Different Etching Times of a One-step Ceramic Primer: Effect on the Resin Bond Strength Durability to a CAD/CAM Lithium-Disilicate Glass-Ceramic.

Abstract

To evaluate the effect of different etching times of a self-etching ceramic primer on the microshear bond strength (µSBS) and topographic surface pattern of a lithium-disilicate glass-ceramic. Ceramic slices were subjected to an in-lab simulation of CAD/CAM milling and randomly allocated to 10 groups (n = 35) considering two factors: "surface treatment" in 5 levels - one control group (5% hydrofluoric acid + silane application [HF5+SIL]), and 4 experimental groups using ceramic etching/primer (Monobond Etch & Prime, E&P) with different passive application times (40 s, 2 min, 5 min, or 10 min); and "aging" factor in 2 levels - short-term (after 24 h), or long-term (storage for 180 days + 12,000 thermal cycles). Composite cement cylinders were built and µSBS tests were run in a universal testing machine. The failure patterns were categorized, and complementary analyses with SEM and Atomic Force Microscopy (AFM) were performed. The groups showed statistically similar bond strengths in the short term (range 22.4 to 25.1 MPa). However, only the E&P 20s+40s (19.3 MPa) and E&P 20s+5min (21.5 MPa) groups maintained stable bond strength in the long term, and HF5+SIL (17.1 MPa) presented statistically significantly lower values than did E&P 20s+5min. The failure pattern was predominantly adhesive. The increased application time of the ceramic primer promoted greater dissolution of the glass matrix; thus, the E&P 20s+10min group presented the most complex surface characteristics in the fractal dimension analysis. The self-etching ceramic primer can be used as an alternative to classical conditioning with HF plus silane, promoting stable bond strength for etching times of 40 s or 5 min of passive application.