Implant-guided supracrestal alveolar bone growth using scaffolds, BMP-2, and novel scaffold-retaining device

Objective: To evaluate the efficacy of various scaffold systems and a Ti scaffold-retaining device with and without non-glycosylated rhBMP-2 (BMP-2) for increasing the vertical alveolar bone growth in the intra-oral mini-pig model. Methods: Forty-eight Straumann Bone Level implants with hydrophilic (SLActive) surfaces were partially embedded in mandibles of 12 adult mini-pigs with the shoulder of the implant located 3 mm above the bone crest. Twenty-four implants were placed in conjunction with BMP-2 (50g) incorporated within resorbable scaffolds. Twenty-four additional control implants were placed with scaffolds only. Scaffolds were placed around the implant and stabilized with a newly developed Ti umbrella scaffold retainer. Scaffolds included (i) HA-coated collagen (Healos); (ii) biphasic HA/-TCP crystals (Straumann Bone Ceramic, SBC); and (iii) SBC crystals infused with polyethylene glycol (PEG) hydrogel. Eight test and control pairs for each scaffold group were implanted. At 9 weeks, soft tissue healing was assessed and the extent of new vertical bone was evaluated with microCT and histomorphometry. Results: microCT analysis revealed a mean of 167 +/- 47 mm(3) new supracrestal mineralized tissue volume formation around the test sites where BMP-2 was released from the scaffold whereas the control group (no BMP-2) showed a significantly lower mineralized tissue volume of 106 +/- 55 mm(3). The SBC+BMP-2 group had the highest mineralized tissue volume of 189 +/- 36 mm(3). Histomorphometry showed bone-to-implant contact of 54.5% for the test groups and 33.3% for the control groups and new vertical bone growth of 2.2 +/- 1.0 and 1.0 +/- 0.9 mm, respectively. The SBC+BMP-2 group again demonstrated the best outcome (2.7 +/- 0.4 mm). The qualitative scoring of soft tissue dehiscence showed that the presence of BMP-2 yielded far superior outcomes, 0.63 vs. 1.75 for all control implant sites (with scores ranging from 0, reflecting no soft dehiscence, to 4, showing a completely exposed umbrella). Conclusion: The release of BMP-2 from a SBC scaffold adjacent to a hydrophilic, rough Ti implant and scaffold retention umbrella consistently regenerated the greatest volume and height of new vertical bone along the length of the implant.