A possible etiology of the internal derangement of the temporomandibular joint based on the MRI observations of the lateral pterygoid muscle.

The purpose of this study was to evaluate the relationship of the temporomandibular joint (TMJ) internal derangement and lateral pterygoid muscle (LPM) by magnetic resonance imaging (MRI). In this study, 115 subjects with TMJ internal derangement (total 230 TMJs) and 21 subjects without clinical symptoms (total 42 TMJs) were included. TMJ disc position and LPM were evaluated using MRI. LPM attachments were categorized into two different types: type 1, where fibers of the superior head of the LPM (SLPM) were attached to the disc and fibers of the inferior head of the LPM (ILPM) were attached to condyle, and type 2, where fibers of the SLPM were attached to the disc and condyle, and fibers of the ILPM were attached to condyle. The presence of muscle atrophy and degeneration were also evaluated. LPM attachments were observed in two different parts. Disc displacements were common in the muscle attachments of both types. Type 1 muscle attachments were seen in 85.9% of all the anterior disc displacement without reduction (ADD) TMJs (total 64 TMJs). Atrophy was seen in a higher proportion (43.7%) in TMJs with ADD (28/64) than in TMJs with normal and anterior disc displacement with reduction (ADDR). Out of 74 TMJs with atrophy, 68 had type 1 muscle attachment. Four TMJs had atrophy in both superior and inferior heads of the lateral pterygoid. However, atrophy was not present only in the ILPM. It has been concluded that since the SLPM only attached to the disc in type 1, the disc may displace anteriorly very easily. Therefore, this situation will reduce the function of the SLPM. Reduced muscle function may cause muscle atrophy. The activity of the SLPM may be more reduced since the disc permanently dislocated in TMJs with ADD. Finally, spasm of the LPM causes disc displacement and atrophy and then the degeneration of the LPM may follow disc displacement.

Relationship of condylar position to disc position and morphology.

INTRODUCTION/OBJECTIVE: The purpose of this study was to assess whether condylar position, as depicted by magnetic resonance imaging, was an indicator of disc morphology and position. METHODS AND MATERIAL: One hundred and twenty two TMJs of 61 patients with temporomandibular joint disorder were examined. Condylar position, disc deformity and degree of anterior disc displacement were evaluated by using magnetic resonance imaging. RESULTS AND DISCUSSION: Posterior condyle position was found to be the main feature of temporomandibular joints with slight and moderate anterior disc displacement. No statistical significance was found between the condylar position, and reducing and nonreducing disc positions. On the other hand, superior disc position was found to be statistically significant for centric condylar position. CONCLUSION: It was concluded that posterior condyle position could indicate anterior disc displacement whereas there was no relation between the position of condyle and the disc deformity.

Relationship between the TMJ disc and condyle position on MRI and occlusal contacts on lateral excursions in TMD patients.

Confusion about the relationship between dental occlusion and the temporomandibular disorders (TMD) has been evident in the literature for many years. Previous studies have supported the concept of a multifactorial aetiology of TMD, the occlusal factor in general being of minor importance. The purpose of the study was to investigate the relationship between condyle and disc positions and occlusal contacts on lateral excursions of the mandible in patients with TMD. A total of 122 temporomandibular joints (TMJs) of 61 patients with TMD were evaluated using magnetic resonance imaging (MRI) and occlusal analyses were made clinically. Non-working-side contacts were found to be statistically significant in TMJ anterior disc displacement. No significant statistical correlation was found between the severity of anterior disc displacement and non-working-side contacts in both canine guidance and group function occlusions. There was no correlation between non-working-side contacts and condyle positions in both occlusion types in the present study. It was concluded that non-working-side contacts had some effect on disc position in TMD, however the presence of these contacts in both canine guidance and group function occlusions did not correlate with anterior disc displacement in TMD statistically. Therefore, non-working-side contacts are not to be regarded as the prime cause of anterior disc displacement.

The evaluation of temporomandibular joint disc position in TMJ disorders using MRI.

The purpose of this study was to correlate disc position and the type of disc displacement, intra-capsular effusion and degenerative changes of the condyle as demonstrated in MRI studies. In this study, 126 temporomandibular joints (TMJs) of 63 patients with TMJ disorders were investigated using clinical examination and MRI. One hundred and twelve TMJs were found to have internal derangement as disc displacement. The angle between the posterior margin of the disc and the vertical line drawn through the centre of the condyle was measured on MRI for each TMJ. The positions of the discs were normal, 0 degrees-10 degrees, in 11.11%; slightly displaced, 11 degrees-30 degrees, in 37.30%; mildly displaced 31 degrees-50 degrees, in 15.08%; moderately displaced, 51 degrees-80 degrees, in 7.14% of the TMJs with anterior displacement with reduction (ADDR). The disc position was severely displaced anteriorly, as over 80 degrees, in all TMJs with anterior disc displacement without reduction (ADD), constituting 27.78% of all cases. We found that the smaller the degree of disc displacement the milder the internal derangement and that the intra-capsular effusion was more frequently associated with TMJ with ADDR. The degenerative condylar changes were more severe with an increased degree of anterior disc displacement.

Magnetic resonance imaging evaluation of temporomandibular joint disc deformities in relation to type of disc displacement.

PURPOSE: This study was undertaken to assess the relationship between the temporomandibular joint (TMJ) disc deformity and the type of internal derangement. PATIENTS AND METHODS: One hundred thirty-three TMJs of 72 patients (53 female and 19 male) with intracapsular dysfunction were studied using clinical and magnetic resonance imaging examinations. RESULTS: Of the 133 TMJ discs, 41.35% had no deformity, whereas 18% of the discs were folded, 19.55% were lengthened, 9.77% were round, 7.51% were biconvex, and 3.75% had thick posterior bands. The frequency of disc deformity was greater with anterior disc displacement without reduction than in cases of anterior disc displacement with reduction (P <.001). Folded and round discs were most common in cases with TMJ anterior disc displacement without reduction (P <.0001). An increase in length was seen in 56.75% of the cases with anterior disc displacement with reduction, whereas 100% of nonreducing discs were mainly folded or rounded. Crepitation was correlated with folded and round disc deformities, whereas lengthening was the feature of reducing discs associated with early and intermediate clicking. CONCLUSIONS: The results show that the degenerative changes in the TMJ disc are influenced by the degree and the type of disc displacement. The more advanced the internal derangement, the more deteriorated the disc configuration.