Conditioning effect on dentin, resin tags and hybrid layer of different acidity self-etch adhesives applied to thick and thin smear layer

Abstract 

Objectives

to assess the conditioning effect (CE) of self-etch adhesives of different acidity applied to thick and thin smear layer (SL), the corresponding resin tags (RT) and hybrid layer (HL).

Methods

Twenty-seven molars had their occlusal dentin exposed and were sectioned into two halves. Each of them was ground with a 60 or 600-grit SiC paper, respectively for thick and thin SL production. Three self-etch adhesives: a mild (Clearfil SE Bond), an intermediary (Optibond Solo SE and Solo Plus) and a strong (Tyrian Self Priming Etchant+One Step Plus) and an etch-&-rinse system (Scotchbond Multi Purpose Plus) were used. For CE evaluation, the self-etch primers were applied and rinsed off with acetone and alcohol prior to SEM preparation. For RT and HL specimens self-etch adhesives were applied and restored with Z-250. For RT specimens, dentin was removed with HCl (6N) and NaClO (1%) baths. The HL specimens were fixed, dehydrated, dried with HMDS, embedded, polished and slightly demineralized (6N HCl) and deproteinized (1% NaClO). After gold sputtering they were observed by SEM.

Results

The thick smear layer was clearly not totally removed by the mild self-etch primer. RT varied in density and shape among the self-etch adhesives. Thicker HL was observed for the strong self-etch and etch-&-rinse adhesives.

Conclusions

The etch-&-rinse adhesive presented the thickest HL and was the only adhesive to produce RT in high density and uniform distribution along the whole dentin surface, independently of the SL thickness.

Keywords: Dentin, Self-etch adhesive, Resin tags, Smear layer, Scanning electron microscopy