Dentin-Ceramic Bonding: Sodium Ascorbate and Time Effect after Non-Vital Bleaching

Objectives: To evaluate the effects of the elapsed time (ET) after non-vital bleaching (NVB) and 10% sodium ascorbate application (SAA) on shear bond strength (SBS) of dentin to ceramic. The null hypothesis was that neither the ET nor the SAA effect the SBS. Methods: Eighty bovine incisors were selected. Sixty teeth were bleached (35% carbamine peroxide) for 9 days and submitted to the following treatments(n=10): Gr1, Gr2, Gr3- luting after 1, 7 and 14 days, respectively; Gr4, Gr5, Gr6- luting after SAA, 1, 7 and 14 days, respectively. Gr7 and Gr8 were not bleached: Gr7- luting 24h after access cavity sealing; Gr8- luting after SAA 24h after access cavity sealing. After NVB, the teeth had their buccal dentin exposed and flattened. The SAA was done on dentin (Gr4, Gr5, Gr6, Gr8) for 10min, washed and dried. A circular enclosed dentin area of each tooth was hybridized (37% phosphoric acid). The adhesive system (Single Bond 2) was applied and light cured. Feldspathic ceramic discs (VM7; 4x3mm) were luted with dual resin cement (RelyX ARC), under 750g load and light cured. After storage in water (24h, 37°C), samples were submitted to shear test on a universal testing machine. The data (MPa) were submitted to ANOVA and Dunnet's test (5%). Results: The means (±SD) obtained were: Gr1(14±4.5), Gr2(14.6±3.1), Gr3(14±3.7), Gr4(15.5±4.6), Gr5(20±4.5), Gr6(16.5±3.7), Gr7(22.8±6.2) and Gr8(18.9±5.4). The effect of the SAA on SBS was statistically significant (p=0.0054). The difference among the SBS values for 1, 7 and 14 days elapsed time before cementation were not statistically significant (p=0.1519). Gr5 and Gr6 presented higher values than the others bleached groups (p<0.05) and similar values to Gr7 (p>0.05). The null hypothesis was partially accepted. Conclusions: After NVB, the adhesive luting to dentin is recommended after seven days if SAA has been done prior dentin hybridization.