Influence of bleaching and desensitizing gel on bond strength of orthodontic brackets

Abstract

OBJECTIVE: The objective of this study was to assess, in vitro, the influence of bleaching gel and the use of desensitizing agent over bond strength of ceramic brackets bonded to bovine enamel. METHODS: One hundred bovine incisors were selected and randomly divided into five groups (n = 20): Group 1, control group (without bleaching); Group 2, bleached with 35% hydrogen peroxide; Group 3, bleached with 35% hydrogen peroxide (three applications, 15 minutes each) and desensitizing agent applied for 10 minutes; Group 4, bleached with 35% hydrogen peroxide for 40 minutes; Group 5, bleached with 35% hydrogen peroxide for 40 minutes with desensitizing agent applied for 10 minutes. Brackets were bonded 7 days after bleaching and submitted to shear bond strength test after 24 hours at a compression rate of 1 mm/minute. After fracture, the adhesive remnant index (ARI) was assessed under stereoscopic at 40 x magnification. Shear strength data (MPa) were submitted to one-way ANOVA and Tukey's test with significance level set at 5%. RESULTS: Group 5 (29.33 MPa) showed significantly higher bond strength than Group 1 (19.19 MPa), Group 2 (20.59 MPa) and Group 4 (23.25 MPa), but with no difference in comparison to Group 3. There was no significant difference among the other groups. The adhesive remnant index showed predominance of score 3, that is, all resin remained adhered to enamel for all groups. CONCLUSION: Bleaching with 35% hydrogen peroxide with calcium associated with desensitizing agent application produced higher bond strength values of brackets bonded to bovine enamel.

Antioxidant potency of mangosteen peel extract topical application in reversing reduced orthodontic brackets tensile strength after bleaching

“…Bleaching agents also affect the collagen network of dentin, resulting in denaturing and relative instability of the dentin organic matrix, thereby decreasing the bond strength. 4 In addition, TBS values of a group undergoing 40% MP extract treatment reached a level almost equal to those of the NC group. It is suggested that treatment with MP extract could approximate the bond strength values of teeth which had not experienced the bleaching procedure.…”

“…2,3 The number of patients seeking orthodontic treatment who might have a history of tooth bleaching is increasing because, following previous procedures, they usually tend to be conscious of orthodontic problems and desire treatment. 4 Unfortunately, bleaching may lead to a reduction in orthodontic bracket bond strength. [5][6][7] In-office bleaching can produce a direct result including residual peroxide on the tooth surface which might inhibit the polymerization of the adhesive.…”

Effect of carbamide peroxide bleaching with and without topical desensitizing gels on enamel roughness, microhardness, and bond strength to orthodontic brackets

“…This reduction in enamel microhardness may be explained by mineral loss from enamel after bleaching procedures, Preliminary studies reported that the application of peroxides could reduce the calcium and phosphate enamel content, as well as its fluoride concentration. 12,14,16,20 It is widely accepted that, surface hardness is used as a characteristic property to determine mineral loss, because it is an established technique for evaluating the mineralization rate of enamel. 17 Beside this, carbopol, which is the thickening agent in most bleaching agents, can decrease the enamel microhardness during bleaching, as carbopol's high calcium-binding capacity and inhibits hydroxyapatite crystal growth.…”

“…So, it is advised to delay bonding to bleached enamel for at least one week after completion of bleaching process to eliminate or reduce the effects of residual oxygen. Within this period, residual oxygen must have been neutralized, thus not interfering with polymerization of resin composite for bonding 16,47 According to Al-Salehi et al 48 there is direct proportional relationship between mineral loss and bleaching agent concentration. As they pointed out that bleaching agents based on 35-38% hydrogen peroxide showed significantly higher values of calcium loss compared to at-home gels (10% carbamide peroxide).…”

“…Firstly, roots were cut from the crowns about 2 mm apical to the cemento-enamel junction using a low-speed diamond saw under water cooling. 16,18,19 Then each tooth was individually embedded in self-cured acrylic resin (Acrostone, Cairo, Egypt) with the labial surface parallel to the (ground) horizontal plane. All labial surfaces were left the enamel exposed for any necessary flattening and/or smoothen on procedures.…”