Adhesion to Ceramic Blocks for CAD/CAM Following Hydrofluoric Acid Treatments

Objectives: This study investigated the effect of different concentrations of hydrofluoric acid (HF) on shear bond strength (SBS) of two ceramic blocks for CAD/CAM.
Methods: Two ceramic blocks for CAD/CAM were tested: IPS e.max CAD (Ivoclar Vivadent) and Suprinity (Vita Zahnfabrik). Ten experimental groups were tested: untreated, sandblasted with Al₂O₃, etching with 10% or 5% hydrofluoric acid (HF) for 60s or 20s followed or not by 37% phosphoric acid (H₃PO₄) cleaning. Silicon molds were positioned over treated ceramic block surfaces and a resin cement (RelyX Veneer, 3M ESPE) was placed into hole of molds to form a resin cylinder (1.5mm diameter and 1.0mm height) after light activation (n=5). Ceramic blocks were stored in distilled water for 24h and tested in universal testing machine (1.0mm/min). SBS data were analyzed by two-way ANOVA and Tukey test (α=0.05).
Results: Untreated ceramics yielded the lowest SBS. For IPS e.max CAD, 5% and 10% HF for 20s without H₃PO₄ produced higher SBS, while for Suprinity different HF concentrations and times resulted in higher SBS.
Conclusions: Specific HF concentrations and times can be indicated to prepare IPS e.max CAD and Suprinity for bonding. Cleaning of etched ceramics with H₃PO₄ was not beneficial for both ceramics.