Authors
1 Oral and Maxillofacial Disease Research Center, Department of Oral and Maxillofacial Radiology, Mashhad University of Medical Sciences, Mashhad, Iran
2 Dental Research Center, Department of Prosthodontics, Faulty of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran
3 Private Oral and Maxillofacial Radiologist, Hakim Hospital of Neyshabur, Neyshabur, Iran
4 Dental Research Center, Department of Oral and Maxillofacial Radiology, Mashhad University of Medical Sciences, Mashhad, Iran
5 Postgraduate Student of Oral and Maxillofacial Radiology, Mashhad University of Medical Sciences, Mashhad, IranMashhad, Iran
Abstract
Keywords
Introduction
Temporomandibular disorders (TMD) are referred to disorders of the masticatory system (muscles, temporomandibular joint, and tendons) (1). It is so prevalent that 28 to 86% of adults and adolescents are affected by one or more signs and symptoms of such disorders (2). Signs and symptoms of TMD include TMJ pain, headache, muscle tenderness, joint stiffness, reduced range of motion in the jaw, locking of the joint, dislocation of the jaw, and joint sounds like clicking and crepitus (1-4). In most cases, clinical signs and symptoms are temporary and treatment is not recommended. Still, in 5% of patients, these disorders and induced dysfunctions can lead to significant pain and degeneration, which justifies the need for urgent and accurate diagnosis before onset of progressive degenerative stages (2). RDC/TMD is a reliable International Diagnostic-Research System that is used with the aim to standardize diagnosis and classification of various clinical forms of TMD. In this system, TMDs are classified into three groups of muscular disorders (group I), disc displacement (group II), and arthralgia osteoarthrosis, osteoarthritis (group III) (5).
Degenerative arthritis or osteoarthritis is an age-related disorder and is the most common pathological TMJ condition. Osseous changes of osteoarthritis include flattening, sclerosis, irregular cortical boundaries, erosions, osteophyte formation, condylar head resorption, and reduced joint space. These changes are commonly observed in the condyle, but may involve the fossa or articular eminence as well. Also, in many studies, a significant and positive relationship has been observed between erosions and osteophyte formation with aging (2,6,7). With widespread destruction, the subcondylar cortical layer is lost and erosion and other osteoarthritis signs appear (16-18).
TMDs are common in both adults and children. According to previous studies, it has a prevalence of 6 to 86% (13-15). Diagnostic radiology plays an effective role in the treatment of patients with TMD (14). Validity of diagnostic systems such as RDC/TMD is reliant on clinical findings and CT and MR imaging. However, MRI is unable to show skeletal changes as well as it could show soft tissue of the joint (15). CT also has high absorption dose and is expensive. Today, cone beam computed tomography (CBCT) imaging is considered an appropriate technique for diagnosis of condylar bone abnormalities (16).
CBCT provides a 3-dimensional image of mineralized maxillofacial tissues with the least distortion (4, 17). Despite clinical importance of TMDs, its radiographic signs have been poorly investigated. Hence, the aim of the current study was to evaluate the bony changes of temporomandibular joint (TMJ) in cone beam computed tomography (CBCT) images of patients with disc displacement and osteoarthritis. Our null hypothesis was that no significant differences would be found in the CBCT images of patients with disc displacement and osteoarthritis.
Materials and Methods
The participants in this cross-sectional study were consisted of patients admitted to the Prosthodontics Department of School of Dentistry, Mashhad, Iran from 2010 to 2011. Based on clinical examination, those who met RDC/TMD criteria were included and were categorized into cases with disc displacement (group II) or osteoarthritis (group III).
Exclusion criteria were:
This study was approved by the Research Deputy of Mashhad University of Medical Sciences regarding ethical and methodological issues. A written consent was obtained from each individual after the objectives and procedures were fully introduced to them and their questions were answered.
A total of 45 patients (37 women and 8 men, 90 joints) with an age ranging from 13 to 82 years that met inclusion criteria were enrolled. Bilateral CBCT imaging of the TMJ joints with closed mouth and maximum intercuspation was performed to evaluate potential changes in bony contours.
The TMJ images of patients were obtained using a Planmeca Promax 3D 8*8 CBCT unit (Planmeca Oy, Helsinki, Finland) with a voxel size of 0.16mm. For interpretation, real time reconstruction was performed using Planmeca Romexis 2.4.2 viewer (Planmeca oy) and the axial, coronal, and sagittal two dimensional (2D) multi-planar reformatted slices were provided. Slides were prepared so that sagittal images were perpendicular to the condylar longitudinal axis, and coronal images were parallel to this axis (18). All images were examined by an experienced oral and maxillofacial radiologist and skeletal changes of the TMJ were recorded. All stages of image examination were performed totally blind. In sagittal images TMJ components were condyle, joint cavity, and articular eminence in terms of skeletal changes including sclerosis (increased density of the cortical lining or the subchondral bone), flattening (loss of the round contour of the condyle at load bearing area) or erosion (interruption or lack of the cortical lining) osteophyte (marginal bone outgrowth), resorption (partial loss of condylar head) (6,11) and other changes were investigated. Conventionally, for any of the above items to be considered as a change, they should be observed in at least two consecutive cuts (18).
The data were collected in PASW software version 18. Appropriate descriptive statistics including mean and standard deviation were considered. Normality of data distribution was evaluated using one- sample Kolmogorov-Smirnov test. Data were analyzed using Chi-squared and Mann-Whitney tests with the confidence interval of 95%.
Results
Of the 90 joints studied, 43 joints were in group II and 46 were in group III, with mean age of 33.60±14.52 and 40.76±16.50 years, respectively. One of the joints lacked any clinical symptoms and was excluded. According to the one-sample Kolmogorov-Smirnov test data the assumption of normality of data distribution was violated (p-value=0.04). Mann-Whitney test for the comparison of mean age between groups II and III was not statistically significant (p-value=0.06).
The most common condylar bony changes in group II in order of frequency were flattening, erosion, sclerosis, osteophyte, and resorption. In group III flattening, erosion, osteophytes, resorption and sclerosis, respectively were the most common (Fig. 1).
All bony changes (except for flattening and sclerosis) were more common in osteoarthritis group when compared with disc displacement group. The difference between groups II and III in terms of erosion, resorption, and osteophytes formation frequency was significant (p-value< 0.05) (Table 1).
Most bony changes were concentrated in various parts of the condyle and articular eminence, and no particular change was observed in the mandibular fossa (Fig. 2).
When considering type of bony changes in articular eminence, the frequency of bony changes in disc displacement group (except for sclerosis) was significantly lower than that in osteoarthritis group (Table 2). The most prevalent changes were erosion, resorption, flattening, and sclerosis, respectively.
The Mann-Whitney test results showed that the group without condylar erosion were significantly younger than the group with erosion (p-value=0.04). However, age was not related to any other variables both in condylar and articular eminence changes
(p-value>0.05) (Table 3).
Table 1. Cross tabulation of condylar bony changes in RDC/TMD groups
|
|
Condylar bony Changes |
|||||
|
Erosion |
Resorption |
Flattening |
Sclerosis |
Osteophyte |
||
|
RDC/TMD Groups |
Disc Displacement |
22 |
5 |
40 |
20 |
12 |
|
Osteoarthritis |
39 |
30 |
43 |
22 |
32 |
|
|
Total |
61 |
35 |
83 |
42 |
44 |
|
|
Pearson Chi-square (p-value) |
18.05 (<0.0005)٭ |
26.75 (<0.0001)٭ |
0.007 (0.932) |
0.015 (0.90) |
15.43 (<0.0001)٭ |
|
* Statistically significant
Table 2. Cross tabulation of articular eminence bony changes in RDC/TMD groups
|
|
Articular eminence bony Changes |
||||
|
Erosion |
Resorption |
Flattening |
Sclerosis |
||
|
RDC/TMD Groups |
Disc Displacement |
6 |
1 |
1 |
1 |
|
Osteoarthritis |
21 |
15 |
13 |
2 |
|
|
Total |
27 |
16 |
14 |
3 |
|
|
Pearson Chi-square (P-value) |
12.05 (<0.0005)٭ |
19.45 (<0.0001)٭ |
14.17 (<0.0001)٭ |
0.055 (0.981) |
|
* Statistically significant
Table 3. Results of Mann-Whitney test for comparing age between two subgroups of studied variables
|
Variables |
N |
Mean |
S.D. |
Minimum |
Maximum |
P-value |
|
|
Erosion |
Yes |
61 |
39.93 |
17.19 |
13 |
82 |
0.04* |
|
No |
28 |
31.57 |
10.83 |
18 |
65 |
||
|
Resorption |
Yes |
35 |
38.03 |
16.91 |
13 |
82 |
0.87 |
|
No |
54 |
36.82 |
15.35 |
13 |
82 |
||
|
Flattening |
Yes |
83 |
37.30 |
15.77 |
13 |
82 |
0.94 |
|
No |
6 |
37.33 |
19.26 |
16 |
65 |
||
|
Sclerosis |
Yes |
42 |
38.57 |
14.95 |
16 |
82 |
0.39 |
|
No |
47 |
36.17 |
16.78 |
13 |
82 |
||
|
Osteophyte |
Yes |
44 |
38.95 |
16.05 |
13 |
82 |
0.46 |
|
No |
45 |
35.69 |
15.75 |
13 |
82 |
||
N: Number of cases
S.D.: Standard Deviation
*: Significant difference
Figure 1. Frequency distribution of condylar bony changes in groups II and III of RDC/TMD
Figure 2. Frequency percentage of bony changes of articular eminence in groups II and III of RDC/TMD
Discussion
The present results showed a significant relationship between age and condylar erosion (p=0.01). These results are in agreement with the findings of dos Anjos Pontual et al. and Alexio et al. studies (4, 6). They found that arthritic change is an age-related disease and severity of changes in condyle and mandibular fossa increases with age.
In the present study, various forms of bony changes including flattening, erosion, osteophyte, sclerosis, and resorption in the condyle were observed, while osteophyte could not be observed in any parts of the articular eminence. Osteophyte was merely specific to the condyle region, especially its anterior aspect. Rohlin et al. also reported osteophytes limited to the condyle (19). This is consistent with studies by Hussain et al. and ML dos (2,4).
The most common radiographic findings of condylar area, we observed were flattening, sclerosis, erosion, resorption, and osteophyte, which is similar to reports by Alexiou (6) study on patients with arthritic degenerative articular changes. Results obtained by Meng et al. (20) and Badel et al. (21) also showed that the most common findings in osteoarthritis were sclerosis, bone proliferation or osteophyte, and ill-defined boundary of cortical bone. The order of frequency of these changes is different in various studies, which can be due to different radiographic techniques, tomogram interpretations, or sample size. Moreover, expressing diagnostic importance of each of these findings in separate form is rather difficult (22).
Among condylar bony changes, flattening with frequency of 93% was the most common finding observed in both RDC/TMD groups (disc displacement and osteoarthritis). Results also indicated insignificant relationship between condylar flattening and RDC/TMD groups (p=0.932). In other words, condylar flattening has no diagnostic value in differentiation between RDC/TMD groups. In fact, flattening is an adaptive physiological response to forces beyond the threshold that lead to deformation of curved surfaces of the joint to flat surfaces. This change occurs in absence of destructive joint changes, so that it can overcome the excess forces by spreading them over a wider surface (23). Frequency of flattening in TMD groups in the present study is in line with that in Hintz et al. study (24). They also reported flattening as the most real findings in the studied joints.
In the present study, similar to flattening, sclerosis also showed an insignificant relationship with RDC/TMD groups; thus, it seems, if this radiographic finding is not associated with specific clinical signs, then it has no diagnostic value in differentiating between RDC/TMD groups. Sclerosis, similar to flattening, also points to an adaptive process in the condyle than a pathological one. In other words, bony parts are trying to better shoulder the burden of excess forces by increasing numbers or thickness of bony trabecules that are observed in the form of increased density or sclerosis, in order to prevent creation or progress of destructive changes (23). These findings are comparable to Weise et al. (22) study results which concluded that sclerosis was somewhat observed in the joints, which can explain lack of a relationship between clinical findings based on RDC/TMD and radiographic findings of sclerosis.
In the present study, erosion, resorption, and condylar head osteophyte formation had significant relationships with RDC/TMD groups (p<0/05). They were also observed with higher frequency in osteoarthritis group than in disc displacement group. These findings are also consistent with Weise et al results (22), indicating clinical diagnosis of osteoarthritis (group III of RDC/TMD classification) has a strong relationship with radiographic findings including erosion, resorption, and osteophyte formation.
Most bony changes were concentrated in various parts of the condyle as well as the articular eminence, and no particular change was observed in mandibular fossa. In examining bony changes of articular eminence, significant relationship was found between RDC/TMD groups and flattening, erosion, and resorption (p<0/05). Furthermore, in articular eminence the most frequency of bony changes except for sclerosis were in osteoarthritis group. Considering that articular eminence area is in abrasive contact with condylar head only when in maximum opening of the mouth, therefore, likelihood of abrasion is significantly less than the joint abrasive factor (condyle), which is likely to have friction along the movement path from glenoid fossa and posterior slope of the articular eminence to inferior parts and even anterior slope of the articular eminence. In other words, when bony changes are observed in the articular eminence, more severe changes can be expected in condylar area (which was clearly evident in examining CBCT images in this study). In other words, bony changes in the articular eminence suggest advanced osteoarthritis in the TMJ area. Thus, further studies with larger sample size, especially in terms of changes in the articular eminence, are recommended.
Conclusion
Acknowledgment
This study was made possible by the generous support rendered by the Vice Chancellor for Research of Mashhad University of Medical Sciences, in the form of grant no 89186 for which the authors are very grateful. Present article is the result of Mohammad Reza Talebzadeh’s postgraduate thesis (no. 432).
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