研發人類牙本質高鍵結強度之新型樹脂黏著劑

Abstract

為了恢復牙齒良好的美觀及功能，玻璃纖維根柱(fiber post)在臨床的使用日益頻繁，然而玻璃纖維根柱的黏著強度仍有改善的空間。有鑒於玻璃纖維根柱的失敗常起因於與牙本質的黏著力不佳，本研究以研發新型樹脂黏著劑(resin cement)，提升樹脂黏著劑與牙本質的結合強度為主要目的。 使用bis[2-(methacryloyloxy)-ethyl] phosphate (2MP)製成bonding agent，並以isobornyl acrylate (IBOA) 及ethylhexylacrylate (EHA)為樹脂黏著劑之原料，透過微拉伸試驗(microtensile test)、推離鍵結試驗(push-out test)及破裂韌性試驗(fracture toughness test)測試含不同比例2MP (30%, 35%, 40%)的bonding agent，和市售樹脂黏著劑(NX3, Variolink II, RelyXUnicem, Panavia F 2.0)所表現之黏著強度，並以長時間恆溫水浴(37℃, 5 months)測試各組別長時間的黏著強度變化。此外，對bonding agent進行保質期測試，透過紅外線光譜儀(ATR-FTIR)，以及微拉伸試驗，觀察保存於4℃中，3個月後，其自聚合程度以及黏著強度的變化。再使用電子能譜儀(XPS)分析牙本質中的膠原蛋白(Collagen Type I) 與bonding agent之間的鍵結機制，並以穿透式電子顯微鏡(TEM)觀察所研發之bonding agent (2MP)與牙本質間形成之hybrid layer。 結果顯示，含35%-2MP的bonding agent，配合含IBOA, EHA的resin cement組別，能達到最佳的牙本質黏著強度。保質期測試結果表示，隨著保存期間的拉長，bonding agent有逐漸自聚合的情形，並影響其黏著強度的表現。電子能譜儀分析顯示，bonding agent中的磷酸根可以與膠原蛋白產生氫鍵，以提供黏著強度的來源。穿透式電子顯微鏡觀察到，在黏著層處能形成穩固的hybrid layer，厚度約為5-6μm。實驗結果證實，2MP, IBOA, EHA 能有效的提高樹脂黏著劑與牙本質的黏著強度，有應用於開發新型樹脂黏著劑之潛力。

Fiber posts have been used more frequently in dental restoration to achieve better aesthetic outcomes. However, the loss of adhesion or detachment of fiber posts from root canals is the primary cause of failure; therefore, the purpose of this study is to formulate a novel type of resin cement that improves the bonding strength of fiber posts at the dentin-cement interface. Three concentrations (30, 35, and 40 wt%) of bis[2-(methacryloyloxy)-ethyl] phosphate (2MP) were prepared as key dentin bonding agent components and isobornyl acrylate (IBOA) and ethylhexylacrylate (EHA) were used as key components to fabricate the resin cement. The specimens were tested after cementation 24 hours and storage in distilled water at 37℃for 5 months to observe long term stability by evaluating the bond strength. The adhesive strength of these fabricated cements to coronal and root canal dentin were tested using a microtensile bond test, push-out bond test, and fracture toughness test, and to make comparisons with 4 commercially available resin cements (NX3, Variolink II, RelyX Unicem, and Panavia F 2.0). In addition, the shelf life of bonding agent was tested by infrared spectroscopy (ATR-FTIR) and microtensile test. Furthermore, we propose a model which explores the underlying mechanism of high bond strength between bonding agent and collagen using depth profiling of X-ray photoelectron spectroscopy (XPS). The interface of the adhesive and dentin was observed under transmission electron microscope (TEM). The results of the bond strength tests show that 30%-2MP, 35%-2MP, and 40%-2MP with IBOA and EHA produce greater or similar adhesion to dentin compared with the 4 commercial resin cements. The shelf life test indicates that inhibitors can prevent spontaneous initiation and promote shelf life. The results of XPS show, when bonding agent was cast on the dentin, the phosphate in the bonding agent can migrate to collagen side and produce more hydrogen-bond to increase bond strength. TEM revealed the morphology of dentin- adhesive interface, with a 5-6 μm-thick hybrid layer. Within the results of this study, the adhesion to the coronal and root canal dentin can be improved significantly by the addition of key components (2MP, IBOA, and EHA) to resin cements. These components exhibit the potential for the development of a novel type of resin cement.