Department of Prosthodontics, School and Hospital of Stomatology, Fujian Medical University, Fuzhou, China.
Research Center of Dental Esthetics and Biomechanics, Fujian Medical University, Fuzhou, China.
BMC Oral Health. 2020 Aug 5;20(1):218. doi: 10.1186/s12903-020-01206-3.
The bond strength of resin composites to dentin was reported to be related to either the remaining dentin thickness (RDT) or bleaching treatment. However, information is limited regarding the effects of RDT on the bond strength of bleached dentin. The present study aimed to investigate the effects of RDT on the microshear bond strength (μSBS) of resin cement to bleached dentin.
A total of 120 dentin specimens were prepared and randomly divided into 2 groups: a bleaching group (group B) and a control group (group C). Hydrogen peroxide with a concentration of 35% (Ultradent, USA) was applied on the dentin surface for 2 × 1 d for group B, while no bleaching treatment was performed for group C. After the treatment, the specimens were finished and polished to obtain different RDTs (2, 1, and 0.5 mm) and divided into 3 groups of 20 specimens each. The bonding procedure was performed using Panavia V5 (Kuraray, Japan) with a bonding area of 0.785 mm. For each group, half of the specimens were subjected to 5000 thermal cycles (subgroup T), while the other half did not receive thermocycling (subgroup N) (n = 10). The specimens were then subjected to the μSBS test using a universal testing machine. Data were analyzed by a three-way analysis of variance (α = 0.05). The fracture modes of the specimens were confirmed with a measuring microscope. Representative specimens with different fracture modes were observed with scanning electron microscopy (SEM).
The μSBS values were significantly affected by bleaching treatment (p < 0.001), whereas no significant effect was observed for thermocycling (p = 0.293). In terms of RDT, a significantly different μSBS value was found among the subgroups with different RDTs in group C (p = 0.003). However, the RDT did not significantly affect the μSBS values of bleached dentin in group B (p = 0.779). The μSBS values were significantly lower in group B than in group C (p < 0.001). A higher percentage of adhesive failure was observed in group B than in group C.
Based on the present findings, it can be concluded that the RDT did not affect the bond strength of resin cement to bleached dentin.
Since RDT did not affect the bond strength of resin cement to bleached dentin, bonding procedures should not be performed immediately after intracoronal bleaching, even if the dentin is planned to be removed due to a tooth preparation process.
树脂复合材料与牙本质的粘结强度据报道与剩余牙本质厚度（RDT）或漂白处理有关。然而，关于 RDT 对漂白牙本质粘结强度的影响的信息有限。本研究旨在探讨 RDT 对漂白牙本质用树脂水泥的微剪切粘结强度（μSBS）的影响。
共制备 120 个牙本质标本，随机分为 2 组：漂白组（组 B）和对照组（组 C）。组 B 用浓度为 35%的过氧化氢（Ultradent，美国）处理牙本质表面 2×1d，组 C 不进行漂白处理。处理后，用 Panavia V5（Kuraray，日本）对标本进行抛光和修整，获得不同的 RDT（2、1 和 0.5mm），每组 20 个标本。每个组的一半样本进行 5000 次热循环（亚组 T），另一半不进行热循环（亚组 N）（n=10）。然后使用万能试验机对标本进行 μSBS 测试。数据采用三因素方差分析（α=0.05）进行分析。用测微显微镜确认标本的断裂模式。用扫描电子显微镜（SEM）观察具有不同断裂模式的代表性标本。
漂白处理显著影响 μSBS 值（p<0.001），而热循环无显著影响（p=0.293）。就 RDT 而言，组 C 中不同 RDT 亚组的 μSBS 值存在显著差异（p=0.003）。然而，RDT 对组 B 中漂白牙本质的 μSBS 值没有显著影响（p=0.779）。组 B 的 μSBS 值明显低于组 C（p<0.001）。组 B 中观察到的黏附性失效比例明显高于组 C。
根据本研究结果，可以得出结论，RDT 不会影响树脂水泥对漂白牙本质的粘结强度。
由于 RDT 不会影响树脂水泥对漂白牙本质的粘结强度，因此即使由于牙体预备过程而计划去除牙本质，也不应在根管内漂白后立即进行粘结程序。
