Can different etching protocols change the properties of a hybrid ceramic?

The aim of this study was to evaluate the effects of different concentrations of hydrofluoric acid (HF) and etching times on the flexural strength, roughness, wettability, and type of failure of a hybrid ceramic (VITA ENAMIC). Blocks of the ceramic material were made according to the norms of International Organization for Standardization standard 6872:2015 and randomly divided into 7 groups (n = 13): control (no treatment); surface etching with 5% HF for 30 (HF5-30), 60 (HF5-60), or 90 (HF5-90) seconds; and surface etching with 10% HF for 30 (HF10-30), 60 (HF10-60), or 90 (HF10-90) seconds. The adhesive surface of 10 specimens in each group was cemented with dual-curing resin cement. The specimens were submitted to biaxial flexural tests and fractographic analysis. Surface analyses were carried out using 3 noncemented specimens from each group. The surface roughness was evaluated through optical profilometry and the surface wettability through goniometry (contact angle). The values obtained were analyzed by a Dunnett test followed by 2-way analysis of variance and Tukey test (α = 5%). The flexural test results indicated a statistically significant reduction in the resistance of the ceramic when conditioned with 10% acid (P < 0.01). Etching with HF, at any concentration used for any applied time, significantly modified the ceramic roughness of the experimental groups (P < 0.01). The wettability was also significantly altered in the HF5-90 group and in all HF10 groups (P < 0.01). The higher the concentration of the acid, the lower the wettability of the ceramic (P < 0.01). Based on these results, a 5% HF concentration is best indicated for the surface treatment of VITA ENAMIC.