Survival studies of dental restorations: criteria, methods and analyses.

The longevity of dental restorations is an important health concern for the patient, the dentist, and the various forms of insurance systems. In this article several methods of evaluating survival time are described and the different ways of presenting the findings of survival studies are discussed. It is stated that only longitudinal studies are appropriate to give an exact insight in the longevity of restorations. A large amount of information is available in dental records and the way these data can be analysed is presented in this paper. It appears that Cox's proportional hazard model is the appropriate way of demonstrating the influence of several factors on the survival rate. An example is provided of the results from a recent survival study of crowns in The Netherlands.