Hydrofluoric acid concentration, time and use of phosphoric acid on the bond strength of feldspathic ceramics

Abstract The objective of this study was to evaluate the influence of hydrofluoric acid (HF) concentration, etching time, and application of phosphoric acid (PA) followed by neutralization with sodium bicarbonate on the bond strength between a feldspar ceramic and resin cement. Thus, 80 blocks (10 x 12 x 2 mm) of glass ceramic (VM - Vita Mark II - Vita Zahnfabrik) were made and randomly assigned to eight groups (n = 10) according to the factors: HF concentration (5 and 10%), etching time (60 and 120 s), and use of phosphoric acid (PA) (with and without). According to the experimental group, 37% PA (Condac, FGM) was applied after HF etching for 60s. Afterwards, samples were immersed in sodium bicarbonate for 1 min then in an ultrasonic bath in distilled water (5 min) for cleaning. After surface bonding treatment, cylinders (Ø = 2 mm; h = 2 mm) of dual resin cement (AllCem / FGM) were made in the center of each block. The samples were then stored in water (37ºC) for 90 days and submitted to the shear bond test (50 KgF, 1 mm/min). Failure analysis was performed by stereomicroscope and scanning electron microscopy. Data (MPa) were analyzed with 3-way ANOVA and Tukey’s test. Only the factor “HF concentration” was significant (p = 0.02). Most failures were of cohesive in ceramic (40%) and mixed types (42.5%). The 10% HF resulted in higher shear bond strength value than the 5% HF. Surface cleaning with phosphoric acid followed by sodium bicarbonate and HF time (60 or 120 seconds) did not influence the resin bond strength to feldspar ceramic.

摘要 本研究旨在评估氢氟酸(hydrofluoric acid, HF)浓度、酸蚀时间，以及先使用磷酸(phosphoric acid, PA)再以碳酸氢钠中和这一预处理流程，对长石陶瓷(feldspar ceramic)与树脂水门汀(resin cement)之间粘结强度的影响。为此，制备了80块尺寸为10×12×2 mm的玻璃陶瓷(glass ceramic)试样（VM - Vita Mark II - Vita Zahnfabrik），并根据以下三个因素随机分为8组（每组n=10）：HF浓度（5%与10%）、酸蚀时间（60 s与120 s），以及是否采用磷酸预处理（是/否）。针对实验组，先以37%浓度的磷酸（Condac，FGM）对经HF酸蚀60 s的试样表面进行处理。随后将试样置于碳酸氢钠溶液中浸泡1 min，再放入盛有蒸馏水的超声清洗槽中超声清洗5 min以完成表面清洁。表面处理完成后，在每块试样的中心制备双固化树脂水门汀(AllCem / FGM)圆柱体试样（直径=2 mm；高度=2 mm）。将所有试样置于37℃去离子水中老化90天后，采用载荷上限50 KgF、加载速率1 mm/min的剪切粘结强度测试进行力学性能评估。采用体视显微镜(stereomicroscope)与扫描电子显微镜(scanning electron microscopy)对试样的失效模式进行分析。以兆帕（MPa）为单位的试验数据采用三因素方差分析（3-way ANOVA）与Tukey多重比较检验进行统计学分析。结果显示仅“HF浓度”这一因素对粘结强度存在显著影响（p=0.02）。试样的失效模式以陶瓷内聚破坏（40%）与混合破坏（42.5%）为主。10% HF酸蚀组的剪切粘结强度显著高于5% HF酸蚀组。经磷酸预处理后辅以碳酸氢钠中和的表面处理方式，以及HF酸蚀时长（60 s或120 s），均未对长石陶瓷与树脂水门汀的粘结强度产生显著影响。