Influence of hydrofluoric acid etching time and concentration on shear bond strength of metal brackets to ceramic surfaces

Abstract Introduction Surface treatment prior to bonding ceramic brackets with hydrofluoric acid is indicated because of its ability to promote morphological changes necessary for adhesion. Objective To evaluate the shear bond strength (RUC) of metal brackets bonded to the feldspar ceramic surface under the action of hydrofluoric acid (AF), in different concentrations (5% and 10%) and different application times (30 and 60 seconds). Material and method Four nickel-chrome metal blocks that received an application of feldspathic ceramic were used, to which 80 metal brackets (Abzil/3M) were bonded and divided into 4 Groups (n=20) according to the acid etching procedure. The blocks were etched with 5% hydrofluoric acid for 30 and 60 seconds (AF5/30 and AF5/60, respectively) and 10% hydrofluoric acid for 30 and 60 seconds (AF10/30, AF10/60, respectively). The resin composite used was Transbond XT (3M) and the presence of a glazer was maintained on the ceramic surface. The specimens were placed on a Universal test machine Instron 4411 (Instron Corp, USA) to which a chisel was adapted to perform the shear test at a speed of 1mm/min. The data were submitted to the analysis of variance (ANOVA) and the Adhesive Remnant Index was evaluated. Result In the time interval of 30 seconds, there was no significant difference for the 5% and 10% hydrofluoric acid concentrations. In the 60-second time interval, the 10% concentration showed significantly higher shear bond strength values (p<0.05). The ARI showed predominance of scores 1 and 2. Conclusion It was concluded that 10% hydrofluoric acid showed higher shear bond strength values in 60 seconds of etching, while 5% hydrofluoric acid showed no significant difference between the etching times.

摘要 采用氢氟酸（hydrofluoric acid, AF）进行陶瓷托槽粘结前表面处理具有临床适应证，因其可促进粘结所需的表面形貌改变。本研究旨在评估不同浓度（5%、10%）氢氟酸（AF）作用不同时长（30秒、60秒）时，粘结于长石质陶瓷表面的金属托槽的抗剪切粘结强度（shear bond strength, RUC）。材料与方法：本研究使用4块镀有长石质陶瓷的镍铬金属块，共粘结80个金属托槽（Abzil/3M公司生产），并根据酸蚀流程分为4组（每组n=20）。具体分组为：5%氢氟酸分别作用30秒（AF5/30）、60秒（AF5/60）；10%氢氟酸分别作用30秒（AF10/30）、60秒（AF10/60）。本研究采用Transbond XT（3M公司）树脂复合材料作为粘结剂，且保留陶瓷表面原有釉层。将试件置于美国英斯特朗公司（Instron Corp, USA）生产的Instron 4411型万能试验机上，加装凿子夹具以1mm/min的加载速度开展抗剪切试验。采用方差分析（analysis of variance, ANOVA）对数据进行统计学处理，并对粘结残留指数（Adhesive Remnant Index, ARI）进行评估。结果：在30秒作用时长下，5%与10%浓度氢氟酸组的抗剪切粘结强度无显著差异；在60秒作用时长下，10%浓度氢氟酸组的抗剪切粘结强度显著更高（p<0.05）。粘结残留指数（ARI）评分以1分和2分为主。结论：本研究结果表明，60秒酸蚀时长下，10%浓度氢氟酸可获得更高的抗剪切粘结强度；而5%浓度氢氟酸在不同酸蚀时长下的抗剪切粘结强度无显著差异。