Effect of elastic behavior of the hybrid layer on dentin bonding stability

在四种已商品化的胶粘剂体系中研究了杂化区弹性性能对牙本质粘接效果的影响。粘接区弹性性能的评价：对人拔牙冠状牙本质表面进行抛光研究。研究中使用了三种类型的湿粘接体系和一种固定蚀刻底漆体系。根据差值计算弹性性能。用通用显微硬度试验机测量10 gf载荷30秒后的总压痕深度与去除载荷后的永久压痕深度之间的关系。对抛光后的牙本质、蚀刻后的牙本质、涂接树脂和复合树脂表面进行压痕试验。牙本质腔体适应：在扁平冠状牙本质上制备直径3.5 mm、深度2mm的圆柱形牙本质腔体。采用上述修复系统修复后，对修复体进行切片。在光学显微镜下观察沿腔壁切片对腔体的适应性。结果和讨论：从未经处理的牙本质到树脂复合材料的整个粘接区域，在三种湿粘接系统中，粘接树脂层的弹性急剧降低，而自蚀刻底漆系统则显示出弹性性能的梯度。关于腔体适应。由收缩应力引起的间隙形成在线角和/或空腔底板。湿粘接系统。自蚀刻底漆系统沿腔壁产生良好的密封性。这些结果表明。杂化层可能起到释放应力的作用。杂化层的应力释放可能是有效的，当键合区域是按弹性分级的，而与杂化层的尺寸无关。

The effect of elastic properties of the hybrid zone on the dentin bonding efficacy was investigated in four commercialized adhesive systems.Evaluation of the elastic properties of the bonding area : Polished coronal dentin surface of human extracted molars were subjected to the study. Three brands of wet bonding system and a set-etching primer system were used in the study. The elastic properties was calculated from the difference. Between the total indentation depth after 10 gf loading for 30 seconds and permanent indentation depth after removal of the load measured by means of a universal microhardness testing machine. Indentation test was performed on the surfaces of polished dentin, etched/primed dentin, bonding resin applied and resin composite.Cavity adaptation in the dentinal cavity : On the flat coronal dentin, a cylindrical cavity 3.5 mm in diameter and 2 mm in depth, was prepared. After restored with the above restorative systems, the restoration was sectioned. Cavity adaptation was evaluated on the section along the cavity wall under a light microscope.Results and Discussion : Across the bonding area from the untreated dentin to resin composite, a drastic reduction of the elasticity was found at the bonding resin layer in the three wet bonding systems, while a self-etching primer system showed a gradient of the elastic properties. Concerning cavity adaptation. gap formation caused by the contraction stresses was seen at the line angle and/or cavity floor in the. wet bonding systems. A self-etching primer system resulted in a good sealing along the cavity wall. These results implied that. the hybrid layer might play a role of stress-releasing. The stress-releasing by the hybrid layer may be effective when the bonding area is graded in terms of elasticity and not related with the dimension of the hybridization.