Objectives: Oral bone defects require bone grafts that are biocompatible, osteoconductive and physically robust to withstand clinical handling. Bovine bone is accepted as a source of suitable grafting material (xenografting). However, the manufacturing process reduces its biological properties and mechanical strength. Therefore, the aim of our study was to develop optimised bovine bone blocks while assessing the effects of different sintering temperatures on their physio-chemical properties, biocompatibility and clinically-relevant mechanical strength.
Methods: Bone blocks/disks (5x5x5 mm/5x2 mm) were divided into four groups; Gp1: Control/Untreated, Gp2: Initial boil (6 hours), Gp3: Sintered at 550°C (6 hours), Gp4: Sintered at 1100°C (6 hours). Samples were tested for purity (thermogravimetric analysis), crystallinity (X-ray diffraction), mechanical strength (compression testing), surface morphology and chemical composition (SEM/EDS). Biocompatibility was tested with human osteoblasts in vitro by measuring viability (PrestoBlue™) and cellular adhesion (phalloidin). Clinical handling was tested by placing a 10x1.5 mm diameter cross-head bone-block screw into blocks drilled at 800 RPM. Statistical analysis was performed using GraphPad PRISM software and Tukey’s multiple comparison test based on one-way ANOVA. P value <0.05 was considered as significant.
Results: Higher temperature sintering (Gp4) removed all organic components but increased crystallinity (95.33%). All test groups (Gp2-4) showed decreased mechanical strength (MPa: 4.21 ± 1.97, 3.07 ± 1.21, 5.14 ± 1.86, respectively) compared with raw bone (Gp1) (MPa: 23.22 ± 5.24, p <0.05), with micro-cracks seen under SEM. However, Gp4 had highest biocompatibility as compared to control (p <0.05). Clinically-relevant bench-top testing showed that Gp4 samples could better withstand drilling and screw placement, but demonstrated high brittleness compared to Gp1.
Conclusion: Bovine bone blocks sintered at higher temperatures resulted in highly pure bone with better biocompatibility and reduced but acceptable mechanical strength and clinical handling. Further animal model studies will demonstrate the suitability of this construct for bone grafting applications.