Penetration of hypochlorites with lowered surface tension into dentine tubules

The purpose of the present study was to assess the effect of concentration and temperature of sodium hypochlorite (NaOCl) with added surfactants and time of exposure on its penetration into human dentine.

Seventy-five extracted permanent maxillary anterior teeth with single canals were shaped by using ProTaper SX hand-operated instruments. Then teeth were sectioned perpendicular to their long axis. The crowns and apical thirds of all the teeth were removed. The remaining roots were processed into 4-mm-long blocks and stained overnight in crystal violet. One hundred fifty stained blocks were further split into halves and treated by six NaOCl-based solutions from different brands: three solutions added with surfactants (Hypoclean, H6, Chlor-Xtra) and their regular counterparts (5.25%, 6%, <%6NaOCl). The dentine blocks were exposed to the solutions for 2, 5, and 20 minutes at 20° C, 37° C, and 45° C, respectively. The depth of penetration of NaOCl was determined by bleaching of the stain and measured by light microscopy at magnifications of 20x and 40x. Statistical analysis was made by using two way ANOVA and by comparing groups two by two with t-test.

The shortest penetration (130.80±1.92μm) was measured after incubation with 5.25%NaOCl for 2 minutes at 20° C; the highest penetration (375.40±3.05μm) was obtained with Chlor-Xtra for 20 minutes at 45° C. Temperature and exposure time had a significant direct relationship with penetration of sodium hypochlorites with lowered surface tension into dentinal tubules.

The exposure time and temperature of sodium hypochlorite as well as the addition of surfactants may influence the penetration depth of irrigants into dentinal tubules.