Simplified Jaw Functional Limitation Scale for Temporomandibular Disorders: Psychometric Evaluation

This study aimed to simplify the Jaw Functional Limitation Scale (JFLS) and evaluate its reliability and validity in assessing jaw function in patients with temporomandibular disorders (TMD) in primary care.

TMD patients and non-TMD participants were assessed using Diagnostic Criteria for Temporomandibular Disorders (DC/TMD). Demographic data and the 8-item JFLS questionnaire were collected to quantify jaw functional restriction. Confirmatory factor analysis tested the validity of JFLS-8 using chi-square, comparative fit index (CFI), root mean square error of approximation (RMSEA), and root mean square residual (RMR). The study selected key items from each domain to create a 4-item JFLS for further testing. Exploratory factor analysis, reliability, and validity tests were conducted.

Analysis included 671 valid questionnaires (502 TMD patients, 169 non-TMD participants). JFLS-8 exhibited satisfactory fit among TMD patients (RMSEA = 0.143, CFI = 0.881, RMR = 0.567). JFLS-4 retained items with high factor loadings: JFLS1 (0.935), JFLS2 (0.923), JFLS7 (0.766), and JFLS5 (0.713). The simplified JFLS-4 showed good reliability (Cronbach's alpha 0.714) and validity (Kaiser-Meyer-Olkin 0.558, Bartlett's test < 0.001) among TMD patients.

A 4-item JFLS was developed and validated, demonstrating good reliability and validity in assessing mandibular function in TMD patients, exhibiting the potential to streamline evaluation processes in clinical practice.