The effect of hydrofluoric acid and resin cement formulation on the bond strength to lithium disilicate ceramic

Abstract To investigate how the hydrofluoric acid (HF) concentrations applied to a lithium disilicate glass-ceramic (EMX) affects the surface morphology and microtensile bond strength (μTBS) of ceramics to dentin, using light-cured resin cements with or without UDMA. Sixty-three EMX square ceramic blocks were etched for 20 seconds using different HF concentrations (1%, 5% and 10%) and luted to dentin using two types of resin cement combinations: BisGMA/TEGDMA and BisGMA/TEGDMA/UDMA (n = 10). Each bonded EMX-dentin block was sectioned to obtain 1 mm2 sticks for μTBS evaluation. Half of the sticks were tested after 24 hours and the other half was assessed after 6 months of water storage. Data were statistically assessed using split-plot three-way ANOVA and multiple comparisons were performed using the Tukey's post hoc test (α = 0.05). One EMX sample from each HF concentration was analyzed using field-emission scanning electron microscope (FE-SEM) to characterize the etching pattern. According to the FE-SEM images, increasing the concentration of HF from 1 to 5 and then to 10% led to increased removal of glassy matrix and greater exposure of lithium disilicate crystals. The 10% HF concentration yielded higher μTBS when compared to 1% for BisGMA/TEGDMA formulation (p < 0.05); whereas HF 1% and 5% showed similar μTBS values when compared to 10% HF for BisGMA/TEGDMA/UDMA resin matrix (p > 0.05) at both storage times. Water aging decreased the μTBS values (p < 0.05), except when 10% HF was associated with BisGMA/TEGDMA resin cement. Resin cement formulation and hydrofluoric acid concentrations can interfere with the immediate and long-term glass-ceramic bond strength to dentin.

摘要 为探究氢氟酸（HF）浓度对二硅酸锂玻璃陶瓷（EMX）表面形貌及其与牙本质的微拉伸粘结强度（μTBS）的影响，本研究采用含或不含氨基甲酸酯二甲基丙烯酸酯（UDMA）的光固化树脂水门汀开展实验。本研究制备63块EMX方形陶瓷块，分别使用1%、5%、10%三种浓度的HF溶液蚀刻20秒，随后采用两种树脂水门汀体系将陶瓷粘接于牙本质表面：双酚A二甲基丙烯酸缩水甘油酯/三乙二醇二甲基丙烯酸酯（BisGMA/TEGDMA），以及双酚A二甲基丙烯酸缩水甘油酯/三乙二醇二甲基丙烯酸酯/氨基甲酸酯二甲基丙烯酸酯（BisGMA/TEGDMA/UDMA），每组样本量n=10。将每一块粘接完成的EMX-牙本质试件切割为1 mm²的粘结试条，用于微拉伸粘结强度测试。其中一半试条于粘接后24小时进行强度测试，剩余一半经6个月水老化储存后开展检测。采用裂区设计三因素方差分析对实验数据进行统计学评估，并通过Tukey事后检验进行多重比较（检验水准α=0.05）。选取每种HF浓度对应的EMX试件各1块，采用场发射扫描电子显微镜（FE-SEM）观察其蚀刻后的表面形貌特征。场发射扫描电子显微镜结果显示，随着HF浓度从1%提升至5%，再升至10%，陶瓷表面玻璃基质的去除程度逐渐升高，二硅酸锂晶体的暴露量也随之增加。对于BisGMA/TEGDMA树脂水门汀体系，10% HF蚀刻组的微拉伸粘结强度显著高于1% HF组（p<0.05）；而对于BisGMA/TEGDMA/UDMA树脂水门汀体系，在两种储存时间下，1%、5% HF组与10% HF组的粘结强度均无统计学差异（p>0.05）。水老化储存会显著降低试件的微拉伸粘结强度（p<0.05），但当采用10% HF蚀刻并搭配BisGMA/TEGDMA树脂水门汀时，该效应并未出现。综上，树脂水门汀配方与氢氟酸浓度均可影响玻璃陶瓷与牙本质的即刻及长期粘结强度。