Portuguese translation, cultural adaptation and psychometric properties of the temporomandibular joint scale: a cross-sectional study.

BACKGROUND: The temporomandibular joint (TMJ) scale assesses the severity of temporomandibular joint disorders (TMD), yet a European Portuguese translation is lacking. OBJECTIVES: To translate, cross-culturally adapt and to examine the psychometric properties (construct validity and reliability) of the TMJ scale. METHODS: Translation and cultural adaptation were carried out according to international recommendations, including initial translation, evaluation of this translation and cultural adaptation by a panel of experts, and back translation. The final Portuguese version was used to examine the reliability and validity, and participants with TMD were recruited from a Portuguese outpatient clinic. Reliability measures included internal consistency with Cronbach's alpha and test-retest reliability with the intraclass correlation coefficient (ICC2,1). The Spearman correlation comparing the TMJ scale with the Fonseca and Helkimo indexes was used to assess the construct validity. RESULTS: A total of 63 participants (23 +/- 2 years; 61,9% female) were included. Similar internal consistency was observed between the two moments of application (0.921 and 0.918), and test-retest reliability was excellent, with an ICC2,1 = 0.998 (95%CI: 0.988-0.999). Robust positive correlations (rho 0.554-0.611, p < 0.001) were found between the TMJ scale and Fonseca and Helkimo indexes. CONCLUSION: The European Portuguese version of TMJ scale is now available to improve the assessment of severity of TMD in routine clinical practice. This version is also reliable and valid.