Validity and reliability of the Turkish version of the 8-item jaw functional limitation scale.

BACKGROUND

Considering that temporomandibular disorder (TMD) can negatively affect individuals' general health and quality of life by limiting orofacial functions, it is important to evaluate jaw-related functional limitations in TMD. This study aimed to investigate the psychometric properties of the Turkish version of the 8-item Jaw Functional Limitation Scale (JFLS-8-TR) in Turkish-speaking TMD patients.

METHODS

A total of 162 patients with TMD and 114 individuals without TMD participated in the study. Face and content validity were assessed. To confirm the construct validity of the JFLS-8-TR, structural (with confirmatory factor analysis (CFA)), convergent (with pain severity and maximum mouth opening (MMO), Oral Health Impact Profile (OHIP-14), Fonseca Anamnestic Index (FAI) and the Turkish version of the 20-item JFLS (JFLS-20-TR)) and known-group validity were analyzed. Cronbach's alpha and intraclass correlation coefficient (ICC) were calculated to examine internal consistency and test-retest reliability.

RESULTS

Both content and face validity were met. The acceptable model fit indices based on CFA confirmed the structural validity of the JFLS-8-TR. Robust associations between the JFLS-8-TR score and pain intensity (r = 0.92), MMO (r = -0.87) and scores on the FAI (r = 0.89), OHIP-14 (r = 0.86) and JFLS-20-TR (r = 0.96) supported the convergent validity (p < 0.05). The JFLS-8-TR was able to discriminate between individuals with and without TMD, indicating that it has known-group validity (p < 0.05). The internal consistency (Cronbach's alpha = 0.91) and test-retest reliability (ICC = 0.93) of the JFLS-8-TR were excellent.

CONCLUSIONS

The JFLS-8-TR is a valid, reliable and useful instrument for a more practical assessment of functional limitations in the masticatory system in Turkish-speaking TMD patients.