Abstract
Internal bleaching is a conservative, non-invasive, and simple treatment that is frequently performed in daily clinical practice. The present in vitro study analyzes the oxygen expansion of different bleaching agents resulting from the oxidation reaction when interacting with enamel and dentin. Enamel and dentin were crushed separately until obtaining a fine powder with particles of an approximate size between 0.06 and 0.2 mm. Each enamel and dentin sample were mixed with 37% carbamide peroxide (CP 37%), 30% hydrogen peroxide (HP 30%), sodium perborate (SP) combined with HP 30% (HP 30% + SP) and SP with distilled water (SP). A total of 280 1 mm diameter glass tubes were used with 70 for each bleaching agent (30 for powdered enamel evaluation, 30 for powdered dentin evaluation, and 10 controls). The bleaching agents were placed in the prepared tubes immediately after mixing the components. As expansion occurred, the oil inside the tube was displaced, through which the resulting expansion was evaluated and measured for 10 days. A significant expansion was observed that varied in magnitude according to the bleaching agent and the tooth structure used. Student’s t test and Welch’s ANOVA were used to analyze the data obtained. The highest mean expansion of both enamel and dentin was observed with 30% HP (66.6 mm for enamel, 94.5 mm for dentin) followed by HP 30% + SP (48.6 mm for enamel, 52.7 mm for dentin), CP 37% (38.4 mm for enamel, 52.6 mm for dentin) and finally SP with water (12.7 mm for enamel, 4.4 mm for dentin). It was observed that the expansion in the SP group with enamel was significantly lower than in the rest of the groups, while that registered for HP 30% was significantly higher. (p < 0.001). The results with dentin were similar, with a significantly lower expansion for SP and higher for HP 30% (p < 0.001). The oxygen expansion observed as a result of the interaction between bleaching agents and dental tissues could contribute to improving our understanding of bleaching and its results. These results suggest that bleaching agents react with the organic component of the tooth structure.
Highlights
Assessment of dental color is one of the most critical components of cosmetic dentistry. [1] Darkening of a single anterior tooth produces a negative aesthetic effect due to the lack of coincidence in color with the rest of the teeth [2,3,4]
A variation in volume with respect to the control was only observed in the group of hydrogen peroxide (HP) 30% + sodium perborate (SP)
On comparing the two groups with carbamide peroxide (CP) 37% as bleaching agent (Groups 1 and 2), the expansion produced was found to be significantly greater for CP with dentin than for CP with enamel (Student t-test; p < 0.05)
Summary
Assessment of dental color is one of the most critical components of cosmetic dentistry. [1] Darkening of a single anterior tooth produces a negative aesthetic effect due to the lack of coincidence in color with the rest of the teeth [2,3,4]. [1] Darkening of a single anterior tooth produces a negative aesthetic effect due to the lack of coincidence in color with the rest of the teeth [2,3,4]. Such color alteration may occur after endodontic treatment and/or following trauma due to pulp hemorrhage and necrosis, or as a result of the use of certain endodontic sealing agents, drugs, or restorative materials [5,6,7]. Non-vital teeth appear to be darker and more saturated and have an increased hue interval, compared to their vital counterparts [1] In these cases, internal bleaching is a conservative, simple, and effective treatment option, focused on lightening the color of the tooth with fast, safe and satisfactory results. It reduces the need for more invasive cosmetic procedures such as veneers and crowns [8]
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