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Mandibular movements in three dimensions
MANDIBULAR
MOVEMENTS
IN THREE DIMENSIONS
JUDSON C. HICKEY, D.D.S., M.Sc.,* MORGAN I.. ALLISON, D.D.S.,** JULIAN B. WOELFEL, D.D.S.,+**
CARL 0. BOUCHER, D.D.S.,****
AND
RALPH W. STACY, PH.D.****+
The Ohio State University, College of Dentistry, Columbus, Ohio of condyle movement is essential in the understanding of occlusion, the treatment of temporomandibular joint disturbances, the effect of occlusion on periodontal health, and the development of tooth forms for dental restorations, Condyle activity has been studied by several different means. Lucer in 1889 photographed the reflection of sunlight from beads placed opposite the condyles. Walker2 in 1896 used a facial clinometer to measure condyle movements. Bennett3 in 1908 traced the pathway of a light positioned opposite the condyle. Hildebrand4 recorded condyle movements by roentgen fluoroscopy. Higley and Logan5 used a series of cephalometric roentgenograms to observe condyle positions. Frank6 made stereoscopic roentgenograms of condylar movement. Posselt? studied condyle movement by profile radiography. Lindbloms and Berry and Hoffman9 reported studies of condyle activity using cineradiographic methods, and Zola and RothchildlO followed mandibular movements with a condylar thesiograph. We felt that information regarding the related function of the condyles and the teeth could be obtained by the use of three-dimensional motion picture photography. A direct approach to investigate condyle activity was devised. The movement of a pin inserted directly into the condyle was observed and compared with the movement of a pin attached to the lower incisor teeth. The activity of both pins was recorded in the horizontal, sagittal, and frontal planes by three synchronously running motion picture cameras, and the film was analyzed by a frame-by-frame projection.
A
KNOWLEDGE
SUBJECTS
Two subjects were tested by this method. Their over-all general and oral health was good. There were no pathologic temporomandibular joint symptoms, and the condyles were located relatively close to the surface of the skin. Both subjects had This investigation was supported in part by Research Grants D-54S(C4) and D-1469 from the division of Research Grants and Fellowships of the National Institutes of Health, U.S. Public Health Service. Read before the Academy of Denture Prosthetics in Colorado Springs, Cola. *Present address: Professor and Chairman, Department of Prosthodontics, College of Dentlstry, University of Kentucky, Lexington, Ky. **Professor and Chairman, Division of Oral Surgery. ***Associate Professor, Division of Prosthodontics. ****Professor and Chairman, Division of Prosthodontics. *****Professor, Department of Physiology. 72
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MANDIBULAR
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full complements of natural teeth with Class I occlusions. The overlap of the anterior teeth was such that orthodontic bands could be cemented on the opposing central incisors and cause no interference with jaw movements. The transverse hinge axis of forcefully retruded mandibular rotation was located on one subject and tattooed on the skin to serve as a guide for the placement of the condyle pin (Fig. 1) . HEAD FIXATION
Head fixation during masticatory tests may not be desirable because of its possible effect on natural jaw movements. However, it was anticipated that condylar activity would be of such a small magnitude that even small movements of the head would seriously interfere with an accurate analysis. Therefore, a head cap was made for each subject immediately preceding the testing (Fig. 2). The head cap was purposely kept out of contact with the skin overlying the temporal muscles, because otherwise a contraction of these muscles caused movement of the head cap. Wire supports were incorporated within the plaster gauze as the head cap was made to stabilize frames containing glass grids that were attached for measure-
Fig. 1.-A, The face-bow is attached to the mandible by means of a clutch that is securely fttened on the lower natural teeth. B, The transverse hinge axis point is permanently marked on the patient’s face by injecting a small amount of dye beneath the surface of the skin.
HICKEY
J. Pros. Den. Jan.-Feb., 1963
ET AL.
c.
D.
Fig. 2.--A, The location of certain landmarks is marked on the gauze so that the finished plaster head cap will be formed properly and not interfere with the musculature. B, A predesigned wire is incorporated in the headcap to support metal frames for measurement purposes. C, The supporting wire is securely attached with plester-gauze. D, The completed headcap is securely fastened to the head support of the dental chair.
Fig. 3.-The
orthodontic
bands and wires are positioned
on opposing central
incisors.
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merit purposes. After the head cap was completed, it was rigidly fixed with the plaster gauze to the head support of the dental chair to eliminate head movement IFig. 2). WIRE FRAME ATTACHMENTS
Orthodontic bands that supported wire frames were attached to the teeth with zinc phosphate cement (Fig. 3). One band and wire was attached to the upper right central incisor and the other to the lower left central incisor. The bands and wires did not interfere with the teeth or lips during jaw movements and mastication. The wires served as a means of attachment for miniature electric lights which were photographed during jaw movement. CONDYLE PIN PLACEMENT
The ear and the skin of the face in the region of the left condyle were scrubbed with bacteriostatic soap and cleansed with alcohol. An aseptic technique was used. A local anesthetic was deposited in the subcutaneous tissues and in the joint space. Then a Steinmann pin was inserted directly into the condyle of one subject by means of an orthopedic hand drill (Fig. 4). On the second subject, a specially designed face-bow was used to guide the pin in the hand drill into the condyle along the mandibular transverse axis (Fig. 5). One of the movable condylar rods of the face-bow was replaced by a pointed tube that contained a hole machined to a precise diameter that would fit and guide the condyle pin during its insertion (Fig. 5, B). A pointed adapter was placed on the other condylar rod so that it could be positioned accurately on the opposite hinge axis point. Premeditation for this subject was 100 mg. of pentobarbital, 75 mg. of meperidine, and 0.04 mg. of atropine (l/150 grain). A cylindrical steel pin 1.5 mm. in diameter and 65 mm. long was placed in
Fig. 4.--A, A local anesthetic is injected before the placement of the condyle pin. B, The condyle pin is inserted at the condyle. There is no pain associated with the procedure.
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HICKEY
J. Pros. Den. Jan.-Feb., 1963
ET AL.
A.
B.
Fig. 5.-A, A pointed guiding tube with a diameter car ,responding in size with the COTidyle pin is located at the left end of the face-bow. A pointed ada .ptor is secured on the movable condylar rod part at the right end of the face-bow. B, The colndyle pin is in the orthopedic drill and is positioned within the specially designed guiding tube.
an orthopedic hand drill and inserted into the hole in the tube of the special face-bow rod. The face-bow rods were positioned on the hinge axis marks on the face (Fig. 6) and then steadied in that position by two of the investigators. The subject held the jaw firmly in centric relation, and then by operation of the hand drill, the pin was inserted into the condyle to a depth of about 1 cm. (Fig. 7). This insured that the pin was rigidly fixed to the condyle with its full length located on the previously determined transverse axis. GRID DESIGN AND LOCATION
Lightweight metal frames were built to hold glass measuring grids in the horizontal, frontal, and sagittal planes alongside both the condyle and incisor pins (Fig. 8). The frames accommodated regular lantern slide glass on which had been printed horizontal and vertical grid lines that were 5 mm. apart. The metal frames were attached to the supporting wire of the‘ head cap and positioned so as not to
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MANDIBULAR
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77
int erfere with pin or jaw movements (Fig. 9). With this arrangement, two me:asuri ing grids (one for the incisor and one for the condyle pins) were visible in all thr -ee views of the motion picture film.
Fig. 6.--A, The face-bow assembly is ready for use. B, The face-bow the ccmdyle pin will be inserted along the transverse hinge axis.
is positioned
so 1.hat
A.
Fig. 7.-A, The condyle pin is firmly embedded shows the position of the pin in the left condyle.
into the condyle.
B,
The
roentgenogram
78
HICKEY
ET AL.
A.
Fig. S.-A, Connecting canL be positioned correctly the metal frames.
rods are attached to the sides of the metal frames so that the fran Les alongside the face. B, The glass measuring grids are in place wit1 lin
Fig. 9.4he metal frames are positioned so that a measuring lie :hts in all three filmed views of the condyle and incisor pins.
grid
is present
behind
the
ic%-E:”
MANDIBULAR
ATTACIIMENT
OF LIGIITS
MOVEMENTS
IN
THREE
79
DIMENSIONS
TO PINS
Small lights 1 mm. in diameter were used for visual and photographic purposes (Fig. 10). Adapters were formed around the lights so that single lights (Fig. 11, A) could be placed on the end of the incisor wires and one on a rigid wire directly above the condyle pin. A double light (Fig. 11, B), one light at right angles to the other, was placed on the exposed end of the condyle pin. The double light facilitated observation of rotation as well as the other movements of the condyle. The single light on the upper central incisor and the one directly above the condyle pin served as reference points for determining the movements of the other lights. The condyle pin with the light on it extended from the skin of the face approximately 63 mm. The incisor pin and light extended from the teeth approximately 65 mm. The complete arrangement for making the motion pictures is seen in Fig. 12. MOTION
PICTURE
FILM
ANALYSIS
The pathways of the moving lights were determined by a frame-by-frame projection of each of three films onto graph paper with the image enlarged 3 times actual size. The views of incisor and condyle pins were analyzed separately to compensate for the different size of their image on each film. A typical sketch of the reference light and pin for a specific view (front, top, or side) was made on the graph paper, and as the film was projected frame by frame, a plot was made of the light attached to the condyle or to the incisor pin as it changed position during function. When the points of the plot were connected, the resultant tracing indicated the pathway of the light for a given movement. Several of the jaw movements and nine masticatory strokes of chewing carrots on the right and on the left sides were analyzed by this method for the subject who had the pin located in the condyle by palpation. Only the results for this subject are given in this report. TRACING
ERROR
Tracings were made of the reference, condyle, and incisor lights from one motion picture frame six different times to determine the measurement error in tracing. When the six tracings of the three lights were superimposed, the widest dis-
Fig.
IO.---The
miniature
light
is compared
in size with
a No. 9 round
bur.
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HICKEY
J. Pros. Den. Jan.-Feb., 1963
ET AL.
Fig. Il.-A, The light is incorporated into an adaptor that :fits over the end of the incisor pin. B, Two lights at right angles to each other fit over the end of the condyle pin to I:bermit a study of rotation as well as other movements of the condyle.
crepancy was 0.5 mm. on a scale 3 times actual size. Thus the tracing error was +0.17 mm. REST POSITION,
CENTRIC
OCCLUSION,
AND
CENTRIC
RELATION
As the mandible moved from the physiologic rest position to centric occlusion, the incisor pin moved up 2 mm., back 0.3 mm., and to the right 0.6 mm. (Fig. 13). During this same movement, the condyle pin moved up 0.6 mm., back 0.4 mm., and to the right 0.3 mm. (Fig. 13). Thus, when the teeth moved from rest position to centric occlusion, the movement of the condyle pin was not one of pure rotation but involved bodily movement in all three dimensions. Centric relation was not in harmony with centric occlusion for this subject. The incisor pin moved up 1.7 mm., forward 1.1 mm., and to the right 0.5 mm. as the teeth moved from their initial contact in central relation into centric occlu-
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MOVEMENTS
IN
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DIMENSIONS
sion (Fig. 14). The condyle pin moved up slightly, straight forward 0.7 mm., and to the right 0.2 mm. (Fig. 14). The rotational light moved forward and upward slightly during this movement, indicating that the condyle rotated as it came forward from centric relation. Apparently, the condyle path was influenced by the direction of the movement of the opposing teeth from their initial contact in centric relation to centric occlusion. CONTROLLEDOPENING
MOVEI~ENTSOFTHEMAND~BLE
The transverse axis of rotation of the mandible was not located on this subject. The position of the pin in the condyle was based on palpation. Nonetheless, during the hinge opening movement, the condyle pin remained in a fixed position and rotated 5 degrees while the incisor pin moved downward 8 mm. (Fig. 15). During this retruded opening, the incisor pin moved downward 18 mm. without lateral deviation and posteriorly 9 mm. A lateral deviation of 2.5 mm. occurred as the mandible reached its maximal opening (Fig. 15). The center of rotation for the arc scribed by the incisor pin during the retruded opening was not in the region
Fig. la.-The motion picture cameras are positioned to record mandibular three planes. Note the camera that is directly above the subject’s head.
movement
in all
82
HICKEY nrsr
TO
?BOYT
cPllIR.Ic
VIEY
oocLIJsIol SXDP
VILY
W
TOP
W
VIlY IRCN?
m
m
COIlDILL PIU
J. Pros. Den. Jan.-Feb., 1963
ET AL.
1 Ii
5m
II ‘00
a’
0
-7
Ll?T
PNJnT
BACK
i
i
cow
Fig. 13.-The condyle and incisor pins moved in all three dimensions as the mandible moved from the physiologic rest position to centric occlusion. R, the position of the pins when the jaw was in rest position. CO, the position of the jaws with the teeth in centric occlusion.
OllTRIC
TO
PLLAZIOr ?POllT
VILY
SIDE
W
PIE
IYCISOR PIh
i
VIXY TOP ImmT
T
m-ul
Lw
IcaT
VIEU W
I
-k
m h
COIDlLl
OCCLDdIOl
CPITPIC
I
;
-0 Rmi?
Im
7 CR.
-W -0
yoI(
Fig. 14.-The movement of the condyle pin reflects the direction of the shift of the mandible from the position of initial contact of the teeth to centric occlusion: CR, the position of the pin when the jaw was in centric relation. CO, the position of the pin with the teeth in centric occlusion.
Volume 13 Number 1
MANDIBULAR
?PalT
MOVEMENTS
IN
EIIGX
QPPIIlG
VI&U UP
SIDE
THREE
83
DIMENSIONS
VIEY
COIDLLL
b
PIG co
m M
m
ImwT
aIT
xncIsoP PI1
-
aIGm
i
-
tM+em
.
-CIOSI
i
Y WY
Fig. 15.-The condyle pin remained in a fixed position during the hinge opening until the incisor pin had reached the position indicated by the arrow. CO, the position when the teeth were in centric occlusion.
PXGULAP
OPllIlG SIDE
COlDXLl
PII
movement of the pin
VILY UP
TOP
VIXY PmnT
Dal
d
a
xIcIsoP PI1
aIGkir t
Fig. 16.--Bodily movement of the condyle pin began at the same time as that of the incisor pm in the regular opening movement. CO, the position of the pin with the teeth in centric occlusion.
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HICKEY
J. Pros. Den. Jan.-Feb., 1963
ET AL.
of the condyle. The small deviations in the tracing of the incisor pin during the hinge opening may have resulted from the irregularities of the surfaces of the condyle and the disc as the rotation between these two structures occurred. The regular opening was not maximal but was wider than would be required during mastication (Fig. 16). The incisor pin moved downward 35 mm., backward 17 mm., and 4 mm. to the left during opening. The closing stroke was to the right and in front of the opening stroke, following a direct pathway back to the beginning position. During the regular opening, the incisor pin was 5 mm. further protruded than for the hinge opening at the widest point of separation. On the regular opening, bodily movement of the condyle pin began at the same time as the incisor pin movement. The condyle pin moved down with 12 degrees of rotation and to the left 0.6 mm. during the total regular opening movement. The pathway of the condyle pin during the closing phase was in front of and to the right of its position during the opening phase (Fig. 16). LATERAL
MOVEMENTS
OF THE MANDIBLE
The lateral sliding movements of the mandible began with the teeth in centric occlusion and were guided by the inclined planes of the teeth, ending when the opposing cuspids passed edge to edge (Fig. 17). The incisor pin moved laterally 12.7 mm. in the left lateral sliding movement as compared with only 6 mm. in the right movement. This difference was caused by the increased horizontal and vertical overlap of the left cuspid teeth as related to the right cuspid teeth. The shape of the tracmg of both the right and left sliding movements was directly related to the guiding influence of the teeth. The movement of the condyle pin in the lateral sliding excursions seemed to be LATLBAL
YLIDIYO FBOEt
xrC1jon
XOVEYIIITB
VIEU
YIDl
PII
VIIY UP
ID!
m SLIDE LE?f %
00
00 SLIDE BIGHT
J
J i++ OUT pay
‘Mix
Fig. 17.-The pathway of the incisor pin in lateral sliding movements reflects the guiding influence of the inclined planes of the teeth. CO, the position of the incisor pin with the teeth in centric occlusion.
Volume 13 Number 1
M!IANDIBULAR LATKPAL
MOVEMENTS
TfIREE
WOVKWKKIS
SLIDING
TEOYT
IN
VIEW UP
DIMENSIONS PIK
COIIDILI
SIDE
85
TOP
VIPY UP
VISY
7
SLIDE LET?
cod
LTTT
nIQuT
KIWI
nAlx
m SLIDE BIQEZ
d
J” mm
Fig. l&-The dip in the pathway of the condyle pin during the lateral sliding movements corresponds in time to the edge-to-edge contact of the cuspids: CO, the position of the condyle pin with the teeth in centric occlusion.
influenced by the guiding factors of the teeth (Fig. IS). The condyle pin in both right and left sliding movements made a dip that was similar in time and form to the edge to edge contact of the cuspids. This dip caused by the guiding influence of the cuspid teeth was not reflected to the same degree in a lateral excursion when the teeth were out of contact (Fig. 19). Th us, the condyles seem to follow pathways that are influenced by tooth contacts. The condyle pin moved laterally (Bennett movement) when the mandible moved to the left side (Fig. 19). However, such lateral movement of the condyle pin could be caused by either a rotation of the left condyle around a vertical axis, by a direct lateral shifting of the mandible, or by a combination of these two factors. To determine the actual lateral movement of the condyle, one tracing was made of the condyle and incisor pins from a motion picture frame from the top view with the teeth in centric occlusion and a similar tracing was made of a motion picture frame with the jaw in its most lateral position. On each of these, tracings lines were drawn through the shafts of the condyle and incisor pins and were extended inward until they intersected (Fig. 20, A). The change in the position of the intersection of the lines with the jaw in the two positions indicated the magnitude of the lateral shift of the mandible. During this maximal lateral movement with the teeth out of contact, the mandible shifted laterally 4 mm. (Fig. 20, B) . This same method for determining lateral movement was repeated for lateral sliding movements and for the maximal range of tooth contact during mastication. The direct lateral movement of the condyle during a left lateral sliding movement (from centric occlusion to the edge to edge position of the cuspids) was 2.7 mm. However, the range of tooth contact during the lateral movements occurring in mastication was much less than in the controlled sliding movements. The maximal
86
HICKEY
J. Pros. Den. Jan.-Feb., 1963
ET AL.
lateral shift of the condyle, found to occur during maintained tooth contact in mastication, was only 0.3 mm. MASTICATION
The pathway of the incisor and condyle pins was traced for all three views as the subject chewed a 3 Gm. portion of carrots on the left side and then another 3 G m. portion * on the right side. Tracings were made from nine selected masticatory cycles, three at the beginning of the chewing, three in the middle, and three just before the chewing was completed. Thus, a total of eighteen masticating cycles was analyzed. Chewing on the Opposite Side From the Condyle Pin (Right Side).-Although there was a similarity in the pattern of the condyle and incisor pin movement during mastication, no two cycles were the same. Starting with the jaw in the open position, the condyle pin was in a downward position from its position in centric occlusion (Fig. 21) . As the incisor pin moved to the right side and started upward and forward so that the teeth could engage the carrots, the condyle pin moved down, forward, and to the right. As the incisor pin moved from its lateral position and continued upward, forward, and medially toward centric occlusion, the condyle pin moved up, back, and medially. The upward stroke of the condyle ended when the teeth were in centric occlusion. On the opening stroke, the condyle pin moved slightly down, backward, and to the left as the mandible rotated around the left condyle. As the incisor pin continued downward, the condyle pin moved further down, slightly forward, and to the right in preparation for the next chewing cycle (Fig. 21). LEPT PROIT
LATKEAL
rxCuPSIOI SIDl
vxru UP
mdP
COlDILl PII
RIOUT
VILU UP
LEn
m?
PmsT
uol
m
m
11c1a00 PI1
Q&k@
D
Fig. lg.-The pathway of the condyle and incisor pins when the jaw is moved laterally with the teeth out of contact is not similar to the pathway followed when the jaw is moved laterally with the teeth in contact (see Figs. 17 and 18). The condyle pin moved laterally during the left lateral excursion (top and front views), but this apparent lateral movement of the condyle pin could be caused by rotation of the left condyle around a vertical axis.
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MANDIBULAR
MOVEMENTS
IN
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DIMENSIONS
87
Fig. 20.--A, The long axes of the condyle and incisor pins are extended inward to an intersecting point from two different motion picture frames: one with the teeth in centric occlusion and the other with the jaw in a maximal left lateral position. The distance between the two intersections depicts the bodily shift of the mandible in the horizontal plane. A scaled drawing of the subject’s mandible was positioned relative to the pins to indicate the effect of the lateral shift of the mandible on both tooth and condyle movement. B, An enlarged view shows the direction of the shift of the left first molar (arrow) and the amount of lateral movement of the left condyle (see scale ).
The distances traveled by the condyle and incisor pins for the nine masticatory cycles on the right side were determined (Table I). All measurements were made from the centric occlusion position. The downward movement of the condyle pin ranged from 3.3 to 4.7 mm. for an average distance of 4 mm. The corresponding downward movement of the incisor pin ranged from 17 to 28.3 mm. for an average distance of 20.1 mm., which was found to be the equivalent of 14 mm. of actual incisor tooth movement. The forward movement of the condyle pin during the masticatory cycles on the right side ranged from 0.5 to 2.1 mm. for an average of 1.6 mm., and the inward movement ranged from 0.7 to 1.6 mm. for an average of 1 mm. The movement of the incisor pin toward the right side that accompanied the forward and inward movement of the condyle pin ranged from 1.7 to 4.6 mm., for an average of 3.4 mm. The backward movement of the incisor pin ranged from 3.1 to 15 mm., for an average of 7.2 mm. The forward and inward component of the condyle pin movement during mastication was associated with lateral movement of the incisor pin and did not seem to be related to the opening movement of the mandible. During the nine masticating cycles on the right side, the rotational light moved
88
HICKEY TABLE
I.
INCISOR
AND CONDYLE
INCISOR
PIN MOVEMENT
PIN MOVEMENT
MASTICATING CYCLE
J. Pros. Den. Jan.-F&., 1963
AL. DURING
(MM.)
RIGHT(ON CLOSING)
a 3
ET
MASTICATIONON
CONDYLE
RIGHTSIDE
PIN MOVEMENT*(MM.)
DOWNWARD
19.6 17.3 21.0
k(: 15:o
2.7 1.7 4.0
3.3 4.2 4.0
0.5 1.9 1.3
0.7 1.3
i 10
:t
20.0 28.3
10.0 6.3
4.0 3.5
3.7 4.0
2.0 1.9
::::
67
1:
21.6 18.3
5.3 6.8
4.6 2.9
%:i
2.1
0.7 1.1
i
“2:
17.0 17.7
4.1 3.1
4.6 2.7
4.0 4.7
1.7 ::i
1.6 1.0
180.8 20.1
65.3 7.2
30.7 3.4
36.2 4.0
14.5 1.6
9.4 1.0
Total Average
All measurements made from centric occlusion position. Note: 20 mm. of incisor pin opening equals approximately *Condyle pin in left condyle. TABLE
II.
INCISOR
AND CONDYLE
INCISOR PIN MOVEMENT
PIN MOVEMENT
14 mm. of incisor movement.
DURING
(MM.)
MASTICATIONONLEFTSIDE
CONDYLE
MASTICATING CYCLE
PIN MOVEMENT*(MM.) -
DOWNWARD
1
59 6.6
BACKWARD
LEFT(ON CLOSING)
DOWNWARD
:t
25.7 20.5 25.0 23.7 23.0
8.3 8.7 8.0 2.:
4.3 5.7 6.0 6.3 6.7
2.8 3.3 2.8 2.3
:;
21.7 18.7
7:1
4.7 2.7
2
15.5 14.3
Z3.4
Total Average
188.1 20.9
60.2 6.7
FORWARD (ON OPENING)
LATERAL (ON CLOSING)
ROTATION (DEGREES)
10
-1.0 0.6
0.7 1.5 1.3 1.0
2.3 2.6
0.3
1.0 1.3
ii
4.0 2.8
2.3 1.7
8:; 0.5
0.7
:6
43.2 4.8
22.4 2.5
0.26 0.3
9.2 1.0
64 7
All measurementa made from centric occlusion position. Note: 20 mm. of incisor pin opening equals approximately *Condyle pin in left condyle.
5
14 mm. of incisor movement.
through an arc that ranged from 5 degrees to 10 degrees for an average of 5.6 degrees. The least amount of rotation occurred during the first one third of the opening stroke, while the greatest amount occurred during the last two thirds. Chewing on the Same Side as the Condyle Pin (Left Side).-A different pattern of condyle activity was observed when the chewing was done on the same side as the condyle pin (Fig. 22). Starting with the jaw in the open position, the
p&yr
‘,”
MANDIBULAR
MOVEMENTS
IN
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89
DIMENSIONS
condyle pin moved up, back, and out, reflecting rotation of the left condyle around a vertical axis as the incisor pin moved to the left and started up. The most lateral and posterior position of the condyle pin corresponded with the most lateral position of the incisor pin in the upward stroke. The condyle pin moved downward, forward, and inward as the teeth came into centric occlusion. As the jaw opened, the condyle pin came down and forward slightly and moved laterally as the jaw was opened in preparation for the next upward stroke. The distances traveled by the condyle and incisor pins for the nine masticatory cycles on the left side were determined (Table II). All measurements were again made from the centric occlusion position. The downward movement of the condyle pin ranged from 1.7 to 3.3 mm., for an average of 2.5 mm. The corresponding downward movement of the incisor pin ranged from 14.3 to 25.7 mm. for an average of 20.9 mm. The forward movement of the condyle pin during the opening phase ranged from zero to 0.7 mm. for an average of only 0.3 mm., while the lateral movement of the condyle pin during the closing phase ranged from 0.7 mm. to 1.5 mm. for an average of 1 mm. The backward movement of the incisor pin during opening ranged from 3.4 to 8.7 mm. for an average of 6.7 mm., and the movement of the incisor pin to the left on closing ranged from 2.7 mm. to 6.7 mm, for an average of 4.8 mm. The rotation of the condyle pin during opening ranged from 5 degrees to 10 degrees for an average of 7 degrees. TOOTH CONTACTS DURING
MASTICATION
On seventeen of the eighteen masticatory cycles analyzed, the incisor pin was in the same position at the top of the cycle as it was when the teeth were in centric EIGHT
CARBOTS PlOllT
VIEY
CICLP SIDP
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cow CGYDXLC PI8
P m
cow &
ill m
&
14 TOP
VIIY mom
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-
m
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PIY
Fig. 21.-Tracings from the three views depict corresponding incisor and condylar pin positions during a masticating cycle on the right side. Arrows above indicate the beginning position and direction of movement of the condyle pin as the incisor pin began its upward movement: CO, the position of the incisor and condyle pins with the teeth in centric occlusion. Cross-lines indicate the closing phase of the masticatory cycle.
90
HICKEY CAPPOTJ roonr
Lrll
SIDE
VIBN G?
CTCLl VIPU w
2 TOP
VIBY mew
co
m
COIDIL~ PIB
J. Pros. Den. Jan.-Feb., 1963
ET AL.
v
P rc
fix
al
ua
IncIIsoB P x B.
~
Fig. 22.-Tracings from the three views depict corresponding incisor and condylar pin movement during a masticatory cycle on the left side. Arrows indicate the beginning position and direction of movement of the condyle pin as the incisor pin began its upward movement. CO, the position of the incisor and condyle pins with the teeth in centric occlusion. Cross-lines indicate the closing phase of the masticatory cycle. occlusion with no food in the mouth. In one cycle, the position of the incisor pin was 0.5 mm. beneath the centric occlusion position. Thus, superimposition of the tracings indicated that the teeth contacted in centric occlusion seventeen of eighteen possible times. The position of the condyle pin at the top of all masticatory cycles was also the same as that of centric occlusion with no food in the mouth. The tracings of the voluntary sliding movements with the teeth in contact were superimposed over tracings of the masticating cycles as the teeth approached centric occlusion. In all instances, on the closing masticatory stroke, the pathway of the incisor pin was similar to its pathway during the beginning of the sliding movement, but only for short distances. However, as the teeth moved laterally past centric occlusion in mastication, the tracings of the incisor pin corresponded with the tracings of the sliding movements in only three instances (two cycles in the left and one on the right). Usually the jaw dropped open from centric occlusion at a steeper angle than the cusps of the teeth. Thus, the mandible was guided by the inclined planes of the teeth for short distances only as it approached centric occlusion. SWALLOWING
POSITION
The position of the incisor and condyle pins during swallowing was identical with that of centric occlusion in all three views. The condyle did not approach the centric relation position at any time during deglutition. As previously mentioned, centric occlusion was not in harmony with centric relation for this subject. The neuromuscular system had apparently adapted the closing movement during swallowing to the position of centric occlusion,
;;*;pe;;” CONDYLAR
MANDIBULAR
MOVEMENT
DURING
MOVEMENTS
INITIAL
IN
THREE
DIMENSIONS
91
OPENING
The position of the incisor and condyle pin was measured on the first motion picture frame of jaw opening from centric occlusion for all eighteen masticatory cycles. The amount of incisor pin opening occurring in l/24 second varied from 0.7 to 5.1 mm. In every instance, there was a corresponding movement of the condyle pin even with the slightest opening of the incisor pin. In most instances, the condyle pin moved downward and shifted slightly forward or back and to the right or left, depending on the direction of incisor pin movetnent. There was no evidence of pure rotation of the condyle without translation during any of the masticatory strokes analyzed. SUMMARY
AND
CONCLUSIONS
A method of studying the relationship of condylar and tooth movements in three dimensions has been described. An analysis of the records of one subject indicates certain conclusions for that individual: 1. A different condylar position was found for rest position, centric occlusion, and centric relation. 2. The condyle could be held in a retruded position as a hinge opening movement was made. However, no center of rotation could be found in the region of the condyle that would produce an arc similar to the arc of movement of the incisor pin. 3. The pathway of the condyle on voluntary lateral sliding movements was different from that of lateral movements with the teeth out of contact. Thus, condylar movement reflected the guiding factors of the teeth. 4. A direct lateral movement of the condyle was present in voluntary lateral movements of the mandible. This lateral movement ranged from 4 mm. in a maximal excursion with no tooth contact to 0.3 mm. during the tooth contact of masticatory function. 5. The condyle followed a general pattern during mastication on a given side. However, this pattern varied between masticatory cycles with changes in the direction of the pathway of the teeth. 6. The movement of the condyle during mastication on one side was not con+ parable with the movement when the chewing was on the opposite side. 7. Forward and lateral movements of the condyle were primarily associated with lateral movements of the mandible and not with opening movements. 8. The condyles and the teeth were in the centric occlusion position during swallowing. 9. The average downward movement of the condyle pin when the chewing was done on the same side was 2.5 mm. as compared with 4 mm. when the chewing was done on the opposite side. Thus, the balancing condyle travels further downward because of the lateral movement of the teeth toward the side on which the food is chewed. The average amount of opening at the incisors for these downward movements was 14 mtn. 10. The a\.erage rotation of the condyle pin around a transverse axis during mastication was approximately 7 degrees. The least amount of rotation occurred in the beginning part of the opening movement.
92
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11. The teeth contacted in centric occlusion in seventeen of eighteen masticatory strokes. The condyles were in the same position at the top of the masticatory cycles as they were when the teeth were in centric occlusion. 12. The pathway of the mandible was guided for short distances by the inclined planes of the teeth as they approached centric occlusion during mastication. The teeth were a guiding factor in only a few instances as the jaw opened from centric occlusion during mastication. 13. The condyle pin shifted bodily with the slightest opening of the teeth from centric occlusion. This movement occurred for all masticatory strokes on both sides. 14. The variation and the amount of movement of the condyles even within the range of the height of the cusps of the teeth seem to make a freedom of cusp movement in centric occlusion desirable. It is very unlikely that any articulator can duplicate condyle movements. Nonetheless, certain phases of complete denture construction can be done more accurately on an articulator than on movable tissue in the mouth. 15. There is probably a range of adaptability of condyle movement within the temporomandibular joint that varies between patients and within the same patient at different periods. This may account for the fact that’ the occlusion of either artificial or natural teeth, if within this range of adaptabilty, may cause no apparent temporomandibular joint discomfort or pathologic condition, but that same occlusion in the same patient at a later time or in a different, older, or unhealthy patient may produce discomfort and pathologic changes. REFERENCES
1. S?instebo, H. R. : C. E. Lute’s Recording of Mandibular Movements, J. PROS. DEN. 11:10681073,1961. 2. St instebij, H. R. i Walker’s Improvements of Bonwell’s System, J. PROS. DEN. 11:10741079, 1961. 3. Bemnett, N. G.: A Contribution to the Study of the Movements of the Mandible, J. PROS. UEN. 8-:41-45, 1958. 4. Hildebrand, C;. Y.: Studies in the Masticatory Movement of the Human Lower Jaw, Skan-
dinav. arch. physiol. sup111.61, 1931.
5. Higley, L. B., and Logan, R. 1A. : Roentgenographic Interpretation of Certain Condyle and Menton Movements, J.A.D.A. 28:779-785, 1941.
D. Digest 54:540-542, 1948. 6. Frank, L. : A Report on Normal Mcwements of the Condyle, ~6”^Xt.I^ LlCLcb A ..a- “U”UI. ^AAe+ “,,,A:..“.. -s &L^ ILy “I LUF IT..-“.. lll.l‘ll*,l I”uuIUI”‘F, 3CauulllaY. 7. Posselt, U.: Studies in the Mobil :c.. 1O:suppl. 10, 1952.
8. Lindblom, G. : A Cineradiographic Study of the Temporomandibular Joint, Acta odont. scandinav. X:141-158, 1957.
9. Berry, H. M., and Hoffman, F. A.: Cineradiographic Observations of Temporomandibular
Function, J. PROS. DEN. 9:21-33, 1959. 10. Zola, A., and Rothschild, E. A. : Condyle Positions in Unimpeded Jaw Movements, J. PROS. DEN. 11:873-881,1961. MEDICAL CENTER UNIVERSITY OF KENTUCKY COLLEGEOF DENTISTRY LEXINGTON, KY.
305 WEST TWELFTH A@. COLUMBUS 10, OHIO
MOVEMENTS
IN THREE DIMENSIONS
JUDSON C. HICKEY, D.D.S., M.Sc.,* MORGAN I.. ALLISON, D.D.S.,** JULIAN B. WOELFEL, D.D.S.,+**
CARL 0. BOUCHER, D.D.S.,****
AND
RALPH W. STACY, PH.D.****+
The Ohio State University, College of Dentistry, Columbus, Ohio of condyle movement is essential in the understanding of occlusion, the treatment of temporomandibular joint disturbances, the effect of occlusion on periodontal health, and the development of tooth forms for dental restorations, Condyle activity has been studied by several different means. Lucer in 1889 photographed the reflection of sunlight from beads placed opposite the condyles. Walker2 in 1896 used a facial clinometer to measure condyle movements. Bennett3 in 1908 traced the pathway of a light positioned opposite the condyle. Hildebrand4 recorded condyle movements by roentgen fluoroscopy. Higley and Logan5 used a series of cephalometric roentgenograms to observe condyle positions. Frank6 made stereoscopic roentgenograms of condylar movement. Posselt? studied condyle movement by profile radiography. Lindbloms and Berry and Hoffman9 reported studies of condyle activity using cineradiographic methods, and Zola and RothchildlO followed mandibular movements with a condylar thesiograph. We felt that information regarding the related function of the condyles and the teeth could be obtained by the use of three-dimensional motion picture photography. A direct approach to investigate condyle activity was devised. The movement of a pin inserted directly into the condyle was observed and compared with the movement of a pin attached to the lower incisor teeth. The activity of both pins was recorded in the horizontal, sagittal, and frontal planes by three synchronously running motion picture cameras, and the film was analyzed by a frame-by-frame projection.
A
KNOWLEDGE
SUBJECTS
Two subjects were tested by this method. Their over-all general and oral health was good. There were no pathologic temporomandibular joint symptoms, and the condyles were located relatively close to the surface of the skin. Both subjects had This investigation was supported in part by Research Grants D-54S(C4) and D-1469 from the division of Research Grants and Fellowships of the National Institutes of Health, U.S. Public Health Service. Read before the Academy of Denture Prosthetics in Colorado Springs, Cola. *Present address: Professor and Chairman, Department of Prosthodontics, College of Dentlstry, University of Kentucky, Lexington, Ky. **Professor and Chairman, Division of Oral Surgery. ***Associate Professor, Division of Prosthodontics. ****Professor and Chairman, Division of Prosthodontics. *****Professor, Department of Physiology. 72
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73
full complements of natural teeth with Class I occlusions. The overlap of the anterior teeth was such that orthodontic bands could be cemented on the opposing central incisors and cause no interference with jaw movements. The transverse hinge axis of forcefully retruded mandibular rotation was located on one subject and tattooed on the skin to serve as a guide for the placement of the condyle pin (Fig. 1) . HEAD FIXATION
Head fixation during masticatory tests may not be desirable because of its possible effect on natural jaw movements. However, it was anticipated that condylar activity would be of such a small magnitude that even small movements of the head would seriously interfere with an accurate analysis. Therefore, a head cap was made for each subject immediately preceding the testing (Fig. 2). The head cap was purposely kept out of contact with the skin overlying the temporal muscles, because otherwise a contraction of these muscles caused movement of the head cap. Wire supports were incorporated within the plaster gauze as the head cap was made to stabilize frames containing glass grids that were attached for measure-
Fig. 1.-A, The face-bow is attached to the mandible by means of a clutch that is securely fttened on the lower natural teeth. B, The transverse hinge axis point is permanently marked on the patient’s face by injecting a small amount of dye beneath the surface of the skin.
HICKEY
J. Pros. Den. Jan.-Feb., 1963
ET AL.
c.
D.
Fig. 2.--A, The location of certain landmarks is marked on the gauze so that the finished plaster head cap will be formed properly and not interfere with the musculature. B, A predesigned wire is incorporated in the headcap to support metal frames for measurement purposes. C, The supporting wire is securely attached with plester-gauze. D, The completed headcap is securely fastened to the head support of the dental chair.
Fig. 3.-The
orthodontic
bands and wires are positioned
on opposing central
incisors.
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merit purposes. After the head cap was completed, it was rigidly fixed with the plaster gauze to the head support of the dental chair to eliminate head movement IFig. 2). WIRE FRAME ATTACHMENTS
Orthodontic bands that supported wire frames were attached to the teeth with zinc phosphate cement (Fig. 3). One band and wire was attached to the upper right central incisor and the other to the lower left central incisor. The bands and wires did not interfere with the teeth or lips during jaw movements and mastication. The wires served as a means of attachment for miniature electric lights which were photographed during jaw movement. CONDYLE PIN PLACEMENT
The ear and the skin of the face in the region of the left condyle were scrubbed with bacteriostatic soap and cleansed with alcohol. An aseptic technique was used. A local anesthetic was deposited in the subcutaneous tissues and in the joint space. Then a Steinmann pin was inserted directly into the condyle of one subject by means of an orthopedic hand drill (Fig. 4). On the second subject, a specially designed face-bow was used to guide the pin in the hand drill into the condyle along the mandibular transverse axis (Fig. 5). One of the movable condylar rods of the face-bow was replaced by a pointed tube that contained a hole machined to a precise diameter that would fit and guide the condyle pin during its insertion (Fig. 5, B). A pointed adapter was placed on the other condylar rod so that it could be positioned accurately on the opposite hinge axis point. Premeditation for this subject was 100 mg. of pentobarbital, 75 mg. of meperidine, and 0.04 mg. of atropine (l/150 grain). A cylindrical steel pin 1.5 mm. in diameter and 65 mm. long was placed in
Fig. 4.--A, A local anesthetic is injected before the placement of the condyle pin. B, The condyle pin is inserted at the condyle. There is no pain associated with the procedure.
76
HICKEY
J. Pros. Den. Jan.-Feb., 1963
ET AL.
A.
B.
Fig. 5.-A, A pointed guiding tube with a diameter car ,responding in size with the COTidyle pin is located at the left end of the face-bow. A pointed ada .ptor is secured on the movable condylar rod part at the right end of the face-bow. B, The colndyle pin is in the orthopedic drill and is positioned within the specially designed guiding tube.
an orthopedic hand drill and inserted into the hole in the tube of the special face-bow rod. The face-bow rods were positioned on the hinge axis marks on the face (Fig. 6) and then steadied in that position by two of the investigators. The subject held the jaw firmly in centric relation, and then by operation of the hand drill, the pin was inserted into the condyle to a depth of about 1 cm. (Fig. 7). This insured that the pin was rigidly fixed to the condyle with its full length located on the previously determined transverse axis. GRID DESIGN AND LOCATION
Lightweight metal frames were built to hold glass measuring grids in the horizontal, frontal, and sagittal planes alongside both the condyle and incisor pins (Fig. 8). The frames accommodated regular lantern slide glass on which had been printed horizontal and vertical grid lines that were 5 mm. apart. The metal frames were attached to the supporting wire of the‘ head cap and positioned so as not to
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77
int erfere with pin or jaw movements (Fig. 9). With this arrangement, two me:asuri ing grids (one for the incisor and one for the condyle pins) were visible in all thr -ee views of the motion picture film.
Fig. 6.--A, The face-bow assembly is ready for use. B, The face-bow the ccmdyle pin will be inserted along the transverse hinge axis.
is positioned
so 1.hat
A.
Fig. 7.-A, The condyle pin is firmly embedded shows the position of the pin in the left condyle.
into the condyle.
B,
The
roentgenogram
78
HICKEY
ET AL.
A.
Fig. S.-A, Connecting canL be positioned correctly the metal frames.
rods are attached to the sides of the metal frames so that the fran Les alongside the face. B, The glass measuring grids are in place wit1 lin
Fig. 9.4he metal frames are positioned so that a measuring lie :hts in all three filmed views of the condyle and incisor pins.
grid
is present
behind
the
ic%-E:”
MANDIBULAR
ATTACIIMENT
OF LIGIITS
MOVEMENTS
IN
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79
DIMENSIONS
TO PINS
Small lights 1 mm. in diameter were used for visual and photographic purposes (Fig. 10). Adapters were formed around the lights so that single lights (Fig. 11, A) could be placed on the end of the incisor wires and one on a rigid wire directly above the condyle pin. A double light (Fig. 11, B), one light at right angles to the other, was placed on the exposed end of the condyle pin. The double light facilitated observation of rotation as well as the other movements of the condyle. The single light on the upper central incisor and the one directly above the condyle pin served as reference points for determining the movements of the other lights. The condyle pin with the light on it extended from the skin of the face approximately 63 mm. The incisor pin and light extended from the teeth approximately 65 mm. The complete arrangement for making the motion pictures is seen in Fig. 12. MOTION
PICTURE
FILM
ANALYSIS
The pathways of the moving lights were determined by a frame-by-frame projection of each of three films onto graph paper with the image enlarged 3 times actual size. The views of incisor and condyle pins were analyzed separately to compensate for the different size of their image on each film. A typical sketch of the reference light and pin for a specific view (front, top, or side) was made on the graph paper, and as the film was projected frame by frame, a plot was made of the light attached to the condyle or to the incisor pin as it changed position during function. When the points of the plot were connected, the resultant tracing indicated the pathway of the light for a given movement. Several of the jaw movements and nine masticatory strokes of chewing carrots on the right and on the left sides were analyzed by this method for the subject who had the pin located in the condyle by palpation. Only the results for this subject are given in this report. TRACING
ERROR
Tracings were made of the reference, condyle, and incisor lights from one motion picture frame six different times to determine the measurement error in tracing. When the six tracings of the three lights were superimposed, the widest dis-
Fig.
IO.---The
miniature
light
is compared
in size with
a No. 9 round
bur.
80
HICKEY
J. Pros. Den. Jan.-Feb., 1963
ET AL.
Fig. Il.-A, The light is incorporated into an adaptor that :fits over the end of the incisor pin. B, Two lights at right angles to each other fit over the end of the condyle pin to I:bermit a study of rotation as well as other movements of the condyle.
crepancy was 0.5 mm. on a scale 3 times actual size. Thus the tracing error was +0.17 mm. REST POSITION,
CENTRIC
OCCLUSION,
AND
CENTRIC
RELATION
As the mandible moved from the physiologic rest position to centric occlusion, the incisor pin moved up 2 mm., back 0.3 mm., and to the right 0.6 mm. (Fig. 13). During this same movement, the condyle pin moved up 0.6 mm., back 0.4 mm., and to the right 0.3 mm. (Fig. 13). Thus, when the teeth moved from rest position to centric occlusion, the movement of the condyle pin was not one of pure rotation but involved bodily movement in all three dimensions. Centric relation was not in harmony with centric occlusion for this subject. The incisor pin moved up 1.7 mm., forward 1.1 mm., and to the right 0.5 mm. as the teeth moved from their initial contact in central relation into centric occlu-
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DIMENSIONS
sion (Fig. 14). The condyle pin moved up slightly, straight forward 0.7 mm., and to the right 0.2 mm. (Fig. 14). The rotational light moved forward and upward slightly during this movement, indicating that the condyle rotated as it came forward from centric relation. Apparently, the condyle path was influenced by the direction of the movement of the opposing teeth from their initial contact in centric relation to centric occlusion. CONTROLLEDOPENING
MOVEI~ENTSOFTHEMAND~BLE
The transverse axis of rotation of the mandible was not located on this subject. The position of the pin in the condyle was based on palpation. Nonetheless, during the hinge opening movement, the condyle pin remained in a fixed position and rotated 5 degrees while the incisor pin moved downward 8 mm. (Fig. 15). During this retruded opening, the incisor pin moved downward 18 mm. without lateral deviation and posteriorly 9 mm. A lateral deviation of 2.5 mm. occurred as the mandible reached its maximal opening (Fig. 15). The center of rotation for the arc scribed by the incisor pin during the retruded opening was not in the region
Fig. la.-The motion picture cameras are positioned to record mandibular three planes. Note the camera that is directly above the subject’s head.
movement
in all
82
HICKEY nrsr
TO
?BOYT
cPllIR.Ic
VIEY
oocLIJsIol SXDP
VILY
W
TOP
W
VIlY IRCN?
m
m
COIlDILL PIU
J. Pros. Den. Jan.-Feb., 1963
ET AL.
1 Ii
5m
II ‘00
a’
0
-7
Ll?T
PNJnT
BACK
i
i
cow
Fig. 13.-The condyle and incisor pins moved in all three dimensions as the mandible moved from the physiologic rest position to centric occlusion. R, the position of the pins when the jaw was in rest position. CO, the position of the jaws with the teeth in centric occlusion.
OllTRIC
TO
PLLAZIOr ?POllT
VILY
SIDE
W
PIE
IYCISOR PIh
i
VIXY TOP ImmT
T
m-ul
Lw
IcaT
VIEU W
I
-k
m h
COIDlLl
OCCLDdIOl
CPITPIC
I
;
-0 Rmi?
Im
7 CR.
-W -0
yoI(
Fig. 14.-The movement of the condyle pin reflects the direction of the shift of the mandible from the position of initial contact of the teeth to centric occlusion: CR, the position of the pin when the jaw was in centric relation. CO, the position of the pin with the teeth in centric occlusion.
Volume 13 Number 1
MANDIBULAR
?PalT
MOVEMENTS
IN
EIIGX
QPPIIlG
VI&U UP
SIDE
THREE
83
DIMENSIONS
VIEY
COIDLLL
b
PIG co
m M
m
ImwT
aIT
xncIsoP PI1
-
aIGm
i
-
tM+em
.
-CIOSI
i
Y WY
Fig. 15.-The condyle pin remained in a fixed position during the hinge opening until the incisor pin had reached the position indicated by the arrow. CO, the position when the teeth were in centric occlusion.
PXGULAP
OPllIlG SIDE
COlDXLl
PII
movement of the pin
VILY UP
TOP
VIXY PmnT
Dal
d
a
xIcIsoP PI1
aIGkir t
Fig. 16.--Bodily movement of the condyle pin began at the same time as that of the incisor pm in the regular opening movement. CO, the position of the pin with the teeth in centric occlusion.
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HICKEY
J. Pros. Den. Jan.-Feb., 1963
ET AL.
of the condyle. The small deviations in the tracing of the incisor pin during the hinge opening may have resulted from the irregularities of the surfaces of the condyle and the disc as the rotation between these two structures occurred. The regular opening was not maximal but was wider than would be required during mastication (Fig. 16). The incisor pin moved downward 35 mm., backward 17 mm., and 4 mm. to the left during opening. The closing stroke was to the right and in front of the opening stroke, following a direct pathway back to the beginning position. During the regular opening, the incisor pin was 5 mm. further protruded than for the hinge opening at the widest point of separation. On the regular opening, bodily movement of the condyle pin began at the same time as the incisor pin movement. The condyle pin moved down with 12 degrees of rotation and to the left 0.6 mm. during the total regular opening movement. The pathway of the condyle pin during the closing phase was in front of and to the right of its position during the opening phase (Fig. 16). LATERAL
MOVEMENTS
OF THE MANDIBLE
The lateral sliding movements of the mandible began with the teeth in centric occlusion and were guided by the inclined planes of the teeth, ending when the opposing cuspids passed edge to edge (Fig. 17). The incisor pin moved laterally 12.7 mm. in the left lateral sliding movement as compared with only 6 mm. in the right movement. This difference was caused by the increased horizontal and vertical overlap of the left cuspid teeth as related to the right cuspid teeth. The shape of the tracmg of both the right and left sliding movements was directly related to the guiding influence of the teeth. The movement of the condyle pin in the lateral sliding excursions seemed to be LATLBAL
YLIDIYO FBOEt
xrC1jon
XOVEYIIITB
VIEU
YIDl
PII
VIIY UP
ID!
m SLIDE LE?f %
00
00 SLIDE BIGHT
J
J i++ OUT pay
‘Mix
Fig. 17.-The pathway of the incisor pin in lateral sliding movements reflects the guiding influence of the inclined planes of the teeth. CO, the position of the incisor pin with the teeth in centric occlusion.
Volume 13 Number 1
M!IANDIBULAR LATKPAL
MOVEMENTS
TfIREE
WOVKWKKIS
SLIDING
TEOYT
IN
VIEW UP
DIMENSIONS PIK
COIIDILI
SIDE
85
TOP
VIPY UP
VISY
7
SLIDE LET?
cod
LTTT
nIQuT
KIWI
nAlx
m SLIDE BIQEZ
d
J” mm
Fig. l&-The dip in the pathway of the condyle pin during the lateral sliding movements corresponds in time to the edge-to-edge contact of the cuspids: CO, the position of the condyle pin with the teeth in centric occlusion.
influenced by the guiding factors of the teeth (Fig. IS). The condyle pin in both right and left sliding movements made a dip that was similar in time and form to the edge to edge contact of the cuspids. This dip caused by the guiding influence of the cuspid teeth was not reflected to the same degree in a lateral excursion when the teeth were out of contact (Fig. 19). Th us, the condyles seem to follow pathways that are influenced by tooth contacts. The condyle pin moved laterally (Bennett movement) when the mandible moved to the left side (Fig. 19). However, such lateral movement of the condyle pin could be caused by either a rotation of the left condyle around a vertical axis, by a direct lateral shifting of the mandible, or by a combination of these two factors. To determine the actual lateral movement of the condyle, one tracing was made of the condyle and incisor pins from a motion picture frame from the top view with the teeth in centric occlusion and a similar tracing was made of a motion picture frame with the jaw in its most lateral position. On each of these, tracings lines were drawn through the shafts of the condyle and incisor pins and were extended inward until they intersected (Fig. 20, A). The change in the position of the intersection of the lines with the jaw in the two positions indicated the magnitude of the lateral shift of the mandible. During this maximal lateral movement with the teeth out of contact, the mandible shifted laterally 4 mm. (Fig. 20, B) . This same method for determining lateral movement was repeated for lateral sliding movements and for the maximal range of tooth contact during mastication. The direct lateral movement of the condyle during a left lateral sliding movement (from centric occlusion to the edge to edge position of the cuspids) was 2.7 mm. However, the range of tooth contact during the lateral movements occurring in mastication was much less than in the controlled sliding movements. The maximal
86
HICKEY
J. Pros. Den. Jan.-Feb., 1963
ET AL.
lateral shift of the condyle, found to occur during maintained tooth contact in mastication, was only 0.3 mm. MASTICATION
The pathway of the incisor and condyle pins was traced for all three views as the subject chewed a 3 Gm. portion of carrots on the left side and then another 3 G m. portion * on the right side. Tracings were made from nine selected masticatory cycles, three at the beginning of the chewing, three in the middle, and three just before the chewing was completed. Thus, a total of eighteen masticating cycles was analyzed. Chewing on the Opposite Side From the Condyle Pin (Right Side).-Although there was a similarity in the pattern of the condyle and incisor pin movement during mastication, no two cycles were the same. Starting with the jaw in the open position, the condyle pin was in a downward position from its position in centric occlusion (Fig. 21) . As the incisor pin moved to the right side and started upward and forward so that the teeth could engage the carrots, the condyle pin moved down, forward, and to the right. As the incisor pin moved from its lateral position and continued upward, forward, and medially toward centric occlusion, the condyle pin moved up, back, and medially. The upward stroke of the condyle ended when the teeth were in centric occlusion. On the opening stroke, the condyle pin moved slightly down, backward, and to the left as the mandible rotated around the left condyle. As the incisor pin continued downward, the condyle pin moved further down, slightly forward, and to the right in preparation for the next chewing cycle (Fig. 21). LEPT PROIT
LATKEAL
rxCuPSIOI SIDl
vxru UP
mdP
COlDILl PII
RIOUT
VILU UP
LEn
m?
PmsT
uol
m
m
11c1a00 PI1
Q&k@
D
Fig. lg.-The pathway of the condyle and incisor pins when the jaw is moved laterally with the teeth out of contact is not similar to the pathway followed when the jaw is moved laterally with the teeth in contact (see Figs. 17 and 18). The condyle pin moved laterally during the left lateral excursion (top and front views), but this apparent lateral movement of the condyle pin could be caused by rotation of the left condyle around a vertical axis.
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87
Fig. 20.--A, The long axes of the condyle and incisor pins are extended inward to an intersecting point from two different motion picture frames: one with the teeth in centric occlusion and the other with the jaw in a maximal left lateral position. The distance between the two intersections depicts the bodily shift of the mandible in the horizontal plane. A scaled drawing of the subject’s mandible was positioned relative to the pins to indicate the effect of the lateral shift of the mandible on both tooth and condyle movement. B, An enlarged view shows the direction of the shift of the left first molar (arrow) and the amount of lateral movement of the left condyle (see scale ).
The distances traveled by the condyle and incisor pins for the nine masticatory cycles on the right side were determined (Table I). All measurements were made from the centric occlusion position. The downward movement of the condyle pin ranged from 3.3 to 4.7 mm. for an average distance of 4 mm. The corresponding downward movement of the incisor pin ranged from 17 to 28.3 mm. for an average distance of 20.1 mm., which was found to be the equivalent of 14 mm. of actual incisor tooth movement. The forward movement of the condyle pin during the masticatory cycles on the right side ranged from 0.5 to 2.1 mm. for an average of 1.6 mm., and the inward movement ranged from 0.7 to 1.6 mm. for an average of 1 mm. The movement of the incisor pin toward the right side that accompanied the forward and inward movement of the condyle pin ranged from 1.7 to 4.6 mm., for an average of 3.4 mm. The backward movement of the incisor pin ranged from 3.1 to 15 mm., for an average of 7.2 mm. The forward and inward component of the condyle pin movement during mastication was associated with lateral movement of the incisor pin and did not seem to be related to the opening movement of the mandible. During the nine masticating cycles on the right side, the rotational light moved
88
HICKEY TABLE
I.
INCISOR
AND CONDYLE
INCISOR
PIN MOVEMENT
PIN MOVEMENT
MASTICATING CYCLE
J. Pros. Den. Jan.-F&., 1963
AL. DURING
(MM.)
RIGHT(ON CLOSING)
a 3
ET
MASTICATIONON
CONDYLE
RIGHTSIDE
PIN MOVEMENT*(MM.)
DOWNWARD
19.6 17.3 21.0
k(: 15:o
2.7 1.7 4.0
3.3 4.2 4.0
0.5 1.9 1.3
0.7 1.3
i 10
:t
20.0 28.3
10.0 6.3
4.0 3.5
3.7 4.0
2.0 1.9
::::
67
1:
21.6 18.3
5.3 6.8
4.6 2.9
%:i
2.1
0.7 1.1
i
“2:
17.0 17.7
4.1 3.1
4.6 2.7
4.0 4.7
1.7 ::i
1.6 1.0
180.8 20.1
65.3 7.2
30.7 3.4
36.2 4.0
14.5 1.6
9.4 1.0
Total Average
All measurements made from centric occlusion position. Note: 20 mm. of incisor pin opening equals approximately *Condyle pin in left condyle. TABLE
II.
INCISOR
AND CONDYLE
INCISOR PIN MOVEMENT
PIN MOVEMENT
14 mm. of incisor movement.
DURING
(MM.)
MASTICATIONONLEFTSIDE
CONDYLE
MASTICATING CYCLE
PIN MOVEMENT*(MM.) -
DOWNWARD
1
59 6.6
BACKWARD
LEFT(ON CLOSING)
DOWNWARD
:t
25.7 20.5 25.0 23.7 23.0
8.3 8.7 8.0 2.:
4.3 5.7 6.0 6.3 6.7
2.8 3.3 2.8 2.3
:;
21.7 18.7
7:1
4.7 2.7
2
15.5 14.3
Z3.4
Total Average
188.1 20.9
60.2 6.7
FORWARD (ON OPENING)
LATERAL (ON CLOSING)
ROTATION (DEGREES)
10
-1.0 0.6
0.7 1.5 1.3 1.0
2.3 2.6
0.3
1.0 1.3
ii
4.0 2.8
2.3 1.7
8:; 0.5
0.7
:6
43.2 4.8
22.4 2.5
0.26 0.3
9.2 1.0
64 7
All measurementa made from centric occlusion position. Note: 20 mm. of incisor pin opening equals approximately *Condyle pin in left condyle.
5
14 mm. of incisor movement.
through an arc that ranged from 5 degrees to 10 degrees for an average of 5.6 degrees. The least amount of rotation occurred during the first one third of the opening stroke, while the greatest amount occurred during the last two thirds. Chewing on the Same Side as the Condyle Pin (Left Side).-A different pattern of condyle activity was observed when the chewing was done on the same side as the condyle pin (Fig. 22). Starting with the jaw in the open position, the
p&yr
‘,”
MANDIBULAR
MOVEMENTS
IN
THREE
89
DIMENSIONS
condyle pin moved up, back, and out, reflecting rotation of the left condyle around a vertical axis as the incisor pin moved to the left and started up. The most lateral and posterior position of the condyle pin corresponded with the most lateral position of the incisor pin in the upward stroke. The condyle pin moved downward, forward, and inward as the teeth came into centric occlusion. As the jaw opened, the condyle pin came down and forward slightly and moved laterally as the jaw was opened in preparation for the next upward stroke. The distances traveled by the condyle and incisor pins for the nine masticatory cycles on the left side were determined (Table II). All measurements were again made from the centric occlusion position. The downward movement of the condyle pin ranged from 1.7 to 3.3 mm., for an average of 2.5 mm. The corresponding downward movement of the incisor pin ranged from 14.3 to 25.7 mm. for an average of 20.9 mm. The forward movement of the condyle pin during the opening phase ranged from zero to 0.7 mm. for an average of only 0.3 mm., while the lateral movement of the condyle pin during the closing phase ranged from 0.7 mm. to 1.5 mm. for an average of 1 mm. The backward movement of the incisor pin during opening ranged from 3.4 to 8.7 mm. for an average of 6.7 mm., and the movement of the incisor pin to the left on closing ranged from 2.7 mm. to 6.7 mm, for an average of 4.8 mm. The rotation of the condyle pin during opening ranged from 5 degrees to 10 degrees for an average of 7 degrees. TOOTH CONTACTS DURING
MASTICATION
On seventeen of the eighteen masticatory cycles analyzed, the incisor pin was in the same position at the top of the cycle as it was when the teeth were in centric EIGHT
CARBOTS PlOllT
VIEY
CICLP SIDP
VIPY
cow CGYDXLC PI8
P m
cow &
ill m
&
14 TOP
VIIY mom
x5
-
m
-9
PICUT
IIcI*oB
PIY
Fig. 21.-Tracings from the three views depict corresponding incisor and condylar pin positions during a masticating cycle on the right side. Arrows above indicate the beginning position and direction of movement of the condyle pin as the incisor pin began its upward movement: CO, the position of the incisor and condyle pins with the teeth in centric occlusion. Cross-lines indicate the closing phase of the masticatory cycle.
90
HICKEY CAPPOTJ roonr
Lrll
SIDE
VIBN G?
CTCLl VIPU w
2 TOP
VIBY mew
co
m
COIDIL~ PIB
J. Pros. Den. Jan.-Feb., 1963
ET AL.
v
P rc
fix
al
ua
IncIIsoB P x B.
~
Fig. 22.-Tracings from the three views depict corresponding incisor and condylar pin movement during a masticatory cycle on the left side. Arrows indicate the beginning position and direction of movement of the condyle pin as the incisor pin began its upward movement. CO, the position of the incisor and condyle pins with the teeth in centric occlusion. Cross-lines indicate the closing phase of the masticatory cycle. occlusion with no food in the mouth. In one cycle, the position of the incisor pin was 0.5 mm. beneath the centric occlusion position. Thus, superimposition of the tracings indicated that the teeth contacted in centric occlusion seventeen of eighteen possible times. The position of the condyle pin at the top of all masticatory cycles was also the same as that of centric occlusion with no food in the mouth. The tracings of the voluntary sliding movements with the teeth in contact were superimposed over tracings of the masticating cycles as the teeth approached centric occlusion. In all instances, on the closing masticatory stroke, the pathway of the incisor pin was similar to its pathway during the beginning of the sliding movement, but only for short distances. However, as the teeth moved laterally past centric occlusion in mastication, the tracings of the incisor pin corresponded with the tracings of the sliding movements in only three instances (two cycles in the left and one on the right). Usually the jaw dropped open from centric occlusion at a steeper angle than the cusps of the teeth. Thus, the mandible was guided by the inclined planes of the teeth for short distances only as it approached centric occlusion. SWALLOWING
POSITION
The position of the incisor and condyle pins during swallowing was identical with that of centric occlusion in all three views. The condyle did not approach the centric relation position at any time during deglutition. As previously mentioned, centric occlusion was not in harmony with centric relation for this subject. The neuromuscular system had apparently adapted the closing movement during swallowing to the position of centric occlusion,
;;*;pe;;” CONDYLAR
MANDIBULAR
MOVEMENT
DURING
MOVEMENTS
INITIAL
IN
THREE
DIMENSIONS
91
OPENING
The position of the incisor and condyle pin was measured on the first motion picture frame of jaw opening from centric occlusion for all eighteen masticatory cycles. The amount of incisor pin opening occurring in l/24 second varied from 0.7 to 5.1 mm. In every instance, there was a corresponding movement of the condyle pin even with the slightest opening of the incisor pin. In most instances, the condyle pin moved downward and shifted slightly forward or back and to the right or left, depending on the direction of incisor pin movetnent. There was no evidence of pure rotation of the condyle without translation during any of the masticatory strokes analyzed. SUMMARY
AND
CONCLUSIONS
A method of studying the relationship of condylar and tooth movements in three dimensions has been described. An analysis of the records of one subject indicates certain conclusions for that individual: 1. A different condylar position was found for rest position, centric occlusion, and centric relation. 2. The condyle could be held in a retruded position as a hinge opening movement was made. However, no center of rotation could be found in the region of the condyle that would produce an arc similar to the arc of movement of the incisor pin. 3. The pathway of the condyle on voluntary lateral sliding movements was different from that of lateral movements with the teeth out of contact. Thus, condylar movement reflected the guiding factors of the teeth. 4. A direct lateral movement of the condyle was present in voluntary lateral movements of the mandible. This lateral movement ranged from 4 mm. in a maximal excursion with no tooth contact to 0.3 mm. during the tooth contact of masticatory function. 5. The condyle followed a general pattern during mastication on a given side. However, this pattern varied between masticatory cycles with changes in the direction of the pathway of the teeth. 6. The movement of the condyle during mastication on one side was not con+ parable with the movement when the chewing was on the opposite side. 7. Forward and lateral movements of the condyle were primarily associated with lateral movements of the mandible and not with opening movements. 8. The condyles and the teeth were in the centric occlusion position during swallowing. 9. The average downward movement of the condyle pin when the chewing was done on the same side was 2.5 mm. as compared with 4 mm. when the chewing was done on the opposite side. Thus, the balancing condyle travels further downward because of the lateral movement of the teeth toward the side on which the food is chewed. The average amount of opening at the incisors for these downward movements was 14 mtn. 10. The a\.erage rotation of the condyle pin around a transverse axis during mastication was approximately 7 degrees. The least amount of rotation occurred in the beginning part of the opening movement.
92
HICKEY
ET
AL.
J. Pros. Den. JawFeb., 1963
11. The teeth contacted in centric occlusion in seventeen of eighteen masticatory strokes. The condyles were in the same position at the top of the masticatory cycles as they were when the teeth were in centric occlusion. 12. The pathway of the mandible was guided for short distances by the inclined planes of the teeth as they approached centric occlusion during mastication. The teeth were a guiding factor in only a few instances as the jaw opened from centric occlusion during mastication. 13. The condyle pin shifted bodily with the slightest opening of the teeth from centric occlusion. This movement occurred for all masticatory strokes on both sides. 14. The variation and the amount of movement of the condyles even within the range of the height of the cusps of the teeth seem to make a freedom of cusp movement in centric occlusion desirable. It is very unlikely that any articulator can duplicate condyle movements. Nonetheless, certain phases of complete denture construction can be done more accurately on an articulator than on movable tissue in the mouth. 15. There is probably a range of adaptability of condyle movement within the temporomandibular joint that varies between patients and within the same patient at different periods. This may account for the fact that’ the occlusion of either artificial or natural teeth, if within this range of adaptabilty, may cause no apparent temporomandibular joint discomfort or pathologic condition, but that same occlusion in the same patient at a later time or in a different, older, or unhealthy patient may produce discomfort and pathologic changes. REFERENCES
1. S?instebo, H. R. : C. E. Lute’s Recording of Mandibular Movements, J. PROS. DEN. 11:10681073,1961. 2. St instebij, H. R. i Walker’s Improvements of Bonwell’s System, J. PROS. DEN. 11:10741079, 1961. 3. Bemnett, N. G.: A Contribution to the Study of the Movements of the Mandible, J. PROS. UEN. 8-:41-45, 1958. 4. Hildebrand, C;. Y.: Studies in the Masticatory Movement of the Human Lower Jaw, Skan-
dinav. arch. physiol. sup111.61, 1931.
5. Higley, L. B., and Logan, R. 1A. : Roentgenographic Interpretation of Certain Condyle and Menton Movements, J.A.D.A. 28:779-785, 1941.
D. Digest 54:540-542, 1948. 6. Frank, L. : A Report on Normal Mcwements of the Condyle, ~6”^Xt.I^ LlCLcb A ..a- “U”UI. ^AAe+ “,,,A:..“.. -s &L^ ILy “I LUF IT..-“.. lll.l‘ll*,l I”uuIUI”‘F, 3CauulllaY. 7. Posselt, U.: Studies in the Mobil :c.. 1O:suppl. 10, 1952.
8. Lindblom, G. : A Cineradiographic Study of the Temporomandibular Joint, Acta odont. scandinav. X:141-158, 1957.
9. Berry, H. M., and Hoffman, F. A.: Cineradiographic Observations of Temporomandibular
Function, J. PROS. DEN. 9:21-33, 1959. 10. Zola, A., and Rothschild, E. A. : Condyle Positions in Unimpeded Jaw Movements, J. PROS. DEN. 11:873-881,1961. MEDICAL CENTER UNIVERSITY OF KENTUCKY COLLEGEOF DENTISTRY LEXINGTON, KY.
305 WEST TWELFTH A@. COLUMBUS 10, OHIO