Abstract:
The purpose of this study was to evaluate the effect of vitamin C containing sodium ascorbate prepared solution on dentin bond strength of resin composite to non-vital bleached tooth and on fracture resistance of restored non-vital bleached tooth. Sixty (30 pairs, left and right) extracted sound human maxillary premolar teeth were collected from 30 patients. All teeth were endodontically treated and each pair was randomized assigned into microtensile bond strength and fracture resistance tests. The teeth were divided into 3 groups for each test which were 1) non-bleach tooth, 2) bleached with 35% hydrogen peroxide and immediately restored with resin composite, and 3) bleached with 35% hydrogen peroxide, followed by application of 10% vitamin C prepared solution and immediately restored with resin composite. Samples of microtensile bond strength test were cut to obtain stick-shaped specimens and tested with a universal testing machine. Samples of fracture resistance test were embedded in acrylic resin with simulated periodontal ligament before subjecting to an axial compression test in the universal testing machine. Results showed that the bleached tooth followed by 10% vitamin C solution application group had the highest microtensile bond strength (55.566 ± 3.514 MPa) while the bleached group had the significant lowest bond strength (36.571± 2.609 MPa). The non-bleached group showed the highest fracture strength (1053.44 ± 183.65 N) and the bleached group had significant less strength (616.98 ± 97.07 N). There was no significant difference between the non-bleached group and vitamin C solution application group in both microtensile bond strength and fracture strength tests (p>0.05). The most failure mode in the microtensile bond strength test for all groups was adhesive failure and was favorable failure in the fracture resistance test. The microtensile bond strength was positively correlated to the fracture resistance (r=0.639, p<0.001). In conclusion, the use of 10% vitamin C containing sodium ascorbate prepared solution could increase the microtensile bond strength and fracture strength of non–vital bleached tooth comparable to non-bleached tooth.
