共沉法製備之三鈣矽酸鹽於牙髓病治療應用性質之探討

Abstract

以鈣矽酸鹽為主成分的三氧礦化聚合物（Mineral trioxide aggregate, MTA），是目前最普遍使用在根管修補治療的材料，但其硬化時間過長是臨床應用上的缺點。為了改善MTA的缺點，我們的研究團隊分別以溶膠-凝膠法（sol-gel technique）研發製備孔洞性的溶膠-凝膠三鈣矽酸鹽（sol-gel C3S），其具有較短的硬化時間與良好的材料強度和生物相容性，並具備表面生物活性，但在封閉性質方面仍需進一步研究。此外，也利用共沉法（coprecipitation method）並添加氟離子穩定產物結構的方式，製備出高純度且硬化時間短的共沉法製備之三鈣矽酸鹽（C3S），依其燒結溫度的不同，分別命名為F1400及F1250，但尚未測試在牙科其它應用的性質。故本研究的目的是要測試共沉法製備之三鈣矽酸鹽F1400與F1250的物理化學性質、水合行為、表面生物活性、生物相容性及封閉性質，以評估其在牙髓病修補治療應用的潛力。 實驗結果發現，F1400和F1250均具有良好生物相容性，細胞在F1400和F1250都有良好的貼附，細胞存活率和控制組相比相當，兩者均不具有細胞毒性。在重金屬含量方面，F1400和F1250兩者幾乎不含有重金屬。同時在水合行為表現相類似。F1400與F1250在SBF中進行水合反應時，隨著反應時間28天後，兩者在電子顯微鏡觀察下，均可以發現在材料表面有球狀結構結晶出現；同時在X光繞射分析可發現，2θ=29.4°∼31.8°範圍出現的波峰與強度有所變化，推測可能和鈣磷酸鹽類結晶形成有關；另外還可以觀察到SBF溶液中磷離子濃度隨著時間增加有急遽下降的變化，推測磷離子有可能參與F1400和F1250表面球狀結晶的生成。綜合上述的實驗結果，推測表面球狀結晶為類氫氧基磷灰石的結構，顯示F1400和F1250都具有表面生物活性的特質。 在pH值部分，水合後放入水中，F1400和F1250皆在數分鐘內就會急遽升高到pH11-12之間，之後直到28天的pH值均無明顯變化。而在SBF的組別則是呈現不同的行為，F1400和F1250均會隨反應時間增加緩慢上升至pH10左右，推測可能是SBF為緩衝液有關。在鈣離子釋放量方面，F1400和F1250在水中與SBF進行水合反應相比較，鈣離子釋放量均隨著時間增加而增加，但在SBF中釋放量是在水中約2倍。而在矽離子釋放方面，除了F1400在SBF反應1天後有微量的矽離子釋放外，F1400和F1250無論是在水中和SBF中進行水合反應，在其他反應時間均未檢測出矽離子。在封閉性質實驗方面，F1400的染劑浸潤深度略大於MTA與sol-gel C3S，但三組間無統計上之顯著差異。 不過F1400和F1250在其他一些物理化學性質表現有明顯差異，和F1250相比較，F1400硬化時間較短、表面微硬度較強及抗壓強度表現較好，顯示F1400有較佳的物理機械性質。在水中進行水合過程中氟離子釋放方面，F1250釋放量約為2.4 ppm，是F1400兩倍。考慮共沉法製備出F1400和F1250含有氟的量為製備過程中原添加物0.4817 g氟化鈉的0.05 wt%，推測材料中所添加的氟離子並未進入C3S晶體系統內，因而於反應時會釋放出來。 總結來說，和市售商品MTA相比較，F1400幾乎不含有重金屬，有明顯較短的硬化時間，較高的表面微硬度，同時在抗壓強度、生物表面活性、生物相容性及封閉性均沒有顯著差異，推測知F1400在牙髓病修補與治療上，為一極具潛力之材料。

Mineral trioxide aggregate（MTA）is the most common used material for the endodontic retrograde filling and perforation repair due to its promising results. But its long setting time may cause some problems. Thus, our research team developed new tricalcium silicate cements via sol-gel process (sol-gel C3S), which have porous structure, shorter setting time, good biological compatibility, and bioactivity. However, their sealing ability remains unknown. Besides, our research team also developed tricalcium silicate with highly purity via coprecipitation method, named F1400 and F1250. However, the properties using in endodontics were unstudied. Thus, the aim of this study is to evaluate the physical and chemical properties, hydration behavior, surface bioactivity, biocompatibility, and sealing ability of coprecipitation tricalcium silicate. The results showed that F1400 and F1250 presented no cytotoxicity and good adhesion to MRPC-1 cells. In addition, both of F1400 and F1250 were similar in the hydration behaviors to form calcium silicate hydrate (CSH) and calcium hydroxide, but they demonstrated significant differences in some chemical-physical properties. Compared to F1250, F1400 demonstrated better physical and mechanical properties by performing shorter setting time, stronger microhardness and higher compressive strength. In the hydration, the fluoride ions released from F1250 were about 2.4 ppm, which were twice than those from F1400. Consider only 0.05wt% fluoride ions were remained in F1250 and F1400 after sintering, the fluoride ions did not integrate into the tricalcium silicate and release from materials when resolving in water. Different to the microstructure observed in the group hydrated in water, a layer of granular crystals with the structure similar to apatite, was found on the hydrated products of F1400 and F1250 in SBF (simulated body fluid) group via SEM. In addition, the peaks over 2θ=29⁰∼34⁰ were shifting and became broad when the time increased to 28 days in the SBF group, which may relate to the formation of calcium phosphate rich products. Furthermore, the phosphate ions in SBF became undetectable within 1 day after reaction, which indicates the phosphate ions may react with F1400 and F1250 to form the calcium phosphate rich layer on their surface. According to the results, we hypothesize F1400 and F1250 are bioactive materials by presenting the ability to form apatite-like layer on their surface when hydrated in SBF. When hydrated in water, the pH values of F1400 and F1250 increased immediately to pH11-12 within minutes and then remained plateau. In contrast, the pH values of both materials in SBF group increased gradually and reached to pH10 with time increased to 28 days. The trend of calcium ions released from F1400 and F1250 over time was similar in SBF and water groups, but the SBF groups released calcium ions twice than the water groups. Besides, both materials hydrated in water and in SBF showed no release of silicon ions except F1400 hydrated in SBF within the first day. In sealing ability test, there was no statistical difference in immersing lengths between F1400, SN200, and GMTA. In conclusions, F1400 demonstrated good biocompatibility and bioactive property, and have shorter setting time and the comparable physical properties of GMTA. F1400 is considered as a potential material in endodontic applications.