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Notizen: Abstract Background: Previous studies have shown a limited potential for bone augmentation following guided bone regeneration (GBR) in horizontal alveolar defects. Surgical implantation of recombinant human bone morphogenetic protein-2 (rhBMP-2) in an absorbable collagen sponge carrier (ACS) significantly enhances bone regeneration in such defects; however, sufficient quantities of bone for implant dentistry are not routinely obtained. The objective of this study was to evaluate the potential of rhBMP-2/ACS to enhance GBR using a space-providing, macro-porous expanded polytetrafluoroethylene (ePTFE) device.Methods: Bilateral, critical size, supra-alveolar, peri-implant defects were surgically created in four Hound Labrador mongrel dogs. Two turned and one surface-etched 10-mm titanium dental implant were placed 5 mm into the surgically reduced alveolar ridge creating 5-mm supra-alveolar defects. rhBMP-2/ACS (rhBMP-2 at 0.2 mg/ml) or buffer/ACS was randomly assigned to left and right jaw quadrants in subsequent animals. The space-providing, macro-porous ePTFE device was placed to cover rhBMP-2/ACS and control constructs and dental implants. Gingival flaps were advanced for primary wound closure. The animals were euthanized at 8 weeks postsurgery for histologic and histometric analysis.Results: Bone formation was significantly enhanced in defects receiving rhBMP-2/ACS compared to control. Vertical bone gain averaged (±SD) 4.7±0.3 and 4.8±0.1 mm, and new bone area 10.3±2.0 and 8.0±2.5 mm2 at turned and surface-etched dental implants, respectively. Corresponding values for the control were 1.8±2.0 and 1.3±1.3 mm, and 1.8±1.3 and 1.2±0.6  mm2. Bone–implant contact in rhBMP-2-induced bone averaged 6.4±1.4% and 9.6±7.5% for turned and surface-etched dental implants, respectively (P=0.399). Corresponding values for the control were 14.6±19.4% and 23.7±9.7% (P=0.473). Bone–implant contact in resident bone ranged between 43% and 58% without significant differences between dental implant surfaces.Conclusions: rhBMP-2/ACS significantly enhances GBR at turned and surface-etched dental implants. The dental implant surface technology does not appear to substantially influence bone formation.