| Summary: | 博士 === 高雄醫學大學 === 牙醫學系碩士班 === 104 === Titanium is widely used in clinical because it’s excellent mechanical strength, highly stable chemical properties and biological compatibility. The breakthrough came in modern dental treatments with the application of titanium implants. The successful rate of dental implants is above 90 % during half century. With research of osseointegration in implant surfaces, we are progressive deepening in not only reducing healing time but also in achieving the harmony of osteoblasts, soft tissue and dental implants.
Many articles indicate that roughness, topography and oxide films of implant surface are significant factors affecting osseointegration. Many methods, such as sandblasting and anodization, can modify the characteristics of implant surface. The first part of this thesis 【Study I】, we used tetracalcium (TTCP) for secondly sandblasting after the commercial sandblasting and acid etching method. We detected the residual particles after secondly sandblasting and found majorly aluminum oxide replaced by TTCP. The residual particles, TTCP , can improve osteoblast the abilities of attachment and proliferation on the surface without affecting other cells, fibroblast and epithelium. We used titanium surfaces modified by this method to measure the relation of attachment and cell number among three differentiated cells; osteoblast, fibroblast and epithelium. We can find epithelium can be affected by the titanium surface than fibroblast. Moreover, we found the ions effect can play more a significantly role than coating on the surface.
Second part of this thesis【Study II】, implant surfaces were modified by the another industrial method, micro-arch oxidation (MAO). MAO is based on the conventional anodic oxidation of processing metals and alloys in aqueous electrolyte solutions accompanied by sparking micro-discharge due to dielectric breakdown, which is also regarded as the intrinsic feature differing from conventional anodizing. It synthesizes a film of titanium dioxide including anatase-TiO2 (A-TiO2), rutile-TiO2 (R-TiO2). Titanium dioxide has been proved playing a curial factor for bone marrow mesenchymal stem cells in osseointegration. In this study, we used H2SO4/H3PO4 as an electrolyte in order to reduce working voltage, and begun oxidation reaction after 100V. The porosity, surface roughness of the MAO coatings and thickness of oxide film increased with increasing working voltage. However, the property of porosity decreases as the working voltage was over 200 V. And anatase phase began to be detected as the working voltage was over 140 V.We cultured mouse bone marrow mesenchymal stem cells in different surfaces and detected mineralization. The highest expression of alkaline phosphatase (ALP) and alizarin red S were found and dominated mineralization in the titanium surface modified in the working voltage 200V. We can modify the characteristic of oxide film by micro-arch oxidation to improve differentiation of mouse bone marrow mesenchymal stem cell.
In the final part of this thesis【Study III】, we designed a biomimetic implant for reducing healing time and achieving early osseointegration to create an active surface. Bone morphogenetic protein-2 (BMP-2) is a strong regulator protein in osteogenic pathways. Due to hardly maintain BMP-2 biological function and specificity, BMP-2 efficient delivery on implant surfaces is the main challenge for the clinic application. In this study, a novel method for synthesizing functionalized silane film for superior modification with BMP-2 on titanium surfaces is proposed. Three groups were compared with and without BMP-2 on modified titanium surfaces in vitro and in vivo: mechanical grinding; electrochemical modification through potentiostatic anodization (ECH); and sandblasting, alkali heating, and etching (SMART). Cell tests indicated that the ECH and SMART groups with BMP-2 markedly promoted D1 cell activity and differentiation compared with the groups without BMP-2. Moreover, the SMART group with a BMP-2 surface markedly promoted early alkaline phosphatase expression in the D1 cells compared with the other surface groups. Compared with these groups in vivo, SMART silaning with BMP-2 showed superior bone quality and created contact areas between implant and surrounding bones. The SMART group with BMP-2 could promote cell mineralization in vitro and osseointegration in vivo, indicating potential clinical use.
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