Abstract
The aim of this study was to assess the effects of intracanal irrigation with sodium hypochlorite (NaOCl) and ethylenediaminetetracetic acid (EDTA) prior to calcium hydroxide medication on the compressive strength of root dentin. Forty-eight roots with single and straight canals were instrumented with a crown-down technique using Flexofile files and Gates Glidden burs, under 0.9% sodium chloride (NaCl) irrigation. Root canals were randomly separated into 4 groups (n=12), according to the irrigating solution: Control Group, 0.9% NaCl; GroupNaOCl, 1% NaOCl; GroupEDTA, 17% EDTA; and GroupEDTA+NaOCl, 17% EDTA and 1% NaOCl. Solutions remained for 40 min, renewed every 10 min, except for GroupEDTA+NaOCl, where the solutions were alternated every 10 min. Canals were dried and filled with calcium hydroxide paste, and radiographed. Each canal was sealed and stored at 37 °C for 30 days. After this period, the roots were cut 1 mm below the cementoenamel junction and 6 mm apically from this point in order to obtain 6 mm-long cylinders. The compressive test was conducted with a crosshead speed of 1 mm/min. The means (±SD) (MPa) of compressive strength were: Control Group, 151.23±94.36; GroupNaOCl, 167.50±57.25; GroupEDTA, 108.79±99.88; GroupEDTA+NaOCl, 60.12±92.10. Significant statistical differences among groups were found (ANOVA and Tukey, a=5%, p=0.02). Control Group and GroupNaOCl showed higher means of compressive strength than GroupEDTA+NaOCl. Intracanal irrigation with 17% EDTA and 1% NaOCl produced a significant reduction of dentin compressive strength 30 days after medication with calcium hydroxide.
Highlights
The endodontic treatment goal is to obtain bacteriafree root canals
The mean compressive force required to break the samples in the Control Group (151.23±94.36 MPa), which were irrigated with saline (NaCl), was statistically different from GroupEDTA+NaOCl (60.12±92.10 MPa) irrigated with 17% ethylenediaminetetracetic acid (EDTA) and 1% NaOCl (Tukey HSD test, p
No statistical difference was observed between Control Group, GroupNaOCl and GroupEDTA
Summary
The endodontic treatment goal is to obtain bacteriafree root canals. The elimination of microorganisms can be achieved using various instrumentation techniques, irrigation solutions and intracanal medicaments (1). An irrigating solution should promote debridement, lubrication, dissolve organic tissue and eradicate the microorganisms from the root canal system (4-8). Irrigation with 15% EDTA and 1% NaOCl removes both inorganic and organic smear layer components (6). Besides the known importance of employing sodium hypochlorite solution and EDTA during canal instrumentation, and prior to intracanal medications and canal filling, there has been much discussion over the effects of using these solutions on root dentin strength. In this way, studies have related sodium hypochlorite irrigation with dentin microhardness reduction (10). Other reports correlate sodium hypochlorite with dentin weakening by reduced dentin flexural strength (3,10,11) and elastic modulus (3,11)
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