Effect of Super-Oxidized Water, Sodium Hypochlorite and EDTA on Dentin Microhardness

Abstract

The present study aimed to evaluate the influence of the following irrigating solutions on the microhardness of root canal dentin: 2% sodium hypochlorite (2NaOCl), 5% sodium hypochlorite (5NaOCl), super-oxidized water (400 ppm Sterilox - Sx) and 17% EDTA (E). Eighty roots from bovine incisors were randomly divided into 8 groups (n=10): 2NaOCl, 5NaOCl, Sx, and 2NaOCl + E, 5NaOCl + E, Sx + E (associated with E as final irrigant for 5 min), E solely and distilled water (dH2O) as the negative control. Root canal preparation was performed by hand instruments, using one of the irrigation protocols for 30 min. Then, 5 mm of the cervical root third were cut out from each sample and subjected to the Vickers microhardness test, at two points, one at approximately 500-1000 µm from the root canal lumen (distance 1), and the other at approximately 500-1000 µm from the external root surface (distance 2). Data were analyzed by Wilcoxon and Kruskal-Wallis tests at 5% significance level. Microhardness values at distance 1 were significantly lower than those at distance 2 for all groups, except 5NaOCl and 5NaOCl + E groups (p>0.05). EDTA showed the lowest microhardness values. However, no statistically significant difference was detected among groups at distance 1 and EDTA was significantly different only from Sx at distance 2. In conclusion, all tested solutions showed lower microhardness at the most superficial root canal dentin layer compared to the one found near the external root surface, except 5NaOCl and 5NaOCl + E; EDTA promoted lower microhardness values in comparison to Sterilox at this site.

Effect of final irrigation protocols on microhardness reduction and erosion of root canal dentin

“…In previous studies, the Vickers indenter method was used for measuring dentin hardness. 8,12,25 Fuentes et al 26 determined the microhardness of superficial and deep dentin by means of two indentation methods (Knoop and Vickers) under two different applied loads. Knoop hardness was significantly higher for superficial dentin than for deep dentin, 26 presenting sensitivity to surface effects and textures, 13 suggesting that superficial dentin, closer to the pulp, should be analyzed with this method.…”

“…13,27 Some studies in the literature have evaluated changes in dentin microhardness after canal irrigation with different solutions. 8,13,25 However, they have not evaluated initial microhardness, which may render the results imprecise, since the teeth have different initial physical characteristics. In the present study, the average of the three indentations at 100 μm and 500 μm before irrigation was obtained to provide a representative value of the initial microhardness of each specimen.…”

Bovine Pulp Tissue Dissolution Ability of Irrigants Associated or Not to Ultrasonic Agitation

“…Due to limitations of NaOCl, especially in relation to toxicity, the use of irrigants known as "electrochemically activated water" (12,13), "oxidative potential water" (14) or "super-oxidized water" (15,16) has been suggested in the literature. Despite different denominations, they are all oxidizing solutions containing hypochlorous acid and produced according to the same principles, i.e., by passing a saline solution over titanium-coated electrodes.…”

Intracanal Irrigating Solutions Prior to Calcium Hydroxide Medication and Its Effects on Root Dentin Strength

“…However, adverse effects of NaOCl irrigation on dentin's mechanical properties (3,10,11,13,19) have been reported, including decrease of microhardness (10), flexural strength (11) and elastic modulus (3). Sodium hypochlorite promoted loss of dentinal organic components (19) because this solution is a non-specific proteolytic agent.…”

“…EDTA solutions are powerful demineralizing agents, leading to dentinal erosion (9), dentinal tubule enlargement (12) and consequently, decreasing dentin microhardness (13). Higher EDTA concentrations (5%, 10% and 15%) cause greater dentinal erosion (14).…”