# Evaluation of The Effect of Nd: YAG and CO2 Laser Dentin Treatment Techniques on Shear Bond Strength of Composite Resin: -

## TL;DR

This study compared how different laser treatments affect the bond strength of composite resin to dentin, finding that acid etching alone provided the strongest bond.

## Contribution

The study evaluates the effect of Nd:YAG and CO2 lasers on composite resin bond strength to dentin, both alone and in combination with acid etching.

## Key findings

- The control group with acid etching had the highest shear bond strength (11.14±1.97 MPa).
- Acid etching followed by Nd:YAG laser showed better bonding than other laser treatments.
- Most failures were adhesive, and no cohesive failures were observed.

## Abstract

Recently, lasers have been used for composite resin adhesion, yielding
conflicting results. The shear bond strength (SBS) of resin composites to
dentin when lasers are used as an alternative to acid etching or in
conjunction with acid etching remains unclear. This study aimed to
investigate the effect of Nd: YAG and CO2 laser as treatment techniques on
composite resin bond strength.

Seventy teeth were divided into seven groups: G1 (control) received 37%
phosphoric acid etching, G2 was treated with a CO2 laser, G3 with an Nd: YAG
laser, G4 with a combination of CO2 and Nd: YAG lasers, G5 underwent CO2
laser treatment after acid etching, G6 received Nd: YAG laser treatment
after acid etching, and G7 underwent a combination of CO2 and Nd: YAG lasers
after acid etching. Adper Single Bond 2 was used. SBS was determined after
thermocycling and statistically analyzed using the Kruskal-Wallis test.
Specimens were examined for fracture types under a stereomicroscope at 40X
magnification.

Control group had highest SBS (11.14±1.97 MPa, p≤0.004 vs all). Acid+Nd:YAG
(8.19±3.13 MPa) showed better bonding than CO2 (2.07±1.38, P=0.001), Nd:YAG
(3.11±2.11, P=0.002), and Acid+CO2 (2.38±1.52, P=0.001). Adhesive failures
dominated (73%); no cohesive failures occurred. Acid+Nd: YAG performed best
among surface treatments.

The SBS decreased following the application of CO2 and Nd: YAG lasers, either
alone or in combination. However, after the application of phosphoric acid,
lasers yielded improved results, although they remained lower than the
control group.