Eradication of enterococci biofilms by lactic acid alone and combined with chlorhexidine and cetrimide

Objective: The antimicrobial activity of lactic acid (LA) alone or in combination with chlorhexidine (CHX) and cetrimide (CTR) against three Enterococcus faecalis strains, E. faecalis ATCC 29212, E. faecalis EF-D1 and E. faecalis U-1765, one Enterococcus durans strain and one dual-species biofilm was investigated. Study Design: The irrigating solutions tested were 20%, 15%, 10%, 5% and 2.5% LA, alone and in combination with 2% CHX and with 0.2% CTR. The biofilms were grown in the MBECTM high-throughput device for 24 hours and exposed to the solutions for 30 seconds and 1 minute. “Eradication” was defined as 100% bacterial kill. Results: Twenty percent LA eradicated all enterococci biofilms after 30 seconds contact time. The association of LA + 0.2% CTR achieved better results than LA alone, in contrast with the results obtained using LA + 2% CHX. E. durans was eradicated by all the tested solutions at 1 minute. The dual-species biofilm, E. faecalis ATCC 29212 + E. durans, gave intermediate values of the pure cultures. Conclusions: LA is capable of eradicating enterococci biofilm at a concentration of 20%. The combination of lower concentrations with 0.2% CTR achieved eradication after 1 minute. Key words:Biofilm, cetrimide, chlorhexidine, enterococcus durans, enterococcus faecalis.     

Antimicrobial activity and enterococcus faecalis biofilm formation on chlorhexidine varnishes

Objective: To evaluate, in vitro, the antimicrobial activity and biofilm formation of three chlorhexidine varnishes in four Enterococcus faecalis strains: E. faecalis ATCC 29212, E. faecalis EF-D1 (from failed endodontic treatment), E. faecalis 072 (cheese) and E. faecalis U-1765 (nosocomial infection), and one Enterococcus durans strain (failed endodontic treatment). Study Design: The direct contact test was used to study the antimicrobial activity. Bacterial suspensions were exposed for one hour to EC40, Cervitec (CE) and Cervitec Plus (CEP) varnishes. “Eradication” was defined as 100% bacterial kill. The formation of enterococci biofilms was tested on the surface of the varnishes after 24 hours of incubation and expressed as percentage of biofilm reduction. Results: EC40 eradicated all strains except E. faecalis ATCC 29212, where 98.78% kill was achieved. CE and CEP showed antimicrobial activity against all the strains, but most clearly against E. durans and E. faecalis 072. EC40 completely inhibited the formation of biofilm of E. faecalis ATCC 29212, E. faecalis 072 and E. durans. CE and CEP led to over 92% of biofilm reduction, except in the case of E. faecalis U-1765 on CEP (76.42%). Conclusion: The three varnishes studied were seen to be effective in killing the tested strains of enterococci and in inhibiting the formation of biofilm, the best results being observed with EC40. Key words:Biofilm, chlorhexidine varnish, direct contact test, Enterococcus durans, Enterococcus faecalis, intracanal medication.     

Residual and antimicrobial activity of final irrigation protocols on Enterococcus faecalis biofilm in dentin

Introduction

The use of root canal irrigating solutions exerting antimicrobial activity and prolonged residual activity is desirable in order to control dentin infection and delay reinfection of the root canal. The aim of this study was to evaluate the residual antimicrobial activity and the capacity to eradicate Enterococcus faecalis biofilm of different irrigating solutions, alone and in combination, in a dentin-volumetric test.

Methods

Solutions of 2.5% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX), 0.2% cetrimide (CTR), 17% ethylendiaminetetraacetic (EDTA), 7% maleic acid (MA), and regimens of 2.5% NaOCl followed by 17% EDTA or 7% MA and 0.2% CTR or 2% CHX were used to determine their residual activity by exposing treated dentin blocks to E. faecalis for 24 hours. Antimicrobial activity was assayed on 3-week biofilm formed on dentin blocks. Results of residual activity and antimicrobial activity were respectively expressed as the inhibition percentage of biofilm formation and the kill percentage of biofilm.

Results

A 2% CHX and 0.2% CTR solution showed 100% biofilm inhibition; 2.5% NaOCl showed the lowest residual activity (18.10%). The kill percentage of 2.5% NaOCl and 0.2% CTR was 100% followed by 7% MA and 2% CHX, whereas 17% EDTA was the least effective (44%). Solutions of 7% MA or 17% EDTA followed by 0.2% CTR or 2% CHX showed 100% residual and antimicrobial activity.

Conclusions

A 0.2% CTR solution alone and the combinations in which 2% CHX or 0.2% CTR was the final irrigating solution achieved the maximum residual and antimicrobial activity.     

持续性根尖周炎优势菌粪肠球菌生物膜形成能力的体外研究

目的：比较持续性根尖周炎优势细菌粪肠球菌( Enterococcus faecalis,E． faecalis)标准菌株与临床菌株生物膜体外形成能力。方法 E． faecalis 标准菌株 ATCC 29212及持续性根尖周炎分离的 E． faecalis 临床株lcl1709,体外形成生物膜,采用激光扫描共聚焦荧光显微镜(LSCM)观察并对比在12、24、36、48h时2种生物膜形成面积;使用96微孔板结晶紫染色法检测并比较在12、24、36、48h时两者生物膜形成量。结果 ATCC 29212菌株培养12、24、36、48h在离体牙根尖表面生物膜形成面积(μm2)分别为47．577±45．221,206．935±122．596,558．782±330．877,1865．023±702．539;lcl1709的为62．227±33．040,461．578±285．281,1211．077±515．262,2632．515±1332．914。36h与48h lcl1709形成的生物膜面积显著高于ATCC 29212(P<0．05)。12、24、36、48h的生物膜OD590值ATCC 29212菌株分别为0．048±0．001,0．130±0．025,0．148±0．022,0．137±0．021;lcl1709菌株分别为0．096±0．029,0．162±0．015,0．201±0．042,0．235±0．078。 lcl1709生物膜OD590值显著高于ATCC 29212(P<0．05),随时间延长,各组OD590值显著增大( P<0．05)。结论 E． faecalis可形成生物膜,持续性根尖周炎分离的E． faecalis菌株生物膜形成能力强于标准菌株,可能与其致病性密切相关。     

Enterococcus faecalis Biofilms Eradication by Root Canal Irrigants

The aim of this study was to evaluate the minimal biofilm eradication concentration (MBEC) of sodium hypochlorite (NaOCl), chlorhexidine (CHX), EDTA, and citric and phosphoric acids after 1, 5, and 10 minutes of exposure to biofilms of Enterococcus faecalis. The biofilms grew in the MBEC high-throughput device for 24 hours at 37°C and were exposed to 10 serial two-fold dilutions of each irrigating solution. The viable cell counts were log₁₀ transformed, and a concentration of an irrigant was considered to eradicate the biofilms when it produced a reduction of ≥ 5 logarithmic units. NaOCl was the most effective agent, capable of eradicating the biofilms after 1 minute at a concentration of 0.00625%. CHX eradicated biofilm after 5 minutes at 2%. EDTA and citric and phosphoric acid solutions were not effective against the biofilms at any concentration or time tested.     

Antimicrobial substantivity of chlorhexidine-treated bovine root dentin

Previous studies have demonstrated antimicrobial substantivity in root canal dentin up to 7 days after treatment with chlorhexidine. This in vitro study assessed the antimicrobial substantivity of chlorhexidine-treated bovine root dentin over a period of 21 days. Sixty standardized bovine root sections were randomly divided into three equal groups, and their canals immersed in one of the following solutions: (i) sterile saline; (ii) 2.5% NaOCl; or (iii) 0.2% chlorhexidine (CHX). Half the specimens in each group were treated with the solution for 5 min and the other half for 7 days. After solutions were removed, the specimens were incubated at 37 degrees C in Brain Heart Infusion broth containing Enterococcus faecalis (ATCC 29212). A fresh inoculum was added to the broth every other day over a 21-day period. The canals were then enlarged with sterile burs, and the dentin shavings collected and cultured for the presence of cultivable bacteria in the dentinal tubules. Specimens treated with CHX for 7 days demonstrated significantly less dentin colonization by E. faecalis than the other specimens. CHX has potential as an intracanal medicament, if it can be applied for a period of at least 7 days.     

Effect of Long-term Exposure to Peptides on Mono- and Multispecies Biofilms in Dentinal Tubules

IntroductionThe aim of this study was to evaluate the antibiofilm effectiveness of 2% chlorhexidine (CHX) and peptides 1018 and DJK-5 used either alone or in a mixture (peptide and 2% CHX) against Enterococcus faecalis and multispecies biofilms in dentin canals after short-term and long-term exposure.MethodsOne hundred eighty dentin blocks were prepared and filled with E. faecalis or multispecies bacteria by centrifugation. Three-week-old biofilms in dentin were subjected to 2% CHX, DJK-5 (10 μg/mL), 1018 (10 μg/mL), DJK-5 + 2% CHX, or 1018 + 2% CHX for short-term (1 or 3 minutes), short-term exposure after 24 hours, and long-term exposure (24 hours of exposure). The antibacterial efficacy was determined by live/dead bacterial viability staining and confocal laser scanning microscopy.ResultsPeptide DJK-5 with or without CHX was the most effective agent against all the biofilms (P < .05), killing 77% of biofilm bacteria in 1 minute. No significant difference in bacterial killing was detected between the first 3 minutes of exposure (>81%) and after 24 hours of exposure (83%) to DJK-5 or DJK-5 + CHX. Chlorhexidine and peptide 1018 had a weaker antibiofilm effect than DJK-5, and their effect was time dependent (P < .05) with a maximum killing of 60% after 24 hours of exposure.ConclusionsPeptide DJK-5 alone and together with CHX had a rapid antibacterial effect against dentin infection. An additional antibacterial effect by CHX and peptide 1018 was achieved after a 24-hour long-term exposure.     

Impact of growth conditions on susceptibility of five microbial species to alkaline stress

The effects of different growth conditions on the susceptibility of five taxa to alkaline stress were investigated. Enterococcus faecalis ATCC 29212, Streptococcus sobrinus OMZ 176, Candida albicans ATCC 90028, Actinomyces naeslundii ATCC 12104, and Fusobacterium nucleatum ATCC 10953 were grown as planktonic cells, allowed to adhere to dentin for 24 hours, grown as monospecies or multispecies biofilms on dentin under anaerobic conditions with a serum-enriched nutrient supply at 37 degrees C for 5 days. In addition, suspended biofilm microorganisms and 5-day old planktonic multispecies cultures were used. Microbial recovery upon direct exposure to saturated calcium hydroxide solution (pH 12.5) for 10 and 100 minutes was compared with control exposure to physiologic saline. Planktonic microorganisms were most susceptible; only E. faecalis and C. albicans survived in saturated solution for 10 minutes, the latter also for 100 minutes. Dentin adhesion was the major factor in improving the resistance of E. faecalis and A. naeslundii to calcium hydroxide, whereas the multispecies context in a biofilm was the major factor in promoting resistance of S. sobrinus to the disinfectant. In contrast, the C. albicans response to calcium hydroxide was not influenced by the growth condition. Adherence to dentin and interspecies interactions in a biofilm appear to differentially affect the sensitivity of microbial species to calcium hydroxide.     

Antibacterial and Anti-biofilm Activity of AH Plus with Chlorhexidine and Cetrimide

Introduction

The use of root canal filling materials with antibacterial activity can be considered beneficial to reduce the remaining microorganisms in the root canal system, where Enterococcus faecalis is often found, and prevent recurrent infection. The aim of this study was to evaluate the antimicrobial activity and capacity for inhibiting E. faecalis biofilm formation of AH Plus, alone and mixed with chlorhexidine (CHX), cetrimide (CTR), and combinations of the two.

Methods

AH Plus alone and mixed with 1% and 2% CHX, 0.1%–0.5% CTR, and combinations of both were tested to assess antimicrobial activity by a modified direct contact test and determine inhibition of E. faecalis biofilm formation at 24 hours. The results were expressed as log₁₀ viable counts. Eradication and inhibition of biofilm formation were understood as no bacterial growth or log₁₀ reduction = 5 with respect to the control (AH Plus alone).

Results

AH Plus + CHX showed a low antimicrobial activity with respect to the control (at 2%, log₁₀ reduction = 1.30). None of the tested concentrations achieved eradication or inhibition of biofilm. AH Plus + CTR showed a direct relationship of concentration-antimicrobial effect, reaching a log₁₀ reduction of 2.92 at 0.5% and inhibition of biofilm formation at 0.2%. With the combination CHX + CTR, lower concentrations were needed for the same effect, and eradication and inhibition of biofilm were achieved.

Conclusions

The addition of CHX, CTR, or some combination of both to AH Plus confers it with bactericidal and anti-biofilm activity against E. faecalis.     

洗必泰葡萄糖酸盐对感染根管细菌生物膜的实验研究

目的：探讨洗必泰葡萄糖酸盐作为根管冲洗药物,对粪肠球菌生物膜的灭菌作用。方法：在无菌盖玻片上制备粪肠球菌生物膜,应用0．2％和5％洗必泰葡萄糖酸盐冲洗,分别作用1min和5min,激光扫描共聚焦显微镜观察灭菌效果。结果：0．2％或5％洗必泰葡萄糖酸盐的灭菌效果随作用时间的延长而增加（P＜0．05）;5％洗必泰葡萄糖酸盐作用1min的灭菌效果明显优于0．2％洗必泰葡萄糖酸盐（P＜0．05）,而其作用5min的灭菌效果与0．2％洗必泰葡萄糖酸盐者无差异（p＞0．05）。结论：洗必泰葡萄糖酸盐具有明显的杀灭粪肠球菌生物膜的作用,其不同浓度和不同作用时间的灭菌效果不同,然而尚不能达到完美的根管冲洗消毒目的。     

Susceptibility of Enterococcus faecalis biofilm to antibiotics and calcium hydroxide

The purpose of this study was to investigate the antimicrobial efficacy of six groups of antibiotics and calcium hydroxide against Enterococcus faecalis biofilm in a membrane filter model. Two-day-old E. faecalis (ATCC 29212) biofilm was exposed to ampicillin, co-trimoxazole, erythr omycin, oxytetracycline, vancomycin, vancomycin followed by gentamicin, Ca(OH)(2), and phosphate-buffered saline (control). After 1 h of exposure, the antimicrobial activity was neutralized by washing each disc five times in PBS, and then the colony-forming units of the remaining viable bacteria on each disc were counted. The results revealed that only erythromycin, oxytetracycline and Ca(OH)2 showed 100% biofilm kill. An ANOVA with a Bonferroni post hoc test (P < 0.05) detected significant differences among the test agents, except in the ampicillin group versus the co-trimoxazole group. It is concluded that erythromycin, oxytetracycline and Ca(OH)2 are 100% effective in eliminating E. faecalis biofilm, whereas ampicillin, co-trimoxazole, vancomycin, and vancomycin followed by gentamicin are ineffective.     

Efficacy of chlorhexidine- and calcium hydroxide-containing medicaments against Enterococcus faecalis in vitro

OBJECTIVE: We sought to assess the efficacy of chlorhexidine (CHX) and calcium hydroxide, Ca(OH)(2), against Enterococcus faecalis in vitro. STUDY DESIGN: The effect of CHX (0.2% and 2% in gel or solution) and Ca(OH)(2) (alone or with 0.2% CHX gel) was evaluated by using the agar diffusion test and an in vitro human root inoculation method, to measure zone of inhibition or bacterial growth with optical density analysis, respectively. For optical density analysis, samples from infected root canals were collected after 7 days of medication and were cultured for 24 hours in brain-heart infusion to detect viable bacteria. RESULTS: In the agar diffusion test, CHX was effective against E faecalis in a concentration-dependent fashion, but Ca(OH)(2) alone had no effect. In the root canal inoculation test, CHX was significantly more effective against E faecalis than Ca(OH)(2) was (P < .05), but there were no significant differences between the modes of medication or concentrations of CHX. CONCLUSIONS: CHX is effective against E faecalis in vitro. Further in vivo studies are needed to confirm the value of CHX in clinical treatment.     

Biofilm disruption by root canal irrigants and potential irrigants

Aim  To investigate the disruption and bactericidal effect of root canal irrigants on single and dual-species biofilms.
Methodology  Single-species ( Streptococcus sanguis , Enterococcus faecalis, Fusobacterium nucleatum, Porphymonas gingivalis) and dual-species ( S. sanguis and F. nucleatum ) biofilms were grown on nitro-cellulose membranes and immersed in either a commonly used root canal irrigant; (NaOCl, EDTA, Corsodyl^®, iodine) or potential root canal irrigant [sodium dodecyl sulphate (SDS), cetyl trimethyl ammonium bromide (CTAB) and Tween^®80] for 1, 5 or 10 min. The number of viable and nonviable bacteria disrupted from the biofilm and those remaining attached to the biofilm were determined using a viability stain in conjunction with fluorescent microscopy. In addition, confocal laser scanning microscopy (CLSM) was used to allow a visual assessment of the disruptive effects of selected agents on the stained biofilms.
Results  Gram-negative species were more susceptible to cell removal than their Gram-positive counterparts, S. sanguis being the least susceptible. The majority of the cell disruption occurred after the first minute of exposure as all of the agents exerted some effect on bacterial disruption and viability; however, the extent varied according to the agent. The most effective root canal irrigant for disrupting biofilms was NaOCl whilst in contrast iodine was generally effective at bacterial killing but not disruption. Of the potential root canal irrigants, CTAB and SDS were both effective in disrupting the biofilm and at bacterial cell-killing.
Conclusions  Biofilm disruption and cell viability were influenced by the species, their co-association in dual-species biofilms and the test agent. The effectiveness of NaOCl as an endodontic irrigant was reinforced.     

In vitro evaluation of the antimicrobial activity of chlorhexidine and sodium hypochlorite

The aim of this study was to investigate in vitro the antimicrobial activity of 0.2%, 1%, and 2% chlorhexidine gluconate (CHX gel and CHX liquid), against endodontic pathogens and compare the results with the ones achieved by 0.5%, 1%, 2.5%, 4%, and 5.25% sodium hypochlorite (NaOCl). A broth dilution test was performed, and the timing for irrigants to kill microbial cells was recorded and statistically analyzed. Both 2.0% gel and liquid formulations eliminated Staphylococcus aureus and Candida albicans in 15 seconds, whereas the gel formulation killed Enterococcus faecalis in 1 minute. All tested irrigants eliminated Porphyromonas endodontalis, Porphyromonas gingivalis, and Prevotella intermedia in 15 seconds. The timing required for 1.0% and 2.0% CHX liquid to eliminate all microorganisms was the same required for 5.25% NaOCl. The antimicrobial action is related to type, concentration, and presentation form of the irrigants as well as the microbial susceptibility.     

Residual Effectiveness of Final Irrigation Regimens on Enteroccus faecalis-infected Root Canals

Introduction

The application of a final irrigating solution that remains active over a fairly long period of time stands as one strategy for preventing bacterial recolonization or eliminating the bacteria that persist after root canal treatment. The aim of this study was to evaluate the residual antimicrobial activity of four final irrigation regimens in root canals contaminated with Enterococcus faecalis.

Methods

Biofilms of E. faecalis were grown in uniradicular roots for 4 weeks. After preparing the roots chemomechanically, four final irrigation regimens were applied: (1) group EDTA-NaOCl, 17% EDTA followed by 5.25% sodium hypochlorite (NaOCl); (2) group MA-NaOCl, 7% maleic acid (MA) followed by 5.25% NaOCl; (3) group EDTA-CHX + CTR, 17% EDTA followed by 2% chlorhexidine (CHX) + 0.2% cetrimide (CTR); and (4) group MA-CHX + CTR, 7% MA followed by 2% CHX + 0.2% CTR. Samples were collected for 60 days to denote the presence of bacterial growth. The Fisher exact test was used to compare the percentages of specimens without E. faecalis regrowth.

Results

All root canals in which the final irrigant was 5.25% NaOCl yielded positive cultures on the fifth day. Groups EDTA-CHX + CTR and MA-CHX + CTR with a final irrigation of 2% CHX + 0.2% CTR showed respective percentages of samples without regrowth of 72.1% and 66.8% at 60 days. There were no statistically significant differences between these groups.

Conclusions

The combination of 2% CHX + 0.2% CTR would be an effective alternative final irrigation regimen given its antimicrobial action over time.     

Ex vivo microbial leakage after using different final irrigation regimens with chlorhexidine

Objective:

To assess the influence of final irrigation protocols with chlorhexidine in the coronal leakage of Enterococcus faecalis in filled root canals.

Material and Methods:

Seventy single-root canals from extracted teeth were prepared using ProTaper instruments. The irrigation protocol accomplished an alternating irrigation with 5 mL of 2.5% sodium hypochlorite (NaOCl) and 17% EDTA between each file. The teeth were randomly divided into four experimental groups (n=15) according to the final irrigation regimen: group 1, without final irrigation; group 2, irrigation with 10 mL 2.0% chlorhexidine (CHX); group 3, with a final application of EC40^TM; and group 4, irrigation with the combination (1:1) of 0.2% CHX + 0.1% cetrimide (CTR). All the teeth were mounted in a two-chamber apparatus and the coronal access was exposed to E. faecalis. The presence of turbidity in the BHI broth over a period of 180 days was observed. The Friedman test was used for statistical analysis.

Results:

EC40^TM varnish showed the least leakage at 180 days, and was statistically similar to 2% CHX. No significant differences were observed between the group without final irrigation and the 2% CHX group or 0.2% CHX + 0.1% CTR.

Conclusions:

In this ex vivo study, EC40^TM showed the longest delayed coronal leakage of E. faecalis, although without significant differences from 2% CHX.     

In vitro antibacterial effect of different irrigating solutions on Enterococcus faecalis

Was evaluated the minimum inhibitory concentration (MIC) and the antibacterial effect (AE) of 2.5% NaOCl, 0.2% chlorhexidine gluconate (CHX) and 17% EDTA on Enterococcus faecalis. The antibacterial capacity was assessed by difusion in agar. The AE was evaluated on contaminated root dentin, employing apical and middle portions of human roots, sterilized and contaminated with Enterococcus faecalis, immersed in the irrigation solutions and incubated at 37 degrees C. Viable cells were counted at 0, 4, 8 and 24 hours. MIC: NaOCl and CHX: 0.2%, EDTA below 5%. Diffusion in agar: NaOCl 2.5% = 21 mm. CHX 0.2% = 14 mm. EDTA 17% = 20 mm. Effect on root dentin: NaOCl 2.5%: Enterococcus faecalis was totally inhibited for 24 hours in the apical area, and for 8 hours in the middle area. CHX 0.2% elicited a reduction of more than 5 log CFU and EDTA 17% induced a reduction of more than 3 log CFU at all the time points examined in the apical and middle areas.     

饥饿期粪肠球菌生物膜毒力因子明胶酶E表达研究

目的:研究粪肠球菌生物膜形成相关毒力因子明胶酶E(gelE)在饥饿期及药物作用后的表达情况。方法:体外建立对数期、稳定期、饥饿期粪肠球菌生物膜模型,分别以1%、2.5%、5.25%次氯酸钠溶液作用于各时期粪肠球菌生物膜后,用Real-time PCR对gelE的基因表达相对量进行检测。结果:gelE基因表达相对量,饥饿期高于稳定期及对数期(P<0.05);用药后,3个期gelE基因表达相对量,5.25%次氯酸钠溶液组低于2.5%次氯酸钠溶液组和1%次氯酸钠溶液组(P<0.05)。结论:饥饿期粪肠球菌生物膜形成相关毒力因子gelE较对数期及稳定期表达增强。次氯酸钠浓度依赖性可抑制粪肠球菌毒力因子gelE的表达。     

再治疗根管内粪肠球菌的分离鉴定及其相关特性研究

目的:研究粪肠球菌在再治疗根管内的检出率及其相关特性(生长情况、生物膜形成能力及耐药性)。方法:收集临床病例样本54例,使用粪肠球菌选择性培养基和胆盐七叶苷琼脂进行分离培养。分离株通过16SrRNA测序法鉴定。将鉴定正确的粪肠球菌临床分菌株和作为对照的粪肠球菌标准株(EfATCC29212)用BHI培养基进行培养,分别对比其生长曲线、生物膜形成能力及耐药性。结果:收集临床病例样本54例,分离鉴定为粪肠球菌的有18例,检出率为33.33%。经统计分析:粪肠球菌在再治疗根管内的检出率在病人性别、年龄、患牙尖周稀疏大小及距离上次根管治疗时间长短等方面无统计学差异(P>0.05);但与上次根管治疗根充是否到位有关,欠填根管中粪肠球菌的检出率明显高于恰填根管(P<0.05),但不同欠填长度组间粪肠球菌的检出率无统计学差异(P>0.05)。此外,粪肠球菌临床分离株与对照菌株在生长曲线、生物膜形成能力及耐药性等方面均无统计学差异(P>0.05)。结论:粪肠球菌在再治疗根管内的检出率为33.33%,其检出率与上次根管治疗根充情况有关。同时,粪肠球菌临床分离株与标准株的生长情况、生物膜形成能力及耐药性基本一致。     

Contemporary Root Canal Irrigants Are Able to Disrupt and Eradicate Single- and Dual-Species Biofilms

IntroductionClinical/microbiological studies have consistently revealed the persistence of some bacteria after conventional root canal debridement. Although this was originally attributed to the complexity of the root canal anatomy and the difficulty of delivering antibacterial agents effectively, it has emerged that the biofilm encasement of bacterial cells may confer a further mechanism of resistance. The purpose of this study was to investigate the relative disruption and bactericidal effects of root canal irrigants on single- and dual-species biofilms of root canal isolates.MethodsBiofilms of Streptococcus sanguinis, Enterococcus faecalis, Fusobacterium nucleatum, and Porphyromonas gingivalis were grown on nitrocellulose membranes for 72 hours and immersed in NaOCl, EDTA, chlorhexidine, and iodine for 1, 5, or 10 minutes. The number of viable and nonviable bacteria disrupted from the biofilm and those remaining adherent were determined by using a viability stain in conjunction with fluorescence microscopy.ResultsGram-negative obligate anaerobe species were more susceptible to cell removal than gram-positive facultative anaerobes. The majority of cells were disrupted after the first minute of exposure; however, the extent varied according to the agent and species. The most effective agent at disrupting biofilms was NaOCl. Iodine was generally effective at bacterial killing but not disruption.ConclusionsBiofilm disruption and cell viability were influenced by the species, their coassociation in dual-species biofilms, the test agent, and the duration of exposure. The effectiveness of NaOCl as an endodontic irrigant was reinforced.