Efeito de diferentes concentrações de ascorbato de sódio na resistência de união ao esmalte clareado

Abstract

After completing the tooth bleaching, reaction products remain in the tooth structure not allowing the correct polymerization of adesives restorations. The purpose of this study was to investigate the antioxidants effects of sodium ascorbate hydrogel on the residual oxygen in the bovine enamel structure bleached with hydrogen peroxide and after restorated with composite resin. One hundred and twenty bovines teeth were divided into twelve groups (n: 10), the groups G1;G2;G3;G4;G5;G6 were subjected to a test of shear strength after one week, the groups G7;G8;G9;G10;G11;G12 were tested after six months (aged), being G1; G7 - restored without bleaching ; G2; G8 - bleached and restored after fourteen days; G3; G9 - bleached and restored at the same day; G4; G10 - bleached, treated with sodium ascorbate hydrogel of 10% and restored; G5; G11 - bleached, treated with sodium ascorbate hydrogel of 20% and restored and G6; G12 - bleached, treated with sodium ascorbate hydrogel of 40% and restored. The results of the shear test were subjected to two ANOVA’s criteria and Tukey's analysis to compare the scores (p≤ 0,05). The groups G1: 152,6N +- 21,2; G2: 183,2N +- 31,4; G5: 171,53N +- 20,6; G6: 179,9N +- 33,1 showed similar resistance to shear and the groups G3: 99,3N +- 33,9; G4: 101,3N +- 29,3 were statistically significant lower resistance. The second group had lower shear resistance, however maintained the same pattern of statistical difference between the groups. The aged groups G7: 98,1 +- 22,6; G8: 111,9 +- 34,0; G11: 91,9 +- 24,0; G12: 90,0 +- 13,1 showed lower shear resistance when compared to the non-aged. However, when compared between the aged, as well as between no-aged, the groups G9: 59,3 +- 19,9; G10: 59,7 +- 10,9 also showed lower resistance when compared to the others groups. We can conclude that the tooth bleaching with 35% hydrogen peroxide promoted reduction of the bond strength. In addition, treatment of the bleached enamel with 20% and 40% sodium ascorbate hydrogel allowed to reach values of bond strength similar of the enamel not bleached.