鈣矽生醫陶瓷材料之開發及其合成機制之固態核磁共振研究

Abstract

鈣矽生醫陶瓷是屬於 CaO-SiO2 系統的生醫陶瓷材料， 適合用於牙髓病修補治療，不易釋出對生物體有害的物質，對人體有高度的生物相容性以及良好的生物活性。鈣矽生醫陶瓷材料的主要成分為三鈣矽酸鹽（Tricalcium silicate, C3S），具有水泥的性質，可藉由與水混合而硬化，其中的化學變化是以三鈣矽酸鹽的水合反應為主導。 因此本論文由三鈣矽酸鹽著手，利用固態核磁共振研究其水合產物的生成，以及其在不同時間點的水合行為表現。傳統方法製成的三鈣矽酸鹽以氧化鈣及二氧化矽粉末於高溫鍛燒的方式製成，但此法的相分離情形嚴重，且產物含有大量的氧化鈣。而本研究以溶凝膠方法降低了三鈣矽酸鹽中相分離的情形及氧化鈣的含量，並以去離子水、磷酸鈉溶液、碳酸鈉溶液等不同緩衝溶液來進行三鈣矽酸鹽的水合反應。 我們以 X-ray 粉末繞射儀（XRD）、微硬度測試儀（Microhardness tester）以及掃描式電子顯微鏡（SEM）探討三鈣矽酸鹽的水合行為及調控機制。更以固態核磁共振追蹤在不同緩衝溶液的調拌下，水合系統的產物變化。比起傳統高溫鍛燒燒製成的三鈣矽酸鹽，我們以溶凝膠製成的材料，其水合反應時間從傳統的二十分鐘大幅縮短至九分鐘， 因此在牙髓病修補治療的應用上更符合需求。我們又發現 pH 約為 12 的緩衝溶液能加快三鈣矽酸鹽水合反應的時間，其中以碳酸鈉溶液作為調拌溶液的產物有更好的生物活性，以磷酸鈉溶液作為調拌溶液會使水合產物有羥基磷酸鈣的產生，我們更成功以添加生物活性玻璃的方式來增加三鈣矽酸鹽水合產物的材料硬度。

Tricalcium silicate (C3S), a kind of calcium silicate bioceramics (CSCs) based on the CaO-SiO2 system, is the major component of dental cements used for endodontic restorative treatments. It should be non-toxic, and have high compatibility and good bioactivity. Utilizing X-ray diffraction (XRD), scanning electron microscope (SEM), and solid-state nuclear magnetic resonance (NMR), we report the hydration behavior and properties of C3S prepared by sol-gel method. We found that the setting time of sol-gel C3S was reduced to 9 min which is significantly shorter than that of C3S prepared by the conventional melt-quench method. Samples of sol-gel C3S were hydrolyzed with distilled water, 10% Na3PO4, and 10% Na2CO3 solution. The hydration product of C3S mixed with the Na3PO4 solution has the best mechanical property. Interestingly, hydroxyapatite (HAp) is found in the hydration product of (C3S + Na3PO4) by solid-state NMR measurements. This finding may provide a practical approach to enhance the microhardness of cementious materials in general. On the other hand, the hydration product of C3S mixed with the Na2CO3 solution has the best biocompatibility. We find that the mechanical properties of these hydration products can be further enhanced by the addition of bioactive glasses. Overall, the materials developed in this work are well suited for root-end-filling therapy.