Quality-assessment of TMD prevalence studies of the last 60 years

Objectives: To evaluate all TMD prevalence studies published in the last 60 years in order to assess quality aspects of the analyzed studies. Methods: Exhaustive on-line literature search with the help of different scientific data-bases (e.g. PubMed, Cochrane, Ovid, Scirus etc.) and search engines was done. Hand search was performed for magazines not electronically accessible. The research was completed by looking into the literature index of every article which was found with the described method. Articles published between 01.01.1949 and 31.12.2006 were included. Additionally, defined inclusion and exclusion criteria were used from the beginning of the survey. The quality of each prevalence study was assessed with the help of a system developed according to epidemiologic criteria. For each study, a Total Quality Score (TQS) was calculated (0=poor, 14=excellent). The methods used for the assessment of TMD prevalence were analyzed and the studies were divided into three categories according to the most frequently used protocols: Helkimo Index (group A), RDC/TMD (group B) and studies not referring the method used (group C). Results: There were found 268 articles in 15 different languages and in 56 different scientific magazines, which fulfilled the inclusion and exclusion criteria. The quality characteristics of these studies were assessed: 88 belonged to group A, 13 to group B and 140 to group C. The remaining 27 had used other diagnostic criteria. The mean TQS was 7.051±2.454 for group A, 10.923±2.691 for group B and 6.250±2.691 for group C. The studies of group B presented significantly higher TQS scores than groups A and C. Conclusions: The general quality of a prevalence study is influenced by the diagnostic method used. Studies which use standardised criteria like RDC/TMD tend to be of higher quality than others which use non standardised diagnostic criteria.