The efficacy of BMP-2 preloaded on bone substitute or hydrogel for bone regeneration at peri-implant defects in dogs

Objectives: The objective of this experiment was to test whether or not a synthetic bone substitute (SBS) was more effective than a polyethylene glycol hydrogel as a carrier material for bone morphogenetic protein-2 (BMP-2) when attempting to regenerate bone.

Material and methods: Two identical, box-type dehiscence defects (4 × 4 mm buccolingually and apicocoronally, and 8 mm mesiodistally) were surgically prepared on buccal sides of the left and right edentulous ridge in five beagle dogs. Following implant placement, the defects either received (i) no graft, (ii) SBS+hydrogel, (iii) SBS+BMP-2 loaded hydrogel, and (iv) BMP-2-loaded SBS+hydrogel. The animals were euthanized at 8 weeks postsurgery. Radiographic and histomorphometric analyses were performed.

Results: The hydrogel alone was not able to stabilize the grafted bone particles at 8 weeks, and SBS+hydrogel group did not significantly differ from the control group in all volumetric measurements. On the other hand, extensively regenerated new bone was connected with most of the remaining SBS particles in the BMP-2 groups. The BMP-2 groups exhibited significantly greater new bone formation (10.65 mm(3) and 1.47 mm(2) in the SBS+BMP-2-loaded hydrogel group; 14.17 mm(3) and 0.93 mm(2) in the BMP-2-loaded SBS+hydrogel) than non-BMP-2 groups (1.27 mm(3) and 0.00 mm(2) in the control group; 2.01 mm(3) and 0.19 mm(2) in the SBS+hydrogel group) in volumetric and histomorphometric analyses (P < 0.001). However, there were no significant differences between both BMP-2 groups.

Conclusion: BMP-2 could yield enhanced bone regeneration in the critical-size peri-implant defects regardless of whether SBS or hydrogel is used for preloading, although the outcomes seem to be more reproducible with BMP-2 preloaded on SBS.