Supracrestal Bone Formation Around Dental Implants: An Experimental Dog Study

To test the osteopromotive activity in large non-spacemaking alveolar bone sites, a total of 20 titanium dental implants were placed superior to a previously modified mandibular alveolar process in five adult beagle dogs. The supracrestal implant position resulted in a mean buccal dehiscence of 5.1 ± 1.03 mm and a mean supra-crestal bone deficit of 2.69 ± 0.45 mm. Three treatment groups were randomly assigned: group I, ten implants treated with a titanium-reinforced expanded polytetrafluoroethylene (ePTFE) membrane (TR); group II, six implants treated with a standard ePTFE membrane (ST); and group III, four implants that received no membrane (control). Before mucoperiosteal flap closure, the bone surface was perforated and peripheral blood was injected around the implants and underneath the membranes. Clinical evaluation of submerged implant sites showed evidence of complete regeneration of the peri-implant bone defects in groups I and II, minimal bone formation in control group III, and a widening of the ridge in group I. Corresponding histologic examination of undecalcified sections demonstrated large amounts of newly formed bone beneath both types of membranes with a superficial layer of loose connective tissue. Mean gain of supracrestal regenerated bone amounted to 1.82 ± 1.04 mm (TR group), 1.90 ± 0.30 mm (ST group), and 0.53 ± 1.34 mm (control group). Mean bone regeneration at the buccal dehiscences was 3.33 ± 1.44 mm (TR group), 2.46 ± 0.51 mm (ST group), and 2.76 ± 0.84 mm (control group). The TR membranes showed evidence of increased alveolar bone width compared to ST membranes and control sites. These results suggest that supracrestal bone regeneration can successfully be enhanced by a submerged membrane technique in the dog model and that the titanium-reinforced membranes were able to maintain a large, protected space for blood clot stabilization without the addition of bone grafts and produced a larger bone quantity when compared to standard membranes. Schlagwörter: bone regeneration, blood clot, dental implants, supracrestal implant placement, titanium-reinforced membranes