Effects Of Titanium Modified By Electrochemical Oxidation On Cell Function Of PDLSCs And Osteoblasts

Implant denture,which is easy to use, beautiful and comfortable, was accepted and loved by the majority of patients gradually in recent years. Titanium and titanium alloys were the best choice for dental implants, due to their good biocompatibility, mechanical strength and stability of the chemical character. But with the continuous clinical development of implant and the study of osseointegration of implant, medical titanium materials have been found still have some shortcomings. So, scholars were increasingly concerned about the titanium surface modification, in order to promote a good osseointegration in the early stage.The electrochemical oxidation method, which mainly included the electrochemical anodic oxidation and micro-arc oxidation (MAO), was more popular recently. In the corresponding electrolyte and the specific process conditions, anodic oxidation could form a neat, orderly and high-density TiO2nanotube arrays layer on titanium surface, through the electrode reaction and the electric field-driven. However, MAO is developed from the anodic oxidation. By using the arc discharge, MAO enhanced and activated the reaction at the anode. Then porous and dense oxide film was formed in the surface of pure titanium. Although the two oxidation method was based on the principle of electrochemical oxidation, But the voltage and oxidation time of them are different. In addition, the surface morphology which they have formed was also different. Therefore, there were more and more studies of this two surface modification methods. To a good osseointegration, not only osteoblasts is the key point, but also other osteoblast-related cells is also crucial. Thus, at the same time of researching into the relationship of bone cells and the surface modification of titanium,many researchers have turned their attention to the other osteogenic-related cells, which included the periodontal ligament stem cells (PDLSCs). Cells which are derived from the periodontal ligament (PDLSCs) have previously been reported to have multipotent stem cells-like characteristics. Because of its specificity, the study of PDLSCs was not only about the reconstruction of the periodontal ligament, but also about induction of its differentiation. All the researcher hoped it can play a guiding role in the treatment which used of stem cells.Experiment OneObjective:To investigate the effect of titanium modified by anodic oxidized TiO2nanotubes on response of osteoblasts, especially the osteogenic differentiation. Method:Two groups were involved in this study, TiO2nanotubes group and control group (smooth titanium). Surface morphologies were observed by scanning electron microscope. Proliferation and alkaline phosphatase activity were carried out in vitro tests. In addition, osteogenic marker genes expression, including Col-I, OCN and Runx-2, was evaluated the by RT-PCR. The mineralization assay of PDLSCs were tested by alizarin red staining. Result:We prepared nominally TiO2nanotubes with100nm diameter on Ti substrates by anodization. No significant difference between the experimental and control group of the proliferative activity on1d and of the ALP activity on4d (p>0.05). However,4and7d, cell proliferative activity of TiO2nanotubes group was lower than the control group (p<0.05). ALP activity were enhanced significantly on the TiO2nanotubes group than control group on7d,14d and21d (P<0.05). The21d, the Col-1, OCN, Runx-2gene expression level of experimental group was significantly higher(p<0.05). mineralization of the experimental group were significantly stronger than the control group on14d (p<0.05). Conclusion:Anodic oxidized porous and orderly TiO2nanotube coating can be successfully fabricated. The proliferation activity of PDLSCs on the TiO2nanotubes less than control group. ALP activity, gene expression and mineralization of PDLSCs, which grow on TiO2nanotubes surface, are considerably higher than on control group. It suggests that PDLSCs are sensitive to nanotubes surface.Experiment TwoObjective:To evaluate the effect of titanium modified by micro-arc oxidation (micro-arc oxidation, MAO) on initial response of osteoblasts, especially the protein synthesis. Method:Two groups were involved in this study, MAO and control group (smooth titanium). Surface morphologies were observed by scanning electron microscope. Proliferation and alkaline phosphatase activity were carried out in vitro tests. In addition, protein syntheses, including Col-I, OCN, OPN and Runx-2, was evaluated the by western blotting test. Result:A porous layer was observed on titanium surface modified by MAO. Initial osteoblasts proliferation and ALP activity were enhanced significantly on the micro-arc oxidized surfaces than that on smooth surface (P<0.05). After cultured for3d, Col-1, OCN, OPN, Runx-2protein expression was increased (P<0.05) in MAO group compared with that in control group. Conclusion:Titanium surface modified by MAO could promote the proliferation, differentiation and protein synthesis of osteoblasts.In future research, we will further compared the similarities and differences between anodic oxidation TiO2nanotubes and MAO. We hope to provide future titanium implant surface modification with a experimental foundation and basis.