Influence of Prolonged Bleaching with 4% Hydrogen Peroxide Containing Calcium and Different Storage Times on the Bond Strength to Enamel

Abstract

Aims:To assess the influence of different bleaching protocols on the bond strength to enamel. Materials and methods:In this laboratory experiment were used forty sound bovine incisors were divided into five groups. G1: No bleaching (control). G2: 14 days bleaching with 4% hydrogen peroxide containing calcium (4% HP+Ca 2+ ) (2 hours/ day) and 24 hours of artificial saliva (AS) storage. G3: 14 days bleaching with 4% HP+Ca 2+ (2 hours/day) and 7 days storage in AS. G4: 28 days bleaching with 4% HP+Ca 2+ (2 hours/day) and 24 hours storage in AS. G5: 28 days bleaching with 4% HP+Ca 2+ (2 hours/day) and 7 days storage in AS. Following storage times, composite resin cylinders were built upon the enamel surfaces and tested for micros hearing. For statistical analysis, two-way ANOVA and Tukey's test was applied to the data (p ≤0.05), for it was evaluated different times of bleaching and stored in artificial saliva. Results:The highest mean was observed in G1 (14.61 MPa), and the lowest in G4 (9.22 MPa). Compared to the negative control (G1), no differences were found in 14 days bleaching and the same between G2 and G3 (p ≥0.01). However, in 28 days bleaching, the effects of the storage periods (24 hours and 7 days) were significantly different (p ≤0.05), besides G4 and G5 were statistically different from G1. Conclusions:Extended bleaching time (28 days) decreased the bond strength, independently of storage time in AS.Clinical significance: If adhesive procedures are required after extended at-home bleaching they may need to be delayed for at least for 7 days for the enamel adhesion ability to recover.

Influence of Prolonged Dental Bleaching on the Adhesive Bond Strength to Enamel Surfaces

“…In SEM observations, it is possible to detect an increase in the exposure of enamel rods and the dissociation of some chemical elements, such as calcium and phosphorous. ese changes are directly related to the time that the substrate is exposed to the bleaching gels [14,22,33,34]. Moreover, the morphological aspect of the enamel bleached for longer periods was comparable to Silverstone's Type III etching pattern.…”

“…us, one can speculate that under extended bleaching protocols, the 7-day AS storage time was not enough to eliminate the greater amount of residual oxygen trapped in the enamel structure [7,28,36,38]. In a recent study by our group, a postbleaching waiting time longer than 7 days was suggested when enamel was exposed to a prolonged bleaching procedure [14].…”

“…Bleaching. Some studies [14,27,28] have proved that waiting between 7 and 21 days is necessary to neutralize the oxidizing effects of bleaching gels on tooth structures. erefore, in this part of the study, the influences of different times of gel exposure and AS storage prior to the bonding procedures were evaluated.…”

“…In the literature, waiting times up to 28 days are mentioned as necessary before restoration. Nevertheless, waiting 21 days to restore bleached teeth is not always feasible for different reasons [14,22]. Beyond that, there are no specific rules for waiting times associated with these different protocols (at home, in office, or a combination of the two).…”

“…is reduction seems to be related to trapped residual oxygen, which interferes with the infiltration of the bonding monomers, the subsequent reduction in length and number of resin tags, and the inhibition of polymerization reaction. erefore, a delay of one to three weeks is recommended before the adhesive restoration procedures take place [11][12][13][14].…”