Kovarik R E, Ergle J W
Department of Oral Health Practice, University of Kentucky College of Dentistry.
J Prosthet Dent. 1993 Jun;69(6):557-60. doi: 10.1016/0022-3913(93)90280-2.
An incremental buildup technique is advocated for placing posterior composite resin restorations. This technique is preferred because it assures complete polymerization of large restorations and also reduces the problem of polymerization shrinkage, which can adversely affect the seal at the gingival margin of class II and large class III restorations. Measurements of tensile bond strengths between layers have been published with conflicting results. This study measured the fracture toughness of layered posterior composite resin within the interfacial layer and in a direction perpendicular to the layering. A compact test-specimen geometry conforming to the ASTM standard E399-83 was used. Three groups were tested: Group A specimens were bulk-cured in one complete increment; group B specimens were incrementally cured in 1.2 +/- 0.2 mm layers perpendicular to the plane of fracture; and group C specimens were incrementally cured with the interface between layers parallel to and in the plane of fracture. The microfilled composite resin showed no significant difference in the mean fracture toughness from the bulk-cured control regardless of layering technique. The hybrid composite resin showed a significant decrease in fracture toughness for fractures occurring in the interfacial layer, and fractures perpendicular to layering showed no significant difference in fracture toughness compared with the bulk-cured control.
对于后牙复合树脂修复体的放置，提倡采用增量堆积技术。之所以首选该技术，是因为它能确保大型修复体完全聚合，还能减少聚合收缩问题，而聚合收缩会对Ⅱ类和大型Ⅲ类修复体龈缘处的封闭产生不利影响。关于各层之间拉伸粘结强度的测量结果已发表，但相互矛盾。本研究测量了层状后牙复合树脂在界面层内以及垂直于分层方向的断裂韧性。使用了符合ASTM标准E399 - 83的紧凑测试样本几何形状。测试了三组：A组样本一次性整体固化；B组样本垂直于断裂平面以1.2±0.2毫米的层厚逐步固化；C组样本在层与层之间的界面平行于且位于断裂平面内的情况下逐步固化。无论采用何种分层技术，微填料复合树脂的平均断裂韧性与整体固化对照相比均无显著差异。混合复合树脂在界面层发生断裂时，断裂韧性显著降低，而垂直于分层方向的断裂与整体固化对照相比，断裂韧性无显著差异。
