Tissue dissolution and modifications in dentin composition by different sodium hypochlorite concentrations

Abstract

Sodium hypochlorite (NaOCl) remains the most used irrigation solution during root canal preparation because of characteristics such as wide-spectrum antimicrobial activity and organic tissue dissolution capacity. However, these solutions can alter dentin composition and there is no consensus on the optimal concentration of NaOCl to be used. Objectives To determine the organic matter dissolution and changes in dentin chemical composition promoted by different concentrations of NaOCl over time. Material and Methods: Fragments of bovine muscle tissue were weighed before and after 5, 10, and 15 min of immersion in the groups (n=10): G1- 0.9% saline solution; G2- 1% NaOCl; G3- 2.5% NaOCl; and G4- 5% NaOCl. Bovine dentin fragments were subjected to the same irrigants and absorption spectra were collected by Attenuated Total Reflectance of Fourier Transform Infrared Spectroscopy (ATR-FTIR) before and after 0,5, 1, 2, 3, 5, 8, and 10 min of immersion in the solutions. The ratios of the amide III/phosphate and carbonate/phosphate absorption bands were determined. The tissue dissolution and carbonate/phosphate ratios were submitted to the two-way analysis of variance (ANOVA) with Tukey’s multiple-comparison test (α<0.05) and to the one-way analysis of variance with Tukey’s (α<0.05). The amide III/phosphate ratio was analyzed by Friedman test (α<0.05) and the Kruskal-Wallis test with Dunn’s post-hoc (α<0.05).Results The increase in NaOCl concentration and contact time intensified the dissolution of organic matter and dentin collagen with reduction in the amide III/phosphate ratio. Significant differences between all groups (p<0.05) were observed in the dissolution of organic matter at 10 min and in the amide III/phosphate ratio between the saline solution and 5% NaOCl at 5 min. The carbonate/phosphate ratio decreased significantly in G2, G3, and G4 after 0,5 min of immersion (p<0.05), but more alterations did not occur in the subsequent periods (p>0.05). Intergroup differences were not observed in this ratio (p>0.05).Conclusions The increase in the exposure time and in the concentration of NaOCl solution lead to an increase in the tissue dissolution and dentin collagen deproteination. Furthermore, some carbonate ions are removed from the dentin inorganic phase by the NaOCl.

Effect of radiotherapy on the chemical composition of root dentin

“…Craig et al and Rautiola and Craig observed that the microhardness of dentin tends to increase as it distances from the dental pulp . Thus, knowing that the microhardness is related to the inorganic matrix, we can assume that the lower proportion of inorganic content in the intracanal region causes an imbalance in the ionic exchanges that occur between phosphate and carbonate, making the dentin more soluble and susceptible to the loss of ions to the artificial saliva . The lower concentration of carbonate favors the development of caries lesions .…”

“…Thus, knowing that the microhardness is related to the inorganic matrix, we can assume that the lower proportion of inorganic content in the intracanal region causes an imbalance in the ionic exchanges that occur between phosphate and carbonate, making the dentin more soluble and susceptible to the loss of ions to the artificial saliva . The lower concentration of carbonate favors the development of caries lesions . This imbalance is related to the lower degree of mineralization and higher density of tubules in the intracanal root dentin region, which also justifies the nonalteration of carbonate in the middle root dentin region.…”

Effect of the combination of several irrigants on dentine surface properties, adsorption of chlorhexidine and adhesion of microorganisms to dentine

“…The initial infrared absorbance spectrum of the samples was obtained over the range of 4000-400 cm À1 at 1 cm À1 resolution using 32 scans and was recorded using the OMNIC Spectra Software. Thereafter, the samples were distributed into four groups (n = 5) and were subjected to irrigation protocols as previously described (Tartari et al 2016). In the first set of experiments, the samples of one group were dipped individually in microtubes containing 1.5 mL of 2% CHX solution for 30 s and ultrasonicated for 15 s. Subsequently, they received a flush in a microtube with 1.5 mL of distilled water for 1 min of which 15 s were under ultrasonic agitation.…”

Proof‐of‐concept study to establish an in situ method to determine the nature and depth of collagen changes in dentine using Fourier Transform Infra‐Red spectroscopy after sodium hypochlorite irrigation

“…,, Tartari et al . ). By monitoring changes in the IR absorption frequencies following NaOCl exposure, it may be possible to assess the depth of any changes due to root canal irrigation.…”