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Objectives To review studies investigating how functional occlusion may relate to TMD and how bruxism may relate to TMD; to review the epidemiology of TMD and relate this to the context of clinical occlusal studies and other aetiological factors. Defi ciencies in study design are highlighted and suggestions made to improve future study designs in order to provide an evidence-base for clinical practice. Design Review article. Methods Electronic databases (MEDLINE and the Cochrane Database of Systematic Reviews) were used to select relevant and frequently cited studies (mean: 40 citations). Citation rate was confi rmed using the Web of Science. Study designs are reviewed and weaknesses and implications discussed. Results Evidence is lacking to suggest functional occlusal factors cause TMD. Investigation of other aetiological factors has been relatively neglected. Conclusions Neither static nor dynamic occlusal factors (including orthodontics) can be said to 'cause' TMD. However, other potential aetiological factors exist which would benefi t from more investigation. This, together with improved study designs, would help provide a stronger evidence-base for clinical practice in the future.