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Effect of carbamide peroxide bleaching agents on tensile strength of human enamel
Vanessa Cavalli1, Marcelo Giannini, Ricardo M Carvalho
1Department of Restorative Dentistry, Operative Dentistry Division, Piracicaba School of Dentistry, University of Campinas, Av. Limeira, 901, Piracicaba, São Paulo 13414-018, Brazil.
Objectives:
The aim of this study was to evaluate the effects of low concentrations of carbamide peroxide bleaching agents (CP) on the ultimate tensile strength of enamel (UTS).
Methods:
Resin composite structure was built-up on the bonded occlusal surface of 12 sound third molars to facilitate specimen preparation for microtensile testing. The bonded teeth were sectioned in a bucco-lingual direction in slices approximately 0.7 mm thick. Each slice was trimmed with a fine diamond bur to reduce the buccal, internal slope enamel of the cusps to a dumb-bell shape with a cross-sectional area at the 'neck' of less than 1 mm2. The sample was randomly divided into six groups of 10 specimens each: Control (C-untreated); Opalescence 10% (O10), Opalescence 15% (O15), Opalescence 20% (O20), Whiteness 10% (W10) and Whiteness 16% (W16). Specimens in each group received the application of the CP for 6 h/day, at 37 degrees C, during 14 days and were stored in artificial saliva in between each application. After the bleaching regimen, specimens were tested with the microtensile method at 0.5 mm/min. Data were analyzed by ANOVA and Tukey test (5%).
Results:
Mean tensile strengths were (MPa): C = 47.5 +/- 6.2a; O10 = 37.6 +/- 5.8b; O15 = 33.2 +/- 6.0b; O20 = 31.2 +/- 3.5b; W10 = 32.5 +/- 6.1b; W16 = 30.6 +/- 7.7b. Specimens subjected to the bleaching regimen presented significantly lower UTS than the control group. No differences were found among the type and concentration of the bleaching agents.
Significance:
Results suggested that bleaching enamel with CP could significantly reduce its UTS within a 14 days treatment.
