University of Bergen, Department of Clinical Dentistry – Cariology, Bergen, Norway.
Oper Dent. 2011 Mar-Apr;36(2):187-95. doi: 10.2341/10-126-L.
This study evaluated the importance of enamel at the cervical margin for support and retention of a class II composite restoration in relation to fracture strength, fracture mode, and leakage.
Sixty-five newly extracted teeth were randomly divided into five groups. Within each group, standardized class II preparations were made at the mesial surface of the tooth with four different preparation designs. Group D (n=15) had the cervical margin placed below the cemento-enamel junction (the dentin group), and in the other three groups (the enamel groups: E1, E2, and E3), the cervical margin was within the enamel (n=15 each). Group E3 had restorations with cuspal coverage, while groups E1 and E2 differed in vertical dimension. Intact teeth without preparation or restoration were tested as controls (n=5). The area of the horizontal part of enamel at the cervical margin of the preparation (available cervical enamel) was calculated. The teeth were restored with a nanofilled composite material and an etch-and-rinse adhesive system. The teeth were subjected to artificial aging consisting of thermocycling and mechanical cyclical loading. The restorations were subsequently loaded until fracture. The teeth were examined microscopically to assess fracture mode and leakage at the interface between the restoration and the tooth substance.
The fracture strength in group D (without cervical enamel) and E3 (with cuspal coverage and cervical enamel) was lower (p<0.01) than in the other two groups (with cervical enamel). There was a correlation between the area of available cervical enamel and fracture strength (p<0.01). The median fracture strength for the control teeth was not significantly different from groups E1 and E2. Group D exhibited a predominance of adhesive fractures, while the other groups revealed more cohesive fractures.
The results from this study indicate that available cervical enamel has an impact on the performance of class II composite restorations.
本研究评估了颈缘釉质对于支持和保留 II 类复合修复体的重要性，涉及断裂强度、断裂模式和渗漏。
65 颗新提取的牙齿被随机分为五组。在每组内，在牙齿的近中面进行标准化的 II 类制备，采用四种不同的制备设计。组 D（n=15）将颈缘置于牙釉质-牙骨质交界处下方（牙本质组），而在其他三组（釉质组：E1、E2 和 E3）中，颈缘位于釉质内（每组 n=15）。组 E3 有牙尖覆盖的修复体，而 E1 和 E2 组在垂直维度上有所不同。无制备或修复的完整牙齿作为对照（n=5）。计算制备体颈缘处釉质水平部分的面积（可用颈缘釉质）。牙齿用纳米复合树脂材料和酸蚀-冲洗粘结系统进行修复。牙齿经过人工老化处理，包括热循环和机械循环加载。然后将修复体加载至断裂。用显微镜检查牙齿以评估修复体与牙体之间的界面的断裂模式和渗漏。
组 D（无颈缘釉质）和 E3（有牙尖覆盖和颈缘釉质）的断裂强度较低（p<0.01），低于其他两组（有颈缘釉质）。可用颈缘釉质的面积与断裂强度之间存在相关性（p<0.01）。对照组牙齿的中位断裂强度与 E1 和 E2 组无显著差异。组 D 显示出以黏附性断裂为主，而其他组则显示出更多的内聚性断裂。
本研究结果表明，可用颈缘釉质对 II 类复合修复体的性能有影响。
