General issues in efficacy, equivalency, and superiority trials: clinical considerations.

The design of clinical trials aimed at treating different types of periodontal diseases must take into account the prevalence of the disease in the population and the relationship of various descriptors, which may vary from disease to disease. For screening purposes, patients should be selected with disease in the high-severity range, in order to maximize the likelihood of detecting a therapeutic effect. Subsequent trials may be designed around a more representative group of subjects. Therapies must be evaluated on the basis of actual clinical changes, rather than their effect on presumed etiologic factors. The observed changes must be of clinical as well as statistical significance. The distribution of periodontal diseases within a dentition may affect as few as one or as many as over one hundred sites. Strategies are needed to correlate events observed at sites within the dentition, i.e. tooth surface-based measurements or scores, with events that are subject-based, e.g. concentration of blood or salivary components.