Guided bone regeneration of large mandibular defects in a primate model

Background: An earlier publication from our laboratory described the use of guided bone regeneration to fill large bone voids in the mandible created through en bloc resection in primates. The present report is an embellishme nt of this paper and describes bone regeneration experiments in 18 adult ma le Macaca mulatta monkeys to determine how long membranes must be in positi on to promote guided bone regeneration. Methods: Thirty-six lesions were created in the mandibles of 18 monkeys in a standardized mandibular defect of 8 x 19 mm. Reinforced ePTFE membranes w ere placed in the animals and held in place with mini screws and sutures fo r anywhere from 1 to 12 months. No material was added to the defect. In add ition to clinical studies, digital subtraction radiology and fluorescent la beling with tetracycline and histomorphometry are described. Results: The results indicate that no bone gain was observed in membranes e xposed for 1 month or less, but bone gain (approximately well over 90% of d efects) was observed at 12 months when membranes were left in situ for 2 to 12 months (P <0.0001). No significant difference in the amount of bone gai ned at 12 months was observed for membranes left in place for intervals ran ging from 2 to 12 months, A significant correlation between the amount of b one gain observed at 3 and 12 months was observed (P <0.0001). Conclusions: Data therefore suggest that membranes left in situ for 1 month or less result in minimal bone gain compared with membranes left in place from 2 to 12 months. In addition, labeling and stained sections clearly sho wed that the bone produced after 2 months of membrane placement is mature.