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

Purpose: 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.

Materials and methods: 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.

Results: 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.

Conclusion: 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.