Response of regenerative tissues to plaque: a histological study in monkeys

This study was designed to determine the histologic response of regenerated tissue to plaque, using an adult Taiwan monkey model with chronically-inflamed, surgically-created, periodontal defects. Standardized 2-walled periodontal defects were surgically created at the mesial of the mandibular lateral incisor on one side. Sutures, 3-0 braided silk, were placed for 8 weeks and tissues positioned so that denuded root surfaces were exposed to plaque, with the subsequent development of the chronically-inflamed periodontal tissues. At 8 weeks the defects were subjected to guided tissue regeneration procedures using expanded polytetrafluoroethylene membrane and allowed to heal for 6 months. Contralateral clinically healthy sites, without surgical procedures, were used as controls. In both experimental (membrane) and control sites, silk ligatures were placed to allow plaque accumulation for 2 or 10 weeks. Four monkeys were sacrificed at each time point and specimens processed for histologic and histometric study. The results indicated that plaque-induced inflammation was less at sites treated by guided tissue regenerative procedures when compared to originally clinically-healthy sites exposed to plaque for the same duration. However, histologically the newly formed osseous tissue was compromised under these conditions.