Microtensile bond strength of resin composite to dentin treated with Er:YAG laser of bleached teeth

Abstract

The objective of this study was to evaluate the influence of Er:YAG laser (λ = 2.94 μm) on microtensile bond strength (μTBS) and superficial morphology of bovine dentin bleached with 16% carbamide peroxide. Forty bovine teeth blocks (7 × 3 × 3 mm(3)) were randomly assigned to four groups: G1- bleaching and Er:YAG irradiation with energy density of 25.56 J/cm(2) (focused mode); G2 - bleaching; G3 - no-bleaching and Er:YAG irradiation (25.56 J/cm(2)); G4 - control, non-treated. G1 and G2 were bleached with 16% carbamide peroxide for 6 h during 21 days. Afterwards, all blocks were abraded with 320 to 600-grit abrasive papers to obtain flat standardized dentin surfaces. G1 and G3 were Er:YAG irradiated. Blocks were immediately restored with 4-mm-high composite resin (Adper Single Bond 2, Z-250-3 M/ESPE). After 24 h, the restored blocks (n = 9) were serially sectioned and trimmed to an hour-glass shape of approximately 1 mm(2) at the bonded interface area, and tested in tension in a universal testing machine (1 mm/ min). Failure mode was determined at a magnification of 100× using a stereomicroscope. One block of each group was selected for scanning electron microscope (SEM) analysis. μTBS data was analyzed by two-way ANOVA and Tukey test (α = 0.05). Mean bond strengths (SD) in MPa were: G1- 32.7 (5.9)(A); G2- 31.1 (6.3)(A); G3- 25.2 (8.3)(B); G4- 36.7 (9.9).(A) Groups with different uppercase letters were significantly different from each other (p < .05). Enamel bleaching procedure did not affect μTBS values for dentin adhesion. Er:YAG laser irradiation with 25.56 J/cm(2) prior to adhesive procedure of bleached teeth did not affect μTBS at dentin and promoted a dentin surface with no smear layer and opened dentin tubules observed under SEM. On the other hand, Er:YAG laser irradiation prior to adhesive procedure of non-bleached surface impaired μTBS compared to the control group.

Effect of Er: YAG Laser on Microtensile Bond Strength of Bleached Dentin to Composite

“…Since the surface is full of unstable free radicals after direct contact with the bleaching agent, it seems that the generated heat makes dentin surface a better substrate for bonding. 23 For the composite bond to tooth structure, Single Bond 2 fifth generation bonding system was used, which is a lightcure, ethanol-based, two-step etch and rinse adhesive. Some studies have shown that use of ethanol-based adhesives may be able to neutralize the negative effects of bleaching on bonding to enamel.…”

“…It seems that the heat created by low-level Er: YAG laser can eliminate free radicals and alter dentin to provide a more suitable substrate for bonding. [22][23][24] The present study sought to evaluate the effect of Er: YAG laser on microtensile bond strength of composite to freshly bleached dentin.…”

Effect of CO2, Nd:YAG and Er:YAG Lasers on Microtensile Bond Strength of Composite to Bleached-Enamel

“…Esthetic dentistry is usually a combination of bleaching treatment and subsequent tooth-colored restorations [ 1 ]. A reduction in bond strength of adhesive restorations to enamel and dentin immediately after bleaching has been reported in the literature [ 2 - 4 ].…”

Effects of Erbium Family Laser on Shear Bond Strength of Composite to Dentin After Internal Bleaching

“…The water molecules among the hydroxyapatite crystals absorb the beams and evaporate; as a result, the internal pressure increases and microexplosions occur leading to substrate ejection and microstructural alterations. 25,28,29 Although several studies have assessed the effects of erbium family lasers on bleached enamel, 3,[30][31][32] to the best of our knowledge no study has compared the effects of Er:YAG and Er,Cr:YSGG lasers on bleached dentin. Based on our results, Er:YAG laser irradiation led to significantly higher bond strength compared to the control group.…”