矽/二氧化矽應用於牙科美白之評估

Abstract

近年來對於牙齒美學的追求日益精緻化，擁有一口亮麗白牙普遍認為有助於提升自信和個人形象。由於需求者眾，市場上牙科美白相關產品琳瑯滿目。常見之牙科診間美白與居家美白多依賴高濃度過氧化物以氧化色基，但此類治療常伴隨牙本質敏感、牙釉質去礦化及牙齦刺激等副作用。為兼顧效果與生物相容性，利用催化材料在降低過氧化物濃度下提升活性氧產生已成為美白研究焦點。 本研究旨在合成富含亞氧化態與氧空缺的非晶雙相矽/二氧化矽奈米顆粒，並將其加入過氧化脲漂白劑中，評估其材料特性、牙齒漂白功效、生物相容性與術後牙釉質完整度。首先透過金屬鈉還原法製備 Si/SiOx 奈米顆粒，再以X射線繞射與拉曼光譜確認其非晶結構，並從X 射線光電子能譜分析材料含大量氧缺陷位，可介導氧化還原反應。本研究所開發之美白劑（Si-8CP-CMC）配方為 8 wt% 過氧化脲、5 wt% 羧甲基纖維素與 1 wt% Si/SiOx，並以常見之16 wt% 過氧化脲為對照。將以紅茶與咖啡染色之牛前牙進行美白效果測試， 由CIELAB 色差（ΔE）評估其漂白效能，再以掃描電子顯微鏡與維氏顯微硬度測試檢驗術後牙釉質完整性。並利用人牙齦纖維母細胞進行細胞毒性測試，以評估其生物安全性。 結果顯示Si-8CP-CMC在 15 分鐘內即達臨床可視美白（ΔE ≥ 3.7），並在 60 分鐘內於茶漬與咖啡漬樣本分別達 ΔE 15.3 ± 0.8 與 14.7 ± 0.9，顯著高於對照組。與細胞共培養 24 小時後，存活率維持在 95% 以上，顯示具生物安全性。透過電子顯微鏡觀察，Si-8CP-CMC美白術後仍可維持牙釉質棱柱結構，其維氏硬度為 332 ± 20 kgf/mm2，與健康牙釉質無顯著差異。 綜上所述，本研究開發之Si/SiOx奈米顆粒可有效催化過氧化物，並在顯著提升美白效果的同時，亦具備良好生物相容性且能維持釉質結構，可望為牙科美白提供更安全且有效的替代方案。

Tooth discoloration, arising from dietary chromogens, aging, medications, or trauma, remains a prevalent aesthetic concern. Conventional in-office and at-home bleaching systems typically rely on concentrated peroxides to oxidize chromophores; however, these treatments frequently lead to dentinal hypersensitivity, enamel demineralization, and gingival irritation. To balance efficacy and biocompatibility, catalytic materials that enhance reactive oxygen species (ROS) generation at reduced peroxide concentrations have become a focal point in bleaching research. This study aimed to synthesize amorphous dual-phase silicon/silicon oxide (Si/SiOx) nanoparticles enriched with suboxide states and oxygen vacancies, incorporate them into a low-peroxide bleaching gel, and evaluate their physicochemical characteristics, whitening efficacy, biocompatibility, and enamel safety. Si/SiOx nanoparticles were synthesized via sodium-assisted thermal reduction. X-ray diffraction and Raman spectroscopy confirmed their amorphous structure, while X-ray photoelectron spectroscopy revealed abundant oxygen-deficient domains capable of redox mediation. A bleaching gel containing 8 wt% carbamide peroxide (CP), 5 wt% carboxymethyl cellulose (CMC), and 1 wt% Si/SiOx (Si-8CP-CMC) was formulated, with a conventional 16 wt% CP gel serving as the control. Bovine incisors stained with black tea and coffee were treated for up to 60 minutes. Whitening efficacy was assessed using total color change (ΔE) in the CIELAB system, while enamel integrity was evaluated via field-emission scanning electron microscopy (FE-SEM) and Vickers microhardness testing. Human gingival fibroblasts (HGF-1) were used for cytotoxicity assessment via WST-1 and Live/Dead assays. The Si-8CP-CMC gel produced clinically perceptible whitening (ΔE ≥ 3.7) within 15 minutes and achieved ΔE values of 15.3 ± 0.8 (tea) and 14.7 ± 0.9 (coffee) after 60 minutes, approximately 73% and 39% higher, respectively, than the CP gel, despite halving the peroxide content. HGF-1 viability remained above 95% after 24-hour exposure to Si-8CP-CMC eluates, whereas CP gel exposure reduced viability below 60% and caused membrane damage. FE-SEM revealed that Si-8CP-CMC preserved enamel architecture, while CP gel induced interprismatic dissolution. Vickers hardness in the Si-8CP-CMC group (332 ± 20 kgf/mm2) was comparable to sound enamel, in contrast to the CP group (255 ± 27 kgf/mm2, p < 0.001). These findings demonstrate that oxygen-vacancy-rich Si/SiOx nanoparticles serve as effective peroxide activators, enabling enhanced whitening efficacy with significantly improved biocompatibility and enamel preservation. This strategy presents a promising, safer alternative for future dental bleaching applications.