RESUMEN

The aim of this study was to evaluate the effect of concentration, exposure time and temperature of sodium hypochlorite (NaOCl) added with surfactants on its penetration into dentinal tubules. Sixty-five extracted human permanent maxillary anterior teeth with single canals were prepared by ProTaper SX hand-operated instruments. The teeth were then sectioned perpendicular to the 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 and thirty stained blocks were further split into halves and treated by nine different types of NaOCl-based solutions. Three solutions were added with surfactants (Hypoclean, H6, Chlor-Xtra) and the others were regular hypochlorites at increasing concentrations (1%, 2%, 4%, 5.25%, <6%, 6% NaOCl) from different brands. The dentin blocks were exposed to the solutions for 2, 5, and 20 min at 20 °C, 37 °C and 45 °C, respectively. The depth of NaOCl penetration was determined by bleaching of the stain and measured by light microscopy at 20x and 40x. Statistical comparisons were made by using a generalized linear model with Bonferroni's post-hoc correction. The shortest penetration (81±6.6 µm) was obtained after incubation in 1% NaOCl for 2 min at 20 °C; the highest penetration (376.3±3.8 µm) was obtained with Chlor-Xtra for 20 min at 45 °C. Varying NaOCl concentration produced a minimal effect while temperature and exposure time had a significant direct relationship with NaOCl penetration into dentinal tubules, especially those with lowered surface tension. 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.

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RESUMEN

Abstract The aim of this study was to evaluate the effect of concentration, exposure time and temperature of sodium hypochlorite (NaOCl) added with surfactants on its penetration into dentinal tubules. Sixty-five extracted human permanent maxillary anterior teeth with single canals were prepared by ProTaper SX hand-operated instruments. The teeth were then sectioned perpendicular to the 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 and thirty stained blocks were further split into halves and treated by nine different types of NaOCl-based solutions. Three solutions were added with surfactants (Hypoclean, H6, Chlor-Xtra) and the others were regular hypochlorites at increasing concentrations (1%, 2%, 4%, 5.25%, <6%, 6% NaOCl) from different brands. The dentin blocks were exposed to the solutions for 2, 5, and 20 min at 20 °C, 37 °C and 45 °C, respectively. The depth of NaOCl penetration was determined by bleaching of the stain and measured by light microscopy at 20 and 40. Statistical comparisons were made by using a generalized linear model with Bonferroni's post-hoc correction. The shortest penetration (81±6.6 μm) was obtained after incubation in 1% NaOCl for 2 min at 20 °C; the highest penetration (376.3±3.8 μm) was obtained with Chlor-Xtra for 20 min at 45 °C. Varying NaOCl concentration produced a minimal effect while temperature and exposure time had a significant direct relationship with NaOCl penetration into dentinal tubules, especially those with lowered surface tension. 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.

Resumo O objetivo deste estudo foi avaliar o efeito da concentração, tempo de exposição e temperatura de hipoclorito de sódio (NaOCl) acrescidos de tensioativos na penetração nos túbulos dentinários. Sessenta e cinco dentes superiores humanos uniradiculares extraídos foram preparadas usando instrumentos ProTaper SX operados manualmente. Os dentes foram seccionados perpendicularmente ao longo eixo. As coroas e o terço apical foram removidos. Os restantes das raízes foram transformadas em blocos de 4-mm de comprimento e coradas durante em violeta de cristal. Cento e trinta blocos foram posteriormente divididos em metades e tratados por nove tipos diferentes de soluções de NaOCl. Três soluções com tensioativos foram adicionadas (Hypoclean, H6, Chlor-Xtra); e os outros foram os hipocloritos regulares em concentrações crescentes (1, 2, 4, 5,25, <6 and 6% de NaOCl) de diferentes origens. Os blocos de dentina foram expostos às soluções de 2, 5 e 20 min a 20 °C, 37 °C e 45 °C, respectivamente. A profundidade de penetração do NaOCl foi determinada pelo branqueamento da mancha e medido em microscopia de luz com ampliações de 20× e 40×. Comparações estatísticas foram feitas usando um modelo linear generalizado com a correção de Bonferroni (post-hoc). A menor penetração (81±6,6 m) foi medida após incubação com 1% de hipoclorito de sódio durante 2 min a 20 °C; a maior penetração (376,3±3,8 m) foi obtida com Chlor-Xtra durante 20 min a 45 °C. Variando a concentração do NaOCl verificou-se um efeito mínimo, enquanto que a temperatura e o tempo de exposição teve uma relação significativa direta com a penetração de hipocloritos de sódio, especialmente aqueles com tensão superficial reduzido, nos túbulos dentinários. O tempo de exposição e temperatura do hipoclorito de sódio bem como a adição de agentes tensioativos pode influenciar significativamente a profundidade de penetração de soluções irrigantes nos túbulos dentinários.

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