Effect of Different Irrigating Solutions on the Microhardness of Dentin

The selection of irrigating solutions during root canal therapy is essential for maintaining dentin structure and ensuring effective disinfection. However, various irrigants can alter the microhardness of dentin, which might have an impact on the treated tooth's mechanical characteristics and long-term viability.

To produce uniform dentin discs from the central portion of the root, forty human premolars were sectioned. Based on the irrigating solution employed, the specimens were split into four groups (n = 10): Group 1 received 2.5% sodium hypochlorite (NaOCl), Group 2 received 17% ethylenediaminetetraacetic acid (EDTA), Group 3 received 2% chlorhexidine (CHX), and Group 4 received distilled water (control). Each specimen was submerged in its respective irrigant for five minutes. A Vickers microhardness tester was used to determine microhardness at 50 g force for 10 seconds both before and after irrigation.

Microhardness decreased significantly in Group 1 (NaOCl), with a mean drop of 18% (from 55 ± 2.3 VHN to 45 ± 1.9 VHN). The greatest reduction, 28%, was observed in Group 2 (EDTA) (from 53 ± 1.8 VHN to 38 ± 2.1 VHN). The microhardness of Group 3 (CHX) decreased by only 5% (from 54 ± 2.0 VHN to 51 ± 1.5 VHN). Microhardness showed no significant change in the control group (Group 4). Significant differences between the groups were found by statistical analysis (ANOVA, P < 0.05), with Group 2 exhibiting the greatest influence on dentin microhardness.

Dentin microhardness was most significantly reduced by EDTA, followed by NaOCl, with CHX showing only a minor effect. These results imply that frequent or extended usage of EDTA and NaOCl may cause the dentin structure to deteriorate.