Recombinant Human Bone Morphogenetic Protein-2 Confined by an Imperforate Titanium Shell over High-Profile Dental Implants in Rabbit Tibiae: A Pilot Bone Augmentation Study

Purpose: To evaluate the use of a nonperforated titanium occlusive device over a bone morphogenetic protein-2 in an absorbable collagen sponge (BMP-2/ACS) in grafting the bone around high-profile (ie, supracrestal) dental implants in rabbit tibiae. Materials and Methods: Eight New Zealand white rabbits were used for the experiment. Two implants were placed in the right tibia of each rabbit, with 4 mm of each implant placed supracrestally ("high-profile" placement) in four groups of two rabbits each: control, titanium shell only, titanium shell over buffered collagen, and titanium shell over BMP-2/ACS. The animals were sacrificed after 3 or 6 weeks. Calcified and nondecalcified histologic preparation was carried out to evaluate bone formation and degree of osseointegration. Results: Three of the eight animals developed tibial fractures. The two BMP-2 test animal tibiae remained intact, with the 3-week specimen showing very little bone formation inside or outside of the titanium chamber and the 6-week specimen showing bone mostly outside of the chamber. Conclusion: The placement of BMP-2 beneath an occlusive nonperforated titanium shell next to a high-profile implant did not result in significant bone formation.