1355 Peroxide Bleaching Effect on Biaxial Strength/Modulus of Bovine Dentin

Saturday, March 24, 2012: 9:45 a.m. - 11 a.m.
Presentation Type: Poster Session
A.O. CARVALHO1, A.P.A. AYRES2, L.L.C.A.G. DE ALMEIDA3, A.L.F. BRISO3, F. RUEGGEBERG4, and M. GIANNINI2, 1Department of Restorative Dentistry, Dental Materials, Piracicaba Dental School - UNICAMP, Piracicaba, Brazil, 2Department of Restorative Dentistry, Piracicaba Dental School / UNICAMP, Piracicaba, SP, Brazil, 3Department of Restorative Dentistry, Operative Dentistry Division, Arašatuba Dental School, Arašatuba, Brazil, 4Oral Rehabilitation, Georgia Health Sciences University, Augusta, GA
Objectives: This study evaluated the effects of carbamide and hydrogen peroxides on biaxial flexural strength and flexural modulus of bovine dentin.

Methods: Thirty coronal dentin discs (0.5 mm thick X 6.0 mm diameter) were prepared from bovine teeth. The dentin discs were randomly divided into three groups (n=10): control group (unbleached group); bleached with 10% carbamide peroxide for 8 hours; bleached with 38% hydrogen peroxide (the gel was applied 3 times consecutively for 15 minutes each application). The dentin discs were stored in 100% humidity during the bleaching or not. The specimens were tested in a biaxial flexural apparatus held in a universal testing machine (Instron 5844) at 1.27 mm/min until failure occurred, and biaxial mechanical properties were calculated. Within a given test parameter, data were statistically analyzed by ANOVA and Fisher`s PLSD test (pre-determined alpha = 0.05).

Results:

Table presents mean (SD) of test parameter results (MPa) among treatment groups.
TEST PARAMETER Control group (unbleached) 10% carbamide peroxide 38% hydrogen peroxide
Flexural Strength 188 (45) A 170 (53) AB 138 (51) B
Flexural Modulus 8969(966) a 8987 (1251) a 6848 (1155) b

Within a test parameter, values having similar letters are not significantly different.

The 38% hydrogen peroxide demonstrated significantly lower flexural strength than the unbleached control group (p=0.0309) Hydrogen peroxide treatment resulted in significantly lower flexural modulus, when compared to control group and carbamide peroxide bleaching (p=0.0002).

Conclusions: Exposure of bovine dentin to hydrogen peroxide significantly reduces both flexural strength and modulus compared to no-treatment control, whereas exposure to carbamide peroxide did not significantly affect either parameter.


Keywords: Biaxial test, Bleach and Dentin