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

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 hours/ day) and 24 hours of artificial saliva (AS) storage. G3: 14 days bleaching with 4% HP+Ca (2 hours/day) and 7 days storage in AS. G4: 28 days bleaching with 4% HP+Ca(2 hours/day) and 24 hours storage in AS. G5: 28 days bleaching with 4% HP+Ca (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 (≤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 ( ≥0.01). However, in 28 days bleaching, the effects of the storage periods (24 hours and 7 days) were significantly different ( ≤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.