Background: The aim of this study was to evaluate the effects of QMix, EDTA + CHX, EDTA + NaOCl and maleic acid on the microhardness of root canal dentine. Methods: Forty recently extracted human maxillary canine teeth were longitudinally sectioned into 80 segments and then embedded in an autopolymerizing acrylic resin. The microhardness of the dentine in the specimen was measured with a Vickers diamond indenter at the coronal, middle and apical thirds of the roots. Finally, the specimens were divided randomly into four groups: 17% EDTA + 2.5% NaOCl; 17% EDTA + 2% CHX; QMix; and 7% maleic acid. Posttreatment microhardness values were obtained and the decrease in microhardness was calculated as a percentage. Microhardness values were statistically analysed using the Kruskal-Wallis and Mann-Whitney U tests. Results: Maleic acid significantly decreased microhardness in all regions, compared to the other groups. In the coronal and middle regions, there was no significant difference among the other groups. In the apical region, there was no significant difference between QMix and 17% EDTA + 2% CHX but these groups presented significant dentine microhardness reduction compared to the 17% EDTA + 2.5% NaOCl group. Conclusions: While maleic acid showed the greatest reduction in dentine microhardness, it was found that QMix, 17% EDTA + 2% CHX and 17% EDTA + 2.5% NaOCl cause the same reduction in the microhardness of root canal dentine in the coronal and middle regions.

In this study, twelve noncarious, freshly extracted human third molar teeth for MTBS and 20 premolar teeth for the microleakage test were used. The teeth were restored using Clearfil Universal Bond + Clearfil APX and Teeth mate Desensitizer (TMD). For MTBS test, Group 1: Self-etch, Group 2: Etch and rinse (G1 and 2, nondesensitizer treatment served as a control), Group 3: TMD/self-etch, Group 4: Acid-etch/TMD/etch and rinse. For microleakage test, Class V adhesive cavities (3 mm × 2 mm × 2 mm) were prepared and restored as mentioned before. The restored teeth were subjected to thermal cycling. The MTBS test was performed in all procedures. The MTBS data were submitted to a one-way ANOVA and post hoc Tukey test (P P Results: Control groups exhibited a higher mean MTBS value than TMD groups, and there were statistical differences between the groups. TMD groups also demonstrated significantly less microleakage than control groups (P Conclusions: This study proves that the application of TMD with a multimode adhesive bonding system produced significantly lower MTBS and microleakage.