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Anteroposterior and posteroanterior movements of the mandible and condylar centricity during function
ANTEROPOSTERIOR
AND
THE
MANDIBLE
AND
IRVING
M. SHEPPARD,
D.M.D."
Montefiore
Hospital,
POSTEROANTERIOR
CONDYLAR
CENTRICITY
MOVEMENTS DURING
OF
FUNCTION
New York, N. Y.
HE PRESENCE OR ABSENCE of condylar centricity appears significant in the evaluation of existing occlusionsand the establishment of new ones. Its presence is important to the theory that these centers control the movements of the mandible. It is further important to the practice of mounting casts from interocclusal records made with the jaws apart and closing into an occlusal position on an articulator. Condyle rotation around a very precise point is considered basic to exact maxillomandibular relationships in the hinge axis technique.i-lo Bennett,il however, came to the conclusion that there is no fixed center of rotation. The findings of others12-27have questioned the existence of condylar centricity. Posselt,” in observations of mastication, showed that in no case was the functional path situated on the hinge movement path or the condylar rotation path. Except for this investigation, which involved the use of thin wax on the occlusal surfaces for five masticatory strokes, Berry and Hofmann’s24and Scully’s2r cinefluorographic techniques, mechanical appliances, cadavers, general anesthesia,curare, and forcedtrained movements were generally used. Such artificial conditions conceivably affect observations of neuromuscular activity.
T
OBJECTIVE
AND
METHOD
In view of the conflicting opinions and observations of condylar-mandibular motion, it was decided to observe mandibular movement during actual mastication with virtually no interference with neuromuscular activity and proprioception. Twenty subjects were studied by means of motion roentgenography. None were dentists or persons familiar with the details of the study. All were over the age of 50 becauseof the radiation safety problem, were shielded with lead from the neck down, and received a maximum of 12 r by cinefluorographic means, or 7.2 r in lateral and 7.2 r in anteroposterior views with rapid serial roentgenography. The dentitions ranged from natural to complete upper and lower dentures (1 subject). Small lead markers were attached in the upper and lower central incisor areas and the molar areas where metallic landmarks were not already present (Fig. 1). Ten of the subjects were studied by means of rapid serial roentgenography in lateral projection as they chewed a walnut meat. No special instructions were given other than to eat the designated food. Six films per second were exposed at l/60 second This investigation was supported in part by research grant D-782 Institute for Dental Research, TJ. S. Public Health Service. *Associate Attending Dentist, Dental and Radiology Departments. 86
CR 1) from
the
National
Volume 12 Number 1
MOVEMENTS
OF MANDIBLE
AND
CONDYLAR
87
CENTRICITY
for a period of 5 seconds96 This provided thirty films (14 by 14 inches) from which representative lower incisor and corresponding molar markers were traced. Lines joining these pairs of markers in the mandible were extended through the ramus area after tracing an outline of the mandible and more than one condyle position. A compass point was inserted in the center of one condyle outline, and an arc was drawn anteriorly to the incisor marker tracings (CC). Another arc (RR) was drawn from the ramus area of the incisor-molar line extensions (Figs. 2 through 11). Ten subjects were studied by means of cinefluorography* at a speed of thirty
Fig.
I.-The
metallic
and
anatomic
landmarks
used
in tracing
mandibular
motion.
frames per second. All were seated and had no confinement of head position. The foods consisted of peeled apple, banana, walnut meat, and a fibrous type of cracker. The films were analyzed+ in slow motion, frame by frame, and the initial strokes traced (Figs. 12 through 16). The time involved with each stroke was approximated on a basis of thirty frames per second. Only representative frames were traced. OBSERVATIONS
The closing masticatory strokes showed irregularity in the lateral view by rapid serial roentgenography with a walnut meat as the bolus. There was no constant arc of opening or closing. There was frequent and sudden shifting of the mandible, anteroposteriorly and posteroanteriorly. The general direction of movement more nearly resembled the arc drawn from the ramus than that drawn from *Picker Amplifilmer; tArno Corp. projector,
Kodak 35 mm. Cineflure Copenhagen, Denmark.
film.
J. Pros. Jan.-Feb.,
SHEPPARD
Fig.
Fig.
Den. 1962
2
3
R c
Fig.
4
the condyIe. There was translatory movement of the condyles in all instances. The cinefluorographic views of the initial strokes of three additional foods of size and texture different from walnut meat showed more anteroposterior and posteroanterior shifting than with the latter bolus in the first stroke. The time involved in these strokes, which in some instances involved an opening component, was 0.16 second to 3.03 seconds. The posteroanterior, anteroposterior shifts appeared to in-
Volume 12 Number 1
MOVEMENTS
OF MANDIBLE
AND
CONDYLAR
CENTRICITY
89
Fig. 5
R c
Fig.
6
R c
Fig. 7
R Figs. 2 through ‘I.-Tracings from 10 subjects representative of the incisor-molar positions with connecting lines extended. Ramus arcs (R) are drawn from the ramus in the area of the incisor-molar line extensions. Condyle arcs (Cl are drawn from the condyle. The bolus was walnut meat, and the technique used was rapid serial roentgenography.
crease the time required for completion of the stroke more than the greater length of a stroke necessitated by the incision of a large bolus.
J. Pros. Jan.-Feb.,
SHEPPARD
Fig.
Fig.
Den. 1962
8
9
DISCUSSION
Rapid serial roentgenography and cinefluorography make possible a more realistic observation of mandibular movement than that obtained by artificially induced means. However, these techniques have limitations of their own: (1) the limitation of the length of recording time because of the radiation hazards involved, (2) the difficulty of tracing cinefluorographic film images, (3) inaccuracies in tracing mandibular movement in complete denture subjects because of the possibility of denture-base movement, and (4) lack of visibility of mediolateral components of posteroanterior and anteroposterior movements in lateral views. In part of this study, five to eight strokes were recorded by rapid serial roentgenography during chewing of a walnut meat. This involved only one food for a limited period of time. With cinefluorography, the mastication of four foods was observed for longer periods, However, only the initial strokes with each bolus are shown in Figs, 12 through 16. Others were observed by means of frame by frame and slow motion viewing. The irregularity of the opening and closing strokes, characterized by anteroposterior and posteroanterior shifts, may be due to the proprioceptive response to the ever-changing status of the bolus and other local conditions. Such irregularity seems to preclude the possibility of a single point of rotation in function. An arc
$kltle; ”
112
.MOVEMENTS
OF MANDIBLE
Fig.
AND
CONDYLAR
CENTRICITY
91
10
Fig.
I1
Figs. 8 through Il.-Tracings from 10 subjects representative of the incisor-molar positions with connecting lines extended. Ramus arcs (R) are drawn from the ramus in the area of the incisor-molar line extensions. Condyle arcs (Cl are drawn from the condyle. The bolus was walnut meat, and the technique used was rapid serial roentgenography.
drawn from a condylar center (Figs. 2 through 11, CC) would bring the mandible more posteriorly on opening than actual function indicates. Such an arc also would bring the mandible further anteriorly on closing than occurs in function. Moss’” indicates that such condylar rotation endangers the inferior alveolar neurovascular bundle and shows laminographic tracings of simple opening to indicate a point of rotation in the mandibular foramen. These findings (Figs. 2 through 11) based on functional movements indicate that an area, rather than a point, in the ramus can provide arcs resembling the general direction of functional mandibular movement in the lateral view. They are grossly similar to those of Ulrich’5 made with rapid movement without occlusally interfering appliances. In his study, when the chewing of grain was attempted, irregularity of the curves was found. NayloP states that the fact that the ramus and condyle move in opposite directions proves that the axis is below the condyle. The presumption that wherever the mandible goes, the hinge goes along with it, and is still the center of motion, is not borne out by arcs drawn from any of the condyle positions traced.
92
SHEPPARD
J. Pros. Den. Jan.-Feb., 1962
A
Fig.
12
1
Fig.
13
Fig.
14
Fig.
15
Fig.
16
Figs. 12 through 16.-Tracings of the initial masticatory (A), banana CBA walnut meat OVA and cracker IT) are shown subject, The tracings were made by means of cinefluorography.
strokes of 5 subjects with with one horizontal row for
apple each
Volume Sumber
12 1
MOVEMENTS
OF MANDIBLE
AND
CONDYLAR
CENTRICITY
93
SUMMARY
Mandibular movements involved in the mastication of a walnut meat were studied by means of rapid serial roentgenography on 10 subjects. Cinefluorography was employed to study the incision and mastication of apple, banana, walnut meat, and cracker by 10 subjects. CONCLUSIONS
1. Translatory condylar movement occurred in all subjects. 2. A constant arc of opening or closing was not found. 3. Masticatory movements tended to be irregular and showed frequent anteroposterior and posteroanterior shifts. 4. Functional movement showed no precise relationship to a fixed condylar or other axis of rotation. 5. The general direction of the irregular mandibular movement in function more nearly approached that of an arc drawn from an area in the ramus than one drawn from the condyles. REFERENCES
1. McCollum, B. B.: Oral Diagnosis, J.A.D.A. 30:1218-1233, 1943. 2. Lucia, V. 0.: The Fundamentals of Oral Physiology and Their Practical Application in the Securing and Reproducing of Records to Be Used in Restorative Dentistry, J. PROS. DEN. 3:213-231, 1953. ?I I Stuart, C. E.: Accuracy in Measuring Functional Dimensions and Relations in Oral Prosthesis, J. PROS. DEN. 9:220-236, 1959. Granger, E. R.: Centric Relation, J. PROS. DEN. 2:160-171, 1952. :I Contino, R. M., and Stallard, H.: Instruments Essential for Obtaining Data Needed in Making a Functional Diagnosis of the Human Mouth, J. PROS. DEN. 7:66-77, 1957. 6. ibreinberg, L. A.: Physiologic Objectives of Reconstruction Techniques, J. PROS. DEN. 10:711-723, 1960. 7. Brotman, D. N.: Hinge Axes. I. The Tranverse Hinge Axis, J. PROS. DEN. 10:436-440, 1960. 8. Hickey, J. C., Woelfel, J. B., and Rinear, L.: Electromyographic Evidence Supporting the Mandibular Hinge Axis Theory, J. PROS. DEN. 7:361-367, 1957. Brekke, C. A. : Jaw Function. I. Hinge Rotation, J. PROS. DEN. 9:600-606, 1959. 13. Page, H. L.: Hinge-Axes: Arguments and Typical Examples: Proof, D. Digest 66:368372, 1960. 11. Bennett, N. G.: A Contribution to the Study of the Movements of the Mandible, Proc. Roy. Sot. Med., Sect. Odont. 1:79-95, 1908. (Reprinted in J. PROS. DEN. 8:41-54, 1958.) 12. Kurth, L. E., and Feinstein, I. K.: The Hinge Axis of the Mandible, J. PROS. DEN. 1:327-332, 1951. Kurth, L. E.: Balanced Occlusion, J. PROS. DEN. 4:150-167 1954. ::: Moss, M. L.: Functional Anatomy of tihe Temporomandibular Joint, ir, Schwartz, L. editor: Disorders of the Temporomandibular Joint, Philadelphia, 1959, W. B: Saunders Company, pp. 73-88. Joint : Kinematics and Actions of the Mas15. Ulrich,. J. : The Human Temporomandibular tlcatory Muscles (condensed and translated from a thesis published in Copenhagen, 1896), J. PROS. DEN. 9:399-406, 1959. 16. Borgh, O., and Posselt, U.: Hinge Axis Registration, J. PROS. DEN. 8:35-40, 1958. 17. Posselt, U.: Occlusal Relationship in Deglutition and Mastication, Transactions of the European Orthodontic Society, 1958. Articula18. Naylor, J. G.: Role of the External Pterygoid Muscles in Temporomandibular tion, J. PROS. DEN. 10:1037-1042, 1960. 19. Shanahan, T. E. J., and Leff, A.: Mandibular and Articulator Movements, J. PROS. DEN. 9:941-945, 1959. 20. Silverman, M. M. : Centric Occlusion and Jaw Relations and Fallacies of Current Concepts, J. PROS. DEN. 7:750-769, 1957.
94
SHEPPARD
J. Pros. Jan.-F&.,
Den. 1962
21. Sheppard, I. M.: The Effect of Hinge Axis Clutches on Condyle Position, J. PROS. DEN. 8 :260-263, 1958. 22. Sheppard, I. M.: The Relation of Occlusion and Temporomandibular Joint Morphology to Temporomandibular Joint Symptoms, J. PROS. DEN. 6:339-346, 1956. 23. Sheppard, I. M.: The Bracing Position, Centric Occlusion, and Centric Relation, J. PROS. DEN. 9:11-19, 1959. 24. Berry, H. M., Jr., and Hofmann, F. A.: Cineradiographic Observations of Temporomandibular Joint Function, J. PROS. DEN. 9:21-33, 1959. 25. Sicher, H.: Positions and Movements of the Mandible, J.A.D.A. 48:620-625, 1954. 26. Sheppard, I. M.: The Closing Masticatory Strokes, J. PROS. DEN. 9:946-951, 1959. 27. Scully, J. J.: Cinefluorographic Studies of the Masticatory Movements of the Human Mandible, Thesis, 1959, University of Illinois. MONTEFIORE HOSPITAL GUN HILL RD. NEW YORK 67, N. Y.
AND
THE
MANDIBLE
AND
IRVING
M. SHEPPARD,
D.M.D."
Montefiore
Hospital,
POSTEROANTERIOR
CONDYLAR
CENTRICITY
MOVEMENTS DURING
OF
FUNCTION
New York, N. Y.
HE PRESENCE OR ABSENCE of condylar centricity appears significant in the evaluation of existing occlusionsand the establishment of new ones. Its presence is important to the theory that these centers control the movements of the mandible. It is further important to the practice of mounting casts from interocclusal records made with the jaws apart and closing into an occlusal position on an articulator. Condyle rotation around a very precise point is considered basic to exact maxillomandibular relationships in the hinge axis technique.i-lo Bennett,il however, came to the conclusion that there is no fixed center of rotation. The findings of others12-27have questioned the existence of condylar centricity. Posselt,” in observations of mastication, showed that in no case was the functional path situated on the hinge movement path or the condylar rotation path. Except for this investigation, which involved the use of thin wax on the occlusal surfaces for five masticatory strokes, Berry and Hofmann’s24and Scully’s2r cinefluorographic techniques, mechanical appliances, cadavers, general anesthesia,curare, and forcedtrained movements were generally used. Such artificial conditions conceivably affect observations of neuromuscular activity.
T
OBJECTIVE
AND
METHOD
In view of the conflicting opinions and observations of condylar-mandibular motion, it was decided to observe mandibular movement during actual mastication with virtually no interference with neuromuscular activity and proprioception. Twenty subjects were studied by means of motion roentgenography. None were dentists or persons familiar with the details of the study. All were over the age of 50 becauseof the radiation safety problem, were shielded with lead from the neck down, and received a maximum of 12 r by cinefluorographic means, or 7.2 r in lateral and 7.2 r in anteroposterior views with rapid serial roentgenography. The dentitions ranged from natural to complete upper and lower dentures (1 subject). Small lead markers were attached in the upper and lower central incisor areas and the molar areas where metallic landmarks were not already present (Fig. 1). Ten of the subjects were studied by means of rapid serial roentgenography in lateral projection as they chewed a walnut meat. No special instructions were given other than to eat the designated food. Six films per second were exposed at l/60 second This investigation was supported in part by research grant D-782 Institute for Dental Research, TJ. S. Public Health Service. *Associate Attending Dentist, Dental and Radiology Departments. 86
CR 1) from
the
National
Volume 12 Number 1
MOVEMENTS
OF MANDIBLE
AND
CONDYLAR
87
CENTRICITY
for a period of 5 seconds96 This provided thirty films (14 by 14 inches) from which representative lower incisor and corresponding molar markers were traced. Lines joining these pairs of markers in the mandible were extended through the ramus area after tracing an outline of the mandible and more than one condyle position. A compass point was inserted in the center of one condyle outline, and an arc was drawn anteriorly to the incisor marker tracings (CC). Another arc (RR) was drawn from the ramus area of the incisor-molar line extensions (Figs. 2 through 11). Ten subjects were studied by means of cinefluorography* at a speed of thirty
Fig.
I.-The
metallic
and
anatomic
landmarks
used
in tracing
mandibular
motion.
frames per second. All were seated and had no confinement of head position. The foods consisted of peeled apple, banana, walnut meat, and a fibrous type of cracker. The films were analyzed+ in slow motion, frame by frame, and the initial strokes traced (Figs. 12 through 16). The time involved with each stroke was approximated on a basis of thirty frames per second. Only representative frames were traced. OBSERVATIONS
The closing masticatory strokes showed irregularity in the lateral view by rapid serial roentgenography with a walnut meat as the bolus. There was no constant arc of opening or closing. There was frequent and sudden shifting of the mandible, anteroposteriorly and posteroanteriorly. The general direction of movement more nearly resembled the arc drawn from the ramus than that drawn from *Picker Amplifilmer; tArno Corp. projector,
Kodak 35 mm. Cineflure Copenhagen, Denmark.
film.
J. Pros. Jan.-Feb.,
SHEPPARD
Fig.
Fig.
Den. 1962
2
3
R c
Fig.
4
the condyIe. There was translatory movement of the condyles in all instances. The cinefluorographic views of the initial strokes of three additional foods of size and texture different from walnut meat showed more anteroposterior and posteroanterior shifting than with the latter bolus in the first stroke. The time involved in these strokes, which in some instances involved an opening component, was 0.16 second to 3.03 seconds. The posteroanterior, anteroposterior shifts appeared to in-
Volume 12 Number 1
MOVEMENTS
OF MANDIBLE
AND
CONDYLAR
CENTRICITY
89
Fig. 5
R c
Fig.
6
R c
Fig. 7
R Figs. 2 through ‘I.-Tracings from 10 subjects representative of the incisor-molar positions with connecting lines extended. Ramus arcs (R) are drawn from the ramus in the area of the incisor-molar line extensions. Condyle arcs (Cl are drawn from the condyle. The bolus was walnut meat, and the technique used was rapid serial roentgenography.
crease the time required for completion of the stroke more than the greater length of a stroke necessitated by the incision of a large bolus.
J. Pros. Jan.-Feb.,
SHEPPARD
Fig.
Fig.
Den. 1962
8
9
DISCUSSION
Rapid serial roentgenography and cinefluorography make possible a more realistic observation of mandibular movement than that obtained by artificially induced means. However, these techniques have limitations of their own: (1) the limitation of the length of recording time because of the radiation hazards involved, (2) the difficulty of tracing cinefluorographic film images, (3) inaccuracies in tracing mandibular movement in complete denture subjects because of the possibility of denture-base movement, and (4) lack of visibility of mediolateral components of posteroanterior and anteroposterior movements in lateral views. In part of this study, five to eight strokes were recorded by rapid serial roentgenography during chewing of a walnut meat. This involved only one food for a limited period of time. With cinefluorography, the mastication of four foods was observed for longer periods, However, only the initial strokes with each bolus are shown in Figs, 12 through 16. Others were observed by means of frame by frame and slow motion viewing. The irregularity of the opening and closing strokes, characterized by anteroposterior and posteroanterior shifts, may be due to the proprioceptive response to the ever-changing status of the bolus and other local conditions. Such irregularity seems to preclude the possibility of a single point of rotation in function. An arc
$kltle; ”
112
.MOVEMENTS
OF MANDIBLE
Fig.
AND
CONDYLAR
CENTRICITY
91
10
Fig.
I1
Figs. 8 through Il.-Tracings from 10 subjects representative of the incisor-molar positions with connecting lines extended. Ramus arcs (R) are drawn from the ramus in the area of the incisor-molar line extensions. Condyle arcs (Cl are drawn from the condyle. The bolus was walnut meat, and the technique used was rapid serial roentgenography.
drawn from a condylar center (Figs. 2 through 11, CC) would bring the mandible more posteriorly on opening than actual function indicates. Such an arc also would bring the mandible further anteriorly on closing than occurs in function. Moss’” indicates that such condylar rotation endangers the inferior alveolar neurovascular bundle and shows laminographic tracings of simple opening to indicate a point of rotation in the mandibular foramen. These findings (Figs. 2 through 11) based on functional movements indicate that an area, rather than a point, in the ramus can provide arcs resembling the general direction of functional mandibular movement in the lateral view. They are grossly similar to those of Ulrich’5 made with rapid movement without occlusally interfering appliances. In his study, when the chewing of grain was attempted, irregularity of the curves was found. NayloP states that the fact that the ramus and condyle move in opposite directions proves that the axis is below the condyle. The presumption that wherever the mandible goes, the hinge goes along with it, and is still the center of motion, is not borne out by arcs drawn from any of the condyle positions traced.
92
SHEPPARD
J. Pros. Den. Jan.-Feb., 1962
A
Fig.
12
1
Fig.
13
Fig.
14
Fig.
15
Fig.
16
Figs. 12 through 16.-Tracings of the initial masticatory (A), banana CBA walnut meat OVA and cracker IT) are shown subject, The tracings were made by means of cinefluorography.
strokes of 5 subjects with with one horizontal row for
apple each
Volume Sumber
12 1
MOVEMENTS
OF MANDIBLE
AND
CONDYLAR
CENTRICITY
93
SUMMARY
Mandibular movements involved in the mastication of a walnut meat were studied by means of rapid serial roentgenography on 10 subjects. Cinefluorography was employed to study the incision and mastication of apple, banana, walnut meat, and cracker by 10 subjects. CONCLUSIONS
1. Translatory condylar movement occurred in all subjects. 2. A constant arc of opening or closing was not found. 3. Masticatory movements tended to be irregular and showed frequent anteroposterior and posteroanterior shifts. 4. Functional movement showed no precise relationship to a fixed condylar or other axis of rotation. 5. The general direction of the irregular mandibular movement in function more nearly approached that of an arc drawn from an area in the ramus than one drawn from the condyles. REFERENCES
1. McCollum, B. B.: Oral Diagnosis, J.A.D.A. 30:1218-1233, 1943. 2. Lucia, V. 0.: The Fundamentals of Oral Physiology and Their Practical Application in the Securing and Reproducing of Records to Be Used in Restorative Dentistry, J. PROS. DEN. 3:213-231, 1953. ?I I Stuart, C. E.: Accuracy in Measuring Functional Dimensions and Relations in Oral Prosthesis, J. PROS. DEN. 9:220-236, 1959. Granger, E. R.: Centric Relation, J. PROS. DEN. 2:160-171, 1952. :I Contino, R. M., and Stallard, H.: Instruments Essential for Obtaining Data Needed in Making a Functional Diagnosis of the Human Mouth, J. PROS. DEN. 7:66-77, 1957. 6. ibreinberg, L. A.: Physiologic Objectives of Reconstruction Techniques, J. PROS. DEN. 10:711-723, 1960. 7. Brotman, D. N.: Hinge Axes. I. The Tranverse Hinge Axis, J. PROS. DEN. 10:436-440, 1960. 8. Hickey, J. C., Woelfel, J. B., and Rinear, L.: Electromyographic Evidence Supporting the Mandibular Hinge Axis Theory, J. PROS. DEN. 7:361-367, 1957. Brekke, C. A. : Jaw Function. I. Hinge Rotation, J. PROS. DEN. 9:600-606, 1959. 13. Page, H. L.: Hinge-Axes: Arguments and Typical Examples: Proof, D. Digest 66:368372, 1960. 11. Bennett, N. G.: A Contribution to the Study of the Movements of the Mandible, Proc. Roy. Sot. Med., Sect. Odont. 1:79-95, 1908. (Reprinted in J. PROS. DEN. 8:41-54, 1958.) 12. Kurth, L. E., and Feinstein, I. K.: The Hinge Axis of the Mandible, J. PROS. DEN. 1:327-332, 1951. Kurth, L. E.: Balanced Occlusion, J. PROS. DEN. 4:150-167 1954. ::: Moss, M. L.: Functional Anatomy of tihe Temporomandibular Joint, ir, Schwartz, L. editor: Disorders of the Temporomandibular Joint, Philadelphia, 1959, W. B: Saunders Company, pp. 73-88. Joint : Kinematics and Actions of the Mas15. Ulrich,. J. : The Human Temporomandibular tlcatory Muscles (condensed and translated from a thesis published in Copenhagen, 1896), J. PROS. DEN. 9:399-406, 1959. 16. Borgh, O., and Posselt, U.: Hinge Axis Registration, J. PROS. DEN. 8:35-40, 1958. 17. Posselt, U.: Occlusal Relationship in Deglutition and Mastication, Transactions of the European Orthodontic Society, 1958. Articula18. Naylor, J. G.: Role of the External Pterygoid Muscles in Temporomandibular tion, J. PROS. DEN. 10:1037-1042, 1960. 19. Shanahan, T. E. J., and Leff, A.: Mandibular and Articulator Movements, J. PROS. DEN. 9:941-945, 1959. 20. Silverman, M. M. : Centric Occlusion and Jaw Relations and Fallacies of Current Concepts, J. PROS. DEN. 7:750-769, 1957.
94
SHEPPARD
J. Pros. Jan.-F&.,
Den. 1962
21. Sheppard, I. M.: The Effect of Hinge Axis Clutches on Condyle Position, J. PROS. DEN. 8 :260-263, 1958. 22. Sheppard, I. M.: The Relation of Occlusion and Temporomandibular Joint Morphology to Temporomandibular Joint Symptoms, J. PROS. DEN. 6:339-346, 1956. 23. Sheppard, I. M.: The Bracing Position, Centric Occlusion, and Centric Relation, J. PROS. DEN. 9:11-19, 1959. 24. Berry, H. M., Jr., and Hofmann, F. A.: Cineradiographic Observations of Temporomandibular Joint Function, J. PROS. DEN. 9:21-33, 1959. 25. Sicher, H.: Positions and Movements of the Mandible, J.A.D.A. 48:620-625, 1954. 26. Sheppard, I. M.: The Closing Masticatory Strokes, J. PROS. DEN. 9:946-951, 1959. 27. Scully, J. J.: Cinefluorographic Studies of the Masticatory Movements of the Human Mandible, Thesis, 1959, University of Illinois. MONTEFIORE HOSPITAL GUN HILL RD. NEW YORK 67, N. Y.