ORIGINAL ARTICLE
Temporomandibular joint and normal occlusion:
Is there anything singular about it? A computed
tomographic evaluation
rcio Jose
da Silva Campos,b Andre
ia Fialho Rodrigues,b
Robert Willer Farinazzo Vitral,a Ma
c
and Marcelo Reis Fraga
Juiz de Fora, Minas Gerais, Brazil
Introduction: The purpose of this study was to investigate the condyle-fossa relationship, the position of the
condyles in their respective mandibular fossae, and the dimensional and positional symmetries between the
right and left condyles in a sample with normal occlusion. Methods: Thirty subjects from 15 to 32 years of
age with normal occlusion had computed tomography scans of their temporomandibular joints. The images obtained from the axial slices were evaluated for possible asymmetries in size and position between the condylar
processes. The images obtained from the sagittal slices were used to assess the depth of the mandibular fossa,
the condyle-fossa relationship, and the centralization of the condyles in their respective mandibular fossae.
Paired Student t tests were applied, and Pearson product moment correlations were determined after
measurements on both sides were obtained. Results: The largest mediolateral diameter of the mandibular condylar processes (P 5 0.022) and the posterior joint spaces (P 5 0.048) showed statistically significant differences between the right and left sides. Statistically significant (P \0.05) anterior positioning of the condyles
(noncentralized position) was observed. Conclusions: No singular characteristic in the temporomandibular
joints of the normal occlusion group was verified. The largest mediolateral diameter of the mandibular condylar
processes and the posterior joint spaces showed statistically significant differences between the right and left
sides. Evaluation of the position of the condyles in their respective mandibular fossae showed noncentralized
positioning for the right and left sides. (Am J Orthod Dentofacial Orthop 2011;140:18-24)
orphologic studies on the temporomandibular
joint (TMJ) in patients with normal occlusion
are rare in the literature. Nevertheless, most
studies evaluated asymptomatic TMJ patients and did
not address a direct relationship with dental occlusion.
Christiansen et al1 observed in their computed tomography (CT) study that the anterosuperior joint space was
smallest in the normal TMJ compared with the superior
and posterosuperior joint spaces. To determine ideal
condylar position in functionally optimal joints without
disc displacement, Ikeda and Kawamura,2 in a conebeam CT (CBCT) study, found noncentered condyles,
M
From the Department of Orthodontics and Pediatrics, Juiz de Fora Federal
University, Juiz de Fora, Minas Gerais, Brazil.
a
Associate professor and chair.
b
Postgraduate student.
c
Professor.
The authors report no commercial, proprietary, or financial interest in the
products or companies described in this article.
Reprint requests to: Robert Willer Farinazzo Vitral, Av Rio Branco 2596/1604,
36010 907 Juiz de Fora, MG, Brazil; e-mail, robertvitral@acessa.com.
Submitted, June 2009; revised and accepted, July 2009.
0889-5406/$36.00
Copyright Ó 2011 by the American Association of Orthodontists.
doi:10.1016/j.ajodo.2009.07.030
18
with the posterior joint space larger than the anterior
joint spaces.
Katsavrias and Halazonetis3 suggested that both the
condyle and the mandibular fossa differ in shape among
patients with various types of malocclusion. However,
the influence of occlusion on TMJ morphology is still
controversial. Although some studies point to a correlation between occlusal factors and joint morphology,4-7
others could not establish a correlation.8-10 Opinions
also differ as to the importance of occlusion in the
condyle-fossa relationship. Studies by Myers et al,11
Mongini,12 Mongini and Schmid,13 Pullinger et al,14
O’Byrn et al,15 and Schudy16 showed significant correlations between these variables. However, Cohlmia et al17
reported no relationship between them.
Several studies attempted to correlate certain characteristics of the TMJ with specific types of malocclusion.8,16-21 By evaluating the TMJ structures in Class I,
Class II, and Class III malocclusions, Burley8 demonstrated that those malocclusions do not produce
functional stimuli capable of altering the articular structures of the temporal bone. No condyle centralization
and no statistically significant articular asymmetry in
Vitral et al
most measurements between right and left sides were
found by Vitral et al18 and Vitral and Telles19 in a sample
of Class II Division 1 subdivision patients, and by Rodrigues et al20,21 in samples of Class I, Class II Division
1, and Class III patients. The noncentralization of the
mandibular condyles was a characteristic also in other
samples of patients with malocclusion.16,17
The use of CT scans in studies on the TMJ was a significant advance in the research of morphology of these
structures and the diagnosis of pathologies that are difficult to identify by conventional radiographs. This is the
method of choice for obtaining images of bone structures.22 Additionally, this examination allows real and
precise measurements of the structures under analysis.23
Unfortunately, most traditional CT scanners are large
and expensive systems, and are not readily available to
orthodontists.24 Today, with CBCT, these examinations
became more accessible to orthodontists, because of
more compact equipment that is affordable for small
diagnostic centers, and with less radiation than conventional CT scans.25
The purpose of this study was to investigate, with CT
imaging, the condyle-fossa relationship, the position of
the condyles in their respective mandibular fossae, and
the dimensional and positional symmetries between
the right and left condyles in a sample of subjects with
normal occlusion.
MATERIAL AND METHODS
After ethical committee's approval, thirty persons
with normal occlusion, ranging in age from 15 to 32
years, had CT scans of their TMJs. All participants met
the following requirements: all permanent teeth erupted
except third molars, no functional mandibular deviations, no evident facial asymmetry, first molars and canines in a Class I relationship, canine guidance with no
working or nonworking side interferences on lateral excursions, anterior guidance with no posterior interferences, normal overbite and overjet, and no crossbite.
Patients with temporomandibular disorders were not included in the sample.
The methodology we used was described by Vitral
et al18 and Vitral and Telles.19
The CT images were obtained with patients in maximum dental intercuspation, and their heads were positioned so that the Frankfort and midsagittal planes
were perpendicular to the floor. The helicoidal, multislice CT scan was performed with a Somaton Spirit device (Siemens, Xangai, China) at 120 kV and 160 mA.
We obtained 1-mm thick tomographic imaging slices
spaced at 1-mm intervals, using the helicoidal technique. Because this procedure provides images in the
19
axial plane, it was reformatted to produce images sagittally. The selected imaging slices were processed in the
same equipment.
The measurements were determined by tracing the
selected image structures. As in most CT images,
the dimensions did not correspond to the real sizes of
the structures. Therefore, a scale for measurement conversion was determined for each image. The following
measurements were assessed on the sagittal plane.
1.
2.
3.
4.
Depth of the mandibular fossa: measured from the
most superior point of the fossa to the plane formed
by the most inferior point of the articular tubercle to
the most inferior point of the auditory meatus
(Fig 1).
Anterior joint space: the shortest distance between
the most anterior point of the condyle and the
posterior wall of the articular tubercle (Fig 2, a).
Superior joint space: measured from the shortest
distance between the most superior point of the
condyle and the most superior point of the mandibular fossa (Fig 2, b).
Posterior joint space: represented by the shortest
distance between the most posterior point of the
condyle and the posterior wall of the mandibular
fossa (Fig 2, c).
The following measurements were assessed on the
axial plane.
1.
2.
3.
4.
5.
The largest anteroposterior diameter of the mandibular condylar processes (Fig 3, a).
The largest mediolateral diameter of the mandibular
condylar processes (Fig 3, b).
The angle between the long axis of the mandibular
condylar process and the midsagittal plane (Fig 3, c).
The distance between the geometric centers of the
condylar processes and the midsagittal plane, measured with a line that passed through the geometric
centers of the condylar processes and perpendicular
to the midsagittal plane (Fig 4, a).
The anteroposterior difference between the geometric center of the right and left condylar processes
as reflected on the midsagittal plane (Fig 4, b). The
point representing the geometric center of the right
condylar process was the 0 point. The variations on
the left side were measured from this point. The
geometric centers situated anterior to the 0 point
were considered positive, and those posterior to it
were considered negative.19-21
Measurements of the anterior and posterior joint
spaces were compared for the right and left sides to evaluate the centralization of the condyles in their respective
mandibular fossae.
American Journal of Orthodontics and Dentofacial Orthopedics
July 2011 Vol 140 Issue 1
Vitral et al
20
Fig 1. CT image representing the depth of the mandibular fossa.
Fig 2. CT image: a, anterior joint space; b, superior joint space; c, posterior joint space.
Paired Student t tests were used for each measurement studied to evaluate the average of differences between the right and left sides for each element of the
sample.
Pearson product moment correlation coefficients (r)
were determined to quantify the degree of correlation
between the values of the right and left sides for each
measurement.
RESULTS
The descriptive statistics for each measurement analyzed are shown in Table I. The descriptive statistics for
the evaluation of the centralization of the condyles in
their respective mandibular fossae are shown in Table II.
The mean depths of the mandibular fossa were 8.43
and 8.46 mm for the right side and left sides,
July 2011 Vol 140 Issue 1
respectively (P 5 0.803; r 5 0.025). The mean anterior
joint spaces were 1.22 and 1.28 mm for the right and
left sides in that order (P 5 0.553; r 5 0.019). The
mean superior joint spaces were 1.67 mm for the right
side and 1.66 mm for the left side (P 5 0.903; r 5
0.000). The mean posterior joint spaces were 1.96 mm
for the right side and 1.76 mm for the left side (P 5
0.048; r 5 0.000).
The mean values for the anteroposterior diameter of
the condylar processes were 9.93 mm for the right side
and 10.13 mm for the left side (P 5 0.283; r 5 0.000).
For the measurement of the mediolateral diameter of
the condylar processes, the values were 22.57 mm for
the right side and 21.92 mm for the left side (P 5
0.022; r 5 0.000).
The measurements for the angle between the plane
of the largest mediolateral diameter (long axis) of the
American Journal of Orthodontics and Dentofacial Orthopedics
Vitral et al
21
Fig 3. CT image: a, greatest anteroposterior diameter of the mandibular condylar process; b, greatest
mediolateral diameter of the mandibular condylar process; c, lateromedial plane angle of the condylar
process/midsagittal plane. L.C.P., Left condylar process; R.C.P., right condylar process; M.S.P.,
midsagittal plane.
Fig 4. CT representations: a, of the distance between the geometric center of the condylar processes
to the midsagittal plane; b, anteroposterior difference of the condylar processes. L.C.P., Left condylar
process; R.C.P., right condylar process; M.S.P., midsagittal plane.
American Journal of Orthodontics and Dentofacial Orthopedics
July 2011 Vol 140 Issue 1
Vitral et al
22
Table I. Statistical analysis
Depth of mandibular fossa (mm)
Anterior joint space (mm)
Superior joint space (mm)
Posterior joint space (mm)
Anteroposterior diameter
of condylar process (mm)
Mediolateral diameter
of condylar process (mm)
Angle, condylar
process/midsagittal plane ( )
Anteroposterior difference
of condylar process (mm)
Distance, condylar
process/midsagittal plane (mm)
Right
side-left
side
0.03
0.06
0.01
0.20
0.20
P value,
paired
Student
t test
0.803
0.553
0.903
0.048
0.283
Pearson
product
moment
correlation (r)
0.025
0.019
0.000
0.000
0.000
Mean,
right side
8.43
1.22
1.67
1.96
9.93
Mean,
left side
8.46
1.28
1.66
1.76
10.13
SD,
right side
0.59
0.44
0.62
0.69
1.24
SD,
left side
0.72
0.53
0.66
0.62
1.30
22.57
21.92
2.65
3.09
0.65
0.022
0.000
68.45
68.66
8.83
7.72
0.21
0.875
0.000
0.00
0.58
0.00
2.82
0.58
0.277
56.31
55.95
3.23
3.87
0.36
0.367
0.000
Table II. Statistical analysis of centralization of the condyles in their mandibular fossae
Position of condyles,
right side (mm)
Position of condyles,
left side (mm)
Mean,
anterior
joint space
1.22
Mean,
posterior
joint space
1.96
SD, anterior
joint space
0.44
SD, posterior
joint space
0.69
1.28
1.76
0.53
0.62
condylar processes and the midsagittal plane were
68.45 for theright side and 68.66 for the left side
(P 5 0.875; r 5 0.000). The average anteroposterior position of the condylar processes as reflected on the midsagittal plane was 0.58 mm (P 5 0.277). The mean
values obtained for the distance from the geometric center of the condylar processes to the midsagittal plane
were 56.31 mm for the right side and 55.95 mm for
the left side (P 5 0.367; r 5 0.000).
In the evaluation of the centralization of the condyles
on the right side, the mean values were 1.22 and 1.96
mm for the anterior and posterior joint spaces (P 5
0.000; r 5 0.872), whereas on the left side, the mean
values were 1.28 and 1.76 mm, respectively (P 5
0.012; r 5 0.041).
DISCUSSION
Although CBCT has been developed for obtaining
images in dentistry,26 the helicoidal, multi-slice CT was
the examination of choice for this study, because this
methodology was used in the other studies of this series,
which evaluated the articular characteristics of the TMJ
July 2011 Vol 140 Issue 1
Anterior
joint
space-posterior
joint space
0.73
0.48
P value,
paired
Student t test
0.000
Pearson
product
moment
correlation (r)
0.872
0.012
0.041
in Class I, Class II, and Class III malocclusions.18-21 By
using the same methodology, a more reliable
comparison between the findings obtained for normal
occlusion and the above-mentioned malocclusions was
ensured. However, CBCT has been considered the examination of choice in orthodontic practice for TMJ evaluations, since it provides high-resolution imaging,
diagnostic reliability, and 40% less radiation than conventional CT, and should be preferred over CT images
in orthodontic practice.25
According to Rodrigues et al,21 to date, it is unknown
whether a morphologic condition or an articular positioning is typical of a specific type of malocclusion.
However, for an articular characteristic to be associated
with a specific type of malocclusion, a comparative parameter should be defined, and, in most instances,
such parameters are those that reflect a condition of
normality.
Most studies aiming at evaluating the TMJ by means
of CT have considered normal asymptomatic joints but
did not give details about the occlusal characteristics
of the patients.1,2 A series of studies using the same
methodology to evaluate the characteristics of the TMJ
American Journal of Orthodontics and Dentofacial Orthopedics
Vitral et al
in specific groups of malocclusion was undertaken, and
this study, the last of this series, aimed at answering the
following question: do patients with normal occlusion
have a singular condition of the TMJs that can be
defined as a comparative pattern for the groups with
malocclusion?18-21
Of all the measurements made on the axial cut, the
linear measurement of the mediolateral diameter of
the condylar process showed a statistically significant
difference (P 5 0.022) between the right and left sides.
There were no significant differences between both sides
in the other measurements.
The samples of Class I,21 Class II Division 1 subdivision,19 and Class III20 patients did not show any significant asymmetry in the measurements on the axial cuts
of the TMJ. A significant difference was found in the distance between the geometric centers of the condylar
processes and the midsagittal plane (P 5 0.019) in the
Class II Division 1 sample.20
Although the value of the difference between the
means in the normal occlusion sample was numerically
low (0.65 mm), it was statistically significant, showing
an asymmetry not found in some types of malocclusions,
including asymmetric patients, such as those with Class
II Division 1 subdivision malocclusion.
A statistically significant difference (P 5 0.048) was
observed when the right and left posterior articular
spaces were compared on the sagittal cut. The left posterior joint space was, on average, 0.20 mm smaller than
the right posterior joint space. The same characteristic
was found in the Class I and Class II Division 1 samples
evaluated by Rodrigues et al.20,21 In the Class I group,
the left posterior joint space was, on average, 0.22 mm
smaller than the right posterior joint space (P 5
0.012); in the Class II Division 1 sample, this difference
was 0.21 mm (P 5 0.049).
Therefore, this difference was not exclusive of normal
occlusion or of any determined malocclusion.
Another common characteristic of all malocclusions
and normal occlusion was the noncentralization of the
condyles in their respective fossae. All samples evaluated
showed anterior joint spaces significantly smaller than
posterior joint spaces, demonstrating a more anterior
condylar positioning in the mandibular fossa.
Similar results had already been observed by Pullinger et al14 and Cohlmia et al17 in malocclusion samples
and by Ikeda and Kawamura2 in patients with optimal
joints without displacement. All these recent studies2,14,17-20 seem to change that long-standing paradigm of the centralized positioning of the condylar
processes.27,28 Most likely, the examination modalities
used in the 1960s and 1970s were not as precise as
they are today.
23
Thus, it can be verified that there is no special characteristic in the TMJs of patients with normal occlusion
in the sample evaluated in this study. As in the malocclusion samples, small asymmetries and no centralized position of the condyles could be observed. Such
noncentralization seems to be, therefore, a characteristic
of asymptomatic joints, even with a malocclusion.
CONCLUSIONS
No singular characteristic in the TMJs of the normal
occlusion group was verified.
The largest mediolateral diameter of the mandibular
condylar processes and the posterior joint spaces showed
a statistically significant difference between the right
and left sides.
Evaluation of the concentric position of the condyles
in their respective mandibular fossae showed a noncentralized position for the right and left sides.
We thank Fundaç~ao de Amparo a Pesquisa do Estado
de Minas Gerais (FAPEMIG) for its support.
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American Journal of Orthodontics and Dentofacial Orthopedics
Andreia Rodrigues