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The objective of this study was to examine alveolar ridge augmentation following implantation of recombinant human bone morphogenetic protein (rhBMP-2) with an allogeneic freeze-dried demineralized bone matrix (DBM) mixed with autologous blood. A second objective was to evaluate bone-to-implant contact in induced bone. Bilateral surgically created supraalveolar ridge defects in five young adult beagle dogs were implanted with the rhBMP-2-DBM-blood device. Transmucosal dental implants were placed at weeks 8 and 16 postsurgery The animals were euthanized 24 weeks following ridge augmentation. Healing was uneventful in all animals. Radiographic observations indicated substantial bone formation, including regions of radiolucency, at week 8. At week 16, the radiolucencies were generally resolved, and the trabecular structure of the induced bone resembled that of the adjacent residual bone. There were no remarkable differences in radiographic observations between weeks 16 and 24 after ridge augmentation. Histologic analysis revealed dense woven and lamellar induced bone. Any residual DBM appeared remineralized, at least in part. A large portion of the dental implants (approximately 70%) were housed in induced bone with evidence of limited crestal resorption. There was no significant difference in bone density between induced and residual bone, and the levels of bone-to-implant contact were similar (approximately 55%). The rhBMP-2 construct used in this study has a potential to augment alveolar ridge defects. Also, no difference in levels of osseointegration may be expected in induced and residual bone following a two-stage procedure of rhBMP-2-induced ridge augmentation and dental implant placement.

This randomized, split-mouth design study evaluated the adjunctive effect of allogeneic, freeze-dried, demineralized bone matrix on guided bone regeneration in a critical-size, supra-alveolar, peri-implant defect model. Contralateral supra-alveolar peri-implant defects, 5 mm in height, each including two titanium implants, were surgically created in five beagle dogs. Demineralized bone matrix in autologous blood was placed over the implants in one randomly selected mandibular jaw quadrant. A space-making expanded-polytetrafluoroethylene membrane was used to provide guided bone regeneration bilaterally. Following a 16-week healing interval, tissue blocks were harvested and prepared for histometric analysis. Differences between experimental conditions (guided bone regeneration sites with and without demineralized bone) were evaluated using paired t tests (n = 4). Demineralized bone particles were discernible, with limited signs of resorption. The bone matrix particles appeared to be solidified within a dense connective tissue matrix and in close contact with the implants. Limited matrix remineralization was apparent adjacent to the alveolar crest. No statistically significant differences were found between experimental conditions for any parameter examined. Peri-implant defect height averaged 5.0 +/- 0.2 mm and 4.9 +/- 0.4 mm, vertical bone regeneration 1.5 +/- 0.9 mm and 1.1 +/- 0.4 mm, osseointegration within the extent of the defect 10.0 +/- 3.9% and 15.3 +/- 5.3%, osseointegration within the extent of regenerated bone 30.4 +/- 13.7% and 52.1 +/- 17.9%, and osseointegration within the alveolar base 68.8 +/- 13.1% and 74.4 +/- 7.1% for guided bone sites with and without demineralized bone, respectively (P > .05). The results suggest that freeze-dried demineralized bone has no adjunctive effect on guided bone regeneration in supra-alveolar peri-implant defects, that guided bone regeneration has a limited potential to enhance alveolar regeneration in this defect model, and that a 16-week healing interval appears insufficient for turnover and maturation of demineralized bone under provisions for guided bone regeneration.

This study evaluated candidate carriers for recombinant human bone morphogenetic protein-2 (rhBMP-2)-driven periodontal regeneration. Previous experiments indicated the ability of rhBMP-2 in a particulate delivery system to result in substantial regeneration of bone and periodontal regeneration. In the present study, canine demineralized bone matrix (DBM), bovine deorganified crystalline bone matrix (Bio-Oss), an absorbable collagen sponge (ACS) of type I bovine collagen, poly(D,L-lactide-co-glycolide) microparticles (PLGA), and polylactic acid granules (Drilac) were tested for their ability to support rhBMP-2 (0.2 mg/mL implant volume)-driven periodontal regeneration. The implants were tested in routine critical size canine supra-alveolar periodontal defects with transgingival tooth positioning. Contralateral defects in six beagle dogs were semirandomly assigned to receive: DBM/rhBMP-2, DBM (no rhBMP-2), Bio-Oss/rhBMP-2, ACS/rhBMP-2, PLGA/rhBMP-2, or Drilac/rhBMP-2. Animals were sacrificed 8 weeks postsurgery, and block sections of the defects were processed for light microscopy. Substantial bone regeneration was observed in all defects implanted with rhBMP-2. Other measures of periodontal healing, including cementum regeneration and presence of ankylosis, were more variable between the implants. DBM and Bio-Oss performed well as carriers for rhBMP-2-driven periodontal regeneration, although other impediments to their clinical use exist. This study indicates that qualities of the carrier system, including its space-maintaining capacity can affect the ability of rhBMP-2 to regenerate both alveolar bone and periodontal attachment.

Histologic studies of periodontal reconstructive therapies have repeatedly shown a zone of nondescript connective tissue adaptation, or collagen adhesion, to the root surface between the apical extension of the junctional epithelium and the coronal extension of identifiable regenerated cementum. To clarify the nature of this zone, supra-alveolar periodontal defects were created bilaterally in the mandibular premolar region in three beagle dogs, and exposed roots were instrumented to remove the cementum. Flaps were then coronally advanced and sutured. Histologic analysis after 12 weeks of healing showed instrumented root dentin not associated with junctional epithelium, new cementum, root resorption, or ankylosis in 27 of 60 root surfaces. In 10 of these specimens subsequently examined by transmission electron microscopy, collagen fibrils were generally oriented parallel to and in close proximity to the root. A mechanism of collagen attachment was, in fact, functioning at sites of collagen adhesion; these areas may validly be included in the histologic attachment level reported in studies of periodontal reconstructive therapy.