The influence of the loss of teeth and attrition articular eminence
on the
Jose I. Granados, D.D.S., MS.* Roswell Park Memorial Institute, Buffalo, N. Y.
T
he temporomandibular joint (TMJ) has been of great interest to the dental profession, and especially to prosthodontists, becauseits anatomy and physiology are intimately related to the function of the masticatory apparatus and therefore to many kinds of prosthodontic treatment. A review of the dental literature indicates that there are still some aspects, such as changes in the angle of the articular eminence, that are somewhat obscure and in which there is disagreement among various authors.‘-26 There is no doubt that the TMJ is one of the most complex joints of the body. Its study is largely complicated by its intimate relationship with the dentition, muscles,and other oral structures. Due to this intimate relationship with the dentition, it is essential for the prosthodontist to have a sound understanding of the stomatognathic system. The purpose of this study was to determine if a correlation exists between changes in the dentition with tooth lossor extreme wear and changes in the angulation of the articular eminence. If a correlation can be found between such easily observed factors as tooth wear or tooth lossand the lesseasily observed changesin the articular eminence, these may be used as predictors of temporomandibular problems.
MATERIALS
AND METHODS
The material was provided by the Department of Physical Anthropology of the National Museum of Natural History at the Smithsonian Institution and consisted of 103 skulls with mandibles. The composition of the skulls was 41 prehistoric American Indians, 31 white Americans, and 31 black Americans. They were categorized according to age, sex, race, and type of dentition as follows: 1. C.D.-Complete dentition (natural), individuals with full complement of teeth with little wear *Resident,
Department
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2. A.E.-Anterior edentulous, individuals without the six anterior teeth in either upper and/or lower arches 3. P.E.-Posterior edentulous, individuals without eight posterior teeth in orlk arch 4. T.E.-Total edentulous, all upper and lower teeth missing 5. A-Attrition, individuals with a compkte a almost complete complement of teeth, with at8ritlon (2 or 3 degreesby Leigh’s standards)*’ Early American Indian skulls and mandible fmm Kentucky and Illinois were chosen. They displaw l range of attrition of the teeth from modente to severe not occurring frequently in either SE the modern American cranial series,but comparibk to that found in the prosthodontist’s aged patie-. Modem white and black American groups *wed somedegree of attrition. However, partial and total edentulism were more common. This group of ah& belong to the Terry Collection,* which is coof 1,728 identified human skeletons. They are from around St. Louis, MO., having an age range from adolescence through old age. The skeleton8 span almost three generations, with birth dates from 1840. Individual data cards were made for each +ull; the information recorded consisted of cataloe Hn., race, age, sex, type of dentition, angulation 4 the right and left eminences, and the shape and ir.&ination of both eminences. Each skull was placed on a ring of cork, with the glenoid fossaefacing uprud. The midportion of the eminence was chose as a reference. This was done to eliminate the threedimensional aspect of the structures and to dd with only two dimensions. The fossa was filled with modeling clay and cut back at the midportioa level *Smithsonian Institution, Washington, DC. Natural History, Department of Phykal
0022-3913/79/070078
+ 0Lwo.80~0
National Mum Anthropol~.
0 1979 The c. v.
of
M&y co.
TOOTH
LOSS
AND
Fig.
1.
ATTRITION
ON ARTICULAR
EMINENCE
Placement of impression material.
Fig. 3. The impressiorl is painted ivith ink
Fig. 2. The Frankfort plane is transferred to the impression.
Fig. 4. The bony contours transierred to paper
of the eminence (sagittal view); this also provided a flat floor for the impression material. Alginate (irreversible hydrocolloid) was prepared and placed over the modeling clay, exerting minimal pressure, so the clay would not distort. The cavity and its surroundings were filled with sufficient material (Fig. 1). To measure the inclination of the eminence, two planes were necessary. One was formed by the anterior wall of the glenoid fossa and the other was the Frankfort horizontal plane. After the material had set, the skull was oriented in the Frankfort plane using a rigid ruler from the upper border of the external auditory meatus to the lower border of the orbit (Fig. 2). The impression material was then cut with a scalpel, following the direction of the plane. In this fashion the plane was transferred to the impression. The impression was then removed and cleaned of excess material. Next the contour of the eminence on the impression was
painted with ink (Fig. 3) and placed over the record card (Fig. 4) so that the ink was transferred to the card. During this procedure, the amount of pressure applied was minimal so as to record the contour without distortion, This was done as rapidly as possible to avoid errors from the shrinking of the irreversible hydrocolloid. Before removing the impression from the card, the upper border of the impression was transferred to the card by locating the posterior and anterior points of this border (Fig. 5). The impression was removed, and a line corresponding to the Frankfort plane was drawn connecting those points. The upper and lower points of the eminence were connected by a straight line which was continued until it intersected the horizontal plane (Fig. 6). The angle between these lines was determined with a protractor. Using this procedure, measuremenrs could be rechecked without the use of the skull. since record-
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CRANADOS
i
Fig. 5. A, The method transferred to paper.
of transferring
Fig. 6. Establishment
the Frankfort
of the inclination
ing of data accompanied the ‘outline of the bony contours. After 206 impressionswere recorded, the information was coded and transferred to computer cards so that a univariant package could be run and the statistical analysis performed. RESULTS Using the angulation of right and left eminences, the mean and the difference, the mean, variance, standard deviation, sum of squares, degreesof freedom, and mean square were calculated for the entire population and its subdivisions according to age, sex, race, and type of dentition. Analysis of variance was performed as well as F-tests to estimate the significance of variation due to each of these factors. Table I describesthe mean angulation and standard deviation of the population distributed by race, age (Y, young up to 20 years old; M, mature up to 40 years old; 0, old more than 40 years old); sex (M, male; F,
80
plane to paper.
angle of the articular
B, Frankfort
plane
eminence.
female), and type of dentition, subdivided by the right and left eminence angulations. The mean of both angulations and their difference were determined. Table II showsthe level of significance of the four variables. Since only race and dentition reached and passed the accepted .Ol level established to determine statistical significance, these two variables are the significant factors affecting the angulation of the eminence. DISCUSSION Race and dentition are not independent, since the sampleswere chosenby type of dentition and not by race. American Indians displayed attrition in different degrees. Therefore attrition is related to this group, and it appears as a low-angulation racial group. A racial difference per se cannot be determined. Dentition is the significant factor affecting the
JULY
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Table I. Eminence angulation
ARTICULAR
EMINENCE
(by sex, age, and race combined) Dentition
CD
Right angulation Indian
AE
Mean
SD
56.0 43.3
15.0 18.5
Mean
PE SD
Mean
TE SD
Mean
A SD
Mean
SD
17.5 I8.h 25.0 IS.8 25.0
11.42 20.10 14.00
47.0
4.20
44.3
4.00
(degrees) YM F MM oM
Black
F F
YM F MM
F
oM F White
YM F MM
F
47.0 52.3 33.0 74.5 76.0 48.5 50.0 -
16.9 8.3 39.5
13.4
15.0 47.5 23.0 29.5 29.5
55.0 59.0
2.1 51.0
38.3
10.9
27.0 51.5
i-
Left angulation Indian
9.50
43.0
oM r
19.0
46.0 10.0 31.0 28.3 30.8
24.7 3.5 12.8 24.2 10.5 4.9 12.8
25.0
(degrees)
Black
YM F
45.0 50.0
M?;1
-
M OF
-
F
75.0 58.3 47.0 84.5 80.0 56.0 7Y.O -
F
-
YM F MM
F
oM F White
YM F MM oM
.\‘otet Y = Young
21.2 5.0
53.0
4.2 13.0 56.0
2.8
34.0 51.5 30.0 40.5 44.2
55.0 63.0
6.3 48.0
10. to 10.70 16.50 12.80
19.0
47.0
21.20
40.6
4.00
4.1 4.2
5.6 38.3
10.2
27.0 32.5
(up to 20 years);
OF PROSTHETIC
20.2 2b.9 25.1 24.8 8.0
44.0
M = Mature
(21-40
years);
0 = Old (more
angulation of the eminence. It is clear that attrition and total edentulism consistently show the lowest angulations as opposed to the complete natural dentition, which is the type of dentition that shows the highest angulation. Anterior or posterior partial edentulism indicates a lower angulation than complete dentition, but the number of samples probably is not significant. Attrition as well as total edentulism modifies the articular eminence so as to reduce angulation in the adult individual. These results are made from statistical analysis and point out that these two changes in
THE RURNAL
type
DENTISTRY
20.5 than
19.0 39.0 27.0 23.6 26.1
5.1 17.4 24.0 15.5
..
40 years)
the dentition correlate with low angulations of the articular eminence. This is contrary to those individuals who had complete natural dentitions with little or no wear and high eminence angulations. Obscrvations of the TMJ bony contours of those skulls displaying attrition and total edentuFsm indicate that osseous changes such as roughing, lipping, and bone erosion (Fig. 7) like those found in vsteoarthritis deformans are present. They cannot be found on those skulls with a complete dentitivn and high eminence angulations (Fig. 8). DS%mnces in eminence angulation exist among individuals with
81
CRANADOS
Fig. 7. A, Osteoarthritic changes. B, Osteoarthritic changes found on the articular eminence. C, Osteoarthritic changes in the glenoid fossa. D, Osteoarthritic changes on the articular changes. eminence. E, Osteoarthritic
Tab1le II. Le !vels of significance
of F ratios
-
obtained
by analysis Level
Variable
Right angnhtion
of variance
of significance
Left angulation
Mean
of variable Difference between right and left
angulation
Race
.OOl
Do1
Sex
Dentition
.292 .OOl
.I69 .CQl
.ool
.232
Age
.999
,999
.999
.999
sound TMJs and complete those differences are found angulation of the eminence.
dentitions. However, in skulls with a high
CONCLUSIONS 1. Osteoarthritic changes were TMJs of the skulls with attrition loss. 82
.ool .241
2. what 3. the hier.‘9.
evident in the or total tooth
.999 ,999
The TMJs are not unadaptable, was stated by McCollum.28 Changes in the dentition produce TMJ, contrary to what was 30
contrary changes stated
to in by
4. Attrition produces osteoarthritic changes in the TMJ with flattening of the articular eminence. Therefore its effects are deleterious to this joint (Fig. JULY
1979
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TOOTH
LOSS
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ATFRITION
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EMINENCE
Fig. 8. A, High articular eminence angulation. with a complete natural dentition.
B, Preservation
of osseous structures on sM1
Fig. 9. A, Attrition of the maxillary teeth. B, Attrition of the mandibular teeth. C, Attrition of the anterior teeth. D, Attrition of the posterior teeth. E, Effects of attrition on the articulal eminence (arrow). F, Flattening of the articular eminence (arrozo).
9). For
this reason, attrition cannot be considered as the3 ideal form of occlusion of man, as was suggested and Murphy.“” by Begg,“’ Fishman,“’ 5. As tooth wear or tooth loss progresses, changes in the TMJ of the osteoarthritic deformans type will be produced (Fig. 10). TH E JOURNAL
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6. Loss of cusp height and anterior guidance displayed in severe attrition was accompanied resorption of the articular eminence, making it m ore shallow and in some patients completely flat. 7. Loss of all teeth and most likely loss of verti cal dimension produce similar effects as attrition does on
il;
83
GRANADOS
Fig. 10. articular the
eminence.
can
be
an
dentures
occlusion
during
8. The
loss that
eminence.
these
at the
proper
there
is
individuals
vertical
no
were
dimension
Loss
to the the
cusps
of posterior
inclination
of the
inclination
articular
will
teeth
is
articular
ments
of the
condyles,
be kept
for
produce
loss
such
as pantographic
a long
period
6.
(decreased
angulation)
in the
my gratitude
to Lucile
St. Hoyrne,
Ph.D.,
7. a. 9.
articular
eminence. The population consisted of 103 adult skulls and mandibles of both sexes and three different races. They included partial and total edentulism, mild to severe attrition, and complete dentitions in good condition. An impression of each of the 206 articular eminences was made and the angulation established. The data were transferred to computer cards and a statistical analysis performed. The level of significance for each of the variables was established and conclusions were made.
84
3.
5.
A review of the literature revealed that changes in the articular eminence associated with changes in the dentition were usually overlooked in most reports. An attempt was made to determine whether changes in attrition and loss of teeth would correlate
I express
2.
4.
SUMMARY
a change
1.
tracings,
of time.
10. Maintenance of dentition integrity and facial dimensions are necessary to maintain healthy TMJs; otherwise, irreversible changes may take place.
with
the Department of Physical Museum of Natural History, cooperation in this study.
eminence.
9. Since the TMJs are able to change due to loss of tooth or tooth substance, no record of the moveshould
of total
tooth
loss on the
Anthropology Smithsonian
of the Institution,
National for her
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However,
only
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10 D.F.
p 20.
INFORMATION
FOR AUTHORS
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