Effect of acid etching on tridimensional microstructure of etchable CAD/CAM materials

Objective: Evaluate if etching protocols affect superficial/internal microstructural integrity of CAD/CAM ceramic materials. Methods: Sixty blocks (3x3x3mm) of IPS/Empress-LEU, IPS/e.max-LDC (Ivoclar-Vivadent) and Enamic-PIC (VITA) were used. Lateral surfaces from each block were isolated with Teflon strip and petroleum jelly to keep them untouched. Specimens were distributed into 6 groups (n=10): 1. no treatment (C); 2. hydrofluoric acid (HF) 5%, 20s (HF5%20s); 3. HF5%60s; 4. HF10%20s; 5. HF10%60s; 6. Monobond Etch&Prime (MBEP). Surface roughness (Sa) and 3D profile were obtained using a confocal-laser-optical-microscope (LEXT OLS 4000, Olympus), while element ratios (Si/K for LEU and LDC; Si/C for PIC) were recorded using energy dispersive spectroscopy (EDS). Superior (treated) and lateral (non-treated) surfaces were analyzed using scanning electron microscopy (SEM) (JSM 5600 LV, JEOL). Etching depth was measured on lateral surfaces. Data were submitted to ANOVA-One-Way and Tukey test (alpha=0.05). Results: For LEU, only HF10% treatments produced statistically different roughness values and Si/K ratios compared to C group. Regarding LDC and PIC, groups HF5%60s and HF10% showed higher roughness values than C group. In the case of PIC, all treatments (except MBEP) produced lower Si/C ratios than C group. All treatments (except MBEP) produced higher etching depth values than C group for all materials, being HF10%60s the highest (LEU:403.2 +/- 11.4 mu m; LDC:617.4 +/- 75.7; PIC:291.6 +/- 6.5 mu m). HF10% produced more aggressive etching morphology patterns on superior and lateral surfaces (SEM). Treatments MBEP and HF5%20s, produced the least aggressive structural alterations. Acid etching produces superficial and internal alterations on ceramics' structural configuration. Significance: Aggressive etching protocols of glass-ceramics may cause internal material loss, consequently, milder etching is recommended to treat those materials before adhesion procedures. (C) 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.