- 學位論文
以斷裂力學觀探討牙本質全酸蝕黏著劑與 自動酸蝕黏著劑之黏著複合破壞模式
Mixed mode failure analysis of total-etch and self-etch dentin-resin adhesion—a fracture mechanics approach
摘要
黏著劑複合材料在牙醫學界已被廣泛運用於將複合樹脂黏著到牙本質或牙釉質的各種修復治療，而黏著劑在使用上的評估已被證實是決定於能預測其黏著強度。在牙科研究傳統上用來測量黏著強度的方法是抗剪和抗拉伸測試，但這些測試是將黏著強度定義為黏著面的截面積破壞時施力荷載。然而，傳統黏著強度測試的平均應力並不能完全解釋其介面斷裂能力。林俊彬學者在1994年發展以斷裂力學觀，評估牙本質─複合樹脂黏著之破壞機轉，在此研究中，應用斷裂力學的理論公式推導求出破壞韌性GIC 、K IC 和最小幾何修正因子係數 Y。本實驗目的為建立一以斷裂力學為基礎之標準化實驗方式，評估人類牙本質─複合樹脂黏著介面抵抗斷裂能力。本研究，在理論上建立有限元素模型分析牙本質─複合樹脂黏著複合型破壞測試，並以Ｊ積分數學計算印證。進而以此標準化之複合型破壞測試評估牙本質全酸蝕劑Single Bond與自動酸蝕黏著劑Prompt L-Pop在黏著介面抵抗斷裂的能力。實驗部分採用剛拔除、無齲蛀之48顆人類恆臼齒，加以研磨並暴露出新鮮之牙本質面。使用上述兩種牙本質黏著劑，將複合樹脂柱黏著在製備完成之獨特幾何設計Chevron-Notch牙本質黏著區(D = 4mm, 2θ=90°, a/D=0.275)。利用各種施力距離施以荷載，評估相角對斷裂能量以及複合模式斷裂試驗的影響，並求出兩種黏著劑在牙本質─複合樹脂黏著介面之破壞韌性。斷裂試件則於掃瞄式電子顯微鏡下檢視其裂紋開始與擴展的情形。在理論上，經由斷裂力學理論基礎分析所導出之公式，可求出KIIC 、KIC 和 Y (YI,6mm=10.2684, YI,1mm=9.1426, YII,1mm =1.5835)。研究結果發現在複合模式斷裂中，可區分其中抗剪與抗拉伸的成分。經由理論公式可計算出Single Bond全酸蝕黏著劑之KIC 與KIIC分別為0.87 ± 0.1 (MN/m3/2) 與0.35 ± 0.03 (MN/m3/2)，以及Prompt L-Pop自動酸蝕黏著劑之KIC 與KIIC分別為0.75 ± 0.11 (MN/m3/2) 與0.25 ± 0.04 (MN/m3/2)。此斷裂面分析所觀察到的現象與理論上有限元素分析結果十分吻合。根據以上研究結果得到的結論：以Chevron-Notch斷裂力學觀所擬議之牙本質─複合樹脂黏著介面複合型破壞測試，確實可以同時評估牙本質黏著之抗拉伸與抗剪破壞韌性。預期此一新的測試方法論對於評估黏著強度以及發展現代復形牙醫學的新材料，均具有極高的應用價值。
並列摘要
Adhesives are extensively applied to the bonding of resin composites to natural tooth materials (dentin and enamel) in restorative dentistry. It has been proved that the performance of adhesive agents can be predicted by assessment of its bond strength. The conventional methods for determining bond strength in dental research are shear and tensile tests, which define adhesive strength as the measured failure load divided by the cross-sectional area of the bonded surface. However, the ambiguous “average stress” of conventional bond strength tests does not fully represent the interfacial failure stress. In 1994, Lin developed a failure criterion of dentin-resin bond test with a fracture mechanics approach. In that study, fracture mechanics-based equations were used to obtain fracture toughness, in terms of GIC, KIC, and Y, a minimum geometric factor coefficient. The objective of this study was to establish a fracture mechanics-based standardized experimental method for measuring the fracture resistance of human dentin-resin interface. Finite element models for this proposed mixed mode dentin-resin adhesion fracture test was created and verified mathematically by the J-integral approach. Furthermore, two dentinal adhesive systems, Single Bond total-etch adhesive and Prompt L-Pop self-etch adhesive, were evaluated via the standardized mixed mode adhesion test. Forty-eight newly extracted, non-caries human permanent molars were ground to expose fresh dentin surface. A composite rod was bonded to the prepared unique Chevron-Notch dentin bonding area (D = 4mm, 2θ=90°, a/D=0.275) with the above adhesives according to the manufacturer’s instructions. Compressive loads were applied with various loadline lengths for evaluating the effect of phase angle on the fracture energy. Fractured specimens were further observed by SEM to characterize the crack initiation and propagation facets. The data was analyzed by deriving fracture mechanics-based equations to obtain KIC, KIIC and Y (YI,6mm=10.2684, YI,1mm=9.1426, YII,1mm =1.5835). We found that the shear and tensile components of the mixed mode failure could be differentiated. Consequentially, the KIC and KIIC of Single Bond total-etch adhesive were calculated as 0.87 ± 0.1 (MN/m3/2) and 0.35 ± 0.03 (MN/m3/2), and the KIC and KIIC of Prompt L-Pop self-etch adhesive were calculated as 0.75 ± 0.11 (MN/m3/2) and 0.25 ± 0.04 (MN/m3/2), respectively. Fractographic results correlated very well with the mathematical finite element analysis. Accordingly, from the results of this study, we can conclude that application of the Chevron-Notch fracture mechanics to this proposed mixed mode dentin-resin interfacial fracture test is appropriate for assessment of the fracture toughness of dentin bonding both in tension and in shear. It is anticipated that this new test methodology will be valuable in bond evaluation as well as the development of new materials for this critical area of modern restorative dentistry.