Abstract
Objective: To investigate if short-term dentin bleaching with low-concentrated substances affects the bond strength of immediate resin composite restorations. Material and Methods: The buccal surfaces of fifty molar crowns were ground for dentin exposure and randomly assigned into 5 groups (n=10), according to the following treatments: sodium perborate + water; sodium perborate + 6% hydrogen peroxide; 6% hydrogen peroxide; 35% hydrogen peroxide (positive control), or no bleaching agent (negative control). The specimens were immediately restored with resin composite. Seven days after treatments, the shear bond test was performed in a universal test machine at a crosshead speed of 0.5 mm/min. Data were analyzed using ANOVA and Tukey’s HSD test (? = 0.05). Results: The shear bond strength mean values for the negative control group were higher than all experimental and positive control groups (p < 0.000), whose differences were not statistically significant (p > 0.05). Conclusion: Short-term dentin bleaching with sodium perborate+water, 6% hydrogen peroxide, or sodium perborate mixed with 6% hydrogen peroxide reduced the shear bond strength of immediate resin composite restorations. KeywordsResins, synthetic; Hydrogen peroxide; Shear strength; Esthetics; Tooth.
Highlights
I ntracoronal bleaching is a relatively noninvasive and highly effective procedure for color whitening of discolored root-filled teeth [1]
Diverse products are available for tooth bleaching in the form of gels and containing varying concentrations of hydrogen peroxide combined with few other substances like stabilizers, catalysts and flavor agents [17]
The whitening agents were not sealed intracoronally [5,18] but applied over the dentin surface, as performed by CarrascoGuerisoli et al [10] and, for this reason, the oxygen released during oxidative agents decomposition was not forced inside dentinal tubules by the resulting pressure increase [19], and the shear bond reduction observed on experimental and positive control groups may have been underestimated
Summary
I ntracoronal bleaching is a relatively noninvasive and highly effective procedure for color whitening of discolored root-filled teeth [1]. Just as important as optimally aesthetic results, a healthy dentin substrate is a basic condition to a stable adhesive union and an adequate sealing of the access cavity after intracoronal bleaching, since it avoids re-contamination with bacteria and improves the fracture resistance of the tooth [4]. The reduction in adhesive polymerization is claimed to respond for provisional bond strength decrease of resin composite restorations following bleaching [1,57]. To prevent restorative failures related to these whitening side effects, it is recommended to seal the bleached tooth provisionally until regular shear bond levels are recovered [1,5,6,8]
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