The influence of direct laser metal sintering implants on the early stages of osseointegration in diabetic mini-pigs

Background: High failure rates of oral implants have been reported in diabetic patients due to the disruption of osseointegration. The aim of this study was to investigate whether direct laser metal sintering (DLMS) could improve osseointegration in diabetic animal models. Methods: Surface characterizations were carried out on two types of implants. Cell morphology and the osteogenic-related gene expression of MG63 cells were observed under conditions of DLMS and microarc oxidation (MAO). A diabetes model in mini-pigs was established by intravenous injection of streptozotocin (150 mg/kg), and a total of 36 implants were inserted into the mandibular region. Micro-computed tomography (micro-CT) and histologic evaluations were performed 3 and 6 months after implantation. Results: The Ra (the average of the absolute height of all points) of MAO surface was 2.3 +/- 0.3 mu m while the DLMS surface showed the Ra of 27.4 +/- 1.1 mu m. The cells on DLMS implants spread out more podia than those on MAO implants through cell morphology analysis. Osteogenic-related gene expression was also dramatically increased in the DLMS group. Obvious improvement was observed in the micro-CT and Van Gieson staining analyses of DLMS implants compared with MAO at 3 months, although this difference disappeared by 6 months. DLMS implants showed a higher bone-implant contact percentage (33.2%+/- 11.2%) at 3 months compared with MAO group (18.9%+/- 7.3%) while similar results were showed at 6 months between DLMS group (42.8%+/- 10.1%) and MAO group (38.3%+/- 10.8%). Conclusion: The three-dimensional environment of implant surfaces with highly porous and fully interconnected channel and pore architectures can improve cell spreading and accelerate the progress of osseointegration in diabetic mini-pigs.