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Effect of sodium hypochlorite on human root dentine – mechanical, chemical and structural evaluation

2007; Wiley; Volume: 40; Issue: 10 Linguagem: Inglês

10.1111/j.1365-2591.2007.01287.x

1365-2591

Monika Marending, Hans U. Luder, Tobias J. Brunner, Sven Knecht, Wendelin J. Stark, Matthias Zehnder,

Dental Trauma and Treatments

Abstract Aim To investigate the mechanical, chemical and structural alterations of human root dentine following exposure to ascending sodium hypochlorite concentrations. Methodology Three‐point bending tests were carried out on standardized root dentine bars ( n = 8 per group, sectioned from sound extracted human third molar teeth) to evaluate their flexural strength and modulus of elasticity after immersion in 5 mL of water (control), 1% NaOCl, 5% NaOCl or 9% NaOCl at 37 °C for 1 h. Additional dentine specimens were studied using microelemental analysis, light microscopy following bulk staining with basic fuchsin, and scanning electron microscopy (SEM). Numerical data were compared using one‐way anova . Bonferroni's correction was applied for multiple testing. Results Immersion in 1% NaOCl did not cause a significant drop in elastic modulus or flexural strength values in comparison to water, whilst immersion in 5% and 9% hypochlorite reduced these values by half ( P < 0.05). Both, carbon and nitrogen contents of the specimens were significantly ( P < 0.05) reduced by 5% and 9% NaOCl, whilst 1% NaOCl had no such effect. Exposure to 5% NaOCl rendered the superficial 80–100 μ m of the intertubular dentine permeable to basic fuchsin. Three‐dimensional SEM reconstructions of partly demineralized specimens showed NaOCl concentration‐dependent matrix deterioration. Backscattered electron micrographs revealed that hypochlorite at any of the tested concentrations left the inorganic dentine components intact. Conclusions The current data link the concentration‐dependent hypochlorite effect on the mechanical dentine properties with the dissolution of organic dentine components.