[Cleaning efficacy of different solvents on sealer-contaminated dentin surface]

To evaluate the influence of an epoxy resin-based sealer on the bond strength of adhesive resins to dentin and the cleaning efficacy of different solvents in removing sealer residues.

The occlusal enamel of 25 freshly extracted human third molars without caries were removed to expose flat surfaces of dentin. The teeth were randomly divided into five groups according to the treatment received: For negative control group, the dentin surfaces were not contaminated with AH-Plus; For the other 4 experimental groups, the samples were contaminated with AH-Plus for 5 min and different measures were taken: For positive control group, the sealer were wiped with dry cotton pellets; For solvents experimental groups: cotton pellets saturated with 95% (volume fraction) ethanol, 99.5% (volume fraction) acetone or 99% (volume fraction) amyl acetate were used to wipe the sealer until the surface appeared clean when viewed through a stereomicroscope under ×10 magnification, then rinsed with de-ionized water for 3 s. After sealer removal, a self-etching adhesive system was applied on the surfaces with resin composite. The samples were sectioned into 1.0 mm×1.0 mm stick specimens (n=45) for microtensile test. Failure modes at the dentin-resin interface were observed using a stereomicroscope. The samples were sectioned into 1.0 mm piece specimens (n=4) for scanning electron microscope observation. The microtensile bond strength data were analyzed by one-way ANOVA. Chi-square test were used to analyse the failure modes between the groups.

There was significant difference among the five groups (P<0.001). For dry cotton pellet group (38.69±8.60) MPa and the ethanol group (37.14±12.01) MPa, the microtensile bond strength significantly declined when compared with negative control group (43.86±7.99) MPa (P<0.05). No significant difference of bond strength was found between the dry cotton pellet group and the ethanol group (P=0.426). There was no statistical significant difference among acetone group, amyl acetate group and negative control group (P>0.05). The bond strength of acetone group and amyl acetate group were (45.94±10.37) MPa and (43.99±7.01) MPa, respectively. The ethanol group exhibited lower bond strength than that of acetone group and amyl acetate group (P<0.05). Scanning electronic microscope observation revealed that in dry cotton pellet group and ethanol group, the resin tags were short and loose. Moreover, sealer residues were identified in the interface in the ethanol group samples, while the resin tags in the acetone and amyl acetate group were as dense and uniform as in negative control group. The distribution of failure modes showed no significant difference in the five groups (P=0.086).

The microtensile bond strength of dentin to composite resin was lower after exposure to sealer. Compared with ethanol and dry cotton pellets, the cleaning effect of acetone and amyl acetate on sealer-contaminated dentin surface were better.