Graphic recordings of mandibular movements: Research criteria

Graphic recordings Research criteria

of mandibular

movements:

Joseph A. Clayton, D.D.S., M.S.,* W. E. Kotowicz, D.D.S., M.S.,** George E. Myers, F.D.S., D.D.S., M.S.*** The University of Michigan, School of Dentistry, Ann Arbor, Mich.

and

I

.nvestigations which have used graphic tracing devices to study mandibular movements have yielded conflicting results. l-12 However, some of the inconsistencies in the previously reported results may have been due to mechanical errors in the use of the recording apparatus. The purpose of this study was to determine whether or not graphic tracings of mandibular movements could be affected by: (1) changes in the occlusal vertical d:Lmension, (2) changes in the central bearing guidance surface, and (3) tooth guidance. A series of pantographic surveys were made from three patients and compared in order to analyze the effect that each variable had on the graphic tracings.

VERTICAL DIMENSION CHANGES AND GRAPHIC TRACINGS Method In the initial phase of this study, a pantograph? was assembled by means of c.ast aluminum anterior clutches to one patient according to the manual’s instructions (Figs. 1 and 2). The styli recording condylar movements on the vertical and horizontal condylar tables were approximately 35 mm. forward of the terminal hinge axis. The anterior tables recording horizontal bodily movements of the mandible were parallel to the recorder side arms and the styli were at right angles to the tables. Five guided border tracings were recorded from centric relation, one with the Read

before

the

American

Academy

This investigation was supported 5321 from the General Research smrces. *Associate

Professor,

Crown

**Assissitant

Professor,

***Professor

and Chairman,

tDenar

Corporation,

Partial Anaheim,

of Crown

and

Bridge

by Public Health Service Support Branch, Division

and Bridge

Department.

Denture

Department.

Crown

and Bridge

Prosthodontics,

Chicago,

Research Grant No. of Research Facilities

Ill.

5 SOl-FRand Re-

Department.

Calif.

287

280

Clayton,

Kotowicz,

and

Myers

.l. Prosth. Mach,

Dent. 1971

F ‘ig. 2

Fig.

Fig.

1. Cast aluminum

clutches

attached

to the anterior

Fig. ‘2. A pantograph assembled and attached used for scriber and table arm extensions.

IL J\ R

v

teeth

to the

with

anterior

v

hd- >

acylic

resin,

clutches.

L

Copper

tubing

was

/// a

Fig. 3. Five guided border tracings made at increased vertical dimensions were recorded on a patient with the pantograph styli not oriented on the terminal hinge axis. (h) is the condylar horizontal tracing, (v) is the condylar vertical tracing, (a) is the anterior tracing and (R) and (L) indicate the patient’s right and left sides.

teeth in contact and four with a removable concave central bearing surface and stud. Tracings made with the bearing surface were made with the teeth just separated and with the stud opened 1, 2, and 3 turns (a total vertical opening at the stud of 4 mm.) (Fig. 3). Five different tracings were recorded on the anterior tables and the condylar vertical recording tables, one at each vertical dimension. All of the tracings on the condylar horizontal tables coincided, Conclusions could be erroneously drawn from these graphic tracings that the condyles came forward with each vertical opening. Articulator

study

To determine whether the different tracings were due to the changesin condyIar positions or mechanical errors in the styli position, the study was repeated on a Hanau Model H articulator where the condylar movement could be fixed and re-

Graphic

Fig. 4. Graphic (position No. angled forward was increased on the left.

tracings recorded were oriented on at position No. 2 and lateral tracings

I)

recordings

of mandibular movements 209

on an articulator, The styli on the left and right tables the hinge axis of the articulator. The right side stylus was and backward at position No. 3. The vertical dimension were made at each vertical opening. No change was made

peated. The anterior styli and tracing tables were positioned so that as the articulator was opened and closed on a hinge the stylus tips remained on a stationary point. This we have termed the “zeroed” position. The styli on the left table and position No. 1 on the right table in Fig. 4 were oriented in this manner. The incisal pin on the articulator was opened from 0 to 9 mm. in 3 mm. increments. Lateral tracings were recorded at each vertical dimension. The three tracings recorded at different vertical dimensions coincided on the left table and at position No. 1 on the Cght table. Next, the stylus on the right table was angled forward from the “zeroed” lrosition to No. 2 position. A new tracing was recorded for each vertical dimension change and each tracing was recorded anterior to the previous tracing. The tracings on the left table coincided indicating that the articulator was moved the same way each time. Finally, the styli on the right table was angled backward from the “zeroed” position to position No. 3. Again, new tracings were recorded for each vertical dimension change and each new tracing was recorded posterior to the previous tracing. The tracings on the left table still coincided. The styli recording the condylar movements were oriented forward of the hinge axis and on the hinge axis. When the styli were forward of the hinge axis, a new -u-acing

was

CDrieuted

on the

recorded hinge

at axis

each

vertical

opening

while

the

tracings

with

the

styli

coincided.

The articulator study showed that the orientation of the styli in relationship to the hinge axis can affect graphic tracings. A schematic drawing of the effect of :jtyli position and guidances is shown in Fig. 5. The same lateral movement can be made each time at increased vertical dimensions and the graphic tracings will

290

Clayton,

Kotowicz,

and Myers

.I. Prosth. Dent. March, 1971

EFFECT OF GUIDANCE ON TRACINGS

vertical changes

condyler

tooth

Fig. 5. A schemtic drawing of the effect of stylus position, vertical changes, and the guidance on graphic tracings. (A) is the anterior recordings, stylus (2) is in the “zeroed” position, stylus (F) is angled forward and stylus (B) is angled backward. (I) is the starting vertical position, and (2) is the opened vertical position. (B) are the condylar tracings and (T.H.A) is the terminal hinge axis. (CR) is the guided border tracing from centric relation and (CO) is the unguided tracing from centric occlusion. (C) anatomic forms. (D) Surface shapes.

coincide if the styli recording condylar movements (B) are oriented on the hinge axis and the anterior styli are oriented on a tangent to an arc from the hinge axis, the “zeroed” position (stylus 2) , (the styli tips maintain a point during opening on a hinge as closely as is possible with a straight stylus). The condylar styli not oriented on the hinge axis will produce different graphic tracings (B tracings 1 and 2). The anterior styli will produce new graphic tracings if the styli are not oriented on an arc of the hinge axis. Styli angled forward (stylus F) will record a different tracing with each increase in vertical dimension and the tracings will move anteriorly. Styli angled backward (stylus B) will record different tracings with each vertical dimension increase and the tracings will move posteriorly. Therefore, graphic recordings can be affected by the styli positions when movements involve changes in vertical dimension and the styli are not oriented on the terminal hinge axis (T.H.A.) . Patient

study

The pantograph study was repeated on three patients with the styli “zeroed.” The styli recording condylar movements were centered on the terminal hinge axis.

Volume Number

Graphic

2.i 3

recordings

of mandibular

movements

291

\ cjR

G h

V

h

R l.

Fig:. 6. graph and

Five tracings at different vertical dimensions recorded on a patient styli oriented on the terminal hinge axis. (CO) is the tracing from (CR) is the tracing from centric relation (see Fig. 3 for legend).

with the pantacentric occlusion

The styli on the anterior tables recording bodily movement of the mandible in the horizontal plane were positioned so that the tip of the styli maintained a point on the tracing table as the patients were guided on the posterior terminal hinge movement. The patients made unguided lateral tracings with the teeth in contact from centric occlusion. The patients were instructed to bring their teeth together in m.a,ximum contact. Additionally, guided border tracings were made from centric relation with the teeth in contact and with the removable concave central bearing surface and the stud in position. Successivetracings were made with the teeth just separated through an increase in vertical dimension of 11 mm. as recorded between the incisor teeth.

There were different tracings recorded on each tracing table when the patient made unguided lateral movements from centric occlusion as compared to those made during movements from centric relation (Fig. 6). Tracings were curved on the anterior tables and the tracings from centric occlusion were recorded anterior to the centric relation tracings (see C, Fig. 5). (On this pantograph all styli are attached to the maxillae and are stationary. The tracing tables are attached to the mandible and move with the mandible.) The curvature of the centric occlusion tracing was due to a cuspal interference guiding the mandible and condyles away from the border tracing and not due to a change in vertical dimension. The guided border tracings from centric relation with the teeth in contact were recorded posterior and lateral to the centric occlusion tracings and the tracings on the anterior tables were relatively straight lines.

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Kotowicz,

and Myers

J. Prosth. Dent. March, 1971

A Fig. 7. Two sets of tracings recorded simultaneously on a patient on the anterior tables. stylus was angled forward at (A) and backward at (B). Tracing No. 1 was unguided centric occlusion, tracing No. 2 was guided from centric relation with teeth in contact, tracing No. 3 was guided from centric relation with a concave central bearing surface bearing stud in place and the vertical dimension increased 2 mm,

The from and and

The condylar tracing tables moved downward, backward and laterally from centric occlusion to record the centric relation border tracings (Fig. 6). The tracings made with the concave central bearing surface and an increased vertical dimension coincided with the centric relation border tracings with the teeth in contact. These border tracings have coincided although the vertical dimension was opened 11 mm. as measuredbetween the incisor teeth. To determine the effect of vertical dimension change and styli position on a patient, the angles of the anterior styli were changed (Fig. 7). The left stylus was angled backward and the right stylus was angled forward from the “zeroed” position. Although both styli were recording simultaneously and recording the same mandibular movements, different graphic tracings were recorded. The styli recording condylar movements were not changed and the tracings coincided. Discussion

All three tracings involve different vertical dimensions. The guidance for the movements, the teeth and a concave bearing surface, involve various vertical dimension changes as lateral movements were made (see D, Fig. 5). The styli angled posteriorly produced tracings that moved posteriorly as the vertical dimension was increased and the tracings were curved posteriorly. The styli angled anteriorly produced tracings that moved anteriorly and the tracings were curved anteriorly. Curved

tracings

can be recorded

when

styli are angled

off the terminal

hinge

axis

and the curvatures will be in the direction of the angulation when the vertical dimension is increasedand decreased. Conclusions

The orientation of styli and recording table affected graphic tracings of mandibular movements when the vertical dimension is changed. Cusps gliding on inclines involved

changes

in vertical

dimension.

In studies of mandibular

movements

the re-

cording device should be oriented to the terminal hinge axis so that’ changesin vertical dimension

do not

cause different

tracings.

If this is not done,

the position

of the

recording device in relation to the terminal hinge axis, the effect on the tracing o.f

G ru p/ LIL ‘. t.ec,oI.d’tugs of tt~andibular

Fig. 8. Removable central bearing surfaw te,:th separated. The removable surfaces w’zre attached to (3) the concave surface.

ircreased vertical dimension, be reported. ‘Inconsistencies, be due to mechanical errors CENTRAL Methods

BEARING

(A) usrd

movetnents

and bearing stud (Bj used for guidance 4th (I) thr wnwx and (2) the flat which

arr

and whether the tracing is guided or unguided previously reported on mandibular movements, in the positioning of the recording apparatus.

SURFACES,

SHAPES,

293

AND

GRAPHIC

should could

TRACINGS

The pantographic apparatus was assembled on anterior clutches attached to the teeth of three patients. Guided border tracings were madt= on the same recording papers as the patient moved against removable concave, flat and convex central bearing surfaces (Fig. 8‘) _ The styli were “zeroed.” Results The border tracings recorded with three different bearing surfaces coincided on all recording tables (Fig. 9). (Note: The protrusive lines on the anterior recording tables are not border tracings and, therefore, do not c.oincide.1 Discussion Different shaped bearing surfaces involve changes in vertical dimension as lateral movements are recorded (see D, Fig. 5). A concave surface would produce a vertical c’pening in lateral movements and a convex surface would produce a vertical closure in lateral movements. The movements of the condyles involve vertical changes as the condyles move on the slopes of the eminences. These vertical dimension changes coupled with different styli orientation can produce different graphic tracings. Conclusions The shape of the central bearing surface can affect graphic tracings &pending on the anguIation of the styli recording the movement. Graphic tracings of mandibular movements recorded against different bearing surfaces will coincide if the styli a.re “zeroed.” Graphic tracings will be different for each surface if the styli are angled forward or backward from the “zeroed” position. In studies of mandibular movements involving central bearing surfaces the

J. Prosth. March,

Dent. 1971

made on a patient with the concave, convex and flat bearing faces, and with the styli “zeroed” (see Fig. 3 for legend).

sur-

294

Clayton,

Kotowicz,

and Myers

L

a Fig. 9. Three recordings

shape of the bearing surface (concave, flat or convex) styli recording the movements should be reported.

and

the angulation

of the

TOOTH GUIDANCE, CHEWING, AND GRAPHIC TRACINGS Method The pantograph was assembled on anterior clutches attached to one patient with a “slide” or difference between centric relation and centric occlusion. The styli were “zeroed.” Two lateral tracings were recorded on the patient. The patient was first instructed to bring the teeth together and move unguided in a left and right lateral movement with the teeth in contact (Tracing No. 1, Fig. 10). The patient was then guided to the terminal hinge position and a guided border tracing was made from centric relation with the teeth in contact (Tracing No. 2, Fig. 10). The patient then chewed test foods-gum, carrots, and peanuts. The chewing pattern for gum is shown in Fig. 10.

Results The patient did not function (chew) to the recorded border tracing from centric relation as recorded on the anterior recording tables. The patient preferred chewing on the left side. The tracings from centric occlusion were tooth guided and interferences prevented functional movements to the border tracings (see C, Fig 5). After the interferences were removed the patient functioned to the border tracing (this and the results of chewing other test food will be reported in another article). Therefore, unguided tracings cannot always be considered border tracings because occlusal interferences and the muscles may prevent movement of the mandible along the border position (see C, Fig 5). Guided border tracings with the teeth in

Graphic

recordings

of mandibular

movements

295

R

a

a

Fig. 10. The relationship between functional movements (chewing), tooth guidance and graphic tracings on a patient. (A) is the normal size of the recording and (B) is an enlargement of the anterior tracings. Tracing No. 1 is from centric occlusion and tracing No. 2 is from centric relation. (C) is a mark placed by the styli when the patient was in edge-to-edge relationship of the canines (see Fig. 3 for legend).

contact or tracings against central bearing surfaces eliminate the effect of the occlusal interferences and the patient can be guided along the border positions. The border movements would be restricted only by the anatomic features of the masticatory system without the influence of the teeth and muscles. Tooth interferences, and muscles conditioned to these interferences, direct unguided movements from coinciding with guided border movements. This is substantiated by tracings of border movements and functional movements recorded in Fig. 10 when the patient chewed gum. The functional movement coincided with the tracings from centric occlusion at least from the canine to canine incisal edge to edge relationship to centric occlusion (see C, Fig. 10). This entire recording was also recorded on movie film. Masticatory strokes frequently started near the canine mark and followed to centric occlusion along the centric occlusion tracing and on beyond centric occlusion. The heavy dark area along the centric occlusion tracing is indicative of the number of times the functional movements coincided with this tracing (for comparison of the relationship of the tracings without the functional movements refer to Fig. 6). In the recorded condylar movements, the functional area was restricted to the

296

Clayton, Kotowicz,

J. Prosth. Dent. March, 1971

and Myers

B Fig. 11. Changes of styli angulation and the (chewing) on a patient. (a) Anterior tracings. the left styli is “zeroed.” (B) The right stylus “zeroed.” Each right and left tracing was recorded

effect

on recording The right stylus is angled backward simultaneously.

(A)

functional is angled and the

movements forward and left stylus is

tracing recorded from centric relation (the border tracing) on the vertical tables. The functional movements coincided with the border tracing on the horizontal tracings. From the condylar recordings, it appears that the functional movement of the condyle may coincide frequently with the centric relation tracing even though movements were restricted to the tracing from centric occlusion on the anterior recordings. To determine the effect of styli position on the recording of functional movements (chewing), the anterior styli angulations were varied. In Fig. 11, A the left stylus was in the “zeroed” position and the right stylus was angled forward (seeA, Fig. 5). The patient chewed gum. Both tracings were recorded simultaneously. The functional area recorded by the forward angled stylus appears to be limited in an anterior-posterior direction and the recording gives the appearance of the patient functioning posterior to the border tracing. In Fig. 11, B the right stylus was then angled backwards and the patient again chewed gum. The left stylus was still “zeroed.” The border tracings were curved posteriorly. The functional movements did not coincide with the left border tracings; however, they did on the “zeroed” stylus tracing. Conclusions

Unguided tracings made by the patient with the teeth in contact may not be true border tracings. Tooth interferences and musclesmay deflect movement away from the border position. Border tracings should be guided when the teeth are in contact, or a central bearing surface should be used to eliminate the influence of

Vohne Nmnber

25 3

Graphic

recordings

of mandibular

movements

297

tooth interferences and muscle conditioning to these interferences. Several tracings should be recorded to insure that tracings are true border tracings. True border movements give stable and repeatable tracings and recordings. Studies involving conclusions as to whether functional movements and the border movements coincide should have recordings of true border movements. The type of occlusion-differences between centric relation and centric occlusion, slides from centric relation to centric occlusion, occlusal contact and occlusal interferenceshould be reported on patients being studied. Occlusal interferences can affect graphic tracings and restrict the parameters of functional movements. In studies of mandibular movements, the effect of the occlusion on the movements should be determined. Again, the positions of the styli can affect the graphic recording of functional movements. The angles of the styli and the positions of styli in relationship to the terminal hinge axis should be reported.

GRAPHIC TRACINGS VS. PANTOGRAPHIC TRACINGS A distinction between graphic tracings and pantographic tracings has been made.3 Graphic tracings are recordings made on a patient from which conclusions a.bout mandibular movements are made directly from the tracings. Pantographic tracings are recordings of mandibular movement of a patient from which an instrument (articulator) is adjusted to follow the tracings. Then conclusions about mandibular movements are made from the movement of casts on the instrument. Stylus positions can affect graphic tracings, therefore, erroneous conclusions can be drawn from graphic tracings. Correct placement of styli is important in studies using graphic tracings. Styli positions in pantographic tracings may not be significant as long as the styli positions are not altered from the tracings recorded on the patient through the adjustment of the instrument. Altering styli position in relationship to the tracings, before the instrument is adjusted, could produce erroneous instrument settings.

ISUMMARY Studies using graphic tracing devices have yielded conflicting results concerning mandibular movements, The purpose of this study was to determine whether graphic tracings could be affected by styli positions in relationship to changes in vertical dimension, by the shape of central bearing surfaces and by tooth contacts and functional movements. A pantograph was used on patients to study the effect of these variables. The results of this study indicate that several variables can affect graphic tracing of mandibular movements. The effects of these variables were shown and suggestions were made to reduce the inconsistencies found in studies using graphic tracings. Research criteria were suggested for conducting and reporting the results of studies of mandibular movements.

CONCLUSIONS Graphic tracings, tracings from which conclusions are drawn, of mandibular movements can be affected by changes in the vertical relations, by different shapes of guiding surfaces and by tooth guidances.

298

Clayton,

The tracings tracings

J. Prosth.

Kotowicz, and Myers

recording represent produced

March,

Dent. 1971

apparatus should be tested to determine whether the graphic recorded mandibular movements or whether they are erroneous by mechanical errors.

References 1. Cohen, R.: The relationship of anterior guidance to condylar guidance in mandibular movement, J. PROSTH. DENT. 6: 758-767, 1956. 2. Kurth, L. E.: Mandibular movements in mastication, J. Amer. Dent. Ass. 29: 1769-1790, 1942.

3. Kotowicz, W. E.: Analysis of pantographic tracings, Ann Arbor, School of Dentistry, 1968 (63 p. typed thesis). 4. 5. 6. 7. 8. 9. 10. 11. 12.

University

of Michigan,

La Pera, F.: Understanding graphic records of mandibular movements, J. PROSTH. DENT. 18: 417-424, 1967. McCollum, B. B.: Fundamentals involved in prescribing restorative dental remedies, Dent. Items Interest 61: 852-863, 1939. McCollum, B. B., and Stuart, C. E.: A research report, South Pasadena, Calif., 1955, Scientific Press. Payne, S. H.: A study of posterior occlusion in duplicate dentures, J. PROSTH. DENT. 1: 322-326, 1951. Posselt, U.: Studies in the mobility of the human mandible, Acta Odont. Stand. 10: l-160 (suppl. lo), 1952. Shanahan, T. E. J., and Leff, A.: Mandibular and articulator movements. Part VII. Concepts of lateral movements and condyle paths, J. PROSTH. DENT. 14: 279-289, 1964. Shanahan, T. E. J., and Leff, A.: Mandibular and articulator movements. Part V. Vertical and sagittal axes myths, J. PROSTH. DENT. 13: 866-872, 1963. Shanahan, T. E. J., and Leff, A.: Mandibular and articulator movements. Part II. Illusion of mandibular tracings, J. PROSTH. DENT. 12: 82-85, 1962. Schweitzer, J. M.: Masticatory function in man, J. PROSTH. DENT. 11: 625-647, 1961. THE UNIVERSITY OF MICHIGAN SCHOOL OF DENTISTRY ANN ARBOR, MICH. 48104