Treatment of surface contamination of lithium disilicate ceramic before adhesive luting

To evaluate the effect of different contamination media and cleaning regimens on the adhesion of resin cement to lithium disilicate ceramic.

Specimens (IPS e.max CAD) (n =15 per group) were etched with 5% hydrofluoric acid gel. While half of the specimens were silanized after etching, the other half was left etched only. After contamination with either saliva or dental stone, they were further divided into four subgroups depending on the cleaning regimens: water rinsing only (WR), 80% ethanol (E), 37% phosphoric acid (PA), cleaning gel (CG). All specimens were re-silanized, coated with adhesive resin (Heliobond) and resin cement (Variolink II) was bonded. After thermocycling (5.000x, 5-55°C), ceramic-cement interface was loaded under shear (1 mm/minute) and failure types were classified. Data (MPa) were analyzed using 3-way ANOVA, Dunnett-T3 tests and Weibull moduli were calculated.

Saliva contamination (4.7±2.2-15.4±2.7) resulted in significantly lower bond strength compared to dental stone (17.8±4.8-23.6±2.7). Silanization before contamination showed protective effect especially for saliva (20.1±4.5-24.7±3.9) compared to non-silanized groups (4.7±2.2-15.4±2.7). Weibull modulus was the lowest for saliva-contaminated groups after cleaning with WR (2.22, 5.01) or E (1.14, 5.77) without and with initial silanization, respectively. Adhesive failures (272 out of 285) were commonly observed in all groups. Saliva contamination decreased the adhesion of luting cement to lithium disilicate ceramic considerably more than dental stone contamination, but silanization prior to try-in prevented deterioration in adhesion.

Preliminary silanization of hydrofluoric acid etched lithium disilicate ceramic prior to saliva or dental stone contamination re-established resin luting cement adhesion, irrespective of the cleaning regimen used.