Comparison of monophasic / biphasic bovine hydroxyapatites on gene expression profiles in a rabbit calvarial defect model

Abstract

Background and Aim: Biomaterials are extensively used for Guided Bone Regeneration in periodontal treatment and implant dentistry. Although release of calcium and phosphate ions is important for bone regeneration, most of the available biomaterials are limited in calcium release. The aim of this study was to explore the effect of bovine hydroxyapatites, either monophasic (BHA) or biphasic (BBHA, loaded with soluble CaP) on gene expression profiles in a rabbit calvarial defect model.Methods: Three different HA-based materials were tested: either monophasic (Bio-Oss, BO) as the positive control, or biphasic (BBHA1, low CaP concentration and BBHA2, high CaP concentration). The 3 materials were randomly implanted in defects performed in rabbit calvarias. A fourth defect was left unfilled as a negative control. All the defects were covered with a collagen membrane. Samples were collected at 5 and 12 weeks post implantation and used for quantitative reverse transcription polymerase chain reaction analysis.Results: When comparing the biphasic biomaterials to the BO group, there was no significant difference for the studied genes at any of the 2 timepoints, except for IL-1b that was overexpressed at 12 weeks in the BBHA2 group (p < 0.001). On the other hand, although it was not significant, RUNX2 expression tended to be higher than in BBHA1 and BO groups at 5 weeks with BBHA2 (p = 0.062). Although there was no significant difference between the two time points, ALP, BMP2, BMP9 and RUNX2 displayed a slight decrease for gene expression from 5 to 12 weeks while the expression of OPN and VEGF genes tended to increase with time.Conclusion: Although BBHA2 induced more IL-1b release at 12 weeks due to the biodegradation process, biphasic HA may have a positive effect on bone regeneration regarding RUNX2 gene expression at the early steps of the regeneration. These results have to be interpreted with tissue level data from histology and NanoCT analysis. PR563Comparison of new bone formation between rhBMP-2 hydroxyapatite and bovine bone in socket preservation Y. Kim, J. Shim Daegu/Korea, Republic OfBackground & Aim: The purpose of this study is to compare the effects of rhBMP-2 applied hydroxyapatite or bovine bone on socket preservation and clinical, radiological and histological analysis of bone formation after 3 months.