Optical changes of human dentin after non-vital bleaching and effect of Er,Cr:YSGG laser on micro-shear bond strength of a self-etch and an etch-and-rinse adhesive system.

The aim was to evaluate the optical changes of bleached human dentin and the efficacy of Er,Cr:YSGG laser on micro-shear bond strength (muSBS) of two adhesive systems for immediate and delayed applications. Seventy-two human dentin specimens (1 mm) were obtained. Colour measurements of 30 specimens (control and bleaching groups) were made at baseline, after bleaching and a 7-day delay. Differences at colour (DeltaE(00)), translucency (DeltaTP(00)) and whiteness (DeltaWI(D)) were calculated by recorded data. Forty-two specimens were used to compare muSBS of a self-etch (Clearfil SE Bond [SE]) and an etch-and-rinse (Prime&Bond NT [PBNT]) adhesive to bleached dentin. Additional to a negative group, six groups were contemplated for each adhesive, considering the time of composite application (immediate, delayed) and whether additional surface treatment by laser (1 W, 2 W) or not. Colour and muSBS data were statistically analysed. For optical analysis, only DeltaE(00) and DeltaWI(D) calculated for the difference between baseline and bleaching were found significantly different for control and bleaching groups. Whiteness of bleached specimens was remarkably decreased after a 7-day delay. Despite immediate applications of SE showing lower muSBS than negative control, delayed applications showed no significant differences except that of the 2 W laser etching. For PBNT, laser etching increased muSBS for both of the immediate and delayed applications, and no significant difference was observed from negative control. Related with the preferred adhesive system, Er,Cr:YSGG laser etching can be an alternative for optimal bond strength of immediate restorations, but the clinicians should always keep in mind that perceived colour and whiteness will change by the passing time which can affect the shade match.