Translating the Research Diagnostic Criteria for Temporomandibular Disorders into German: Evaluation of Content and Process

Aims: To develop a German-language version of the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) through a formal translation/back-translation process, to summarize available data about their psychometric properties, and to provide new data about psychometric testing of components of the RDC/TMD. Methods: To cross-culturally adapt the instrument, the RDC/TMD were translated using a forward- backward method, except for measures of somatization and depression, because German-specific instruments of these already existed. The psychometric properties of the RDC/TMD were examined, and the literature on this topic was reviewed. Results: The available literature about reliability of clinical examination methods (4 studies) showed at least acceptable results, with a median intraclass correlation coefficient (ICC) of 0.60. Reliability of RDC/TMD components Jaw Disability List (JDL) and Graded Chronic Pain Scale (GCPS) was sufficient (ICC for retest reliability [n = 27] was 0.76 for JDL and 0.92 for GCPS; Cronbach's alpha for internal consistency [n = 378] was 0.72 and 0.88, respectively). A priori hypothesized associations between GCPS or JDL summary scores and self-report of general health, oral health, oral health-related quality of life, or dysfunctional pain, which were measured by means of the Multidimensional Pain Inventory, were confirmed in a convenience sample of clinical TMD patients (n = 378). These correlations were interpreted as support for the validity of the GCPS and JDL. The original RDC/TMD include measures for somatization and depression (SCL-90-R); however, equivalent German instruments to assess these constructs ("Beschwerdenliste," "Allgemeine Depressionsskala") have wellestablished validity and reliability in the German cultural environment. Conclusion: The psychometric properties and international comparability of the German version of the RDC/TMD (RDC/TMD-G) make this instrument suitable for the assessment of TMD in Germany. Keywords: cross-cultural adaptation, orofacial pain, reliability, temporomandibular disorders, validity