Effect of hydrofluoric acid concentration and etching time on resin-bond strength to different glass ceramics

Abstract: The objective of this study was to evaluate the effect of the hydrofluoridric acid (HF) concentration and time of acid conditioning on bond strength of three glass ceramics to a resin cement. Thus, fifty blocks (10 mm x 5 mm x 2 mm) of each ceramic (LDCAD: IPS e.max CAD; LCAD: IPS Empress CAD and LDHP: IPS e.max Press) were made and embedded in acrylic resin. The surfaces were polished with sandpaper (#600, 800, 1000, and 1200 grits) and blocks were randomly divided into 15 groups (n = 10) according to the following factors: Concentration of HF (10% and 5%), conditioning time (20 s and 60 s) and ceramic (LDCAD, LDHP, and L). After conditioning, silane (Prosil / FGM) was applied and after 2 min, cylinders (Ø = 2 mm; h = 2 mm) of dual resin cement (AllCem / FGM) were made in the center of each block using a Teflon strip as matrix and light cured for 40 s (1,200 mW/cm2). Then, the samples were thermocycled (10,000 cycles, 5/55°C, 30s) and submitted to the shear bond test (50 KgF, 0.5 mm/min). The data (MPa) were analyzed with 3-way ANOVA and Tukey's test (5%). Failure analysis was performed using a stereomicroscope (20x) and a scanning electron microscope (SEM). ANOVA revealed that the “concentration” factor (p = 0.01) and the interaction “acid concentration X ceramic” (p = 0.009) had a significant effect, however, the “ceramic” (p = 0.897) and “conditioning time” (p = 0.260) factors did not influence the results. The LDHP10`s (10.98 MPa)aA* group presented significantly higher bond strength than LDHP10 s (6.57 MPa)bA, LCAD5 s (6,90 ±3,5)aB and LDHP5`s (5.66 ± 2,9MPa)aA* groups (Tukey). Failure analysis revealed that 100% of specimens had mixed failure. In conclusion, etching with 5% HF for 20 seconds is recommended for lithium disilicate and leucite-reinforced CAD/CAM ceramics. However, for pressed lithium disilicate ceramic, 10% HF for 60 s showed significantly higher bond strength to resin cement.

摘要：本研究旨在评估氢氟酸（hydrofluoridric acid, HF）浓度与酸蚀处理时长，对三种玻璃陶瓷与树脂水门汀粘结强度的影响。为此，我们制备了每种陶瓷的50个试样块（尺寸为10 mm × 5 mm × 2 mm），分别为锂二硅酸盐CAD陶瓷（LDCAD：IPS e.max CAD）、白榴石增强CAD陶瓷（LCAD：IPS Empress CAD）以及压制型锂二硅酸盐陶瓷（LDHP：IPS e.max Press），并将其包埋于丙烯酸树脂中。采用粒度为600、800、1000、1200目的砂纸对试样表面进行抛光，随后根据以下三个因素将试样随机分为15组（每组n=10）：氢氟酸浓度（10%与5%）、酸蚀时长（20 s与60 s）以及陶瓷类型（LDCAD、LDHP及LCAD，原文此处为笔误，结合前文应为LCAD）。酸蚀处理完成后，涂布硅烷偶联剂（Prosil / FGM），2分钟后，使用特氟龙条作为成型模具，在每个试样块的中心制备双固化树脂水门汀（AllCem / FGM）圆柱试样（直径Ø=2 mm，高度h=2 mm），并进行40秒的光固化（光照强度为1200 mW/cm²）。随后将试样进行热循环处理（10000个循环，温度区间为5℃至55℃，单循环时长30 s），随后开展剪切粘结强度测试（加载载荷为50千克力，加载速率为0.5 mm/min）。测试所得数据（单位为MPa）采用三因素方差分析（3-way ANOVA）与Tukey多重比较检验（显著性水平为5%）进行统计分析。采用体式显微镜（放大倍数20×）与扫描电子显微镜（scanning electron microscope, SEM）开展失效模式分析。方差分析结果显示，“氢氟酸浓度”因素（p=0.01）以及“酸蚀浓度×陶瓷类型”的交互作用（p=0.009）对粘结强度存在显著影响；而“陶瓷类型”（p=0.897）与“酸蚀时长”（p=0.260）因素对实验结果无显著影响。其中，LDHP 10 s组（10.98 MPa）aA*的粘结强度显著高于LDHP 10 s组（6.57 MPa）bA、LCAD 5 s组（6.90 ± 3.5 MPa）aB以及LDHP 5 s组（5.66 ± 2.9 MPa）aA*组（Tukey检验结果）。失效模式分析显示，所有试样均出现混合失效模式。综上，对于锂二硅酸盐与白榴石增强型CAD/CAM陶瓷，推荐采用5%氢氟酸酸蚀20秒。但对于压制型锂二硅酸盐陶瓷，采用10%氢氟酸酸蚀60秒可显著提升其与树脂水门汀的粘结强度。