Overview of clinical trials on periodontal regeneration

Periodontal regeneration means healing after periodontal surgery that results in the restoration of the tooth-supporting tissues; namely, cementum, alveolar bone, and periodontal ligament. The response of the periodontium to conventional periodontal flap surgery is primarily repair. Regenerative flap procedures involve modifications intended to alter variables in the normal wound healing response to shift the outcome from repair to regeneration. Technical manipulations, devices, pharmacological agents, and biologicals have been used to obtain regeneration. Evaluation of periodontal therapy is done by clinical and histological assessments. Human clinical trials depend on probing, re-entry, and radiographic measurements which cannot distinguish between periodontal repair and regeneration. Histological studies are difficult in humans because they require the retrieval of tissue blocks containing the teeth and their surrounding tissues, and for this reason these studies have largely been done in animal models; however, the use of animal models creates problems of interpretation when applying the information to the human. There are other fundamental problems related to assessment of new methods of periodontal regeneration. Ideally, periodontal regeneration is attempted after resolving the periodontitis that produced the loss of periodontal support. Does the type of periodontal disease affect the outcome? If it does, then separate clinical trials would be indicated to manage defects produced by different diseases. Furthermore, certain types of periodontal defects apparently respond better than others (for example, intrabony defects versus suprabony defects). Does each type of defect require a separate trial? Do subjects respond differently and, if so, how should this be factored into selection of the study population and sample size? There appear to be more questions than answers concerning the design of clinical trials for periodontal regeneration. This is not surprising since regeneration has been possible for only a few years, is apparently unpredictable, and the origin and nature of the new tissue are poorly understood. These factors make it important that the design of clinical trials be openly and thoroughly discussed so that practical solutions are forthcoming.