De novo bone formation underneath the sinus membrane supported by a bone patch: a pilot experiment in rabbit sinus model

Aims: The objectives of this study were to evaluate bone regeneration beneath a newly devised bone substitute combined with collagen membrane (called a bone patch) lying over a concomitantly placed mini-implant following sinus floor elevation and verify its usefulness as a carrier system for recombinant human bone morphogenetic protein-2 (rhBMP-2) in rabbits. Materials and methods: The sinus floor elevation procedure was performed bilaterally in five rabbits. Either a plain bone patch (control group) or an rhBMP-2-loaded patch (experimental group) was randomly placed beneath the elevated sinus membrane (SM) of both sinuses, where the mini-implants were concomitantly placed. Micro-computed tomographic and histologic analyses were performed at 4 weeks post-surgery. Results: In micro-computed tomography, the median values of the total augmented volume and the mineralized bone volume were significantly higher in the experimental group than in the control group (161 vs. 122 mm³ [P < 0.01] and 48 vs. 42 mm³ [P < 0.05], respectively). Histometric analysis revealed the same outcomes, with new bone areas of 6.41 and 2.97 mm² in the experimental and control groups, respectively (P < 0.001), and bone-to-implant contact ratios of 22.6% and 5.2%, respectively (P < 0.001). Conclusion: The newly devised bone patch in this study can support the elevated SM and facilitate bone regeneration from the basal bone with a reduced amount of biomaterial. The addition of rhBMP-2 may shorten the healing time for multidirectional bone regeneration toward the implant.