Requirements for clinical trials.

Significant progress and valuable contributions have been made by pioneers in the field of dental implantology during the past 20 years. The feasibility of clinical application of dental implants for specific prosthodontic conditions has been demonstrated by several reports based upon retrospective data or surveys of clinical experiences. However, there is a lack of reliable scientific information to determine the clinical efficacy of implant-supported prostheses or the physiological merits of the two types of implant-bone interface. Similarly, there are no known studies that have tested the relative efficacy of different implant systems. The claims of success rates for different implants can only be substantiated when controlled, independent studies are made, following research protocols that meet the requirements of clinical trials in terms of delineation of hypothesis, definition of treatment, entry and treatment allocations, exclusions and withdrawals, sample size, and a coordinated plan for the statistical analysis of data and interpretation of results. The study design of the VA Cooperative Study has followed the essential requirements of clinical trials in comparing the efficacies of the two treatment modalities--traditional removable partial dentures versus fixed partial dentures supported by implants.