牙科CAD/CAM用玻璃-樹脂複合材料其機械性質與顏色變化之研究

Mechanical Properties and Discoloration of Glass-PMMA Composites for Dental CAD/CAM

張稚蕙(ZHI-HUI ZHANG)

指導教授 ： 許世光

中臺科技大學/健康科學院/牙體技術暨材料系碩士班/碩士(2020年)

摘要

目的
近年來，CAD/CAM 系統在牙科領域之應用日新月異，特別地，在此系統可利用易於加工及具審美性之材料製作牙科贋復物，廣受患者的喜愛。現今，應用於牙科 CAD/CAM 系統之修復材料具有多樣性，包括陶瓷、樹脂及複合材料等。其中，複合材料具備仿真的美學、易於研磨加工與修復，以及可降低對咬牙的磨耗等優點，在臨床應用上備受重視。因此，本研究旨在開發與評估自有品牌之玻璃樹脂-複合材料 (Glass-PMMA composites, GPC），俾利於牙科 CAD/CAM 系統之應用。

材料與方法
以實驗室自製之 AA 玻璃粉末 (平均粒徑小於45 µm) 和 PMMA 粉末相混合，置於不鏽鋼模具中經單軸油壓機加壓成型，再將壓製後之試片放入 55℃ 的壓力鍋中固化反應 30 分鐘。AA 玻璃粉末添加之比例分別為 0、50 和 75 wt%，並依此序命名為 0-GPC、50-GPC 及 75-GPC，再以市售之 SHOFU 複合材料塊作為對照組進行分析。機械性質之評估是依據 ISO 6872：2008 之規範進行測試。在切削加工中，利用牙科 CAD/CAM 機器加工自製複合材料塊，並評估可加工性和加工精度。在顏色變化中，將試片浸泡於不同的飲料中，經浸泡 16 週後，再利用分光光度計 (400-700 nm) 進行分析顏色變化量。在細菌貼附檢測中，分別將試片與伴放線桿菌或變形鏈球菌共培養 20 小時，利用 ELISA 分析細菌生物膜的形成變化。最後，分析 L929 纖維母細胞與試片共培養後之細胞活性與生長型態，藉此評估試片之細胞毒性。

結果
由 SEM 觀察顯示，AA 玻璃顆粒均勻地分布在所有測試材料的 PMMA 有機相中。在所有測試材料中的水接觸角均呈現親水性 (θ為59至77°)，其中，75-GPC 的接觸角為 71.26°，此結果與人類牙釉質的水接觸角度極為相似。在四組試片中，其彎曲強度和硬度分別為 78 至 178 MPa 和 20 至 75 HV。在切削加工中，75-GPC 並未有平順的邊緣完整性，但具有較佳的加工精度。試片浸泡於不同溶液 16 週後其顏色之變化為，0-GPC 和 SHOFU 浸泡於人工模擬唾液中呈現出明顯的顏色變化，反之，50-GPC 和 75-GPC 則變化較小。在細菌貼附和生物膜形成檢測中，經結晶紫染色分析其吸光值介於 0.2 至 0.6 之間，與 0-GPC 和 SHOFU 相比，伴放線桿菌與變形鏈球菌在 75-GPC 材料表面上所形成的生物膜明顯最少，顯示其不利於細菌之貼附與生長。在 75-GPC 材料中，L929 纖維母細胞呈現較佳的細胞貼附和生長型態，以及細胞活性。
結論
綜合上述研究結果得知，75-GPC 的彎曲強度和維氏硬度分別與人類牙釉質和牙本質極其相似。在切削加工中，50-GPC 與 75-GPC 具有較佳的加工精度。在顏色變化中，浸泡 16 週後的所有試片均顯示出可見的顏色變化，其中，50-GPC 和 75-GPC 在浸泡人工模擬唾液 8 週後呈現出臨床上無法察覺的顏色變化。所有試片與伴放線桿菌或變形鏈球菌共培養後，75-GPC 顯示較小的細菌貼附情況。而且，75-GPC 呈現較佳的細胞貼附與細胞增生活性，顯示具有良好的生物相容性。

關鍵字：
玻璃-樹脂複合材料、機械性質、顏色變化、細胞毒性

關鍵字

玻璃-樹脂複合材料 ； 機械性質 ； 顏色變化 ； 細胞毒性

並列摘要

Objective
Recently, the applications of CAD/CAM systems are more attracting and growing in dentistry, especially, because the systems facilitate the fabrication of restorations using machinable and esthetical materials. The diversity of material restoration is widely used in CAD/CAM system, including ceramics, resins and composites. Among them, composite materials have clinical advantages, like superior esthetics, ease of milling, simple intraoral repair, and less wear on opposing teeth. Therefore, in this study, the own-brand glass-PMMA composite (GPC) blocks was developed and evaluated for dental CAD/CAM application.

Materials and methods
The AA-glass powders with an average particle size less than 45 µm, and were obtained from our lab. The AA powder and PMMA powder were mixed and placed in a uni-axial press stainless model, subsequently, a press-molded was cured at 55ºC for 30 min. The final GPCs were obtained and coded as 0-GPC, 50-GPC and 75-GPC containing 0, 50 and 75 wt% of AA-glass, respectively. A commercially available SHOFU block was used as a control. The mechanical properties were measured according ISO 6872:2008. The composite blocks was finished by dental CAD/CAM machine milling and evaluate machinability and marginal accuracy. In discoloration, specimens were immersed in different beverages. After 16 weeks, the samples were analyzed with a spectrophotometer (400-700 nm). Bacterial adhesion, GPC specimens were co-cultured with A. actinomycetemcomitans and S. mutans, respectively, for 20 hours and analyzed bacterial biofilm production by ELISA. Finally, cell activity and morphology of L929 fibroblast cell co-cultured with specimens were investigated for cytotoxicity.

Results
The SEM images show that AA particles were evenly distributed within PMMA organic phase in all test materials. The contact angle results showed that all test materials were hydrophilic with θ of 59 to 77°. Further analysis found that 75-GPC revealed a contact angle of 71.26°, and the results was similar to enamel of human teeth. The flexural strength and hardness of the four groups ranged from 78 to 178 MPa and from 20 to 75 HV, respectively. In the machinability, 75-GPC exhibit high accuracy of milled margine compared with the other specimens. In discoloration, the most pronounced color changes were found with 0-GPC and SHOFU in artificial saliva. However, 50-GPC and 75-GPC specimens showed less color change for 16 weeks immersion. In bacterial adhesion and biofilm formation, the absorbance value showed from 0.2 to 0.6 by crystal violet staining. The biofilm formed by A. actinomycetemcomitans and S. mutans on 75-GPC was significantly reduced compared to that of 0-GPC and SHOFU. The cytotoxicity result showed that L929 fibroblast cells were flattened, well spread, and displayed high cellular activity on 75-GPC material.

Conclusion
From above results indicate that the flexural strength and Vickers hardness of 75-GPC material were much similar to human enamel and dentin, respectively. In the machinability, 50-GPC and 75-GPC have better marginal accuracy. In discoloration, after 16 weeks, all specimens showed visible color changes. Among them, particularly, 50-GPC and 75-GPC presents a clinically unperceivable color change after immersion in artificial saliva for 8 weeks. After co-culturing all specimens with A. actinomycetemcomitans and S. mutans, 75-GPC showed a small amount of bacteria adhesion. Furthermore, 75-GPC exhibited well cell adhesion and higher proliferation, indicating good biocompatibility.

Keywords:
Glass-PMMA composite, Mechanical properties, Discoloration, Cytotoxicity

並列關鍵字

Glass-PMMA composite ； Mechanical properties ； Discoloration ； Cytotoxicity

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