In-vivo Bone Regeneration With Two Grafting Materials: A MicroCT Study

Objectives: The purpose of this study was to evaluate the in vivo bone regeneration of two grafting materials in a critical size rat calvaria model with a three-dimensional micro-computed tomography.

Methods: Two kinds of bioresorbable bioceramics, ReOss^TM (R, nano Hydroxyapatite) and Synthograft^TM (S, β-TCP) were used in the as received form. Twenty male Wistar rats with body mass around 0.5Kg were used. Two critical defects with 4.0 mm in diameter were created bilaterally in the calvaria and were allowed to heal for periods of 4 and 8 weeks. One defect was filled with one of the grafting materials and the other was the control (C, blood cloth). The amount of bone filling in the defects was examined using micro-computed tomography (μCT 40, Scanco Medical, Basserdorf) with a resolution of 30 μm slice. Statistical analysis was performed by one-way ANOVA at 95% level of significance and multiple comparisons were performed by Tukey's post-hoc.

Results: The new bone volume to total defect volume ratios at 4 weeks were R=14.79%^a, S=16.11%^a, and C=6.55%^b. The new bone percentage was observed for both materials at 8 weeks, R=22.63%^a, S=19.89%^a, and C=7.43%^b (non significant compared to 4 weeks). Qualitative analysis showed that newly formed bone was in perfect continuity with the host cortical and trabecular bone structure for both materials and times in vivo. However, R material presented more bone at the central regions of the defect whereas the S material presented bone healing patterns closer to the defect margins.

Conclusions: This study provided 3D description of bone substitution associated with the implantation of ReOss^TM and Synthograft^TM. The μCT imaging technique allowed not only a precise qualitative description of bone ingrowth but also to perform quantitative bone morphometry measurements. Despite non-significant differences, the healing patterns observed suggest different degrees of the materials osseoconductivity.