Risk factors for the occurrence and prevention of temporomandibular joint and muscle disorders: Lessons from 2 recent studies

Introduction: Our objectives were to demonstrate how standard epidemiologic measurements can assist in evaluating the risk factors for tempormandibular joint and muscle disorders (TMJMD) and to determine whether prevention is feasible. Methods: We reviewed 2 recent studies that examined third-molar extractions and severe mandibular retrognathia as risk factors for TMJMD. Cumulative incidences were available from these studies. By using these values, standard epidemiologic measurements of risk, including population attributable risk (PAR), attributable risk (AR), population attributable risk percent (PAR%), and attributable risk percent (AR%), were calculated. (PAR and AR are reported as the numbers of cases per 10,000 per year.) Results In the third-molar extraction study, PAR, AR, PAR%, and AR% were 5, 10, 25%, and 40%; in the severe mandibular retrognathia study, they were 0.5, 17.5, 10%, and 80%, respectively. Conclusions This review supports the current consensus that most risk factors explain only a small portion of TMJMD in the population. However, some factors might explain a significant portion of TMJMD in persons exposed to particular risk factors. This review supports the current consensus that prevention, by screening the population for risk factors and intervening, is probably not justified. Modification of certain risk factors among exposed persons to prevent TMJMD might be warranted. Incidence data and epidemiologic measurements of risk are needed to evaluate the importance of risk factors for the occurrence and prevention of TMJMD, in both the population and exposed persons.