Subjective symptoms and clinical signs and imaging features related to temporomandibular disorders in juvenile idiopathic arthritis

Abstract

Introduction: Temporomandibular disorder (TMD) is an umbrella term for orofacial muscle pain and temporomandibular joint (TMJ) conditions. Unfortunately, children and adolescents with juvenile idiopathic arthritis (JIA), who should be spared additional health problems, are frequently affected by TMD. As knowledge gaps in the literature covering TMD in young individuals with JIA have been identified, more research in this field is needed.

Aims: The overall aim of this thesis was to gain knowledge of TMD in JIA. Subgoals were to investigate the prevalence of TMD in children and adolescents with JIA compared to their healthy peers and investigate potential associations between JIA and TMD; investigate the reliability of diagnostic imaging by examining the precision of imaging measures commonly used to assess mandibular morphology in children and adolescents with JIA; compare CBCT and MRI in the measurement of condylar height; and lastly, analyse whether there are associations between clinical signs of TMD pain and arthritis affected TMJ using CBCT as an imaging tool.

Methods: This thesis has its origin in the Nordic JIA Study Group (NorJIA), a longitudinal multicentre study (2015-2020) addressing 228 children and adolescents (aged 4–16 years) diagnosed with JIA and recruited from three university hospitals in Norway. Among these, seven did not participate in TMD assessments and were excluded from studies I and II. The thesis comprised three studies based on baseline data originating from the 2015-2018 NorJIA study. Paper I was a matched comparative study with a cross-sectional design according to gender, age, and a centre site of 221 children and adolescents with JIA (mean age 12 years). The standardised TMD assessments were based on shortened protocols of the diagnostic tools “Axis I Clinical Examination for DC/TMD” and “TMJaw Recommendations for Clinical TMJ Assessment in Patients Diagnosed with JIA”. In Paper II, the precision of three imaging techniques (MRI, CBCT and a lateral cephalometric radiograph (ceph) used for the assessment of mandibular morphology was examined. A subset of 90 children and adolescents with JIA underwent a MRI, CBCT of the TMJs and ceph. The agreement of continuous measurements was assessed with a 95% limit of agreement according to Bland-Altman and MDC at an individual level. Paper III was a cross-sectional study that included 72 children and adolescents with JIA from the Bergen cohort. A newly devised and validated CBCT score for the overall impression of deformity (sound (no deformity), mild or moderate/severe deformity) was used to examine associations between clinical TMD signs/symptoms such as pain on palpation of the TMJs, pain on jaw movement, or a combination of the two.

Results: In the first study, 26.7% of participants with JIA self-reported TMD jaw pain during the past 30 days vs. 5% of healthy controls. JIA participants revealed a lower vertical unassisted jaw movement than the controls, with a mean of 46.2 mm vs. 49.0 mm. Both painful masticatory muscles and TMJs on palpation were present in 50.2% of the JIA patients vs. 28.2% of the healthy controls. We examined three MRI, one CBCT and nine ceph-based measurements in the second study, of which the ceph-based SNA, SNB and RL3/ML3 (gonion angle) and the MRI-based total mandibular length had the highest test/retest reliability, with 95% limits of agreement (LOAs) within 15% of the sample means. In the third study, 29.2% of the subjects had palpatory pain at and around the lateral pole, and about 57% had TMJ pain upon jaw movement. Of 141 TMJs, 18.4% showed mild, and 14.2% moderate/severe, TMJ deformity on CBCT. No statistically significant associations were seen between pain on palpation and TMJ deformity on CBCT or between pain on jaw movement and CBCT findings.

Conclusions: TMD was found in approximately half of the participants with JIA, as compared to about one-fourth of their healthy peers. The consistency of the tested imaging modalities used for the assessment of TMJ growth disturbances differed, highlighting the importance of applying the most precise imaging markers under the premise of acceptable diagnostic accuracy, both at a patient level and for clinical trials. This resulted in acceptable reproducibility for one MRI-based, one CBCT-based, and three ceph-based parameters. We found no associations between pain and TMJ deformity assessed by CBCT.