| Background:Titanium and titanium alloy are the ideal materials of restorations for dental implants due to its many excellent properties, low elastic modulus; very corrosion resistance and fine anti-fatigue performances; non-toxic and good biocompatibility1. However, because titanium is a Bio-inert material, these substitutes are unable to bond with the host bones directly. A great number of biophysical researches have been done in the study of the different surfaces and methods that aim to accelerate the osseointegration of dental implants.Many studies found that modification of titanium implants surfaces can contribute to both early fixation and long-term mechanical stability, giving higher interaction with the cells and tissues around the implant. Currently, studies focus on the coating of the titanium implant. Calcium phosphate (CP) coating has been testified to facilitate the express of the osteoblastic phenotype11and increase the roughness of titanium implant, due to its good biocompatibility, excellent bioactivity, self-setting characteristic, low setting temperature, and easy shaping into any complicated geometry. However, in light of long-term behavior, the brittleness and dissolution of CP coating will limit its application35. On the other hand, studies have confirmed that Type I collagen-coated titanium alloy exhibits favorable effects on the initial adhesion and growth activities of osteoblasts8, leading to an enhanced tissue vascularization and a reduced inflammatory response6.It is, therefore, hypothesized that the coating of titanium with calcium phosphate/Collagen I complex will induce implant-tissue interaction and osseointegration synergistically. Moreover, the ductile properties of collagen I will compensate for the poor fracture toughness of calcium phosphate. Our study in vitro had proved the effect of titanium CP/COL-I coating could lead to a better cell response and improve the expression of COL-I, ALP, and OC.Objective:In this research, we investigate the osseointegration of implants equipped with the novel CP/COL-I surface compared with conventional standard Ti implants of the same design in a rabbit model.Methods:The CP/COL-I coated titanium was obtained by electrolytic deposition, including multi-porous and dense coating. Implants were divided by the different surface modification, titanium with no coating (n=24), with CP coating(n=24), with multi-porous CP/COL-1coating(n=24), and with dense CP/COL-I coating(n=24). The coatings were observed using scanning electron microscope(SEM). All implants were implanted in both lateral femoral condyles of48New Zealand white rabbits. Animals were sacrificed after2,4,8and12weeks, respectively. The osseointegration of the implants were comprehensive assessed by imageology, biomechanics, histological analysis and immunohistochemistry analysis.Results:1. SEM observation:The surface of Titanium was smooth and uneven, and pure CP coating showed flake crystal structure. The surface morphologies of CP/COL-â… complex coating(including the multi-porous and the dense) were observed that the collagen fibrils were mineralized through the deposition of CP crystals, and the composite coating with porous structure formed on the substrates. These mineralized collagen fibrils had more porosities and better structure in the multi-porous group than in the dense group.2. Imageology observation:No visibly difference was seen between the experiment groups and the control groups in x-ray radiography. Spiral CT showed CP/COL-I complex coating groups have higher density around the implant than Ti group and CP group at4th week and12th week respectively. The multi-porous CP/COL-â… group got the highest density at12th week.3. Biomechanical testPull-out test showed that the bone binding of the implant with CP/COL-â… complex coating between implant and bone tissue was significantly higher than the untreated implant and the implant with pure CP coating. After8weeks, the multi-porous groups revealed higher pull-out forces (F=72.13N) compared with the dense groups (F=60.82N),P<0.05. 4. Histological investigationHistological analysis included H&E and Masson stainning. At the8th week after operation, large scale of new bone were formed around the implant, especially the CP/COL-I groups. However, the titanium group had more fibrous connective tissue visibly. Formation of new bone in the12th week had the same tendency.5. Immunohistochemistry analysisImmunohistochemistry analysis indicated that the expression of OC reach highest in all groups after4weeks. And the expression level was highest in the multi-porous groups than in three other groups.Conclusion:The titanium coated with CP/COL-I exhibits better biocompatible and osteoconductive, resulting to better osteogenic capability, which is a feasible and promising titanium implants coating for clinical application. |
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