Shear bond strength of composite resin to dentin after Er, Cr: YSGG laser irradiation or phosphoric acid etching

The aim of this in vitro study was to evaluate the surface roughness, pulpal temperature and shear bond strength (SBS) of composite resin to the dentin surface etched with Er, Cr: YSGG (erbium, chromium-doped yttrium-scandium-gallium-garnet) laser or phosphoric acid.

A total of 43 extracted premolars were collected and prepared by sectioning the occlusal surface within the level of the central grooves to expose the whole dentin surface. The cutting procedure was done by a diamond disk with copious water irrigation and the dental surveyor was used to mount the specimens in acrylic blocks. Specimens (n = 10) were randomly assigned into three groups: group (A) dentin surfaces were etched with a 37% phosphoric acid gel for 15 s, group (B) dentin surfaces were etched using Er, Cr: YSGG at 1 W, 20 Hz with a 10% water and 10% air and group (C) samples were etched using Er, Cr: YSGG at 1.5 W, 20 Hz, with a 10% water and 10% air. Surface topography and surface roughness were tested using SEM. Pulpal temperature during laser etching was also evaluated with the aid of a thermocouple at 37 °C. All samples were tested for SBS using a universal testing machine.

Surface roughness of Er, Cr: YSGG laser treated groups was significantly (p ≤ 0.05) higher than the acid etched group. Pulpal temperature during laser irradiation did not reach the critical value of pulp necrosis. SBS was significantly higher for Er, Cr: YSGG laser-irradiated groups than acid etched groups.

Etching with Er, Cr: YSGG laser significantly improved dentin surface topography in terms of SBS and surface roughness.