Interfacial Stress and Bond Strength of Bulk-Fill or Conventional Composite Resins to Dentin in Class II Restorations

Abstract The aim was to evaluate the microtensile bond strength (mTBS) to dentin and interfacial stress in a class II cavity restored with bulk-fill or conventional composite resins and the margin interfaces. Vertical slot class II cavities in the mesial face, with the gingival end in dentin, were prepared in 72 third molars, being divided into groups (n=24): G1-Tetric N-Ceram; G2-Tetric N-Ceram Bulk-Fill; G3-SonicFill. Clearfil SE Bond adhesive system was used in all groups. Half of the teeth in each group (n=12) were submitted to thermo-mechanical cycling (TMC). Restored teeth (n=9) were cut perpendicular to obtain beams, which were submitted to a mTBS test in an EMIC machine. The cervical margins in dentin of the restored teeth (n=3) were assessed using SEM through epoxy resin replicas as well as the section of the restoration. Interfacial stresses after load application were calculated by 2D finite element analysis. The mTBS means-MPa followed by different letters represent statistical difference by ANOVA and Games-Howell’s test (p<0.05): Without TMC: G1-15.68±6.10a; G2-10.08±5.21ab; G3-7.98±3.76b. With TMC: G1-9.70±5.52a; G2-5.79±1.42a; G3-4.37±1.87a. Interfacial stress (MPa) was 4.4 for SonicFill, 3.9 for Tetric N-Ceram, and 3.5 for Tetric N-Ceram Bulk-Fill. SEM images showed continuous margins for all composite resin restorations. It was possible to conclude that SonicFill obtained a slightly higher interfacial stress and lower bond strength to dentin in comparison with Tetric N-Ceram and Tetric N-Ceram Bulk-Fill. Continuous margin interfaces were obtained for Tetric N-Ceram, Tetric N-Ceram Bulk-Fill, and SonicFill. However, voids were observed in the SonicFill restorations.

摘要 本研究旨在评估分别采用大块充填型与传统复合树脂修复II类洞型后，修复体与牙本质的微拉伸粘结强度（microtensile bond strength, mTBS）以及界面应力，并分析其边缘界面状态。选取72颗第三磨牙，在其近中面制备龈端位于牙本质内的垂直槽型II类洞型，随后分为3组（每组n=24）：G1组采用Tetric N-Ceram传统复合树脂修复；G2组采用Tetric N-Ceram Bulk-Fill大块充填复合树脂修复；G3组采用SonicFill复合树脂修复。所有组均使用Clearfil SE Bond粘结系统。每组中一半样本（n=12）接受热机械循环（thermo-mechanical cycling, TMC）处理。将每组中9颗修复后的牙齿沿垂直于修复面的方向切割为微拉伸试件，随后在EMIC试验机上开展微拉伸粘结强度测试。每组中另外3颗修复后牙齿，通过环氧树脂复型标本及修复体切面，利用扫描电镜（scanning electron microscope, SEM）观察其牙本质颈缘界面。通过二维有限元分析法计算载荷施加后的界面应力。经方差分析（ANOVA）与Games-Howell检验，带有不同字母标识的微拉伸粘结强度均值（单位：MPa）组间差异具有统计学意义（p<0.05）：未接受热机械循环处理组：G1组为15.68±6.10a；G2组为10.08±5.21ab；G3组为7.98±3.76b。接受热机械循环处理组：G1组为9.70±5.52a；G2组为5.79±1.42a；G3组为4.37±1.87a。各组界面应力（单位：MPa）分别为：SonicFill组4.4，Tetric N-Ceram组3.9，Tetric N-Ceram Bulk-Fill组3.5。扫描电镜观察结果显示，所有复合树脂修复体的边缘界面均保持连续完整。研究结果表明，与Tetric N-Ceram及Tetric N-Ceram Bulk-Fill相比，SonicFill的界面应力略高，但牙本质粘结强度更低。Tetric N-Ceram、Tetric N-Ceram Bulk-Fill与SonicFill三种复合树脂的修复体边缘界面均保持连续完整，但SonicFill修复体内部可见孔隙。