GUIDED TISSUE REGENERATION - COMPARISON OF BIOABSORBABLE AND NON-BIOABSORBABLE MEMBRANES - HISTOLOGIC AND HISTOMETRIC STUDY IN DOGS

THIS STUDY EXAMINED HISTOLOGIC AND HISTOMETRIC RESPONSES to 2 bioabsorbable membranes made from a synthetic copolymer of glycolide and lactide. They were tested for their biocompatibility, resorption characteristics, and ability to support periodontal regeneration. Expanded polytetrafluoroethylene (ePTFE) was used as control. Nine fox hound dogs with no periodontal disease were used. They were sedated and their teeth thoroughly scaled and root planed. Plaque control was maintained. Two weeks later, each dog was anesthetized using gas anesthesia. Buccal and lingual mucoperiosteal flaps were reflected in the mandibular premolar areas. Randomly selected, buccal alveolar bone was reduced on the 2nd and 4th premolars to a level 5 to 8 mm apical to the cemento-enamel junction creating a Class II buccal furcation defect on one quadrant, while the other quadrant received a Class II buccal defect only on the 4th premolar. Root surfaces were denuded of periodontal ligament and cementum, and notches were placed at the bone level of each root. In one quadrant, one site received Type I membrane and the other site received Type II. The contralateral quadrant received ePTFE. Flaps were positioned slightly coronally and sutured. Sutures were removed 1 week later. One month after surgery, 3 dogs were sacrificed and ePTFE barriers were removed from the remaining 6 dogs. Of these, 3 were sacrificed 3 months after surgery and the other 3 at 6 months. Undemineralized experimental tissues were embedded in methylmethacrylate and 8 to 10 mu m thick sections were cut in a bucco-lingual direction throughout the mesiodistal extension of the tooth. These sections were evaluated by descriptive histology and linear measurements of the periodontal tissues made. A two-factor analysis of variance was carried out on these measurements to test for differences between control and test membranes within an animal for connective tissue attachment, cementum, bone, and epithelium. Analyses were performed on data 1, 3, and 6 months post-healing. Histologic and histometric evaluation demonstrated that, in spite of early resorption of resorbable membranes associated with the normal inflammatory reaction, the reformation of a connective tissue attachment was favored by the placement of the membranes. New cementum with inserting collagen fibers was observed on the previously denuded surfaces of test roots, similarly to that seen in the controls. Hence, these findings indicate that, from a clinical and histological stand point, similar results can be achieved in guided tissue regeneration procedures, whether bioabsorbable barriers or the non-bioabsorbable ePTFE is applied.