Effect of silane and MDP-based primers on physico-chemical properties of zirconia and its bond strength to resin cement.

OBJECTIVE: To evaluate the effect of surface treatments on yttria-tetragonal zirconia polycrystal (Y-TZP) characteristics and on resin-mediated zirconia bond. METHODS: Y-TZP slabs were grit blasted with 45mum alumina or with 30mum silica-coated alumina particles. The chemical treatments were: no-chemical treatment (NC), silane-containing primer (SP), MDP (10-Methacryloyloxydecyl dihydrogen phosphate) and silane-containing primer (MPS), MDP-containing primer (MP) and MDP and silane-containing adhesive (MPA). Contact angle as a function of surface roughness (theta(m)) and surface roughness parameter (Sdr) were measured using Fringe Projection Phase Shifting (FPPS). Surface free energy (gamma(s)(TOT)) was calculated with a goniometer. Chemical interaction between primers/adhesive and zirconia was analyzed using time-of-flight secondary ion mass spectrometry (ToF-SIMS). Resin cement microshear bond strength (muSBS) was analyzed at either 24-h or 8-months water storage (37 degrees C). theta(m) values, Sdr values, gamma(s)(TOT) and muSBS values were analyzed using Analysis of variance (ANOVA) and post hoc Tukey test (alpha=0.05). RESULTS: Chemical treatment had an effect (p<0.001) on all surface parameters analyzed: theta(m), gamma(s)(TOT) and Sdr. MP-treated group showed higher incidence of P-O-Zr bonds than the other groups, indicating more chemical linkages. Grit blasting (p<0.001) and the interaction chemical treatment*storage (p<0.001) did not affect muSBS; all silane-containing primers showed significant drop in muSBS after aging. SIGNIFICANCE: MDP and/or silane-based solutions affect the physicochemical properties of blasted-zirconia. An MDP-based primer is fundamental to achieve a stable resin-zirconia bonding, but the chemical reactivity of MDP is impaired when this molecule is present in a multicomponent system.