STABILITY OF THE BOND BETWEEN TWO RESIN CEMENTS AND AN YTTRIA-STABILIZED ZIRCONIA CERAMIC AFTER SIX MONTHS OF AGING IN WATER

Statement of the problem. The behavior of the luting cement and the cementation protocol are essential in the clinical success of ceramic restorations. Purpose. The purpose of this study was to evaluate the bond stability of 2 resin cements and a yttria-stabilized tetragonal polycrystalline zirconia (Y-TZP) ceramic submitted to 2 surface treatments. Material and methods. Sixty plates of a Y-TZP ceramic were assigned to 3 groups according to the surface treatments: control, as sintered surface; methacryloxydecyl dihydrogen phosphate (MDP), coated with an MDP-based primer, and tribochemical silica-coating (TSC), coated with tribochemical silica. The plates of each group were further divided into 2 subgroups according to the resin cement as follows: RelyX adhesive resin cement (conventional) and RelyX Unicem (self-adhesive). Cylinders of resin cements (circle divide=0.75 mm x 0.5 mm in height) were built up on the ceramic surFaces, and the plates stored in distilled water at 37 C for either 24 hours or 6 months before being submitted to a microshear bond strength test. The data were submitted to 3-way ANOVA and the Tukey honestly significant difference test (alpha=.05). Results. Three-way ANOVA showed statistical significance for the 3 independent factors: resin cement, surface treatment, and period of water immersion (P<.001). Unicem presented the highest microshear bond strength after 24 hours (MDP, 37.4 +/- 2.3 and TSC, 36.2 +/- 2.1 MPa). Except for RelyX adhesive resin cement applied on ceramic surfaces treated with TSC, the microshear bond strength of all the other groups decreased after 6 months of aging in water. The microshear bond strength decreased most in the control groups (-81.5% for ARC and -93.1% for Unicem). In the group treated with TSC, the microshear bond strength for Unicem decreased by 54.8% and in that treated with MDP-based primer by -42.5%. In the group treated with MDP-based primer, the microshear bond strength for RelyX ARC decreased by -52.8%. Conclusions. Irrespective of surface treatments, self-adhesive resin cement was not able to maintain the bond to Y-TZP ceramic after 6 months of aging in water.