CBCT Findings in Different Types of Temporomandibular Joint Ankylosis

Ankylosis of temporomandibular joint describes the pathological development of bony connections or fibrosis that occurs in the region between the condylar head of the mandible and the glenoid fossa of the temporal bone. This condition can severely affect the function of temporomandibular joint and its mobility. The aim of this study was to evaluate the practicality of CBCT imaging in different types of temporomandibular joint ankylosis.

This cross-sectional study involved 32 cases of ankylosed temporomandibular joint from 26 patients (12 males and 14 females) aged 8-65 years (mean age: 29.8±14.3) who had visited a private maxillofacial clinic between 2013 and 2016 for CBCT images of temporomandibular joint and had been diagnosed with ankylosis by a maxillofacial surgeon. The present study relied on both Dongmei’s and Sawhney’s classifications to assess the different types of joint ankylosis. A number of morphological parameters, including: D1 (the mediolateral diameter of the condyle), D2 (the width of the bony fusion area), D3 (the degree of calcification in the bony fusion area) and D4 (the D2/D1 ratio) were also defined and registered.

All of the four variables (D1, D2, D2/D1 and D4) showed a negative correlation with the extent of mouth opening, but the amounts were non-significant (P>0.05). The level of agreement between the two classification approaches was significantly low (P=0.003). The highest degree of coronoid hyperplasia was seen in types II and III according to both Sawhney’s and Dongmei’s classifications. The greatest measure of condylar head displacement was observed in types II and III of Sawhney’s, and type III of Dongmei’s classification. Connection in the lateral side of the joint in type III of both Sawhney’s and Dongmei’s classifications was the most frequent case. More severe cases of ankylosis were commonly associated with older ages, but the relationship was not significant (P>0.05).

CBCT seems to be the most advantageous modality of imaging as far as temporomandibular joint abnormalities are concerned, including ankylosis. Although the application of the two conventional classifications (Sawhney’s and Dongmei’s) produced little agreement in terms of radiological findings, it seems that the employment of such classifications in conjunction with CBCT imaging is a promising method for the diagnosis and evaluation of temporomandibular joint ankylosis.