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 引言：采用氢氟酸（hydrofluoric acid）对陶瓷托槽粘接前的陶瓷表面进行预处理是临床推荐的操作，因其可诱导产生粘接所需的形态学改变。目的：评估氢氟酸（hydrofluoric acid，简称AF）在不同浓度（5%、10%）及不同作用时长（30秒、60秒）条件下，金属托槽粘接于长石质陶瓷表面的剪切粘结强度（shear bond strength，原文缩写RUC）。材料与方法：本研究制备4块涂覆有长石质陶瓷的镍铬金属块，粘接80个金属托槽（Abzil/3M），并根据酸蚀方案分为4组（每组n=20）。各组分别采用以下处理：5%氢氟酸蚀刻30秒（AF5/30）、5%氢氟酸蚀刻60秒（AF5/60）、10%氢氟酸蚀刻30秒（AF10/30）、10%氢氟酸蚀刻60秒（AF10/60）。所用粘接复合树脂为Transbond XT（3M），且陶瓷表面保留原有釉层。将试样置于英斯特朗4411型万能试验机（美国英斯特朗公司，Instron Corp）上，加装凿形夹具，以1mm/min的加载速率开展剪切试验。采用方差分析（analysis of variance，ANOVA）对试验数据进行统计分析，并评估粘结残留指数（Adhesive Remnant Index，简称ARI）。结果：蚀刻时长为30秒时，5%与10%浓度氢氟酸组的剪切粘结强度无显著差异；蚀刻时长为60秒时，10%浓度氢氟酸组的剪切粘结强度显著更高（p<0.05）。粘结残留指数以1分和2分占主导地位。结论：本研究结果表明，10%浓度氢氟酸蚀刻60秒时可获得更高的剪切粘结强度，而5%浓度氢氟酸的不同蚀刻时长之间无显著差异。