Maximal mouth opening is a simple method to evaluate the treatment outcome of temporomandibular joint arthritis in patients with juvenile idiopathic arthritis.

Objective: Temporomandibular joint (TMJ) arthritis is a common finding in juvenile idiopathic arthritis (JIA) patients. TMJ arthritis can cause significant disturbances in TMJ function and growth without treatment. Our aim was to evaluate the effectiveness of medical treatments used to manage TMJ arthritis and how to evaluate the outcome of the treatment. Furthermore, this study aimed to ascertain the prevalence of TMJ arthritis in JIA patients and investigate the potential impact of specific factors.

Material and methods: Between 2015 and 2019, a total of 194 JIA patients who received treatment at the Department of Oral and Maxillofacial Diseases, Helsinki University Hospital, Finland were included in the study. We retrospectively screened the patient records and imaging studies to find out how many patients had TMJ arthritis and what medication was used to treat it.

Results: Maximal incisal mouth opening (MIO) increased significantly with patients whose TMJ arthritis was successfully treated with intra-articular corticosteroid injection (IACI). Almost all patients with TMJ arthritis were treated with an IACI at some point during their treatment. Overall, 99 patients (51%) had been diagnosed with TMJ arthritis. No statistical difference was found between the prevalence of TMJ arthritis and different JIA subtypes, JIA onset time, gender, or immunological factors.

Conclusion: MIO is an easy way to evaluate the treatment outcome and possible disease activation of TMJ arthritis. The prevalence of TMJ arthritis is high among JIA patients. In our study, we could not find any parameters that predict TMJ arthritis, and despite systemic medication, TMJ arthritis might occur.