This study aimed to evaluate the titanium (Ti) implants coated with collagen type I crosslinked using gamma-irrigation or glutaraldehyde (GA). The in vitro surface observations, quantification assay, and cell studies using human mesenchymal stem cells (hMSCs) were conducted. For in vivo experiments, the implants were divided into three groups and inserted into the rat tibias: control group (non-treated Ti implant), GA group (Ti implants coated with GA-crosslinked collagen) and 25 kGy group (Ti implants coated with gamma-radiation-crosslinked collagen at dose of 25 kGy). The animals were sacrificed at 4 weeks after implantation and the tissue sections were obtained. New bone volume (mm3) and bone-to-implant contact (BIC, %) within the region of interest (ROI) was measured. The in vitro results showed the highest osteogenic differentiation and levels of osteogenesis-related gene expressions in the 25 kGy group without cytotoxicity. The new bone volume of GA group was significantly higher than the control (p < 0.05). In the result of the BIC, the 25 kGy group was significantly higher than the control (p < 0.05). However, there was no significant difference between the experimental groups. Within the limitations of this study, Ti implant coated with gamma-radiation-crosslinked collagen has potential utility without side effects from chemical agents.

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This study was undertaken to compare new bone formation between non-expired and expired bovine-derived xenogeneic bone substitute (expired, out-of-use period) and to evaluate the efficacy of argon (Ar)-based atmospheric pressure plasma (APP) treatment on expired bone substitute in rat calvarial defect. The groups were divided into (1) Non/Expired group (Using regular xenografts), (2) Expired group (Using expired xenografts), and (3) Ar/Expired group (Using Ar-based APP treated expired xenografts). Surface observation and cell experiments were performed in vitro. Twelve rats were used for in vivo experiment and the bony defects were created on the middle of the cranium. The bone substitute of each group was implanted into the defective site. After 4 weeks, all the rats were sacrificed, and the volumetric, histologic, and histometric analyses were performed. In the results of osteogenic differentiation and mineralization, Non/Expired and Ar/Expired groups were significantly higher than Expired group (p < 0.05). However, there was no significant difference between groups in the animal study (p > 0.05). Within the limitations of this study, the surface treatment of Ar-based APP has a potential effect on the surface modification of bone grafts. However, there was no significant difference in bone regeneration ability between groups in vivo; thus, studies on APP to enhance bone regeneration should be carried out in the future.