Effect of tooth bleaching on shear bond strength of a fluoride-releasing sealant

Abstract

Objective: To evaluate the effect of an in-office plus at-home bleaching protocol on shear bond strength of orthodontic buttons when using a fluoride-releasing sealant. Materials and Methods: Extracted human molars (160) were randomly divided into bleached (n 5 80) and unbleached groups (n 5 80). The bleached group was treated with 45% carbamide peroxide for 30 minutes, followed by five applications of 20% carbamide peroxide at 24-hour intervals. After 2 weeks, lingual buttons were bonded on the teeth in both groups using either Transbond XT primer or Pro Seal sealant. The teeth were then stored in artificial saliva and subjected to shear testing at 24 hours and 3 months using a Zwick Universal Test Machine. Comparisons of mean shear bond strength values were made with the analysis of variance test. The Fisher's exact test was used to evaluate the adhesive remnant index scores. Results: The analysis of variance of the 24-hour results indicated a significant difference between the four subgroups (P , .0011). Further simple t-tests indicated that the differences were significant only between bleached and unbleached subgroups (P , .0011). The 3-month results showed the mean shear bond strengths of the unbleached group using Pro Seal sealant was significantly lower than that of the other, though still greater than clinically minimal suggested bond strengths. Interestingly, 15% of the bleached teeth exhibited enamel fracture at the 3-month testing. Conclusion: Both Pro Seal sealant and Transbond XT primer demonstrated reliable shear bond strength values on both bleached and unbleached teeth over time. (Angle Orthod. 2012;82:546-551.)

Tooth whitening affects bond strength of adhesive systems in enamel

“…Enamel exposed to whitening agents can undergo mild to moderate morphological surface changes, including increased porosity, reduced hardness, loss of mineral content and modification to prismatic shape, resulting in an over-conditioned enamel appearance [18,19]. Thus, bleaching could affect the dental substrate.…”

Does the time interval after bleaching influence the adhesion of orthodontic brackets?

“…The enamel exposed to bleaching agents underwent slight or moderate morphologic surface changes, including increased porosity and decreased microhardness, as well as the loss of mineral content and prismatic form, that resulted in the enamel surfaces appearing to be over-etched 18,19,24. These changes seem to be both time- and concentration-dependent.…”

“…This reduction could be explained by the high residual peroxide concentration at the enamel surfaces, as residual oxygen that is released from the bleaching agent may interfere with the infiltration of resin into the etched enamel or inhibit resin polymerization 13,17,24,25. The in-office bleaching method most often uses 35 - 50% hydrogen peroxide, which is considered to have a strength that is 7- to 16-times higher than that of the concentration used in at-home bleaching techniques 16.…”

“…The increase in SBS over time can be explained by the diffusion and release of oxygen absorbed by the enamel from the external environment 11,24. Once the entrapped peroxide is eliminated, the enamel surfaces may show increased adhesiveness 10.…”

Morphology and Composition Analysis of Enamel Surface With Dental Adhesive Following the Application of Nd:yag Ablation

“…The increasing percentage of carbon is due to the presence of the composite adhesives on the surface. Blūgloo composite adhesive contains about 10-20 wt.% of bisphenol A diglycidyl ether methacrylate (BADGE), which is a large molecular methacrylate monomer used in most composite adhesives [24]. The molecular formula of BADGE is C21H24O4, which contributes to the presence of carbon element in the composite adhesives.…”