Baseline Oral Behaviours in Relation to Follow-Up Temporomandibular Joint Disease Severity After Intra-Articular...

Background/Objectives: Intra-articular injectable platelet-rich fibrin (I-PRF) is increasingly used in the management of joint-origin temporomandibular joint (TMJ) disorders, but variability in follow-up TMJ disease severity remains substantial. This study assessed whether baseline oral behaviors were associated with follow-up TMJ disease severity after intra-articular I-PRF therapy, using baseline-adjusted analyses of follow-up HI. Methods: This secondary exploratory cohort analysis was conducted within the framework of a registered clinical trial (NCT05883982). Fifty-one consecutive adult patients treated with intra-articular I-PRF were included. Baseline oral behaviors were assessed using the Oral Behaviors Checklist (OBC-21), and TMJ disease severity was quantified using the Helkimo Index (HI) at baseline and final follow-up. Associations between baseline predictors and follow-up HI were evaluated using baseline-adjusted linear regression models including baseline HI as a covariate. Results: Mean (SD) HI decreased descriptively from 7.0 (6.2) at baseline to 2.5 (3.0) at final follow-up (p < 0.001). Baseline HI was strongly associated with follow-up HI (β = 0.32, 95% CI 0.22 to 0.41, p < 0.001), whereas symptom duration (β = 0.02, 95% CI -0.10 to 0.15, p = 0.70) and injection laterality (β = -0.42, 95% CI -1.73 to 0.89, p = 0.52) were not. No OBC-21 item showed a clear baseline-adjusted association with follow-up HI after correction for multiple comparisons. The largest absolute baseline-adjusted regression coefficients were observed for awake bruxism (β = 0.80, 95% CI 0.08 to 1.52, FDR-adjusted p = 0.60) and singing (β = -0.58, 95% CI -1.41 to 0.25, FDR-adjusted p = 0.83). Conclusions: Baseline oral behaviors did not emerge as strong standalone baseline-adjusted factors associated with follow-up HI after intra-articular I-PRF therapy. However, the observed associations may still have been influenced by baseline disease severity dimensions not fully captured by total baseline HI, such as structural disease stage, pain intensity, psychosocial burden, or other unmeasured clinical severity features. The observed nominal and directional item-level patterns should be interpreted only as hypothesis-generating and require confirmation in larger, better-characterized cohorts.