Morphology and microtensile bond strength of adhesive systems to in situ-formed caries-affected dentin after the use of a papain-based chemomechanical gel method.

Purpose: To evaluate the microtensile bond strength of adhesive systems to caries-affected dentin formed in situ after the use of a papain-based chemomechanical removal method.

Methods: 84 human dentin specimens (5 x 5 x 3 mm) were sterilized and randomly distributed on palatal devices of 14 volunteers. Each palatal device, containing six dentin slabs, was used for 14 days according to a caries induction design involving plaque accumulation and sucrose use. After this, fragments were removed from devices and randomly assigned to two groups according to the caries removal method: (1) Chemomechanical (papain-based gel followed by curette), or (2) Mechanical (curette--control group). Specimens were subdivided into three subgroups according to the adhesive system tested: (SB) a two-step etch-and-rinse (Adper Single Bond 2); (SE) a two-step self-etching adhesive (Clearfil SE Bond) and (TriS) a one-step self-etching adhesive (Clearfil Tri-S Bond) and subsequently restored with microhybrid composite resin. After 24 hours, resin-tooth blocks were sectioned into 0.9 mm thick slabs, with one slab of each block being prepared for adhesive interface analysis by scanning electron microscopy, and the remaining blocks were sectioned into 0.8-mm2 sticks that were subjected to tensile stress (0.5 mm/minute). Data were subjected to two-way ANOVA and Tukey's test at a 5% level of significance.

Results: The application of the chemomechanical and mechanical methods to demineralized dentin did not affect the bond strength values. SB and SE adhesives promoted statistically similar and significantly higher bond strength values than the TriS. SEM analysis showed no interference of papain-based gel in the formation of hybrid layer; SB showed the thickest hybrid layer with presence of numerous tags; SE showed an intermediate hybrid layer thickness and quantity of tags and the TriS showed no evidence of tag formation.