Abstract
Objective: The aim of this study was to evaluate the morphological and chemical alterations in enamel, dentin and cementum after internal bleaching using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). Material and Methods: Seventy-two bovine incisor teeth were prepared, cut and bleached for 7 days as follows: HP: 35% hydrogen peroxide gel; HP+SP: 35% hydrogen peroxide gel + sodium perborate; CP: 37% carbamide peroxide gel; CP+SP: 37% carbamide peroxide gel + sodium perborate; SP: sodium perborate + water; and control: deionized water. The specimens were sectioned and prepared for morphological analysis under SEM and analysis of calcium, phosphorus, oxygen and carbon levels using EDS. Results: A significant reduction was found in the calcium levels in enamel after treatment with CP + SP and CP (p < 0.05). Carbon (organic part) was hardly altered in enamel. A significant reduction in the calcium levels was found in dentin in Groups HP+SP, CP and CP+SP. Phosphorus levels increased after SP+H20 (p < 0.05) and CP (p < 0.05). Carbon levels showed little variation and the largest amount was found in Groups CP and CP+SP (p < 0.05); in the other groups there was no alteration. A significant reduction in the calcium levels was found in the cementum in Group CP+SP (p < 0.05). Conclusion: Alterations in the enamel, dentin and cementum compositions occurred after bleaching and these alterations showed to be less significant with sodium perborate and water.Keywords: Carbamide peroxide; Hydrogen peroxide; Scanning electron microscopy; Sodium perborate; Tooth bleaching.
Highlights
Bleaching of discolored and endodontically treated teeth is a widely used esthetic option that preserves the dental tissues when compared with other esthetic treatments [1]
A significant reduction was found in the calcium levels in enamel after treatment with CP + SP and CP (p < 0.05)
The phosphorous levels remained similar in CP + SP (p < 0.05); in the other groups these levels significantly increased with HP and CP (p < 0.05)
Summary
Bleaching of discolored and endodontically treated teeth is a widely used esthetic option that preserves the dental tissues when compared with other esthetic treatments [1]. Penetration of the bleaching agent into the tooth structures occurs due to its low molecular weight and capacity to denature proteins, which increases movement of ions through the tooth structure [5] causing alterations in the chemical composition of the tooth, reducing the calcium and phosphate ratio of enamel and dentin [6] and changing the texture of bleached teeth, decreasing microhardness [7], as well as increasing permeability of enamel and penetration of dyes and oxidative radicals [8,9] and bonding failures of dentin and enamel [2,10,11]. Few studies have evaluated the effects of bleaching agents used in internal bleaching and the chemical composition of hard dental tissues. The aim of this study was to evaluate the morphological and chemical alterations in enamel, dentin and cementum after internal bleaching using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS)
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