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.

摘要与引言：采用氢氟酸对陶瓷托槽粘接前的待粘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表面形貌变化。
目的：评估不同浓度（5%、10%）氢氟酸（hydrofluoric acid，AF）作用不同时长（30秒、60秒）时，金属托槽与长石陶瓷表面间的剪切粘结强度（shear bond strength）。
材料与方法：本研究使用4块表面涂布长石陶瓷的镍铬金属块，粘接80个金属托槽（Abzil/3M），并根据酸蚀流程分为4组（每组n=20）。各组分别采用以下处理：5%氢氟酸（AF5）分别作用30秒（AF5/30）、60秒（AF5/60），10%氢氟酸（AF10）分别作用30秒（AF10/30）、60秒（AF10/60）。粘接所用树脂复合材料为Transbond XT（3M），且陶瓷表面保留原有釉层。将试样置于适配凿形夹具的美国Instron公司Instron 4411型万能试验机上，以1mm/min的加载速度开展剪切强度测试。采用方差分析（analysis of variance，ANOVA）对数据进行统计分析，并评估残留粘结剂指数（Adhesive Remnant Index，ARI）。
结果：当酸蚀时长为30秒时，5%与10%浓度氢氟酸组的剪切粘结强度无显著差异；当酸蚀时长为60秒时，10%浓度氢氟酸组的剪切粘结强度显著更高（p<0.05）。残留粘结剂指数以1分和2分占主导地位。
结论：本研究结果表明，10%浓度氢氟酸酸蚀60秒时可获得更高的剪切粘结强度，而5%浓度氢氟酸的不同酸蚀时长组间剪切粘结强度无显著差异。