Influence of Er,Cr:YSGG Laser Treatment on Microtensile Bond Strength of Adhesives to Enamel

Abstract

The current trend towards minimum-intervention dentistry has introduced laser technology as an alternative technique for cavity preparation. This study assessed the null hypothesis that enamel prepared either by Er,Cr:YSGG laser or conventional diamond bur is equally receptive to adhesive procedures. The buccal and lingual surfaces of 35 sound human molars were prepared with Er,Cr:YSGG laser or a medium-grit diamond bur. One etch&rinse (OptiBond FL) and three self-etch adhesives (Adper Prompt L-Pop, Clearfil SE Bond and Clearfil S3 Bond) were applied on laser-irradiated and bur-cut enamel, followed by the application of a 5-6 mm build-up of Z100. The micro-tensile bond strength (microTBS) was determined after 24 hours of storage in water at 37 degrees C. Prepared enamel surfaces and failure patterns were evaluated using a stereomicroscope and a field-emission-gun scanning electron microscope (Feg-SEM). The pTBS to laser-irradiated enamel was significantly lower than to bur-cut enamel (p<0.05), with the exception of Clearfil S3 Bond, which bonded equally effectively to both substrates. The latter presented the highest microTBS on laser-irradiated enamel, though it was not statistically different from the microTBS of OptiBond FL. SEM analysis revealed significant morphological alterations of the laser-irradiated enamel surface, such as areas of melted and recrystalized hydroxyapatite and deep extensive micro-cracks. In conclusion, the bonding effectiveness of adhesives to laser-irradiated enamel depends not only on the structural substrate alterations induced by the laser, but also on the characteristics of the adhesive employed.

Effect of Er,Cr: YSGG Laser on the Microtensile Bond Strength of Two Different Adhesives to the Sound and Caries-affected Dentin

“…In addition, microcracks were observed in most laser irradiated samples, indicating surface damage caused by laser irradiation. 9 Cardoso and others 22 reported that morphological alterations produced by Er,Cr:YSGG laser-irradiation adversely influenced the bonding effectiveness of adhesives to dentin. Some studies present the acid resistance of dentin by laser, reporting the possibility of erbium lasers to diminish the solubility of irradiated dentin when immersed in an acid solution.…”

Cervical Margin Integrity of Class II Resin Composite Restorations in Laser- and Bur-Prepared Cavities Using Three Different Adhesive Systems

“…This leads to better infiltration and proper coverage of demineralized dentin. 9 Cardoso et al 26 reported that the bonding efficacy of adhesives to laser-irradiated dental tissue depends not only on the structural substrate alterations induced by the laser but also on the characteristics of the adhesive employed. Adper Easy One contains nanofiller particles in its composition.…”

“…Different adhesive systems can interact differently with lased surfaces. 26 Adper Easy One, a one-bottle self-etching adhesive formulation, includes a carefully balanced combination of phosphoric acid esters, water, and methacrylates in order to optimize stability. In addition, it contains bonded nanosilica fillers.…”

The effect of Er,Cr:YSGG irradiation on microtensile bond strength of composite resin restoration

“…16) Cardoso et al 23) suggested that the irregularities on the laserirradiated dentin were so prominent that they may reduce the bond strength by preventing uniform stress distribution at the adhesive-dentin interface. Moreover, because of these irregularities, the thickness of the adhesive layer was not uniform on the dentin surface, thus resulting in diminished bonding effectiveness.…”

“…Thus the denatured collagen fibrils are fused together and poorly attached to the underlying unaffected dentin, preventing proper dentin hybridization. 23) These altered microstructures would hamper the infiltration of primer and the hybrid layer would become more susceptible to hydrolysis. 24) Also, it has been demonstrated that the denatured organic matrix blocks the diffusion pathways of adhesive in dentin.…”