Effect of Hydrofluoric Acid Concentration and Thermal Cycling on the Bond Strength of Brackets to Ceramic

Abstract This study to evaluate the effects of different hydrofluoric acid (HF) concentrations and thermal cycling on the shear bond strength (SBS) of brackets to ceramic. Cylinders of ceramic were divided into 10 groups (n=15), according to HF concentrations: 1-1%;2-2.5%;3-5%;4-7.5%;5-10% (storage 24 h); 6-1%;7-2.5%;8-5%;9-7.5%; and, 10-10% (thermal cycling). All cylinders were etched for 60s and received one layer of silane. Metallic brackets were bonded to the cylinders using Transbond-XT, light activated for 40 s, using a LED (Radii Plus) and stored in deionized water at 37o C for 24h. The groups 6 to 10 were submitted to thermal cycling (7,000 cycles - 5o/55oC). SBS was performed in an Instron at crosshead speed of 1.0 mm/min. Data were submitted to two-way ANOVA and Tukey’s post-hoc test (α=0.05). The Adhesive Remaining Index (ARI) was evaluated at 40x magnification. The different HF acid concentrations influenced on the SBS of the brackets to ceramic (p<0.05). The thermal cycling decreased the SBS of the brackets to ceramic for all acid concentrations (p<0.05). The ARI showed a predominance of scores 0 for all groups, with an increase in scores 1, 2 and 3 for the group storage for 24 h. In conclusion, the different HF acid concentrations 5.0%, 7.5% and 10% influenced on the SBS of brackets to ceramic. The thermal cycling decreased significantly the SBS of brackets to ceramic.

摘要 本研究旨在评估不同浓度氢氟酸（HF）及热循环处理对陶瓷托槽剪切粘结强度（SBS）的影响。研究将陶瓷圆柱试样按氢氟酸浓度分为10组（每组n=15）：第1组为1%浓度、第2组为2.5%浓度、第3组为5%浓度、第4组为7.5%浓度、第5组为10%浓度（仅浸泡24小时）；第6组为1%浓度、第7组为2.5%浓度、第8组为5%浓度、第9组为7.5%浓度、第10组为10%浓度（需进行热循环处理）。所有试样均经60秒酸蚀处理，并涂覆一层硅烷偶联剂。采用Transbond-XT粘接剂将金属托槽粘接于陶瓷圆柱试样上，使用型号为Radii Plus的发光二极管（LED）固化灯进行40秒光固化，随后将试样置于37℃去离子水中浸泡24小时。其中第6至10组需接受7000次热循环处理（温度区间为5℃至55℃）。采用Instron万能试验机以1.0mm/min的十字头加载速度开展剪切粘结强度测试。实验数据采用双因素方差分析（two-way ANOVA）及Tukey事后检验进行统计分析（显著性水平α=0.05）。采用40倍放大倍率评估粘结残留指数（Adhesive Remaining Index，ARI）。

不同氢氟酸浓度对陶瓷托槽的剪切粘结强度存在显著影响（p<0.05）。热循环处理可显著降低所有氢氟酸浓度组的陶瓷托槽剪切粘结强度（p<0.05）。粘结残留指数结果显示，所有组别均以0分占主导，但仅浸泡24小时的组别中，1、2、3分的占比有所提升。

综上，5.0%、7.5%及10%浓度的氢氟酸处理可显著影响陶瓷托槽的剪切粘结强度；热循环处理可显著降低陶瓷托槽的剪切粘结强度。