Remineralization of Dentin with Cerium Oxide and Its Potential Use for Root Canal Disinfection

Objective

This study was to investigate a novel antibacterial biomimetic mineralization strategy for exploring its potential application for root canal disinfection when stabilized cerium oxide was used.

Material and Methods

A biomimetic mineralization solution (BMS) consisting of cerium nitrate and dextran was prepared. Single-layer collagen fibrils, collagen membranes, demineralized dentin, and root canal system were treated with the BMS for mineralization. The mineralized samples underwent comprehensive characterization using various techniques, including transmission electron microscopy (TEM), high-resolution TEM (HRTEM), Fourier transform infrared spectroscopy (FTIR), scanning transmission electron microscopy (STEM), selected-area electron diffraction (SAED), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and micro-CT. Additionally, the antimicrobial properties of the BMS and the remineralized dentin were also analyzed with broth microdilution method, live/dead staining, and SEM.

Results

Cerium ions in the BMS underwent a transformation into cerium oxide nanoparticles, which were deposited in the inter- and intra-fibrillar collagen spaces through a meticulous bottom-up process. XPS analysis disclosed the presence of both Ce (III) and Ce (IV) of the generated cerium oxides. A comprehensive examination utilizing SEM and micro-CT identified the presence of cerium oxide nanoparticles deposited within the dentinal tubules and lateral canals of the root canal system. The BMS and remineralized dentin exhibited substantial antibacterial efficacy against E. faecalis, as substantiated by assessments involving the broth dilution method and live/dead staining technique. The SEM findings revealed the cell morphological changes of deceased E. faecalis.

Conclusion

This study successfully demonstrated antibacterial biomimetic mineralization as well as sealing dentinal tubules and lateral branches of root canals using cerium nitrate and dextran. This novel biomimetic mineralization could be used as an alternative strategy for root canal disinfection.

Antimicrobial effect of grape seed extract as a potential intracanal medicament combined with Nd:YAG laser

This study evaluated the antimicrobial efficacy of grape seed extract medicament combined with Nd:YAG laser, against Enterococcus faecalis, Staphylococcus aureus and Candida albicans biofilms. Root canals infected with 4-week-old biofilms were divided into five groups (n = 11): calcium hydroxide, 6.5% GSE, Nd:YAG laser (1064 nm, 1.5 w, 15 Hz and 100 mj) and 6.5% GSE followed by Nd:YAG laser and normal saline (control). Dentin chips were collected using Gates-Glidden and cultured to obtain colony-forming units. Statistical analysis was performed using Kruskal-Wallis and Mann-Whitney U test. GSE showed higher antibacterial activity against all species investigated compared to Ca(OH)2 . However, the lowest microbial count was obtained using a combination of GSE and Nd:YAG laser (p < 0.001). No significant difference in the susceptibility of tested pathogens to each of the protocols was observed (p > 0.05). Application of Nd:YAG laser following GSE medicament is efficient against endodontic biofilms; also, GSE can be considered as an alternative to Ca(OH)2 dressing.

Analyze the clinical effect of YAG laser combined with sodium hypochlorite in root canal treatment of pulpitis

OBJECTIVE

To compare and analyze the clinical therapeutic effects of sodium hypochlorite combined with Nd: YAG laser and sodium hypochlorite alone for root canal disinfection in patients with pulpitis.

METHODS

Patients with pulpitis were divided into control group and observation group according to random number table method. Both groups received root canal treatment, while the control group received root canal irrigation with 1% sodium hypochlorite. The observation group was irrigated with 1% sodium hypochlorite combined with Nd: YAG laser. Periodontal index, inflammatory index, life quality score and bacterial infection clearance rate of the two groups were compared before and 3 months after treatment.

RESULTS

The total effective rate of the observation group was 95.35%, which was higher than that of the control group 79.07% (p < .05). After 3 months of treatment, the periodontal index and inflammation level of both groups decreased, and the observation group was lower than that in the control group (p < .05). The life quality score and infection clearance rate of observation group were significantly higher than control group (p < .05).

CONCLUSION

Compared with root canal irrigation with 1% sodium hypochlorite alone, sodium hypochlorite combined with Nd: YAG laser for root canal disinfection can significantly improve the therapeutic effect, relieve inflammatory reaction, and decrease bacterial infection.

Antimicrobial effectiveness of ultrasonic irrigation in root canal treatment: a systematic review of randomized clinical trials and meta-analysis

OBJECTIVE

The objective of this systematic review and meta-analysis (SRM) was to answer the question as to whether the use of ultrasonic irrigation (UI) results in better antimicrobial activity in root canal disinfection compared to conventional irrigation (CI).

METHODS

A literature search was performed in the main scientific databases, carried out until October 2021. The eligibility criteria were randomized clinical trials (RCTs). Two meta-analyses were conducted using R software with the "META" package. The mean difference (MD) and odds ratio (OR) measure of effect were calculated. The fixed effect model was applied with a 95% confidence interval. The Cochrane collaboration scale was used to assess risk of bias and the GRADE tool to assess the quality of evidence.

RESULTS

A total of 1782 records were screened, and 12 studies meeting the criteria were included in this review. A low risk of bias was observed for most domains, except allocation concealment that was considered unclear. The certainty of evidence was classified as moderate in the OR meta-analyses and low in the MD meta-analyses. Ultrasonic irrigation resulted in a better antimicrobial effect in both meta-analyses, MD 1.42 [1.60; 1.23] p < 0.0001, I² = 80%; and OR 3.86 [1.98; 7.53] p< 0.0001, I² = 28.7%.

CONCLUSION

Within the limitations of this SRM, UI presented better antimicrobial efficacy than CI.

CLINICAL RELEVANCE

UI should be used by clinicians as it promotes better antimicrobial efficacy in patients undergoing endodontic treatment.

Microbiological Aspects of Root Canal Infections and Disinfection Strategies: An Update Review on the Current Knowledge and Challenges

The oral cavity is the habitat of several hundreds of microbial taxa that have evolved to coexist in multispecies communities in this unique ecosystem. By contrast, the internal tissue of the tooth, i.e., the dental pulp, is a physiologically sterile connective tissue in which any microbial invasion is a pathological sign. It results in inflammation of the pulp tissue and eventually to pulp death and spread of inflammation/infection to the periradicular tissues. Over the past few decades, substantial emphasis has been placed on understanding the pathobiology of root canal infections, including the microbial composition, biofilm biology and host responses to infections. To develop clinically effective treatment regimens as well as preventive therapies, such extensive understanding is necessary. Rather surprisingly, despite the definitive realization that root canal infections are biofilm mediated, clinical strategies have been focused more on preparing canals to radiographically impeccable levels, while much is left desired on the debridement of these complex root canal systems. Hence, solely focusing on "canal shaping" largely misses the point of endodontic treatment as the current understanding of the microbial aetiopathogenesis of apical periodontitis calls for the emphasis to be placed on "canal cleaning" and chemo-mechanical disinfection. In this review, we dissect in great detail, the current knowledge on the root canal microbiome, both in terms of its composition and functional characteristics. We also describe the challenges in root canal disinfection and the novel strategies that attempt to address this challenge. Finally, we provide some critical pointers for areas of future research, which will serve as an important area for consideration in Frontiers in Oral Health.

Effect of sodium hypochlorite on biofilm of Klebsiella pneumoniae with different drug resistance

BACKGROUND

Biofilm formation is a major factor in the resistance mechanism of Klebsiella pneumoniae. This study aimed to evaluate the effects of sodium hypochlorite on the biofilm of K. pneumoniae with different drug resistance.

METHODS

We collected 3 different types of K. pneumoniae respectively. The growth trend of biofilms of different drug-resistant K. pneumoniae was quantified by measuring the OD₅₉₀ for 7 consecutive days using crystal violet staining. Scanning confocal fluorescence microscopy was used to observe biofilm morphology.

RESULTS

After adding sodium hypochlorite, there were significant differences between the OD₅₉₀ value of the 200, 500, and 1,000 µg/mL groups and the positive control group (all P < .05) on the fifth day. Concentrations of 2,000 and 5,000 µg/mL sodium hypochlorite were added after the biofilm had matured. In the 5,000 µg/mL sodium hypochlorite group, the OD₅₉₀ of K. pneumoniae biofilm in the 3 groups decreased significantly compared with the blank control group (all P < .05).

CONCLUSIONS

Sodium hypochlorite inhibited and cleared the biofilm of K. pneumoniae with different drug resistance, and the effect was enhanced with the increase of concentration in the range of bacteriostatic and bactericidal concentration.

Antibacterial efficacy of antibiotic pastes versus calcium hydroxide intracanal dressing: A systematic review and meta-analysis of ex vivo studies

Background

Conflicting findings on the potency of antibiotic pastes versus calcium hydroxide (CH) have been evident in the literature.

Aims

To compare the antibacterial efficacy of single antibiotic paste (SAP), double antibiotic paste (DAP), triple antibiotic paste (TAP), and modified TAP (mTAP) with CH on bacterial biofilms.

Methods

PubMed, Scopus, and Embase were comprehensively searched until August 23, 2021. The study protocol was registered in the PROSPERO. Ex vivo studies performed on Enterococcus faecalis or polymicrobial biofilms incubated on human/bovine dentin were selected. The quality of the studies was assessed using a customized quality assessment tool. Standardized mean difference (SMD) with a 95% confidence interval (CI) was calculated for the meta-analysis. Meta-regression models were used to identify the sources of heterogeneity and to compare the efficacy of pastes.

Results

The qualitative and quantitative synthesis included 40 and 23 papers, respectively, out of 1421 search results. TAP (SMD = -3.82; CI, -5.44 to -2.21; P < 0.001) and SAPs (SMD = -2.38; CI, -2.81 to - 1.94; P < 0.001) had significantly higher antibacterial efficacy compared to the CH on E. faecalis biofilm. However, no significant difference was found between the efficacy of DAP (SMD = -2.74; CI, -5.56-0.07; P = 0.06) or mTAP (SMD = -0.28; CI, -0.82-0.26; P = 0.31) and CH. Meta-regression model on E. faecalis showed that SAPs have similar efficacy compared to TAP and significantly better efficacy than DAP. On dual-species (SMD = 0.15; CI, -1.00-1.29; P = 0.80) or multi-species (SMD = 0.23; CI, -0.08-0.55; P = 0.15) biofilms, DAP and CH had similar efficacy.

Conclusions

Ex vivo evidence showed that antibiotic pastes were either superior or equal to CH. The studied SAPs had considerably higher or similar antibacterial effectiveness compared to DAP, CH, and TAP. Hence, combined antibiotic therapy was not necessarily required for root canal disinfection ex vivo.

Comparing the Antifungal Effect of Sodium Hypochlorite Gel versus Different Types of Root Canal Medicaments at Different Time Intervals Using the Agar Diffusion Test: An In Vitro Study

Aims

The purpose of this study was to compare the antifungal activity of sodium hypochlorite gel to those of four intracanal medicaments at various time intervals.

Materials and Methods

The agar well diffusion technique was utilized to test the antifungal activity of the following medicaments against Candida albinans (C. albicans): sodium hypochlorite gel, chlorhexidine gel, calcium hydroxide paste, Ledermix, and Diapex Plus. The inhibition zone related to each medicine was measured in millimeter after 24, 48, and 72 hours of incubation at 37°C. The data were analyzed using one-way ANOVA and Games–Howell tests, at a significance level of P < 0.05.

Results

Except for Ledermix and Diapex Plus, which had no antifungal action, all of the medicaments showed varied inhibitory zones for C. albicans. At all periods, the NaOCl gel had the most significant inhibition zones, followed by the CHX gel and calcium hydroxide. At all time intervals, the NaOCl gel demonstrated comparable antifungal efficacy. When compared to a 24-hour time interval, the CHX gel showed an increased antifungal activity at the 48-hour and 72-hour intervals. Calcium hydroxide, on the other hand, showed a decrease in its antifungal activity at the 72-hour interval.

Conclusion

The antifungal activity of sodium hypochlorite gel was the highest among the investigated medicaments. Chlorhexidine gel's antifungal activity improved over time, whereas calcium hydroxide's antifungal activity declined. Diapex Plus and Ledermix did not have any antifungal properties.

The Effect of Different Final Irrigation Regimens on the Dentinal Tubule Penetration of Three Different Root Canal Sealers: A Confocal Laser Scanning Microscopy Study In Vitro

This study evaluated the effects of different final irrigation regimens on the dentin tubule penetration of three different root canal sealers using confocal laser scanning microscopy (CLSM). A total of 160 single-rooted extracted mandibular premolar teeth were divided into five groups (n = 32 each) according to the solution used in the final rinse protocol, as follows: 17% ethylenediaminetetraacetic acid (EDTA) (group 1), 17% EDTA and 2% chlorhexidine gluconate (CHX) (group 2), 7% maleic acid (MA) (group 3), 7% MA and 2% CHX (group 4), and 5.25% NaOCl (group 5). Two roots from each group were examined under scanning electron microscopy (SEM) to visualize smear layer removal. Experimental groups were then split randomly into three subgroups (n = 10) and obturated using a cold lateral condensation technique with 0.1% rhodamine B-labelled sealers [either AH Plus (group A), EndoREZ (group E), or Tech BioSealer Endo (group T)] and gutta-percha. Specimens were sectioned and observed by CLSM to evaluate the percentage and maximum depth of sealer penetration at the apical, middle, and coronal levels. Statistical comparison was performed on grouped (apical, middle, and coronal segments) and ungrouped data using two-way ANOVA with Bonferroni post hoc test (p < 0.01). AH Plus showed the greatest tubule penetration while Tech BioSealer Endo showed the least. Resin-based sealers displayed deeper and more consistent penetration. CHX irrigation positively influenced sealer tubule penetration.

Mesoporous Calcium-Silicate Nanoparticles Loaded with Low-Dose Triton-100+Ag+ to Achieve Both Enhanced Antibacterial Properties and Low Cytotoxicity for Dentin Disinfection of Human Teeth

Mesoporous calcium-silicate nanoparticles (MCSNs) are excellent biomaterials for controlled drug delivery and mineralization induction. In this study, MCSNs were loaded with low-dose silver ion (Ag⁺) and Triton X-100 (TX-100) as the M-AgTX to achieve both enhanced antibacterial properties and low cytotoxicity for dentin disinfection. The physicochemical property, biocompatibility, infiltration ability into dentinal tubules, anti-bacterial ability against both planktonic Enterococcusfaecalis (E. faecalis) and its biofilm on dentin, effects on dentin microhardness and in vitro mineralization property were systematically investigated. Results confirmed that the MCSNs and M-AgTX nanoparticles showed typical morphology of mesoporous materials and exhibited sustained release of chemicals with an alkaline pH value over time. M-AgTX also exhibited excellent biocompatibility on MC3T3-E1 cells and could eliminate 100% planktonic E. faecalis after 48-h treatment. On dentin slices, it could enter dentinal tubules by ultrasonic activation and inhibit the growth of E. faecalis on dentin. M-AgTX could completely inactive 28-day E. faecalis biofilm. TEM confirmed the destruction of cell membrane integrity and Ag⁺ infiltration into bacteria by M-AgTX. Besides, dentin slices medicated with M-AgTX nanoparticles displayed an increased microhardness. After being immersed in SBF for 7 days, apatite crystals could be observed on the surface of the material tablets. M-AgTX could be developed into a new multifunctional intra-canal medication or bone defect filling material for infected bone defects due to its sustained release profile, low cytotoxicity, infiltration ability, enhanced anti-bacterial and mineralization features.

Antibacterial Properties of Aloe vera on Intracanal Medicaments against Enterococcus faecalis Biofilm at Different Stages of Development

Background

Use of herbal compounds as an intracanal medicament in the field of endodontics has become noteworthy, one of which is the Aloe vera compound whose antibacterial effect has already been proven in the planktonic form of Enterococcus faecalis. The purpose of this study is to evaluate the antibacterial effect of Aloe vera on E. faecalis biofilms at the 4^th and 6^th week of development.

Materials and Methods

130 single root canal teeth without anomalies and caries were used. They were divided into two groups of 65 teeth for four and six weeks of biofilm production. Five samples of each group were examined for confirmation of biofilm formation under an electron microscope. Study groups were investigated with an antimicrobial agent as an intracanal medicament including 20 samples treated with Aloe vera, calcium hydroxide, and phosphate-buffered saline, and biofilm and survival of pathogens were investigated. Dentin chip suspensions were used for colony-forming unit (CFU) counting to estimate remaining E. faecalis counts.

Results

The CFU mean in the 4^th week subgroup in Aloe vera, phosphate-buffered saline, and calcium hydroxide was 0, 69166.66 ± 31688.58, and 25000 ± 30822.07, and in the 6^th week, it was 136.36 ± 323.33, 95000 ± 12247.44, and 27501.66 ± 36570.34, respectively, which showed a significant difference between the used materials (p < 0.05).

Conclusion

Aloe vera, in contrast to calcium hydroxide, eliminated 4^th and 6^th week biofilms and showed remarkable antibacterial properties against E. faecalis biofilm. These results support potency of Aloe vera to use as a natural antimicrobial material in the intracanal medicament.

Characterization of Enterococcus faecalis in different culture conditions

The aim of this study was to investigate how carbohydrates (glucose or sucrose) affect the characteristics of Enterococcus faecalis (E. faecalis) planktonic and biofilm in vitro. For this study, E. faecalis was cultured in tryptone-yeast extract broth with 0% glucose + 0% sucrose, 0.5% glucose, 1% glucose, 0.5% sucrose, or 1% sucrose. Viability of E. faecalis was examined by colony forming unit counting assays. Biofilm formation was assessed by measuring extracellular DNA (eDNA), a component of the biofilm matrix. Quantitative real-time PCR (qRT-PCR) was performed to investigate the expression of virulence-associated genes. Field emission scanning electron microscopy analysis, confocal laser scanning microscopy analysis, and crystal violet colorimetric assay were conducted to study E. faecalis biofilms. E. faecalis showed the highest viability and eDNA levels in 1% sucrose medium in biofilms. The result of qRT-PCR showed that the virulence-associated genes expressed highest in 1% sucrose-grown biofilms and in 1% glucose-grown planktonic cultures. E. faecalis showed highly aggregated biofilms and higher bacteria and exopolysaccharide (EPS) bio-volume in sucrose than in 0% glucose + 0% sucrose or glucose. The results indicate that the production of eDNA and EPS and expression of virulence-associated genes in E. faecalis are affected by the concentration of carbohydrates in biofilm or planktonic culture.

Respiratory symptoms of exposure to substances in the workplace among Bulgarian dentists

OBJECTIVES

Dentists are exposed to a variety of airborne chemicals that can act as irritants and sensitizers and may give rise to work-related respiratory symptoms. The aim of this study was to estimate the prevalence of respiratory symptoms of exposure to substances in the workplace and associated risk factors in Bulgarian dentists.

METHODS

A cross-sectional study was performed among Bulgarian dentists by using a self-report questionnaire. A direct acyclic graph (DAG) was elaborated to illustrate the direct and indirect causal pathways between exposure to irritants and/or allergens from dental environment and work-related respiratory symptoms among dentists. Multiple logistic regression analysis was conducted in order to investigate the relationship between sex, work experience, daily exposure to chemicals from dental environment, history of atopic disorder and work-related respiratory symptoms.

RESULTS

A total of 4675 dentists completed the questionnaire (response rate 48.1%). The prevalence of self-reported work-related respiratory symptoms was 20.7%. The most common repeated causes of respiratory reactions were disinfectants (65.7%) and materials based on acrylic resins (29.7%). Factors associated with work-related respiratory symptoms are personal history of asthma (odds ratio (OR) 2.50, 95% confidence interval [CI]: 1.71-3.64), work experience >20 years (OR 2.17, 95% CI: 1.74-2.70) and female gender (OR 2.14, 95% CI: 1.81-2.56).

CONCLUSION

Work-related respiratory symptoms are frequent among dentists and indicate a need for efforts to establish effective programmes and techniques of reducing or eliminating direct exposure to airborne chemicals in the dental environment.

Antibacterial efficacy and discolouration potential of antibiotic pastes with macrogol for regenerative endodontic therapy

This study aimed to evaluate the antibacterial efficacy and discolouration potential of antibiotic pastes containing macrogol. Seventy single-rooted teeth were contaminated with a culture of Enterococcus faecalis for 30 days. Double (DAP) and triple antibiotic pastes (TAP) containing propylene glycol or macrogol as vehicles were applied. After 15 days, bacterial viability was compared. Change in teeth coronal colour was measured by a spectrophotometer. Statistical analysis was performed using anova and Tukey's test (P < 0.05). TAP containing clindamycin and propylene glycol was the only medicament that led to the presence of contamination, while the same combination of antibiotics containing macrogol did not result in bacterial growth (P < 0.05). Only the pastes containing minocycline in formulation resulted in coronal discolouration (P < 0.05). Both DAPs evaluated and the TAP containing clindamycin and macrogol showed to be the preferable options for regenerative endodontic therapy, as they were effective against E. faecalis biofilm and did not promote tooth discolouration.

Near-infrared NIR irradiation and sodium hypochlorite: An efficacious association to counteract the Enterococcus faecalis biofilm in endodontic infections

New strategies are necessary for the prevention of endodontic infections caused by Enterococcus faecalis, a common resistant pathogen and biofilm producer. Aim of the present study was to compare the effects of Near-Infrared (NIR) Light-Emitting Diode (LED) irradiation and different concentrations of sodium hypochlorite (NaOCl) alone or combined to each other on the E. faecalis biofilm, on artificial and human dentin surfaces. E. faecalis ATCC 29212 preformed biofilms, on polystyrene wells and on dentin discs, were treated with 880 nm NIR irradiation and NaOCl at 4%, 2.5%, 1% and 0.5% alone and combined to each other (NIR irradiation plus NaOCl 1% or 0.5%) at 5 and 10 min. Treated biofilms were compared to the controls for (i) biofilm biomass evaluation, (ii) CFU count for the quantification of cultivable cells and (iii) cells viability. All the detected experimental conditions displayed a significant reduction of biofilm biomass (p < 0.001) and CFUs/mL (p < 0.01) in respect to the controls on both tested surfaces. The effects on the E. faecalis biomass, colony count and cell viability were not time-dependent except for NaOCl 2.5% and 1% in the biofilm biomass reductions on human dentin discs. NIR-LED irradiation alone showed a reduction of E. faecalis aggregates without interfering with cell viability whereas NaOCl alone expressed a killing effect in a concentration dependent way. The combination of NIR-LED irradiation with NaOCl 1% and 0.5% displayed a double effect of cluster disaggregation and cell killing. In particular, NIR-LED irradiation combined with NaOCl 0.5% displayed an anti-biofilm activity major than those expressed by NaOCl 0.5% alone (p = 0.001) with a reduction of biomass 93% vs 71% and 97% vs 25% after 10 min, on polystyrene wells and human dentin discs, respectively. The innovative use of NIR-LED irradiation combined at short times with low concentration of NaOCl (1% and 0.5%) is capable to reach a significant effect on E. faecalis biofilm, especially on human dentin discs.

Effect of sodium hypochlorite solution and gel with/without passive ultrasonic irrigation on Enterococcus faecalis, Escherichia coli and their endotoxins

Background: Sodium hypochlorite (NaOCl) is the most commonly used irrigant in endodontics . The purpose of this study was to evaluate the effect of NaOCl solution (2.5%) and gel (3%) with/without passive ultrasonic irrigation (PUI) on Enterococcus faecalis, Escherichia coli, and their endotoxins, lipopolysaccharide (LPS) and lipoteichoic acid (LTA).

Methods: 40 human lower premolars were contaminated with E. coli (ATCC 25922) for 28 days and E. faecalis (ATCC 29212) for 21 days. Specimens were randomly divided into four groups: (1) 2.5% NaOCl irrigating the canals without PUI activation; (2) 2.5% NaOCl with PUI; (3) 3% NaOCl gel irrigating the canals without PUI; and (4) 3% NaOCl gel with PUI. 40 mL of irrigant was used for each group. PUI activation was carried out using E1-Irrisonic stainless-steel tip at 10% frequency. After treatment, all specimens were filled with 3mL of 17% ethylenediaminetetraacetic acid (EDTA) for 3min and then washed with nonpyrogenic saline solution. Three samples were collected from the canals: S1, at baseline to confirm biofilm formation; S2 after treatment; and S3 after EDTA. Samples were assessed for E. coli and E. faecalis colony forming units, and LPS and LTA were assessed using chromogenic kinetic LAL assay and ELISA, respectively. Data were analyzed by Kruskal-Wallis, Friedmann and Dunn tests with α≤0.05.

Results: All groups were effective in reducing the microbial load of E. coli and E. faecalis after treatment without a significant difference among the groups. NaOCl and NaOCl gel groups had no significant difference in reducing LPS and LTA. Statistically increased reduction was seen for NaOCL + PUI and NaOCl gel + PUI compared for groups without PUI.

Conclusions: NaOCl gel has the same antimicrobial action of NaOCl solution and can partially detoxify endotoxins. PUI improves NaOCl (gel or solution) action over E. faecalis and E. coli and their endotoxins.

Pattern of Disinfection of Root Canal Dentin by Alternated Acid-Base Irrigating Regimen

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.