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A head positioner for temporomandibular joint roentgenography
A h ead positioner for tem p orom an d ib u lar jo in t roentgenograph y
William L. Lawther, D.D.S., Lakewood, Ohio
A head positioner for use in roentgenog raphy of the temporomandibular joint was designed by the author and con structed at Walter Reed Army Hospital. Its use makes it possible to take roent genograms of the condyles of individuals and at the same time maintain the same relation to the roentgen ray source and film. It allows the dentist to make serial roentgenographic examinations o f the temporomandibular joint o f the same patient over an extended period, and to compare the effect of different dental operations. The apparatus was based on the funda mental principles of the Broadbent1 technic for stabilizing the head while making cephalometric roentgenograms. The two external acoustic meati and the bridge of the nose are the areas used for stabilization. T w o ear rods and a nasion rest attachment are used. The BroadbentBolton cephalometer is a satisfactory base to which an attachment can be added for positioning the head for temporoman dibular joint studies, as the platen which supports the lateral and frontal film cas settes and the nasion rest attachment are held in place by the two bolts seen on the under side of the head positioner near the upright part o f the cephalometer. The new attachment can be substituted for the platen and bolted in place. The base of the cephalometer and the x-ray tubes are bolted to the floor, thus placing
the head positioner and the x-ray source in a fixed relationship to each other. H E A D P O S IT IO N E R
The head positioner is seen in Figure 1. The plastic ear rod at A is fixed and positioned so that the central ray of the x-ray tube passes through it. The ear rod at B is adjustable to the lateral dimen sions of each individual’s head, and the support for this rod can be moved along the track E. The track has a millimeter scale inscribed on it so that any position of the ear rod can be recorded and dupli cated at a later date. The upper half of the ear rod supporting structure can be rotated on the base so that the rod is always pointing directly at the stationary ear rod. The degree of rotation is read on a scale inscribed on the ear rod sup port base and can be noted for use in making subsequent records. There are two nasion rest attachments. G and D. The patient is rotated 180 de grees between the making of the roent genograms of one side and of the other; this is why two nasion rest attachments are needed. Figure 2 shows the position Formerly, Captain, Dental Corps, U. S. Army Reserve Corps. Dental service, W alter Reed Arm y Hospital, department of dental research, Arm y Medical Service Graduate School, W alter Reed Arm y Medical Center, Washington, D.C. I. Broadbent, N. Holly. A new x-ray technique and its application to orthodontia. A ngle Orthodont. 1:45, 1931. 47
48 • THE J O U R N A L O F THE A M E R IC A N D EN T A L A S S O C IA T IO N
Fig. I • Tem porom andibular joint head posi tioner. A : Stationary ear rod. B: A djustab le ear rod. C : N asion rest attachm ent used when making roentgenogram s of left side. D: N asion rest at tachm ent used when making roentgenogram s of right side. E: Millim eter scale. F: Film cassette channel. G : Su ppo rtin g base for adjustable ear rod
of the patient when roentgenograms of the right and left temporomandibular joints are being taken. The same x-ray tube is used for the two sides. The nasion rest attachments are at a fixed vertical height and can be adjusted to the antero posterior dimensions of the patient. The height of the nasion rest attachment is set so that the orbital point on the side
for which the roentgenograms are being made is approximately on the same hori zontal plane as the porion point. The head is positioned so that the porionic axis, instead of being parallel to and coinciding with the central ray of the x-ray tube as it is in cephalometric work, is at an angle downward and for ward. The porionic axis is at an angu lation of 10 degrees downward and 12.5 degrees forward to the central ray. With the head in this position, the central ray enters the head a little above and behind the ear and leaves at the external acoustic meatus on the side being filmed. From determinations with the head in this po sition it has been found that the central ray of the x-ray tube is nearly parallel to the long axis of the condyle. Although the angulation of the condyle will vary in each individual, and will even vary between the right and left sides of the same individual, it is felt that it is better to position each person’s head at the same angulation— the average found for the long axis of the condyles. If determina tions were made for the angulations of condyles for each temporomandibular joint, it would be necessary to change the angulation of the person’s head only a few degrees. This change o f angulation
Fig. 2 • Left: Individual positioned for film ing right tem porom andibular joint. Right: Positioned for filming left tem porom andibular joint
L A W T H E R . . . V O L U M E 55, JU LY 1957 • 49
would have relatively little effect on the resulting roentgenogram. The film for the temporomandibular joint roentgenograms is at right angles to the central ray of the x-ray tube and is 68.5 inches from the tube target. A distance of this magnitude from the tube reduces enlargement to a minimum and makes it possible to interpret structures, such as the orbitale, and to use them as reference points. This is impossible with most of the other technics used for temporomandibular joint roentgenog raphy because o f the enlargement and distortion caused by the closeness o f the x-ray tube to the film. Tracings were made of the roentgeno grams (Fig. 3) for most o f the diagnostic and temporomandibular joint studies. On these tracings it was possible to trace the condyle, the glenoid fossa, the pos terior border and angle o f the ramus, the superior outline of the sphenoid bone, and the orbit. On the side being filmed, a metal ring was imbedded on the stationary ear post (Fig 4 ). The most superior point on this ring defines porion. The most inferior point of the orbit on the side being filmed is the orbital point. A line is drawn between porion and orbitale. This is the reference line used in the measurements and angu lations in the assessment of the temporo mandibular joint roentgenograms. Lines, parallel to the porion-orbital line, are drawn on the tracing (Fig. 3 ). One of these is at the most superior point o f the inner surface of the glenoid fossa, one at the most superior point on the con dyle, and one from the lowest point of the articular eminence. By measuring the distances between these parallel lines in the different roentgenograms, the fol lowing measurements can be recorded: (1) the height of the fossa, (2) the dis tance from the condyle to the height of the fossa and (3) the relationship of the fossa height to the porion-orbital line. The anteroposterior movements o f the condyle are measured from the center
Fig. 3 • Tracing of tem porom andibular joint roentgenogram show ing various measurements m ade in assessment. A : Fossa height. B: Porion to fossa height. C : Top o f condyle to fossa height. D: Porion to center o f condyle. E: A n gu la tio n of ramus to porion-orbital line. F: A n gu la tio n of slope o f articular eminence to porion-orbital line. O : O rbitale. P: Porion
o f a circle inscribed in the condyle to a line perpendicular to the porion-orbital line from the porion point (Fig. 3 ). Tw o angulations are recorded: (1) the ramus to the porion-orbital line meas ured from a line drawn tangent to the posterior border of the ramus, and (2) the slope of the articular eminence to the porion-orbital line measured from a
Fig. 4 • Tem porom andibular joint roentgenogram made with patient's head positioned in head positioner
50 • THE J O U R N A L O F T H E A M E R IC A N D EN T A L A S S O C IA T IO N
line tangent to the straightest portion of the slope o f the articular eminence. Tracings of roentgenograms o f vari ous jaw positions, or tracings of serial roentgenograms of the same joint can be superimposed on each other and di rect comparisons o f the relation of the condyle to the glenoid fossa can be made. The superpositioning of these tracings is made possible through the utilization of anatomic points and structures out side of the joint which can be used for orientation. The anatomic points and structures used are porion, the superior surface of the sphenoid and the orbit. Direct comparison o f the relation of the condyle to the glenoid fossa is extremely valuable in following the changes in the temporomandibular joint articulation brought about by different dental pro cedures. Comparison of the relative posi tion of the condyle to the glenoid fossa in different jaw positions, centric occlusion and physiologic rest position is also possible.
other age groups, and one will also be conducted on edentulous individuals. 2. The observations made in normal individuals o f the relative position of the condyle to the glenoid fossa are be ing utilized as a diagnostic yardstick for interpretation of roentgenograms o f in dividuals complaining of temporoman dibular joint discomfort. 3. Serial standardized temporoman dibular joint roentgenograms of an in dividual are being used as before, dur ing and after treatment records. The dental operator can see the effects of dental treatment on the temporoman dibular joint. SU M M A RY
A head positioning attachment for mak ing temporomandibular joint roentgeno grams is being utilized at the Walter Reed Army Hospital Dental Clinic. This attachment, designed by the author, ac curately positions each individual’s head in a precise relation to the x-ray source and the film. The target-film distance is RESU LTS 68.5 inches, which eliminates distortion The three main objectives that prompted and enlargement and permits the use the designing and construction o f the of anatomic structures and anthropo temporomandibular joint head positioner metric points outside the joint for refer are being attained. Specifically: ence points in measurements. The roent1. Studies are being made to deter genographic results obtained when this mine if there is a consistent uniformity head positioner is used are o f value in in the relationship of the condyle and studying the normal articulations of the the glenoid fossa. These studies are be temporomandibular joint, in diagnosing ing done by age groups on white men. temporomandibular joint disturbances, In the 20 year age group there is a and in studying the joint o f the same fairly high degree of uniformity in the individual during extended periods of relative position o f the condyle to the treatment. fossa. This study is being carried out in 14717 Detroit Avenue
Investigation • W hen we investigate clinically some disease, or some manifestation o f it, we may be seriously handicapped by circum stances; but we are possessed of the certain knowledge that what w e study is precisely what w e set out to study. Lewis.
William L. Lawther, D.D.S., Lakewood, Ohio
A head positioner for use in roentgenog raphy of the temporomandibular joint was designed by the author and con structed at Walter Reed Army Hospital. Its use makes it possible to take roent genograms of the condyles of individuals and at the same time maintain the same relation to the roentgen ray source and film. It allows the dentist to make serial roentgenographic examinations o f the temporomandibular joint o f the same patient over an extended period, and to compare the effect of different dental operations. The apparatus was based on the funda mental principles of the Broadbent1 technic for stabilizing the head while making cephalometric roentgenograms. The two external acoustic meati and the bridge of the nose are the areas used for stabilization. T w o ear rods and a nasion rest attachment are used. The BroadbentBolton cephalometer is a satisfactory base to which an attachment can be added for positioning the head for temporoman dibular joint studies, as the platen which supports the lateral and frontal film cas settes and the nasion rest attachment are held in place by the two bolts seen on the under side of the head positioner near the upright part o f the cephalometer. The new attachment can be substituted for the platen and bolted in place. The base of the cephalometer and the x-ray tubes are bolted to the floor, thus placing
the head positioner and the x-ray source in a fixed relationship to each other. H E A D P O S IT IO N E R
The head positioner is seen in Figure 1. The plastic ear rod at A is fixed and positioned so that the central ray of the x-ray tube passes through it. The ear rod at B is adjustable to the lateral dimen sions of each individual’s head, and the support for this rod can be moved along the track E. The track has a millimeter scale inscribed on it so that any position of the ear rod can be recorded and dupli cated at a later date. The upper half of the ear rod supporting structure can be rotated on the base so that the rod is always pointing directly at the stationary ear rod. The degree of rotation is read on a scale inscribed on the ear rod sup port base and can be noted for use in making subsequent records. There are two nasion rest attachments. G and D. The patient is rotated 180 de grees between the making of the roent genograms of one side and of the other; this is why two nasion rest attachments are needed. Figure 2 shows the position Formerly, Captain, Dental Corps, U. S. Army Reserve Corps. Dental service, W alter Reed Arm y Hospital, department of dental research, Arm y Medical Service Graduate School, W alter Reed Arm y Medical Center, Washington, D.C. I. Broadbent, N. Holly. A new x-ray technique and its application to orthodontia. A ngle Orthodont. 1:45, 1931. 47
48 • THE J O U R N A L O F THE A M E R IC A N D EN T A L A S S O C IA T IO N
Fig. I • Tem porom andibular joint head posi tioner. A : Stationary ear rod. B: A djustab le ear rod. C : N asion rest attachm ent used when making roentgenogram s of left side. D: N asion rest at tachm ent used when making roentgenogram s of right side. E: Millim eter scale. F: Film cassette channel. G : Su ppo rtin g base for adjustable ear rod
of the patient when roentgenograms of the right and left temporomandibular joints are being taken. The same x-ray tube is used for the two sides. The nasion rest attachments are at a fixed vertical height and can be adjusted to the antero posterior dimensions of the patient. The height of the nasion rest attachment is set so that the orbital point on the side
for which the roentgenograms are being made is approximately on the same hori zontal plane as the porion point. The head is positioned so that the porionic axis, instead of being parallel to and coinciding with the central ray of the x-ray tube as it is in cephalometric work, is at an angle downward and for ward. The porionic axis is at an angu lation of 10 degrees downward and 12.5 degrees forward to the central ray. With the head in this position, the central ray enters the head a little above and behind the ear and leaves at the external acoustic meatus on the side being filmed. From determinations with the head in this po sition it has been found that the central ray of the x-ray tube is nearly parallel to the long axis of the condyle. Although the angulation of the condyle will vary in each individual, and will even vary between the right and left sides of the same individual, it is felt that it is better to position each person’s head at the same angulation— the average found for the long axis of the condyles. If determina tions were made for the angulations of condyles for each temporomandibular joint, it would be necessary to change the angulation of the person’s head only a few degrees. This change o f angulation
Fig. 2 • Left: Individual positioned for film ing right tem porom andibular joint. Right: Positioned for filming left tem porom andibular joint
L A W T H E R . . . V O L U M E 55, JU LY 1957 • 49
would have relatively little effect on the resulting roentgenogram. The film for the temporomandibular joint roentgenograms is at right angles to the central ray of the x-ray tube and is 68.5 inches from the tube target. A distance of this magnitude from the tube reduces enlargement to a minimum and makes it possible to interpret structures, such as the orbitale, and to use them as reference points. This is impossible with most of the other technics used for temporomandibular joint roentgenog raphy because o f the enlargement and distortion caused by the closeness o f the x-ray tube to the film. Tracings were made of the roentgeno grams (Fig. 3) for most o f the diagnostic and temporomandibular joint studies. On these tracings it was possible to trace the condyle, the glenoid fossa, the pos terior border and angle o f the ramus, the superior outline of the sphenoid bone, and the orbit. On the side being filmed, a metal ring was imbedded on the stationary ear post (Fig 4 ). The most superior point on this ring defines porion. The most inferior point of the orbit on the side being filmed is the orbital point. A line is drawn between porion and orbitale. This is the reference line used in the measurements and angu lations in the assessment of the temporo mandibular joint roentgenograms. Lines, parallel to the porion-orbital line, are drawn on the tracing (Fig. 3 ). One of these is at the most superior point o f the inner surface of the glenoid fossa, one at the most superior point on the con dyle, and one from the lowest point of the articular eminence. By measuring the distances between these parallel lines in the different roentgenograms, the fol lowing measurements can be recorded: (1) the height of the fossa, (2) the dis tance from the condyle to the height of the fossa and (3) the relationship of the fossa height to the porion-orbital line. The anteroposterior movements o f the condyle are measured from the center
Fig. 3 • Tracing of tem porom andibular joint roentgenogram show ing various measurements m ade in assessment. A : Fossa height. B: Porion to fossa height. C : Top o f condyle to fossa height. D: Porion to center o f condyle. E: A n gu la tio n of ramus to porion-orbital line. F: A n gu la tio n of slope o f articular eminence to porion-orbital line. O : O rbitale. P: Porion
o f a circle inscribed in the condyle to a line perpendicular to the porion-orbital line from the porion point (Fig. 3 ). Tw o angulations are recorded: (1) the ramus to the porion-orbital line meas ured from a line drawn tangent to the posterior border of the ramus, and (2) the slope of the articular eminence to the porion-orbital line measured from a
Fig. 4 • Tem porom andibular joint roentgenogram made with patient's head positioned in head positioner
50 • THE J O U R N A L O F T H E A M E R IC A N D EN T A L A S S O C IA T IO N
line tangent to the straightest portion of the slope o f the articular eminence. Tracings of roentgenograms o f vari ous jaw positions, or tracings of serial roentgenograms of the same joint can be superimposed on each other and di rect comparisons o f the relation of the condyle to the glenoid fossa can be made. The superpositioning of these tracings is made possible through the utilization of anatomic points and structures out side of the joint which can be used for orientation. The anatomic points and structures used are porion, the superior surface of the sphenoid and the orbit. Direct comparison o f the relation of the condyle to the glenoid fossa is extremely valuable in following the changes in the temporomandibular joint articulation brought about by different dental pro cedures. Comparison of the relative posi tion of the condyle to the glenoid fossa in different jaw positions, centric occlusion and physiologic rest position is also possible.
other age groups, and one will also be conducted on edentulous individuals. 2. The observations made in normal individuals o f the relative position of the condyle to the glenoid fossa are be ing utilized as a diagnostic yardstick for interpretation of roentgenograms o f in dividuals complaining of temporoman dibular joint discomfort. 3. Serial standardized temporoman dibular joint roentgenograms of an in dividual are being used as before, dur ing and after treatment records. The dental operator can see the effects of dental treatment on the temporoman dibular joint. SU M M A RY
A head positioning attachment for mak ing temporomandibular joint roentgeno grams is being utilized at the Walter Reed Army Hospital Dental Clinic. This attachment, designed by the author, ac curately positions each individual’s head in a precise relation to the x-ray source and the film. The target-film distance is RESU LTS 68.5 inches, which eliminates distortion The three main objectives that prompted and enlargement and permits the use the designing and construction o f the of anatomic structures and anthropo temporomandibular joint head positioner metric points outside the joint for refer are being attained. Specifically: ence points in measurements. The roent1. Studies are being made to deter genographic results obtained when this mine if there is a consistent uniformity head positioner is used are o f value in in the relationship of the condyle and studying the normal articulations of the the glenoid fossa. These studies are be temporomandibular joint, in diagnosing ing done by age groups on white men. temporomandibular joint disturbances, In the 20 year age group there is a and in studying the joint o f the same fairly high degree of uniformity in the individual during extended periods of relative position o f the condyle to the treatment. fossa. This study is being carried out in 14717 Detroit Avenue
Investigation • W hen we investigate clinically some disease, or some manifestation o f it, we may be seriously handicapped by circum stances; but we are possessed of the certain knowledge that what w e study is precisely what w e set out to study. Lewis.