Coelho-de-Souza Fábio Herrmann, Camacho Guilherme Brião, Demarco Flavio Fernando, Powers John M
School of Dentistry, Lutheran University of Brazil, Cachoeira do Sul, RS, Brazil.
J Adhes Dent. 2008 Feb;10(2):113-7.
The aim of this study was to evaluate the effect of material technique, bevel placement, and aging on the fracture resistance of composite restorations bonded to sectioned incisal edges.
For the retention test, the incisal thirds of 80 mandibular human incisors were sectioned. Ten sound incisors were used as a control group. Teeth were divided into two groups according to storage time (24 h and 180 days with 1000 thermal cycles). In each group, subgroups were randomly formed as follows: beveled or nonbeveled direct resin composite restorations (Adper Single Bond/Filtek Z250) and beveled or nonbeveled indirect composite restorations (prepolymerized Filtek Z250 cemented with Adper Single Bond/Rely X ARC). For each experimental group, 20 specimens were prepared (10 tested after 24 h and the remaining after 180 days). The specimens were subjected to shear testing in a universal testing machine with a crosshead speed of 0.5 mm/min. Failure patterns were analyzed by stereomicroscopy (30X). Data were statistically analyzed with ANOVA and Tukey's and Student's t-tests for retention resistance, and with Fisher's exact test for fracture patterns at the 0.05 level of significance for all tests.
After 24 h, beveled restorations exhibited higher fracture strength values than nonbeveled restorations and showed resistance similar to the sound teeth. After 6 months, beveled restorations still presented better results than nonbeveled restorations. Thermal cycling and water storage decreased the fracture resistance in the majority of the groups. Adhesive failures were mainly observed in nonbeveled restorations and mixed failures in beveled restorations.
Within the limitations of the study, it was concluded that storage with thermal cycling decreased fracture resistance, beveling improved fracture resistance, and indirect restorations had a fracture resistance similar to direct restorations.
本研究旨在评估材料技术、斜面位置及老化对粘结于离体切缘的复合树脂修复体抗折强度的影响。
为进行固位力测试，将80颗下颌中切牙的切端三分之一处截断。选取10颗完好的中切牙作为对照组。根据储存时间（24小时和180天并经过1000次热循环）将牙齿分为两组。每组再随机分为以下亚组：有斜面或无斜面的直接树脂复合树脂修复体（Adper单组分粘结剂/Filtek Z250）以及有斜面或无斜面的间接复合树脂修复体（预聚合的Filtek Z250用Adper单组分粘结剂/Rely X ARC粘结）。每个实验组制备20个样本（10个在24小时后测试，其余在180天后测试）。样本在万能材料试验机上以0.5毫米/分钟的十字头速度进行剪切测试。通过体视显微镜（30倍）分析失败模式。所有测试均采用方差分析、Tukey检验和Student t检验对固位力进行统计学分析，采用Fisher精确检验对断裂模式在0.05显著性水平下进行统计学分析。
24小时后，有斜面的修复体比无斜面的修复体表现出更高的抗折强度值，且与完好牙齿的抗力相似。6个月后，有斜面的修复体仍比无斜面的修复体表现更好。热循环和水储存降低了大多数组的抗折强度。粘结失败主要见于无斜面的修复体，而有斜面的修复体则主要为混合性失败。
在本研究的局限性范围内，得出以下结论：热循环储存会降低抗折强度，制备斜面可提高抗折强度，间接修复体的抗折强度与直接修复体相似。
