Effect of calcium hypochlorite and sodium thiosulfate on the bond strength to pulp chamber dentin: A laboratory investigation

Abstract

This study aimed to compare the effect of sodium hypochlorite (NaOCl) and calcium hypochlorite [Ca(OCl)₂] on the bond strength to pulp chamber dentin when followed or not by the use of sodium thiosulfate (Na₂S₂O₃). The pulp chamber of fifty human molars were divided into five groups (n = 10) according to the immersion protocol: 2.5% NaOCl; 2.5% NaOCl + 5% Na₂S₂O₃; 2.5% Ca(OCl)₂; 2.5% Ca(OCl)₂ + 5% Na₂S₂O₃; and 0.9% sodium chloride (NaCl; control). Subsequently, the samples were restored with resin composite. Three sticks each were obtained and subjected to microtensile testing. SEM/EDS analyses of the pulp chamber roof (n = 8) were carried out for mineral quantification. Elemental analysis data were investigated via one-way ANOVA and Tukey's post hoc, and bond strength data by post hoc pairwise comparisons using the Kruskal–Wallis test. Use of 2.5% NaOCl was associated with the lowest value of bond strength, while 2.5% Ca(OCl)₂ had similar bond strength to that of the 0.9% NaCl control. Using 5% Na₂S₂O₃ was able to increase the bond strength after 2.5% NaOCl, but not after 2.5% Ca(OCl)₂. The group treated only with 2.5% Ca(OCl)₂ had a higher Ca/P ratio on the dentin surface. Dentin treated with Ca(OCl)₂ was not affected by Na₂S₂O₃ and showed bond strength similar to the 0.9% NaCl.