Download Cephalometric Characteristics of Patients with Temporomandibular

Asim Mustafa Khan
ORIGINAL ARTICLE
Cephalometric Characteristics of Patients with
Temporomandibular Joint Disorders: A Radiographic
Cross-Sectional Study
Asim Mustafa Khan
ABSTRACT
Objective: To compare cephalometric features of patients with
temporomandibular joint disorders (TMDs) and asymptomatic
controls using digital lateral cephalometric analysis.
Study design: 38 patients with TMDs and 32 asymptomatic
subjects underwent lateral cephalometric analysis using
software after a thorough examination based on Research
Diagnostic Criteria for TMDs (RDC/TMD). SNA, SNB, ANB,
Mandibular plane to SN plane, Upper incisor line to SN plane,
lower incisor line to mandibular plane angles and Gonionarticulare line length were recorded and subjected to comparison
for any significant variations between the experimental and
control group using independent-t test. Also experimental group
subjects were distributed based on etiology and subjects without
any obvious cause of TMDs were compared with controls.
Results: There was a significant difference (between the
experimental and control groups with respect to SNAº, Upper
incisor line to SN plane angle (UI-SN) and lower incisor line to
mandibular plane angle (LI-MP). No significant variations were
obtained when craniofacial morphology was purely tested as
cause of TMDs by comparing subjects with TMDs due to
unknown etiology with the controls.
Conclusion: Subjects with reduced forward development of
maxilla and more retroclined upper and lower central incisors
are predisposed to TMDs but this may not be the only reason
for the occurrence of TMDs.
Keywords: Cephalometry, Digital analysis, Temporomandibular
Joint disorder.
How to cite this article: Khan AM. Cephalometric Characteristics
of Patients with Temporomandibular Joint Disorders: A
Radiographic Cross-Sectional Study. J Indian Acad Oral Med
Radiol 2013;25(4):268-273.
Source of support: Nil
open bite, retruded contact position (>2 mm), increased
overjets (>4 mm) and five or more missing and unplaced
posterior teeth have been suggested as the possible etiologies
of TMDs.1 The role of micro and macrotrauma in TMDs
are also significant.1 A lot of research has been done to
attribute all the above to TMDs. A few reports show that
the steep maxillary incisor angle2 and shorter posterior facial
height3 as strongly related to temporomandibular disorders.
Most of the studies have focussed on the relationship of
asymmetry in lower facial structures and TMDs, and, have
used Lateral Cephalometry3-5 and to some extent, Posterioanterior skull view4 to quantify facial and dental relationships.
Lateral cephalographs assess more accurately the extent to
which a patient deviates from normal facial and dental
morphologies.6 Almost, none of the studies have included
the Research Diagnostic Criteria (RDC/TMD) in their
protocol as a screening tool for TMD patients in such studies.
Reports suggest RDC/TMD to be a highly sensitive tool to
evaluate the signs and symptoms of TMD.7 Associations
between craniofacial morphology and TMD have been
contradictory and inconclusive.3,8,9 Although magnetic
resonance imaging is the gold standard to assess TMJ
disk displacement, it is still expensive and not easily
accessible to all groups of patients. Therefore, assessing the
predisposition to TMD using lateral cephalometry forms an
economical alternative to MRI. Hence, this study was
designed to determine the cephalometric characteristics in
TMD patients and test the hypothesis that there is no
difference in cephalometric measurements in patients with
and without TMD.
Conflict of interest: None
INTRODUCTION
A temporomandibular disorder is an orofacial disorder that
causes many clinical problems in the temporomandibular
joint (TMJ), the masticatory muscles, the dental occlusion,
and the neuromuscular system. The main symptoms of TMJ
disorder are mandibular joint and masticatory muscle pain,
a TMJ sound, headache and pain in adjacent muscles. These
symptoms can appear alone or simultaneously as the
disorder progresses. Temporomandibular disorders are
divided into joint and muscle disorders. The causes of TMJ
disorder are complex. The presence of a skeletal anterior
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MATERIALS AND METHODS
Thirty eight patients with symptomatic TMDs were included
in case group and thirty two asymptomatic, age and gender
matched subjects referred for lateral cephalometric
radiography intended for orthodontic purpose were taken
as controls. Subjects in the age group of 20 to 27 years
were selected for the study. The study was conducted
between November 2012 and April 2013 in Department of
Oral Medicine and Radiology with the approval from
Institutional Review Board and the Ethics Committee of
Coorg Institute of Dental Sciences, Virajpet. A few subjects
in the case group were also picked up from group
JIAOMR
Cephalometric Characteristics of Patients with Temporomandibular Joint Disorders: A Radiographic Cross-Sectional Study
undergraduate students of Coorg Institute of Dental sciences
who were experiencing TMD. They were included based
on a modified questionnaire for TMDs which also included
questions 7, 8 and 9 from RDC/TMD Axis I.10 Subjects
were exposed to radiation only after obtaining an informed
consent and under optimal radiation protection principles.
Each subject was asked to wear a lead apron during the
radiographic procedure.
Subjects with a chief complaint of pain, clicking/
crepitus or pain alone in the pre-tragal region with or without
reduced mouth opening were considered to form case group
in the study. Only the subjects who fit in to class I and
IIa (disk displacement with reduction), IIb (disk displacement
without reduction and limited mouth opening), IIc (disk
displacement without reduction and without limited mouth
opening) according to RDC/TMD Axis I were inducted in
case group. Patients with a history of arthrosis, arthritis and
arthralgia (i.e. class III according to RDC/TMD Axis I),
ankylosis, severe debilitating diseases and pregnancy were
excluded from the study.10
Before a thorough TMJ examination, each subjects’
history of present illness was carefully recorded and
scrutinized to delineate the etiology for the symptoms.
A standard RDC/TMD examination protocol was
followed which included extra and intra-auricular palpation,
range of movements by measurement of unassisted and
assisted mouth opening, right and left lateral movements,
recording of any joint noises and finally, assessing any
deviation or deflection on mouth opening and gauging
midline deviation if any.10
The TMJ examination proceeded with exposing the
cases and controls to lateral cephalometric radiography using
Orthophos-XG (Sirona Technologies, Germany). All the
images were stored in DICOM format (Digital Imaging and
Communications in Medicine) in the computer database.
These lateral cephalographs were then analyzed digitally
using the Ax.CEPH Cephalometric software Version 2.0
(Audax Technologies, Slovenia) (Fig. 1) and were saved in
the database.
A selected few lateral cephalometric parameters were
chosen which are as follows:
• SNA, SNB and ANB angles (Fig. 2) to classify subjects
into Class I, II, III. SNA and SNB angles are reliable
indicators of relative position of maxilla and mandible
to cranial base respectively.6 ANB angle denotes the
relative position maxilla and mandible6 to each other
and is the difference between SNA and SNB angle. ANB
angle <4º indicated skeletal class I, whereas ANB angle
4º indicated a skeletal class II relation which signified
maxilla to be forwardly placed than mandible. Negative
ANB angle denoted a class III skeletal relation.6
•
Mandibular plane to SN plane angle (Fig. 3) was used
to assess if the subjects had a horizontal or vertical
growth pattern.6
• Upper incisor line to SN plane angle (Fig. 4) and lower
incisor line to mandibular plane angle (Fig. 5) to assess
the proclination of teeth.6
• Gonion-articulare line length (Fig. 6) to assess the
posterior facial height is another criterion to find out if
the subject has a horizontal or vertical growth pattern.6
All the above cephalometric landmarks were observed
by an oral radiologist and orthodontist with 10 years of
experience for any errors in landmark placement.
Inter-examiner and intra examiner reliability was
assessed using Cohen’s Kappa coefficient statistics with
values of 0.75 and 0.86 respectively.
Fig. 1: Postanalysis
Fig. 2: SNA° (sella-nasion-point A); SNB° (sella-nasion-point B);
ANB° (point A-nasion-point B)
Journal of Indian Academy of Oral Medicine and Radiology, October-December 2013;25(4):268-273
269
Asim Mustafa Khan
Fig. 3: SN-MP° (SN plane to mandibular plane)
Fig. 4: UI-SN° (upper incisor line to SN plane angle)
Fig. 5: LI-MP° (lower incisor line to mandibular plane angle)
STATISTICAL ANALYSIS
Statistical analysis was done by SPSS software and applying
Independent t-test with a confidence interval of 95% (p  0.05).
Fig. 6: AR-GO (articulare-gonion line length in mm)
of 22.55 ± 4.65 years. The mean ages of males and females
in control group were 20.75 ± 3.75 and 21.45 ± 2.75 years
respectively (Table 1).
A majority of subjects in experimental group were in
class IIa group (n = 18) (disk displacement with reduction)
of RDC/TMD. Three subjects were in class IIb (disk
displacement without reduction and limited mouth opening),
eight subjects were in class IIc group (disk displacement
without reduction and without limited mouth opening) and
the remaining nine were in class I group (tenderness of
muscles of mastication) (Graph 1).
Based on history and clinical evaluation 10 subjects in
the experimental group had missing teeth as their cause for
TMD. Four subjects had history of previous dental treatment
which proceeded with TMD symptoms. Two subjects had
symptoms because of occlusal discrepancies due to faulty
restorations and two had TMD symptoms due to orthodontic
treatment. Only one symptomatic subject also had
symptomatic cervical spondylitis. Remarkably, there were
19 subjects whose symptoms could not be attributed to any
of the etiologies of TMD and therefore formed an unknown
etiology group (UnE) (n = 19) (Graph 2).
The rationale behind delineating the causes of TMD in
experimental group is to draw attention to the subjects in
UnE and to check and compare their cephalometric features
with the controls for any significant variations. This would
eliminate all other causes of TMD and would purely test
hypothesis of craniofacial morphology as a cause of TMD.
RESULTS
COMPARISON OF CASE GROUP
WITH THE CONTROLS
In a total of 70 subjects, a majority of them were females
(70%) and the remaining were males. The experimental case
group was also consistent with this trend reporting females
in majority (71.05%). The males in experimental group were
in age range of 21.2 ± 5.25 years and females in age range
The cephalometric values of experimental case group were
compared with those of the control group (Table 2). There
was a significant difference (p  0.05) between the two
groups with respect to SNAº (p = 0.030); upper incisor line
to SN plane angle (UI-SN) (p = 0.006) and lower incisor
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Cephalometric Characteristics of Patients with Temporomandibular Joint Disorders: A Radiographic Cross-Sectional Study
line to mandibular plane angle (LI-MP) (p = 0.014).
However, no significance (p > 0.05) between the case and
control group was observed in Mandibular plane to SN plane
angle (SN-MP) (p = 0.446), Gonion-articulare line length
(AR-GO) (p = 0.472), SNBº (p = 0.502) and ANBº
(p = 0.360) (see Table 2).
COMPARISON OF UNE GROUP WITH
CONTROL GROUP (TABLE 3)
No significant differences were found between the two
groups in relation to any of the following cephalometric
measurements-SNA° (p = 0.387), SNB° (p = 0.955), ANB°
(p = 0.458), SN-MP° (p = 0.063), AR-GO (p = 0.705),
UI-SN° (p = 0.061) and LI-MP° (p = 0.139).
DISCUSSION
Graph 1: Experimental group distribution according to RDC/TMD
Graph 2: Subgroup distribution based on etiology (UnE: Unknown
etiology group; MT: Missing teeth group; DP: Dental procedures
group; OT: Orthodontic treatment group; OD: Occlusal discrepancy
group, others)
Table 1: Demographic data
Groups
Age (mean)
Females (%)
Males (%)
Cases
Controls
20.5 ± 5.75
20.75 ± 2.25
71.05 (n = 27)
68.75 (n = 22)
28.94 (n = 11)
31.25 (n = 10)
70
30
Total
Although associations between TMJ disk displacement and
facial pattern have been demonstrated, a cause-effect
relationship cannot be assumed.11 Disk displacement may
affect facial growth or disk displacement may occur as a
consequence of biomechanics associated with an altered
facial pattern.11
Four occlusal features, have also been pointed out mainly
in TMD patients and were rare in normal subjects: (1) the
presence of a skeletal anterior open bite, (2), retruded contact
position (RCP)/ICP slides of greater than 2 mm, (3) overjets
of greater than 4 mm, and (4) five or more missing and
unreplaced posterior teeth.1
In this study, the SNA°, UI-SN° and LI-MP° values of
cases were significantly less than those of the controls. This
indicates that TMDs seen in experimental group are with
less developed maxilla and retroclined upper and lower
incisors. Also, there were no significant variations between
experimental and control group in relation to SNB°, ANB°,
AR-GO and SN-MP°. Carlos and co-workers (2006)
reported that TMJ disk abnormality was associated
with reduced forward growth of the maxillary and
mandibular bodies and reduced downward growth of the
mandibular ramus.8
Ahn et al (2006) in a study on 134 women inferred that
SNB° values of the subjects with disk displacement with/
without reduction were less compared to those of subjects
with normal disk position. A similar trend was also noticed
with respect to AR-GO values between the groups. This
implied that subjects with decreased forward growth of
mandible and reduced ramal height were predisposed to
TMDs. However, in the present study no significant
Table 2: Comparison of experimental and control
Groups
Experimental
Controls
p-value
Lateral cephalometric parameters (mean)
SNA°
SNB°
ANB°
SN-MP°
AR-GO (MM)
UI-SN°
LI-MP°
84.22
86.13
0.030
80.66
81.41
0.502
4.56
5.09
0.360
33.67
34.89
0.446
45.52
46.38
0.472
110.13
116.17
0.006
96.88
102.03
0.014
Journal of Indian Academy of Oral Medicine and Radiology, October-December 2013;25(4):268-273
271
Asim Mustafa Khan
Table 3: Comparison of unknown etiology group (UnE) and control
Groups
UnE
Controls
p-value
Lateral cephalometric parameters (mean)
SNA°
SNB°
ANB°
SN-MP°
AR-GO (MM)
UI-SN°
LI-MP°
85.30
86.13
0.387
81.49
81.41
0.955
4.53
5.09
0.458
31.34
34.89
0.063
45.79
46.38
0.705
110.93
116.17
0.061
98.68
102.03
0.139
variations were found concerning SNB° and AR-GO and
therefore cannot be recognized as cause of TMDs.5
Chung-Ju (2006) also used SNA°, mandibular ramus
length and upper and lower incisor inclination to determine
the relationship between craniofacial skeletal structures and
TMJ disorders by using lateral cephalogram. It was found
subject with a TMJ disorder had a greater ramus height and
more lingual tilting of the maxillary incisors.3 Nickerson
and Boering equated TMJ osteoarthrosis and internal
derangement and reported that adolescents with this
condition can have retrognathic mandibles, small and
deformed condyles, shortened ramal heights, and prominent
antegonial notching.12 But Brand et al (1995) contradicted
shortened ramal height as a cause of TMDs.13 However in
our study the relationship between TMDs and mandibular
ramus length could not be established.
The relationship of retroclined upper and lower incisors
to TMDs was explored by Sonnesen and Svensson (2008).
They believed that reduced UI-SN and LI-MP would cause
a posterior forced bite and altered bite forces leading to
TMDs.9,14 However, in their study no significant differences
were observed in the bite force assessment of experimental
and control group.
Loss of normal disk position compromises the load
distribution of the joint, sets up areas of increased shear
and compressive stress, reduces the lubrication of the joint
surfaces, and ultimately results in tissue damage with
inflammation. Compromised nutrition, oxygenation, and
lubrication, superimposed on an inflammatory zone, results
in biochemical alterations which, with the progress of time,
are expressed as cellular changes and morphological
alterations in tissues.15,16
Our inference of nonsignificant differences between
cephalometric values of UnE group and control group could
be mostly because of smaller number of sample of UnE
group. Therefore, a larger sample size with a more
heterogeneous group might be helpful in establishing a link
between craniofacial morphology and TMDs. Further, the
use of MRI to localize disk and condyle would have been a
better approach to include the subjects in the study. Also,
bite force analysis would have been helpful in exactly
assessing the stress on masticatory muscles due to
craniofacial morphology. Due to limited resources, lateral
272
cephalometry and RDC/TMD were the only tools available
at the hands of the researcher.
CONCLUSION
Reduced forward development of maxilla and decreased
upper and lower incisor inclination predisposes an individual
to TMDs. Also, lateral cephalometry can be used as an
auxiliary diagnostic tool to help identify patients with
potential TMDs.
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Cephalometric Characteristics of Patients with Temporomandibular Joint Disorders: A Radiographic Cross-Sectional Study
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ABOUT THE AUTHOR
Asim Mustafa Khan
Senior Lecturer, Department of Oral Medicine and Radiology, Coorg
Institute of Dental Sciences, Virajpet, Karnataka, India, Phone:
8095532245, e-mail: [email protected]
Journal of Indian Academy of Oral Medicine and Radiology, October-December 2013;25(4):268-273
273