Objective: To evaluate effects of different healing times on integration of titanium mini-screws and bones under unloaded conditions by histomorphometric observations.
Methods: Thirty titanium mini-screws, 6.0 mm long and 1.9mm in diameter, were used in this study. A total of 10 male, 3-month-old New Zealand White rabbits (mean weight, 4.0 kg) were randomly divided into five groups with different healing times. Three titanium miniscrews were implanted into each tibia of the New Zeland White rabbit at a distance of 10 mm between 2 miniscrews. Animals were sacrificed immediately, 1, 2, 4 and 8 weeks after operation respectively. Samples of the screws with surrounding bone tissue were examined by HE staining.
Results: Progressive changes were observed in the implant bone interface.1 and 2 weeks after operation collagen fibers, locally absorbed areas and cancellous bones with loose connective tissues were found. 4 weeks after operation, new bone, particularly woven bone was observed on implant-bone interfaces. 8 weeks after operation lamellar bone and second remodeling were found.
Conclusion: Mini-screw healing is a continuous process , Osseointegration between implanted miniscrew and bone tissue may complete in 8 weeks in rabbit tibia.