Microtensile resistance of an adhesive system modified with chitosan nanoparticles

AIM: The aim of this study was to evaluate whether 2.5% chitosan applied after dentin acid etching or incorporated into the adhesive system interferes with the microtensile strength of the interface tooth-resin. SUBJECTS AND METHODS: Sixty healthy bovine teeth had the incisal thirds and the roots sectioned and were randomly allocated into three groups (n = 60). G1 (control): acid attack + Clearfil SE Bond + Z350 resin; G2: treatment with 2.5% chitosan + Clearfil SE Bond + Z350 resin; G3: treatment with 2.5% chitosan incorporated into dentin adhesive + Z350 resin. The stick-shaped specimens made in each group were randomly divided into two subgroups and subjected to degradation of the adhesive interface (with aging: specimens immersed in 2.5% sodium hypochlorite for 12 h and washed in distilled water for 1 h, and without aging). The groups were submitted to a microtensile strength test with a 0.5 mm/min speed until rupture. Statistical analysis of the data was performed according to normal distribution. RESULTS: Microtensile data were obtained by calculating the area of each toothpick, obtaining values in megapascal. No aging: G1 – 5251.69, G2 – 5.52 ± 1.46, and G3 – 3.91 ± 1.21. With aging: G1 – 3.45 ± 1.29, G2 – 2.75 ± 0.78, and G3 – 3.53 ± 1.33. Statistical analysis showed that the aging factor and adhesive modification decreased the bonding strength of the resin-dentin (P = 0.001). As well, the interaction between the analyzed factors showed statistically significant differences (P = 0.002). CONCLUSIONS: Accelerated aging decreases the adhesion strength in G1, even when chitosan is previously applied to the adhesive system. However, when adding chitosan to the adhesive, adhesion remained similar after aging but lower when compared to the other groups.