Recovery of Enterococcus faecalis after single- or multiple-visit root canal treatments carried out in infected teeth ex vivo

AIM: To assess the presence of Enterococcus faecalis after root canal treatment in single or multiple visits in an ex vivo model. METHODOLOGY: Forty-five premolar teeth were infected ex vivo with E. faecalis for 60 days. The canals were then prepared using a crowndown technique with System GT and Gates-Glidden burs and irrigated with 2% chlorhexidine gel. The specimens were divided into five groups (G1, G2, G3, G4 and G5) according to the time elapsed between chemical-mechanical preparation and root canal filling, the irrigant solution used and the use or nonuse of a calcium hydroxide intra-canal medicament. The teeth were then root-filled and incubated for 60 days at 37 degrees C. Dentine chips were removed from the canal walls with sequential sterile round burs at low speed. The samples obtained with each bur were immediately collected in separate test tubes containing Brain-Heart Infusion broth. These samples were placed onto agar plates and colony forming units were counted after 24 h at 37 degrees C. Data were ranked and analysed using the Kruskal-Wallis statistical test. RESULTS: Enterococcus faecalis was recovered from 20% (three of 15 specimens) of G1 (chlorhexidine irrigation and immediate root filling in a single visit), 25% (four of 15 specimens) of G2 (chlorhexidine irrigation and filling after 14 days use of a calcium hydroxide dressing in multiple visits), 40% (two of five specimens) of G3 (chlorhexidine irrigation and filling after 7 days), 60% (three of five specimens) of G4 (saline irrigation and filling after 7 days) and from 100% (five of five specimens) of G5 (saline irrigation and immediate filling without sealer). CONCLUSIONS: Neither single- nor multiple-visit root canal treatment ex vivo, eliminated E. faecalis completely from dentinal tubules. Up to 60 days after root filling, E. faecalis remained viable inside dentinal tubules. When no sealer was used, E. faecalis presented a higher growth rate.     

In vitro evaluation of the antimicrobial effects of a root canal sealer-antibiotic combination against Enterococcus faecalis

The purpose of this in vitro study was to evaluate the antimicrobial effects of five antibiotics when added to Kerr Pulp Canal Sealer EWT against Enterococcus faecalis. Five antibiotics: amoxicillin, penicillin, clindamycin, metronidazole, and doxycycline, were added separately to Kerr sealer. Thirty brain heart infusion agar plates were inoculated with E. faecalis and sterile paper discs containing a sealer-antibiotic combination were randomly assigned to the inoculated plates. Kerr sealer on a sterile paper disc and a blank sterile paper disc served as the controls. Fifteen plates were incubated aerobically and the remaining 15 plates were incubated anaerobically at 37 degrees C. The zones of inhibition were measured at 48 hours. No significant differences (p > 0.05) were found between aerobic and anaerobic groups. The groups were combined and data analysis using a one-way ANOVA and Tukey's post hoc test was performed. Results revealed that sealer-antibiotic combinations containing amoxicillin, penicillin, clindamycin, and doxycycline had a significant difference (p < 0.001) in the mean zones of inhibition when compared to Kerr EWT sealer alone. No significant differences (p > 0.05) were found between the metronidazole-sealer combinations and Kerr EWT sealer alone.     

次氯酸钠对根管内粪肠球菌杀菌效果的体外实验

目的评价次氯酸钠对根管内粪肠球菌的杀菌效果。方法将45个离体前磨牙的感染根管标本分为6组，1、2组用5．25％及2．5％次氯酸钠冲洗，3组用0．9％NaCl冲洗，4、5组在根管预备时辅以5．25％及2．5％次氯酸钠冲洗，6组在根管预备时辅以0．9％Nacl冲洗。冲洗前、冲洗后即刻及冲洗后72h分别取样培养。结果6组根管内的细菌量均显著下降。1、2组差异无统计学意义（P〉0．05），但均好于3组（P〈0．05）。4、5和6组差异均有统计学意义（P〈0．05）。根管冲洗后培养72h均有细菌生长。结论2．5％次氯酸钠基本可达到更高浓度的灭菌效果，但是经过机械预备和次氯酸钠化学消毒后的根管内仍有细菌残留。     

羧甲基壳聚糖及其复合物对根管内粪肠球菌的作用评价

目的：探讨羧甲基壳聚糖(carboxymethyl chitosan,CMCS)及其复合物对根管内粪肠球菌的抑菌作用,为在根管治疗方面的应用积累数据。方法：建立粪肠球菌感染根管模型,随机分为A、B、C、D 4组,分别将2%氯己定、140 mg/mL羧甲基壳聚糖氯己定合剂、5 mg/mL羧甲基壳聚糖、Ca(OH)2糊剂注满相应组的各样本根管腔内,培养7 d。封药前、后取样,分别接种在BHI琼脂平皿上,48h后计数菌落形成单位(CFU/mL)。采用SPSS13.0软件包对数据进行统计学分析。结果：封药前,各组根管内细菌量差异无显著性(P>0.05)。封药后即刻,各组根管内细菌量的减少差异显著(P<0.05)。A组与B组的抗菌活性显著优于C组、D组。结论：2%氯己定与140 mg/mL羧甲基壳聚糖氯己定合剂对粪肠球菌具有较强的抗菌活性。     

Survival of Enterococcus faecalis in infected dentinal tubules after root canal filling with different root canal sealers in vitro

AIM: To investigate the ability of different endodontic sealers and calcium hydroxide to kill bacteria in experimentally infected dentinal tubules. METHODOLOGY: Fifty-six human root segments were enlarged to size 2 (ISO size 090) Largo Peeso Reamer. After treatment with 17% EDTA and 5% NaOCl for 4 min each, the specimens were infected with Enterococcus faecalis for 3 weeks. The roots were divided into eight groups and filled with gutta-percha and AH Plus (AH); Grossman's sealer (GS); Ketac-Endo (KE); Apexit (AP); RoekoSeal Automix (RSA); or RoekoSeal Automix with an experimental primer (RP), or calcium hydroxide (CH) only. One group of specimens was left unfilled for control (CT). Following storage in humid conditions at 37 degrees C for 7 days, the root canals were re-established with new sterile Largo size 2. Dentine samples from each canal were then collected using a sterile size 5 (ISO size 150) Largo Peeso Reamer. The number of colony-forming units (CFU) was determined for each sample. RESULTS: The mean log10 CFU in all test groups was significantly lower (P < 0.05) than that in the CT group. Root filling with AH and GS killed bacteria (mean CFU = 0) in the dentinal tubules. The mean log10 CFU for the CH group (0.53) was lower than that of RSA, AP, RP and KE (1.36, 1.40, 1.46 and 1.94, respectively), but only the difference between the CH and the KE groups was statistically significant (P < 0.05). CONCLUSION: Root fillings in vitro with gutta-percha and AH or GS were effective in killing E. faecalis in dentinal tubules. Other endodontic sealers, as well as CH, were less effective.     

不同根管冲洗方式对粪肠球菌生物膜清除效果评价

目的 比较不同根管冲洗方式对粪肠球菌感染根管预备、冲洗的清除效果,评价不同根管冲洗液残余药量的抗菌效果,为临床上选择根管冲洗方法提供参考。方法 将32颗离体牙（前磨牙、单根管）消毒,接种粪肠球菌60 d,随机分为4组（第1组：生理盐水;第2组：生理盐水+超声1 min;第3组：1%NaOCl;第4组：1%NaOCl+超声1 min）,使用ProTaper器械按照冠向下法进行根管预备,并在预备冲洗前及预备至F2进行冲洗后分别取样、计数,进行统计学分析。将预备好的离体牙再次消毒,随机分为2组,分别浸泡生理盐水和1%NaOCl;浸泡30 min后取出,置于接种粪肠球菌标准菌株（ATCC33186）的培养液内,分别在培养2、6、24、48 h时取样、计数。采用SPSS19.0软件包对数据进行统计学分析。结果 4组在预备至F2冲洗结束后,根管中的细菌数量均不同程度降低,其中,使用1% NaOCl结合超声冲洗1 min,几乎可完全去除根管内的细菌。经1% NaOCl浸泡的牙根样本内的细菌,在培养48 h时后总量少于生理盐水。结论 1%NaOCl是有效的根管冲洗液,用于根管化学预备后的残余液体,也可发挥有效的抗菌效果。联合使用超声器械,可以使其抗菌效果最大化。     

微创开髓下3种根管消毒方法对粪肠球菌清除效果比较

目的:比较微创和常规开髓下的不同根管消毒方法,获得一种基于微创开髓的高效简便的根管消毒方法.方法:将66颗离体上颌第一磨牙随机分为实验组(计算机辅助引导下开髓)和对照组(常规开髓),均预备至ProTaper Univer-sal F2,建立粪肠球菌感染模型.每组再随机分为NaCl0+EDTA冲洗(A)、NaClO+ED...     

Carisolv在根管机械化学预备过程中对根管清洁能力的影响

目的:探讨Carisolv作为根管预备的化学制剂对根管清洁度的影响.方法:将60例经亚甲蓝染色符合纳入标准的离体牙随机分为3组,分别采用Carisolv、2%氯亚明 3%过氧化氢和2.5%次氯酸钠不同的化学制剂处理根管.使用紫外可见分光光度仪测量荡洗液中亚甲蓝的吸光度值,并使用扫描电镜观察根管清洁度.采用SPSS11.5软件包对结果进行双因素方差分析及Kruskal-Wallis秩和检验.结果:经Carisolv处理过的根管,其荡洗液中亚甲蓝的吸光度值显著高于2%氯亚明 3%过氧化氢组(P＜0.05),与25%次氯酸钠组之间的差异不具有统计学意义(P＞0.05).扫描电镜结果与亚甲蓝吸光度的化学检测结果相吻合.结论:Carisolv作为根管预备化学制剂,对根管的清洁能力与2.5%次氯酸钠相近,可以去除玷污层及感染物质,又不引起过度脱矿.     

The effectiveness of three instrumentation techniques on the elimination of Enterococcus faecalis from a root canal: an in vitro study

The in vitro reduction of a bacterial population in a root canal by mechanical instrumentation using three techniques was evaluated. Root canals inoculated with a Enterococcus faecalis (E. faecalis) suspension were instrumented using hand Hedstroem files, Giromatic files, and Hero 642 rotary instruments. Irrigation was performed using sterile saline solution. Root canals were sampled before and after instrumentation. After serial dilutions, samples were plated onto Mitis-Salivarius agar and the colony forming units grown were counted. All instruments tested were able to significantly reduce the number of bacterial cells in the root canal, however, the results of this study indicated that Hedstroem files, Giromatic, and Hero 642 techniques were not significantly different in their ability to reduce intracanal bacteria.     

XP-endo Finisher锉对根管内壁玷污层清除效果的体外研究

目的 评估XP-endo Finisher（XPF）锉与被动超声冲洗（PUI）对根管内壁玷污层的清除效果。方法 选择60颗离体单直根管下颌前磨牙,距根尖16 mm处截冠,采用S3镍钛锉预备到3S,根据终末处理方式不同将样本随机分成6组。A组：3 mL 3%次氯酸钠溶液联合XPF处理1 min;B组：3 mL 3%次氯酸钠溶液联合XPF处理1 min,再用4 mL 17%乙二胺四乙酸（EDTA）溶液冲洗1 min;C组：3 mL 3%次氯酸钠溶液联合PUI处理1 min;D组：3 mL 3%次氯酸钠溶液联合PUI处理1 min,再用4 mL 17%EDTA溶液冲洗1 min;E组：3 mL 3%次氯酸钠溶液30号侧方冲洗针冲洗1 min;F组：3 mL 3%次氯酸钠溶液30号侧方冲洗针冲洗1 min,再用4 mL 17%EDTA溶液冲洗1 min。采用扫描电子显微镜观察玷污层形态,并比较根尖1/3区、根中1/3区牙本质小管开口数。结果 A、C、E组实验样本整个根管壁都有玷污层覆盖,A组与C组牙本质小管开口数明显高于E组（P<0.05）,而A组与C组的差异无统计学意义（P>0.05）;F组根中区、B组和D组根尖区有少量玷污层覆盖,牙本质小管开放或半开放;F组根尖区可见玷污层,牙本质小管封闭或半封闭;B和D组根中区根管壁玷污层均被有效去除;在根尖1/3区和根中1/3区,B组与D组牙本质小管开口数高于其他4组（P<0.05）,而B组和D组间的差异无统计学意义（P>0.05）。结论 XPF锉对根管内壁玷污层的清洁效果与PUI无明显差异,可用于根管预备后提高根管清洁效果。     

两种镍钛机动器械根管预备的比较研究

目的:评价两种镍钛机动器械预备后牙弯曲根管的效果。方法:选择根管弯曲度10°~20°之间,及>25°的单根管前磨牙各24个,包埋于Branmante模型中。采用Hero642和Profile镍钛机动系统进行根管预备。测定根管预备前后根尖、根中、根冠段的牙本质切削面积、形态因子,并记录操作时间和器械折断情况。结果:Hero642对根尖段及重度弯曲根管根中段的牙本质切削大于Profile,在根管预备过程中体现出较短的操作时间和器械折断率;根管预备后的截面形态在两者间无显著差异。结论:Hero642和Profile镍钛机动系统具有良好的根管成形作用,较高的工作效率,可作为临床上弯曲根管的预备器械。     

Susceptibilties of two Enterococcus faecalis phenotypes to root canal medications

This study aimed to investigate and compare the efficacy of selected root canal irrigants and a medicament on a clinical isolate of Enterococcus faecalis grown as biofilm or planktonic suspension phenotype. A cell-dense pellet "presentation" prepared from planktonic phenotype was also tested. Each bacterial presentation was exposed to calcium hydroxide (pH 12.3), 0.2% chlorhexidine gluconate, 17% ethylene-diamine-tetra-acetic acid, 10% povidone iodine, or 3.0% sodium hypochlorite (NaOCl) for a range of time periods (1, 2, 4, 8, 15, 30, and 60 min). Phosphate buffered saline was used as a control agent. The difference in gradients of bacterial killing among the biofilm, planktonic suspension or pellet presentation was significant (p < 0.05) and dependent upon the test agent except in the case of NaOCl and calcium hydroxide where no difference could be detected. NaOCl was the most effective agent and achieved 100% kills for all presentations of E. faecalis after a 2 min contact time.     

Short-term antibacterial activity of root canal sealers towards Enterococcus faecalis

AIM: To investigate the antimicrobial activity of root canal sealers on Enterococcus faecalis, either allowing or avoiding direct contact between sealers and bacteria. METHODOLOGY: Filter paper discs were immersed in standardized E. faecalis suspensions and exposed to freshly mixed sealers (MCS, AH Plus, Grossman's sealer, Sealapex, Apexit) in teflon wells for 30 min, with or without a filter membrane placed between filter paper discs and sealers (membrane-restricted contact test and direct contact test, respectively). After exposure, the filter paper discs were transferred to vials containing phosphate-buffered saline (PBS) and glass beads, and vigorously vortexed. PBS with resuspended bacterial cells was serially diluted and 25 microL droplets were seeded on TSA plates. The plates were incubated in air at 37 degrees C for 24 h and colony-forming units were counted. Using alpha = 0.05 as level for statistical significance, the data obtained were analysed using Student's t-test. RESULTS: In the direct contact test, MCS and AH Plus killed the bacteria to a level below the detection limit. They were followed in decreasing order of efficacy by Grossman's sealer, Sealapex and Apexit. In the membrane-restricted contact test, the sealers ranked: MCS, AH Plus, Grossman's sealer, Apexit and Sealapex, in descending order of antibacterial potency. MCS, AH Plus and Grossman's sealer significantly reduced the number of viable bacteria in both tests. Sealapex and Apexit were not statistically different from control. CONCLUSIONS: MCS, AH Plus and Grossman's sealer were effective in reducing the number of cultivable cells of E. faecalis. Calcium hydroxide-based sealers, Sealapex and Apexit were ineffective in this short-term experiment.     

Bacteriophages induced from lysogenic root canal isolates of Enterococcus faecalis

Introduction:  Bacterial viruses play crucial roles in the pathogenesis of many systemic diseases. They are known to inhabit the oral cavity, both as free virions and as prophages in lysogenic bacterial strains; however, there has been no report of bacteriophages in endodontic infections. In this study, we sought to detect, isolate, and describe temperate bacteriophages harbored by Enterococcus faecalis strains isolated from endodontic infections.
Methods:  Ten E. faecalis strains were isolated from root canals of teeth undergoing retreatment following unsuccessful endodontic therapy. Mitomycin C was used to induce any prophages present in the bacterial isolates. The induced phages were purified and examined using electron microscopy. The DNA extracted from one of the phage isolates was subjected to restriction endonuclease digestion and agarose electrophoresis analysis.
Results:  Lysogeny was demonstrated in 4 of the 10 E. faecalis strains. Three of the lysogenic strains yielded phages exhibiting a Siphoviridae morphology, with long, non-contractile tails 130 nm in length, and spherical/icosahedral heads 41 nm in diameter. The virus induced from the fourth lysogenic E. faecalis strain had a contractile tail characteristic of Myoviridae. Restriction endonuclease analysis of Nsi I and Nde I DNA fragments from one of the Siphoviridae phage isolates (phage φEf11) indicated a genome size of approximately 41 kbp.
Conclusion:  This is the first report of lysogenic bacteria and their inducible viruses in infected root canals.