Abstract
Objective To quantify Enterococcus faecalis density in root canal dentin after chemomechanical preparation (CMP) using alternated irrigating regimen. Methodology Root canals (RC) were contaminated with E. faecalis (ATCC 19433) for 3 weeks and evident biofilms were obtained. After initial sampling (S1), the CMP was aided by irrigants: saline solution (control; n=12), a conventional regimen (CR) (group 1; n=12) using 5.25% NaOCl and a final rinse with 17% EDTA, and an alternating regimen (AR) of intercalated use of NaOCl and EDTA (group 2, n=12), followed by a second sampling (S2). After 2 weeks, S3 was obtained. Two roots were analyzed by scanning electron microscopy. Each root was divided into cervical, mild, and apical segments and sampling of the superficial (n=90) and deep (n=90) dentin layers was obtained using Gates-Glidden burs. The E. faecalis density (CFU/mg) in log10 was categorized as residual (0 > 0.2), moderate (0.2 ≥ 0.5), or elevated (> 0.5). The prevalence of positive samples in BHI and BHI-A was analyzed by Pearson's chi-square test. The data were normalized by a log10 transformation of CFU and were analyzed by one-way ANOVA and Tukey's tests. Results Biofilms were observed only in the control root canal walls. Topographically, the controls and CR showed similar distributions of E. faecalis in the dentin. Microbiologically positive root canals harbored much E. faecalis in the adjacent dentin (p < 0.05). Irrigating saline provided moderate density of E. faecalis in the dentin while CR and AR resulted in a residual density of microorganisms (p < 0.05). Conclusions The Enterococcus faecalis density in dentin was influenced by the irrigating regimen and the microbiological status of the root canal. The CMP aided by the alternating regimen interfered with the recolonization of the root canal and topographic distribution of Enterococcus in root dentin.
Highlights
In the teeth with pulp necrosis the spaces of the pulp cavity become unprotected by the immune system and this makes this environment favorable to the proliferation of various microorganisms [1]
After chemomechanical preparation the CFU average reduction was similar between conventional regimen (CR) and alternating regimen (AR) irrigation (p > 0.05), which were significantly superior to the control (p < 0.05)
In CR and AR, scattered E. faecalis were in the root canal wall (Figure 2(b)) and dentinal tubules (Figure 2(c))
Summary
In the teeth with pulp necrosis the spaces of the pulp cavity become unprotected by the immune system and this makes this environment favorable to the proliferation of various microorganisms [1]. From a therapeutic point of view, an important focus is oriented to achieve negative microbiological culture prior to root canal [5,6,7] and the efficacy of antisepsis protocols can be routinely assessed through the microbiological culture and confocal laser scanning microscopy [2]. In root canal treatment failures, anatomical factors and operative technical errors [12] add to the microbiological aspect [7, 13], with high prevalence of Enterococcus faecalis [14] These bacteria form biofilms [15, 16], present resistance to some antiseptic agents [15, 17], and colonize the dentin tubules [16, 18]. The dentin acts as a reservoir for the microorganisms [19, 20], which should be the most reasonable explanation for the resurgence of the apical periodontitis lesion [12, 21]
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