Bonding of adhesives to Er:YAG laser-treated dentin

Abstract

Objective: The shear bond strength of adhesives applied to dentin was investigated after irradiation with an erbium-doped yttrium aluminum garnet (Er:YAG) laser.

Methods: Superficial and deep dentin specimens from human molars were treated either with carbide bur or an Er:YAG laser. Two etch and rinse adhesives (Single Bond and XP Bond) and two self-etch adhesives (Prompt L-Pop and Xeno III) were employed to bond the composite. Shear bond strength (SBS) was determined after storage in water for 24 h using a universal testing machine with a crosshead speed of 0.5 mm/min. Failure patterns and modes were analyzed and evaluated using a stereomicroscope. In addition, samples were processed for Scanning Electron Microscopy SEM evaluation. A linear mixed model was used, and pairwise comparisons were made using the Bonferroni test.

Results: Results showed significant differences between the levels of dentin treatment (p=.01) in carbide bur-cut dentin and lased dentin, as well as significant interaction effects due to the depth of dentin and the bonding system used. The etch and rinse adhesives bonded less effectively with lased dentin than with carbide bur-cut dentin, while self-etch adhesives bonded equally well with lased and bur-cut superficial dentin but much less effectively with lased deep dentin than with bur-cut deep dentin. SEM revealed a predominantly adhesive failure mode in laser-ablated fractured specimens, while a mixed failure mode was apparent in the bur-cut fractured specimens.

Conclusions: Cavities prepared by laser seem less receptive to adhesive procedures than conventional bur-cut cavities.

Keywords: Er: YAG laser; Laser irradiation; etch and rinse adhesives; self-etch adhesives; shear bond strength.

Figure 1.

Adhesive values of the adhesive bonding system: pairwise comparisons between carbide bur-cut and laser ablation treatment.

Figure 2.

Adhesive values of the adhesive bonding system: pairwise comparisons between deep dentin and superficial dentin.

Figure 3.

Adhesive values of the adhesive bonding system: pairwise comparisons between total-etch and self-etch adhesive systems.

Figure 4a.

SEM micrograph of the debonded dentin specimen from XP Bond (total-etch adhesive) and laser-treated superficial dentin. The interface failed to be uniformly adhesive within dentin. In addition, many micro-cracks can be observed.

Figure 4b.

SEM micrograph of the debonded dentin specimen from XP Bond and carbide-treated superficial dentin. A mixed failure mode was observed.

Figure 5a.

SEM micrographs of the debonded dentin specimen from Xenon III (self-etch adhesive) and laser-treated superficial dentin. Adhesive failure was observed.

Figure 5b.

SEM micrograph of the debonded dentin specimen from Xenon III- and carbide-treated deep dentin. A cohesive failure mode was observed.

Figure 6.

SEM micrographs of the debonded dentin specimen from Prompt L-Pop (self-etch adhesive) and laser-treated (a) superficial or (b) deep dentin.

Figure 6.

SEM micrographs of the debonded dentin specimen from Prompt L-Pop (self-etch adhesive) and laser-treated (a) superficial or (b) deep dentin.