 DEXTAL RADIOGRAPHY 39. Tn eases of Cementoma. Cementomata (or cases of hypercementosis, as they are often called) are sometimes the cause of neuralgia. There are no means at our disposal whereby they (cementomata) can be diagnosed save by the use of the radiograph. ***rr. V Fig. Fig. 244. Fig. 243. A case of replantation of the lower second bicuspid two years and four months after the operation. The root is almost entirely absorbed. (Radiograph by Kells, of New Orleans.) Fig. 244. Artificial porcelain root with no bony attachment at all save just at the apex. (Radiograph by Ream, of Chicago.) These radiographs illustrate cementomata, which Tigs. 246 and 247. were responsible for persistent neuralgias. Extrac- tion was necessary in both cases. 40. Tn Gases of Bone "Ulborls." The term bone whorl is used to designate particularly dense areas of bone occurring in bone. Bone whorls may be caused by a prolonged, mild irritation, like that produced by an impacted tooth, for example. They are sometimes responsible for facial neuralgia. In answer to a letter ask- ing him if be ever found it necessary, or ever expected to find it necessary, to open into the bone and surgically break up whorls to relieve neuralgia, 1 )r. Cryer replies, "I have found it necessary in several cases to open into the bone and remove the whorls, or bard bone, and I fully expect to do rain." From the nature and location of whorls, it is obvious that they can be found only by the use of the radiograph. THE USES OE THE RADIOGRAPH IN DENTISTRY 215 A case in the practice of Dr. Oyer. The patient Tigs. 248 and 249. was suffering from pain on one side of the face. A radiograph of the case (Fig. 248) shows an im- pacted lower third molar. It was thought hest to remove the second molar Fig. 245. Two artificial roots implanted in the «ppe\ jaw. (Radiographer not known.) Fig- -M... Fig. 247. Fig. 246. Cementoma on lower, second, shell-crowned molar. (Radiograph by Ream, of Chicago.) Fig. 247. Cementoma. (Radiograph by Ream, of Chicago.) first, then the third molar. This was done, and the neuralgia disappeared for about ten days, then pain returned. Another radiograph (Fig. 249) was made which shows a bone whorl in the region from which the second molar had been removed. Another operation was done removing the whorl, after which the neuralgia disappeared altogether. 2l6 DENTAL RADIOGRAPHY Fig. 248. An unerupted lower third molar. The arrow points to a bone "whorl." (Radiograph by Pancoast, of Philadelphia.) Case in the practice of Dr. Robert H. Ivy, of fjg. 250. Philadelphia. "The patient had suffered from neu- ralgia of the mandibular division of the fifth nerve on the right side, for two years. In February, 191 1, she was treated by an alcohol injection of thi> division, which gave relief from pain for six months, after which the trouble returned, but not so severely as before. In January, 1912, a skiagram was made, showing a dense spot in the n of the first molar tooth, and in close relation to the inferior dental nerve. This is so dense as to appear like a piece of tooth root, but when cut down upon with the surgical engine, nothing but dense bone was found. The patient has been without neuralgia since the operation, though it is too soon yel to say whether the relief will be permanent." THE USES OF THE RADIOGRAPH IX DENTISTRY 217 Fig. 249. The same as Fig. 248 after the extraction of the lower second and third molars. The arrow points to a dark, three-sided shadow — a bone "whorl." The X on the shadow is caused by a scratch en the negative. (Radiograph by Pancoast, of Philadelphia.) 41. to Locate Stones (Calculi) in the Salivary Ducts or Glands. The history of this case given me by Dr. Sidney Tifl. 251. Lange, of Cincinnati, Ohio, is as follows: Patient, female, age about forty, suffered recurrent attacks of swelling and pain in the region of the submaxillary gland on one side. The attacks seemed to follow the taking of sour foods. A radiograph (Fig. 251) was made. The arrow points to a stone in the submaxillary duct. Because the patient had had a stone removed from the same duct several years previously, and because the gland was considerably thick- ened, simple removal of the stone was thought to be contraindicated, and a more radical operation involving the removal of the entire gland was performed. 218 DEXTAL RADIOGRAPHY 42. Tn Cases of Bone Cysts. "A cyst is an organized structure consisting of a sac-like wall to- gether with its contents, especially one of pathological formation or abnormal development." — Appleton's Medical Dictionary. The dark shadow to which the arrow points is a bone "whorl.' Pancoast, of Philadelphia.) (Radiograph by According to this definition all chronic alveolar abscesses are cysts — hone cysts, because they occur in bone. But the name cyst is usually not applied until the abscess sac assumes a great size. The abscess in Fig. [93 i- large enough to he called a cyst, in the generally used sense of the term. This radiograph shows a large cyst in the lower j\%. 252. jaw. Tlie two roots of the lower first molar are doubtless responsible for tin- cyst formation. In cyst case- there i- often considerable and disfiguring enlargement of the bone, and such cases are spoken of as cystic tumors, a tumor, of course, being simply an abnormal enlargement or growth. THE USES OF THE RADIOGKAI'II IN DENTISTRY 219 A man, age about thirty-seven, was referred to Tigs. 253 and 254. the college clinic "to have a growth on the lower jaw cut off." There was no "growth" to "cut off." There was a definite enlargement of the bone in the lower first molar region. Fig. 251. The arrow points to a stone in the submaxillary duct. (Radiograph by Lange, of Cincinnati.) giving the man the appearance of carrying a large lump of tobacco in the vestibule of the mouth. The patient suffered local pain, and the involved area was tender to palpation. The first molar tooth was missing from the jaw. A radiograph was made and showed a cyst involving the second bicuspid and second molar. (I regret that the radiograph has been lost.) Neither the second bicuspid nor the second molar had cavities nor fillings in them. Considering the evidence of neglect of the mouth and teeth, it was not deemed worth while to try to conserve the teeth. Ac- cordingly the second bicuspid was extracted, which permitted the escape of considerable watery, brown pus. A doubt then arose as to whether the radiograph showed an involvement of the molar or not. Another radiograph (Fig. 253) was made. It shows that the molar is involved. It was extracted and more serous pus evacuated. Antiseptic solutions 220 m:\r.iL kj d i o g R; why could now be washed from one tooth socket, through the cyst, and out at the other tooth socket. The cyst was curetted, cauterized and packed with sterile gauze. Healing except from within outward was prevented by the use of gauze, and the case recovered. Relief from pain and soreness was Fig. 252. Large cyst in the lower jaw. The more or less oval-shaped light area represents the cyst. (Radiograph by Lewis, of Chicago.) Fig. 253. Fig. 254. Fig. 253. A bone cyst in the lower jaw. Fig, 254. Same as Fig. ■.'•">:;. with the cyst outlined to enable the reader to observe Fig. 258 to advantage. The circle A is the alveolus from which the second bicuspid was extracted. immediate. It required two or three months for all of the enlargement of the jaw to disappear. hi my experience a^ a radiographer I have observed that the general practitioner of dentistr) shows great reluctance to extract a tooth, no matter what the condition he is treating may he. On the other hand, the 77//:' USES OF THE RADIOGRAPH IN DENTISTRY 221 specialist in oral surgery extracts teeth sometimes without making the slightest effort to conserve them. I believe, however, that the oral surgeon is less often mistaken. A man may make a greater mistake than the ex- traction of a tooth. For example : failure to extract a tooth which is causing otherwise incurable suppuration, general sepsis, nervous dis- orders, necrosis or distracting pain. Fig. Cio. A very large cyst of the lower jaw. The light area represents the cyst. This radio- graph shows the hyoid bone. (Radiograph by Lange, of Cincinnati.) Dr. Sidney Lange. of Cincinnati, made the radio- Tig. 255. graph shown in Fig. 255, but did not treat the case. Dr. Lange was, however, able to furnish the follow- ing history : Patient, boy. about eighteen. Very large swelling in the lower jaw. Xo pain or tenderness in the region of enlargement. A radio- graph ( Fig. 255) was made, and the case diagnosed as a "benign bone cyst." The boy was taken to a hospital and the cyst drained of a straw- 222 DENTAL RADIOGRAPHY colored fluid, curetted and packed with gauze, through an opening made inside of the mouth to the buccal. The patient left the hospital in a week or two after the operation. Case: Male, age about twenty-five. Enlarge- J\Q. 2$b. ment of the mandible at the symphysis. Tenderness, intermittent local pains. The radiograph shows a large cyst. Failing to keep an appointment, the patient has not been heard of since the radiograph was made. Fig. 256. Bone cyst of the lower jaw. 43. In Cases of Dentigerous Gyst. Any cyst containing a tooth body, or tooth bodies, is said to be a dentigerous cyst. Dentigerous cyst of the jaws are not uncommon. Their definite diagnosis is possible only when the radiograph is used. Because the apex of the tooth extends into the pus sac a chronic dento-alveolar abscess is sometimes called a dentigerous cyst. But this use of the term is considered improper. Case in the practice of Dr. M. II. Oyer. I quote fig. 257. Dr. Cryer: "The patient, a child of nine, had a swelling of the left side of jaw for about two years. This gradually increased to the sizr of a hen's egg, causing considerable deformity. A radiograph of the case (Fig. 2^j | shows a retained de- THE USES OF THE RADIOGRAPH IX DENTISTRY 223 Fig. 257. Dentigerous cyst of the lower jaw in child nine years old. The arrow points to the tooth in the cyst. The light area represents the cyst. (Radiograph by Pancoast, of Philadelphia.) ciduous second molar tooth at the lower border of the jaw and surrounded by an ovoid clear area. A diagnosis of dentigerous cyst was made. "At operation through the mouth the shell of bone was found to con- tain, not the usual fluid, but a resilient mass of pinkish-white tissue sur- rounded by a sac of darker color. The contents, including the soft tissues, the tooth shown in the picture and the sac, were removed and the cavity lightly packed with gauze. The patient is making an uneventful recovery. The further diagnosis of the case will depend on microscopic examination of the tissue." Fig. 258 was made for a patient of Dr. J. G. Tigs. 258 and 259. Lane, of Philadelphia. Age of patient, eight. The radiograph shows an unerupted second bicuspid sur- rounded by a light area representing a dentigerous cyst. The upper wall 224 DENT. II. RADIOGRAPHY - A dentigerous cyst containing a lower second bicuspid. of Philadelphia.) (Radiograph by Pancoast, of the cyst and its fluid contents were removed, leaving the tooth in place. A later radiograph I Fig. 259) shows that the tooth is gradually erupting into position. (This history is quoted from a paper by Dr. Cryer.) 44. In eases of tumor, Benign or malignant. 1 have already reported a case of cystic tumor, which was referred to the college clinic to have the tumor "cut off." There was nothing to "cut off," and a radiograph showed a cavity in the hone, aspiration of which accomplished a cure. The following cases occurred in the practice of fig. 260. Dr. Cryer: "The two patients were sent by different practitioner- from different portions of the State of THE USES OF THE RADIOGRAPH IN DENTISTRY 22s Fig. 259. Same as Fig. 25S after removal of the fluid contents and upper wall of the cyst, showing the second bicuspid erupting into place. (Radiograph by Pancoast, of Philadelphia.) Pennsylvania, but came for examination on the same day. They were two women patients of about the same age, both wearing full upper arti- ficial dentures and partial lower ones, and both suffering from a similar character of pain, the only difference being that in one patient the pain was located on the left side of the lower jaw, while the other was on the right side of the lower jaw. Physical examination revealed the fact that the right cervical lymphatic glands in one of the patients were slightly enlarged. The history obtained of the cases did not aid in diagnosis. Both patients claimed that the molar teeth on each side had been ex- tracted years ago. X-rays were made of the jaws with the following results : "Fig. 260 was made from the patient whose cervical glands were 226 DEXT.1L RADIOGRAPHY Fig. 200. Myelosarcoma of the lower jaw. In appearance it resembles a bone cyst somewhat. (Radiograph by I'ancoast, of Philadelphia.) enlarged. The picture shows a breaking down of the bone, with the two dark shadows indicating abnormal density of the bone in some portions. From tin- appearance, together with the slight enlargement of the glands, the case was diagnosed as myelosarcoma. A microscopic examination of the tissue removed, confirmed the diagnosis." I do not reproduce the radiograph of the other case because the print I have i- not dear enough to permit of a good halftone reproduction. The print before me shows fairly well three impacted lower teeth, one a rudi- mentary bicuspid, the others a second and third molar. THE USES OF THE RADIOGRAPH IX DENTISTRY 227 Dr. Cryer says: "There seemed to be very little difference in these two cases from the history and physical examination, but the wonderful work of the X-rays revealed a very great dissimilarity. On the one hand the skiagraph indicated the sad necessity of removing the entire right side of the jaw and submaxillary lymphatic glands, with the possibility of the disease returning, while in the other case the extraction of the three im- pacted teeth was the only thing required." Fig. 261. Fig. 862. Fig. 261. Osteoma (?) of the lower jaw. Fig. 262. Hypertrophy of the gums and alveolar process. The radiograph show.- no irritant cause for the condition, and none was found otherwise. My readers are by this time acquainted with the Tig. 261. appearance of normal alveolar process and jaw bone. Fig. 261 shows what I believe to be an osteoma. The patient would not consent to the removal of tissue for microscopical examination. The radiograph shows only that the bone is diseased. The exact nature of the disease must be determined by the microscope. Case : Enlargement of the gums about the upper Tig. 262. anterior teeth, causing considerable disfigurement. Fig. 262 shows what was thought to be hyper- trophy of the gum tissue and alveolar tissue. [Microscopic examination verified the diagnosis. The teeth and the hypertrophied tissue were re- moved. At the age of thirteen a permanent lateral had Tig. 263. failed to erupt. A radiograph was made to learn whether or not it was present in the jaw. Fig. 263: shows the permanent lateral, and shows also why it has not erupted. In 228 DENTAL RADIOGRAPHY the path of eruption is seen what I believe to be an "epithelial, com- posite"* odontoma. Odontomata sometimes assume considerable size. To be abso- lutely sure in diagnosis, and to be certain of their complete removal, the radiograph should be used. '.:>. The upper arrow points to the permanent lateral incisor. The lower arrow points to an odontoma. (Radiograph by Flint, of Pittsburgh.) ""The case illustrated in Fig. 264 presents j jg. 264. many interesting features from the standpoint of diagnosis and treatment. The patient was a woman about thirty-five years of age, who suffered for a number of years from pains in the ear and the tonsilar region, as well as from difficulty in masti- cation and deglutition, while her general health had deteriorated to such an extent that she became very anemic, having suffered from malnutrition due, no doubt, to imperfect mastication and the absorption of pus prod- ucts. In this condition she was referred to the extracting specialist who was unable, from the ankylosis present, to arrive at any definite conclusion as to the possibility of an impacted tooth which was suspected, while the only evidence that pointed in this direction was a free discharge of pus through a fistulous opening in the soft tissues over the third molar region of the right inferior maxillary. "She was therefore referred to the radiographer when the true con- dition, as shown in Fig. 264. was revealed. The necessity for removing the displaced second molar, as well as the odontoma, presented a situation which was not a pleasing one to contemplate. The patient, as well as her friends, were informed of the probability of fracturing the mandible in the endeavor to remove the molar and the dental tumor, which together ♦Barrett "Oral Pathology and Practin " THE USES OF THE RADIOGRAPH IN DENTISTRY 229 Fig. 264. A large composite odontoma. (Radiograph by Chene, of Detroit.) occupied almost the entire body of the mandible at the angle of the ramus. Under a general anesthetic of nitrous oxide and oxygen, which was followed by ether, the tumor was removed, as was also the impacted molar, without any great difficulty, but when the circumscribed bony structure about the molar was drilled and chiseled sufficiently to permit of an ele- vator passing under one corner of it and pressure applied, the expected happened, and a break in the body of the mandible occurred. This acci- dent was of no serious consequence, however, for under an occipito- mental bandage, which a few days later was reinforced by wire fixation, the fracture healed and the case proceeded to an uneventful and speedy recovery, with complete restoration of health. The odontoma was of composite structure, the central part being made up of what may have been the third molar, about which were arranged concentric layers of cementum, and probably some compact bony structures." For the report of this case I am indebted to Dr. Don M. Graham, of Detroit. Mich. 230 DENTAL RADIOGRAPHY 45. Co Observe Anomalous Conditions Such as the Tusion of the Roots of two teeth for example. Case : Child about twelve. The crowns of two of Tig. 2b$. the lower incisors seemed fused together. To ac- complish regulation of the teeth it became expedient in the opinion of the operator handling the case to extract one of the Fig. 265. Show? that the two lower incisors are not fused together. incisors. The choice of the tooth to extract fell to one of the two which seemed fused together. The question arose : "Are the roots of the teeth fused also?" A radiograph (Fig. 265) shows they arc not. It shows further that the crowns arc not fused cither, though, let me admit, I shared in the mistake of the man who referred the case thinking they were; and failed, as he had, in an attempt to pass a ligature between them. It was not until I had the radiograph before me, showing me that 1 was not attempting the impossible, that I succeeded in getting a silk ligature between the teeth. One of the teeth was slightly malformed; they wen- almost mortised together in consequence, and in contact from the incisal edge to beneath the gum margin. ond and third molars are sometimes fused together. I recall hav- ing extracted the upper second and third molars in an effort to remove the third, the roots of the two teeth having been coalesced. Had I used radiographs, and known the condition which existed, T might have con- served the third molar, and so saved the second molar, which latter was a useful tooth. ( )r, had it been necessary to remove the teeth, I might have saved my patient considerable pain by a more inclusive use of my local anesthetic. THE USES OF THE RADIOGRAPH IN DENTISTRY 231 46. Co Observe the Location and extent of a necrotic or Carious Condition of Bone. This radiograph is of a case of arsenical necrosis. Tig. 266. which would not yield to the usual treatment of curettement and drug stimulation. The arrow point? to the line of demarcation, below which can be seen the sequestrum. The case recovered promptly upon removal of the sequestrum. The arrow points to the line of demarcation, beneath which can be seen the sequestrum. Case: Necrosis of the lower jaw, caused by an Tigs. 2t>~ and 2&S. abscessed tooth. The patient suffered for a year from recurrence of an abscess in the lower jaw. Dur- ing this time he made several changes from one dentist or physician to another. At the time the case came under the care of Dr. Gilmer, of Chicago, the symptoms were alarming. There were two external pus sinuses along the lower border of the mandible in the bicuspid region. The patient had been unable to lie down for a period of ten days because of the intense pain which resulted from assuming a recumbent position. The body temperature rose and fell by turns. Stupor and coma occurred. A radiograph of the case (Fig. 267) shows a sequestrum about the size of the first joint of the thumb along the lower border of the mandible in the bicuspid and cuspid region. The line of demarcation can be seen fairly well in the plate before me. I regret that I was unable to obtain a good print of this case. The negative was an excellent one, but the photographer who made the print from it did poor work. The operation, done by Dr. Gilmer, of Chicago, was as follows : An external incision was made along the lower border of the mandible in the region of the sequestrum, and the sequestrum removed through it. The bone was curetted, a drainage tube inserted, and the incision sewed up. The first bicuspid and cuspid were extracted. - - DEXT.IL radiography Fig. 2C7. The arrow points to a sequestrum about the size of the first joint of the thumb. (Radiograph by Porter, of Chicago.) 68. Same as Fi«. 867, with the line of demarcation outlined to enable th<- readei to observe it better than in Fig. 267. THE USES OF THE RADIOGRAPH IN DENTISTRY 233 Fig. 269. EE, ends of overlapping bone. Had the operator not had a radiograph to guide him in his work he could not possibly have performed the operation as quickly, thoroughly, and intelligently as he did, for he would not have known just where, and just how big, the sequestrum was. A case of phosphor necrosis of the lower jaw Ti/■' THE RADIOGRAPH IN DENTISTRY 235 Fig. 271. Radiograph of a dry skull. One antrum is filled with lead shot, the other lias a molar tooth in it. This radiograph is clearer than one made from the living subject be- cause there were no soft part.- or circulating blood to blot out detail. in a permanent cure. The size, shape and location of the antrum can best be observed stereopticallv. Often, however, a good idea of its size, shape and location can be obtained from a radiograph, like Fig. 276, for example. Radiographs of the antrum made on films held in the mouth 23< • DEXTAL RADIOGRAPHY A. antrum with \>u< B, healthy antrum. Louis.) (Radiograph by Carman, of St. are very misleading and confusing, as witnessed in Fig. 275, which was made on a film held in the mouth, and is of the antrum filled with lead shot — illustrated in Fig. 271. The dots outline a very large antrum. An open- fig. 276. ing made at the favorite site for opening into the antrum through the mouth, above their apices, be- tween the second bicuspid and first molar (the first molar has been ex- tracted;, would not puncture this antrum at its lowest point. The root of the second molar seems to penetrate the antrum. Whether it actually penetrates the floor of the antrum or not I cannot say definitely, because THE USES OF THE RADIOGRAPH IN DENTISTRY 237 Fig. 273. A, diseased antrum. The shadow pointed to by the arrows is an impacted third molar. B, healthy antrum, CC, turbinate bones, EE, very small frontal sinuses. (Radiograph by Pfahler of Philadelphia.) of the lack of perspective in the radiograph. I am inclined to think, how- ever, that it does not — the lower part of the antrum and the end of the root overlap, the tooth root passing to the lingual of the antrum. Because of its unusual size the lower part of the antrum was thought to contain a malignant growth. Dr. Oyer rejected this interpretation, saying that the antrum must have been of the size shown in the radio- graph before the formation of the second and third molars, and that the large antrum was responsible for the pinched-together condition of their 238 DENTAL RADIOGRAPHY Fig. 274. Lateral view of the same case illustrated in Fig. 273. This radiograph shows the impacted tooth clearly. (Radiograph by Pfahler of Philadelphia.) roots. lie theorized further, accounting for the pain the patient suffered by surmising that the pinched condition of the roots of the third molar was causing pressure on the dental pulp. In his description of the case Dr. Cryer does not mention the faulty canal filling in the second molar as a possible cause for the pain. Both molar teeth were extracted and the patient was freed from neuralgia. 4Q. to Locate Toreifln Bodies, Such as tooth Roots or Broaches, in the Antrum. Fig. 2jj shows a piece of tooth root in the an- TiflS. 277 and 27$. trum. It is a portion <>i the second bicuspid, which had been extracted ( ?) about a week previous to the time when the patient presented to Dr. Virgil Loeb for treatment. The THE USES OF THE RADIOGRAPH IN DENTISTRY 239 Fig. 27"). Antrum tilled with lead shot. The same as Fig. 271. Fig. 276. The dots outline a very large antrum. A septum is seen in this antrum dividing it into two parts. The arrows point to the lower part. (Radiograph by Pfahler, of Philadelphia.) 240 PF.XTAL RADIOGRAPHY Fig. 877. The arrows point to a piece of tooth root in the antrum, of St. Louis.) (Radiograph by Carman, first molar was extracted, an opening made into the antrum through one of its alveoli, and the piece of root removed. The object of the operation to remove the piece of tooth root from the antrum. This was accom- plished. And again let me repeat what I have said before: An operator may make a greater mistake than that of the extraction of a tooth — he may conserve the tooth at the expense of the health and happiness of the patient. Conservative dentistry often, all too often, means conservation • .I* disease. THE USES o/ : THE RADIOGRAPH IN DEXTISTRY 241 Fig. 278. Same case as Fi 277 after removal of the piece of tooth root. (Radiograph by Carman, of St. Louis.) Dr. Cryer says of Fig. 279: "It is mark Ti. resulting in ankylosis. The ankylosis had existed for several months at the time Fig. 289 was made. The dots outline the missing parts, i.e., the anterior border of the ramus and Fig. 285. Fracture of the mandible at t lie symphysis, (Radiograph by Blum, of New York City. ) the coronoid process. The disease of the bone could not have failed to affect the temporal and masseter muscles. It [s my belief that in this case the true muscular tissue was destroyed and replaced with cicatricial tissue, which condition caused a false ankylosis. I consulted two surgeons, but neither was able to suggest a corrective operation. An orthodontist was unable to move a tooth into proper occlusion. He referred the case to me, thinking perhaps the presence of a super- numerary tooth body was responsible for the immobility of the tooth. A radiograph demonstrated the absence of any such body, and showed that the tooth had practically no peridental membrane at all. There was a condition of partial ankylosis, to overcome which it was necessary for the orthodontist to reinforce his anchorage and exert more force on the re- fractory tooth. I do not print a radiograph of this case because of the great difficulty of showing the peridental membrane, or the absence of it, in a half tone. S3, to Observe the Tield of Operation before and after Resection of the mandible. Resection of the mandible is a difficult, radical operation, and one which has been performed comparatively few times. With the excep- tion of Dr. Ballin (Items of Interest, June. 1908). operators who have done this operation have not, so far as I am able to learn, availed them- 248 i > i:\r.ii. radiography Fig. 28r,. Fracture at the angle of the mandible. Displacement of fractured ends gra; h by Pancoast, of Philadelphia.) (Radio- Fig. 280 aft' r i _ « «l»i<-ti.»ii an rl ad juMin. nl (Radiograph by Pancoast, of Philadelphia.) dental splint. THE USES OF THE RADIOGRAPH IN DENTISTRY 249 Fig. 288. Double comminuted fracture of the mandible. That the reader may understand the picture, observe the following: A, zygomatic arch; B, sigmoid notch; C, upper part of ramus; D, one fracture; E, the other fracture; F, fragment of bone between fractures. selves of the assistance which good radiographs of the case would have rendered. Resection of the mandible might become necessary as a re- sult of an existing pathological condition of the bone, or it might be done to correct a bad case of prognathism. For whatever reason the operation may be done, the operation itself is the same, in that a piece of the man- dible is removed. Consider the operation for prognathism, for example : A piece of the body of the mandible from each side is cut out and re- moved. The anterior part is then forced back and the cut ends of the bone (four of them) wired into apposition. That anti- and post-operative radiographs of such a case would be of value is apparent. 54. Tn Jill Cases of facial neuralgia with an Obscure etiology. Cases of facial neuralgia with an obscure etiology, the exciting cause for which was disclosed by the radiograph, have already been described under more specific headings — Figs. 159, 164, 176, 177, 170. --4. 246. 247, 248, 249, 250, 264, and others. Until the exciting cause is found when it then receives a more specific name, any dental pain is likely to be referred to as neuralgia. 250 DENTAL RADIOGRAPHY When making radiographs to learn the cause of trifacial neuralgia, it is expedient usually to make a large 8 x 10 picture of the affected side. This radiograph can then be studied and, if some lesion is discovered, another radiograph of the particular region of the lesion made on a small film. The second radiograph, on the film, will be clearer than the one on the plate, and will verify or disprove the findings in the larger picture. Fig. 289. The 'lots outline the missing parts — i.e., the anterior border of the ramus and the coronoid process. (Radiograph by Cole and Raper.) Case: Married woman, middle age, suffered Tigs. 290 and 291. from pains in the region of the upper bicuspids. The dentist could find no lesion that might be responsible for the trouble. A radiograph (Fig. 290) was made, but does not show the upper teeth clearly. It does, however, show a shadow in the body of the mandible in the region of the lower first molar, which tooth is missing from the jaw. A radiograph (Fig. 291) of the region in which the shadow appeared was made on a small film held in the mouth. The film was not placed in exactly the proper position and, as a result of this mis- take, pictures only a part of the lesion. It shows the crown of a super- numerary lower bicuspid with three supernumerary bodies (denticles) above it. Though the lesion in the lower jaw was not at the location in which pain occurred, it was doubtless responsible for the neuralgia. THE USES OF THE RADIOGRAPH IN DENTISTRY 251 The patient would not submit to an operation. The case, if not operated upon, will probably progress to a large dentigerous cystic tumor. Evidence of this can already be noticed in Fig. 290 by the lack of normal density of the surrounding bone. Fig. 290. The arrow points to a shadow in the body of the mandible in the region of the lower first bicuspid. (Radiograph by A. M. Cole, of Indianapolis.) Case: Married woman, physician's wife, about Tig. 292. fort) r -eight years old. had suffered for twenty-five or thirty years with attacks of neuralgia occurring four or five times a year, each attack lasting for several days. None save dental operations were performed, though she received palliative treat- ment for ear, mastoid cells and antrum trouble. Xo treatment gave relief. She left her home in Indiana and spent one winter in South Carolina, hoping the milder climate would ward off the attacks of pain, but this proved futile. At no time did her temperature rise above normal, prov- 252 DENTAL RADIOGRAPHY ing. or seeming to prove, that whatever the irritation, there was little or no suppuration attending it. A radiograph (Fig. 292) was finally made, and showed an impacted upper third molar. This tooth was removed, and since then, now over four years ago, she has not had a single attack of neuralgia. Attention is called to the fact that up to the time of making the radio- graph this was a typical case of idiopathic facial neuralgia. Fig. 291. The same case as Fig. 290. A radiograph of the upper part of "the shadow." It shows the crown of a supernumerary bicuspid with three denticles above it. The white spot at the apex of the second bicuspid is caused by an air "bell" attaching itself to the film in that region at the time it was in the developing solution. (Radiograph by A. M, Cole, of Indianapolis.) ss. Co Observe the Inferior Dental Canal. Often, but not always, we are able to radiograph the inferior dental canal. (See Fig. 190.) To the man contemplating resection of the in- ferior dental nerve anywhere throughout its course in this canal a radio- graph showing the location of the canal would be of value. Dr. Virgil Loeb, of St. Louis, reports a case of anesthesia of the lower lip. and that part of the face 011 one side which receives its nerve supply from the nerves passing through the mental foramen. The anes- thesia followed the extraction of a lower third molar. A radiograph of the case showed that the roots of the third molar had penetrated the in- ferior dental canal. Knowing this, it was deduced that, at the time of extraction, the inferior dental nerve had been stretched, and a few fibers torn at the mental foramen. Lately I have personally observed such a case. I do not print radiographs of either Dr. Loeb's or my own case, because they are not clear enough to permit of good half-tone reproduc- tion. Such cases as the ones now under consideration recover slowly, the time required varying from one to several months. Treatment with the high-frequency current maw or may not, hasten recovery slightly. Though slow, complete recovery may be expected. THE USES <>/■' THE RADIOGRAPH IN DENTISTRY 253 Immediately after the filling of the canals of a lower second molar a patient suffered most severe pain in the region of the filled tooth. A radiograph was made and showed the canal filling penetrating the apical foramen of the distal root, projecting into the inferior dental canal, and Fig. 293. The arrow points to an impacted upper, third molar, the cause of "idiopathic" neu- ralgia, from which the patient had suffered recurrently for from between twenty-five to thirty years. (Radiograph by A. M. Cole, of Indianapolis.) doubtless pressing the inferior dental nerve. An effort to remove the canal filling met with failure, and the tooth was extracted to relieve the patient of the intense pain. Again I do not print radiographs of the case because the prints are not sufficiently clear to permit of good half-tone reproductions. 56. Tn eases of Eudwig's Angina. Angina is defined in Dorland's Medical Dictionary as "any disease or symptom characterized by spasmodic suffocative attacks" : Ludwig's angina as "purulent inflammation seated around the submaxillary gland." Whenever there is a pus sinus opening on the neck in the region of the submaxillary gland, the patient is said to have Ludwig's angina. This is the popular application of the term, and it seems to the writer unfor- 2>l DENTAL RADIOGRAPHY Fig. 293. Photograph of a case of so-called Ludwig's angina. Also a radiograph of the case showing an abscess of the first permanent molar. The fistulous tract cannot be seen. tunate, for there is seldom angina — i.e., suffocative attacks — in these cases of suppuration of the neck. Fig. 2