Abstract: BACKGROUND: Research on adolescent patients with temporomandibular joint osteoarthritis is less reported. In the past, traditional X-ray examination was used. In recent years, cone-beam CT analysis shows marked advantages in image data analysis, which can not only be used to understand the changing characteristics of the condyle but also provide reference for the clinical diagnosis and treatment of temporomandibular joint osteoarthrosis in adolescents.
OBJECTIVE: To evaluate the abnormal morphology and influential factors based on cone-beam CT images of adolescent patients with temporomandibular joint osteoarthrosis. 
METHODS: Eighty adolescents with temporomandibular joint osteoarthrosis (experimental group) and 80 healthy adolescents (control group) were subjected to the cone-beam CT scan in the intercuspal position. The three-dimensional reconstruction images of the temporomandibular joint were measured by Invivo 5.2 software in both groups. (1) Sagittal measurements: upper, anterior and posterior joint spaces; (2) axis measurements: anterior and posterior diameters, internal and external diameters of the condyle; (3) three-dimensional imaging: the height of the mandibular ramus; and (4) the percentage of different pathological change types due to temporomandibular joint osteoarthrosis in the experimental group. 
RESULTS AND CONCLUSION: According to statistics, there were 27 males and 53 females in the experimental group, and the ratio of male to female was about 1:2. Intra-group comparison: there were significant differences between the supra-articular and posterior spaces of the bilateral temporomandibular joints in the experimental group (P < 0.05). There was no significant difference between the measurements of the bilateral temporomandibular joints (P > 0.05). Inter-group comparison: Compared with the control group, the supra-articular space, posterior space, anterior and posterior diameters of the condyle, internal and external diameters were significantly reduced in the experimental group (P < 0.05), while the other measurements showed no significant difference (P > 0.05). The experimental group had the highest incidence of local osteolysis, defect or extensive erosion or destruction of the condyle (about 27%), followed by flattened and shortened condyle (about 24%), blurred and disappeared condylar cortical bone (about 21%), displaced condyle in the articular fossa (about 16%), hyperosteogeny and formation of osteophytes (about 8%), and micro-cystoid degeneration of the condyle (about 4%) in order. To conclude, the condyle in the articular fossa is displaced in adolescent patients with temporomandibular joint osteoarthrosis. The condylar process tends to become small, the height of the mandibular ramus tends to become short, and condylar bone destruction appears. The changes of the condylar process in the intraarticular fossa space are correlated with the location of bone destruction. 

Key words: cone-beam CT, temporomandibular joint osteoarthrosis, adolescent, idiopathic condylar resorption, articular fossa