Evaluation of the frequency of temporomandibular disorders in patients with ankylosing spondylitis and its relationship with craniocervical posture and disease activity

Introduction: Temporomandibular disorders (TMD) is a public health problem that affects 5-12% of the population. Most common cervical deformity in AS patients is cervical kyphosis. There are contradictory results in the relevant literature about the relationship between objective determinants of craniocervical posture (angles and distances) and TMD, whereas no study has worked on AS and TMD relationship. The aim of this study is to evaluate the frequency of TMD in patients with AS and its relationship with craniocervical posture and AS disease activity. Method: 98 AS patients aged between 18-50 years and consecutively admitted to Hacettepe University Physical Medicine and Rehabilitation and Rheumatology outpatient clinics between 20.09.2018 - 20.04.2019 were recruited to the study. Demographic features and AS related data of the patients were recorded. The diagnosis of TMD was established according to 'Diagnostic Criteria for Temporomandibular Disorders (DC/TMD)' criteria. Spinal mobility was assessed by Bath Ankylosing Spondylitis Metrology Index (BASMI); disease activity by Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Ankylosing Spondylitis Disease Activity Scorte (ASDAS) and neck disability by Neck Disability Index. Craniocervical angle, cercival curvature angle, suboccipital distance (mm), atlas-axis distance (mm), anterior translation distance (mm) were measured by using the lateral cervical X-rays. Results: A total of 98 (58,2% female) patients with a mean age of 37,48,2 years.were included in this study. The diagnosis of TMS was established in eighty-eight (59,2%) patients. Demographic features were similar between patients with and without TMD. Smoking and bruxism were found to be more common among patients with TMD. Spinal mobility and craniocervical posture measurements were similar among two groups. Patients with TMD had significantly higher values of ASDAS and neck disability index. Multivariate analysis revealed active smoking (RR:6,82; CI:1,69-27,4; p=0,007) and neck disability (RR:7,32; CI:2,31-23,1; p=0,001) as independent risk factors for the development of TMD in patients with AS. Conclusion: No relationship between the craniocervical posture measurements and TMD was found in patients with AS. Although the frequency of bruxism and AS disease activity were higher in patients with TMD, only active smoking and the presence of neck disability were found to be as independent factors that may predict the development of TMD in AS patients. Prospective, large-scaled studies are needed to elucidate the underlying mechanisms.