- 學位論文
探討熱處理前後不同製程鈷鉻合金的性質變化
Investigate on the properties of cobalt-chromium alloys with different processes before and after heat treatment
摘要
鈷鉻合金為非貴金屬中被廣泛應用於牙科的金屬材料，然而，傳統失蠟鑄造方式(wax lost casting, traditional casting, TC)製造牙科贋復物，容易因操作者手法導致牙科贋復物品質不穩定。近年來，隨著數位牙科的發展，軟切割電腦輔助設計/電腦輔助製造(computer aided design/computer aided manufacturing soft-cutting, CAD/CAM SC)與雷射熔融 (selected laser melting, SLM)製程也被相繼應用在臨床上，並解決了部分傳統製程面臨的問題。臨床上，鈷鉻合金表面會進行燒瓷以增加美觀性，為了使鈷鉻合金表面與陶瓷材料有更好的鍵結，故常透過熱處理使材料表面形成氧化層，然而，熱處理對於不同製程的鈷鉻合金的影響至今仍較少受到討論與研究。因此，本研究之目的為探討，市售鈷鉻合金在TC、CAD/CAM SC與SLM三種製程之顯微結構、機械性質、抗腐蝕性及細胞毒性上的差異。三種製程分別依其廠商規範之製作程序製成10×10×3 mm3的試片，並進行熱處理。藉由掃描式電子顯微鏡分析顯微結構，機械性質方面由維氏硬度機與萬能試驗機進行評估，抗腐蝕特性則藉由恆電流電位儀進行分析，另外細胞相容性透過NIH-3T3細胞進行細胞存活率分析。實驗結果透過SPSS 20.0軟體，進行重複測量變異數 (repeated measures two-way ANOVA)統計分析並進行事後比較。本研究之結果分述如下：(1)顯微結構：TC經熱處理前後顯微結構皆為樹枝狀結構；CAD/CAM SC經由熱處理後，透過均質化改善合金孔洞缺陷；SLM在熱處理前後也均呈現緻密的針狀結構。(2)硬度：經熱處理後，TC的硬度由375.32±20.68 Hv降至351.99±18.72 Hv；CAD/CAM SC則由466.08 ±14.37 Hv降至276.47±10.02 Hv；SLM由464.03±13.00 Hv升至468.79 ±15.45 Hv。(3)電化學腐蝕電位：TC經熱處理後腐蝕電位由-0.159 eV升至-0.134 eV；CAD/CAM SC由-0.171 eV降至-0.223 eV；SLM從-0.286 eV升至-0.206 eV。(4)細胞存活率：TC、CAD/CAM SC及SLM的細胞存活率依序為90.75%、91.52%與90.62%，皆展現良好的生物相容性。TC及SLM製程之鈷鉻合金經過熱處理後，可提升其機械及抗腐蝕性質，而CAD/CAM SC製程之鈷鉻合金則反之，故CAD/CAM SC製程不建議進行熱處理。
並列摘要
Cobalt-chromium alloy (Co-Cr alloy) is a non-noble metal widely used in dentistry. However, the traditional casting method (TC) (wax lost casting) is used to perform dental restoration, which is easily destabilized depending on the operator's technique. In recent years, with the development of digital dentistry, computer-aided design/computer-aided manufacturing soft-cutting (CAD/CAM SC) and selected laser melting (SLM) processes have been applied to solve some of the problems of traditional methods in the clinical dentistry. Clinically, the porcelain-fused-to-metal is often used to for aesthetic purposes. In order to make the surface of the Co-Cr alloy bond better with the ceramic material, an oxide layer is formed by heat treatment. However, there are few studies on the effect of heat treatment on different processes using the Co-Cr alloy. Therefore, the purpose of this study is to investigate differences in the microstructures, mechanical properties, corrosion resistance, and cytotoxicity of commercially available Co-Cr alloys used in TC, CAD/CAM SC, and SLM processes. The dimensions of the specimens are 10 × 10 × 3 mm3, which were made according to the manufacturer's specifications, and then heat-treated. The microstructures of different Co-Cr alloys were analyzed by scanning electron microscopy . The mechanical properties were evaluated by a Vickers hardness machine and universal testing machine. Corrosion resistance was analyzed by electrochemical method with a potentiostat, and cell compatibility was tested by NIH-3T3 cells with MTT assay. The experimental results were analyzed by SPSS 20.0 software, and repeated two-way ANOVA measures were performed. The results of this study are as follows. (1) Microstructure: TC had dendritic structure before and after heat treatment; the pore defects of CAD/CAM SC decreased after heat treatment; and SLM had a dense needle-like structure before and after heat treatment. (2) Hardness: After heat treatment, the hardness of TC decreased from 375.32 ± 20.68 Hv to 351.99 ± 18.72 Hv; CAD/CAM SC decreased from 466.08 ± 14.37 Hv to 276.47 ± 10.02 Hv; and SLM increased from 464.03 ± 13.00 Hv to 468.79 ± 15.45 Hv. (3) Electrochemical tests: After heat treatment, the corrosion potential of TC increased from -0.159 eV to -0.134 eV; CAD/CAM SC decreased from -0.171 eV to -0.223 eV; and SLM increased from -0.286 eV to -0.206 eV. (4) Cell compatibility: The cell viability of TC, CAD/CAM SC, and SLM was 90.75%, 91.52%, and 90.62%, respectively, all showing good biocompatibility. The TC and SLM processes achieved higher mechanical properties and corrosion resistance after heat treatment, whereas the reverse is true for Co-Cr alloys of the CAD/CAM SC process. Therefore, heat treatment is not recommended for the CAD/CAM SC process.