Antibacterial Efficacy of MTAD Final Rinse and Two Percent Chlorhexidine Gel Medication in Teeth with Apical Periodontitis: A Randomized Double-blinded Clinical Trial

IntroductionClinical assessment of the efficacy of novel root canal disinfection protocols is an important focus in endodontic research. This randomized double-blinded study assessed the antibacterial efficacy of a final rinse with BioPure MTAD (MTAD) and intracanal medication with 2% chlorhexidine gel (CHX) in teeth with apical periodontitis.MethodsCanals in 30 teeth (single-rooted and multi-rooted) were prepared by using 1.3% NaOCl, rinsed with MTAD or saline in random sequence, medicated with CHX for 7 days, irrigated with 1.3% NaOCl, and filled. Bacteriologic root canal samples were obtained by aspiration before (1A) and after (1B) canal preparation, after the final rinse (1C), after CHX was flushed (2A), and after final irrigation (2B). Bacteria were enumerated by epifluorescence-microscopy (EFM) by using 2 staining methods and by colony-forming-unit (CFU) counts after 14 days of incubation.ResultsBacterial counts (EFM) in 1B were greater than 95% decreased from 1A. Low bacterial densities in 1B, 1C, 2A, and 2B did not differ significantly from each other. EFM counts were consistently higher than CFU counts.ConclusionsThe final rinse with MTAD and medication with CHX did not reduce bacterial counts beyond levels achieved by canal preparation with NaOCl.     

Bacterial quantification in teeth with apical periodontitis related to instrumentation and different intracanal medications: a randomized clinical trial

The antibacterial efficacy of intracanal medication with calcium hydroxide [Ca(OH)2], 2% chlorhexidine gel (CHX), and a combination of both [Ca(OH)2/CHX] was assessed in teeth with chronic apical periodontitis. Thirty-three canals were instrumented, randomly divided into three groups, and medicated with either Ca(OH)2, CHX, or Ca(OH)2/CHX. Bacteriological samples obtained from the operative field and the root canals before (S1) and after instrumentation (S2) in the first treatment session, and after medication (S3) in the second session 1 week later, were assessed for bacterial growth, observed by turbidity and in agar plates, and viable colony-forming unit (CFU) counts. Bacterial growth and CFU counts decreased significantly from S1 to S2 (Mann-Whitney, p<0.05). Differences in growth and counts between S2 to S3 were not statistically significant for all three intracanal medication groups. It was concluded that the antibacterial efficacy of Ca(OH)2, CHX, and Ca(OH)2/CHX was comparable.     

Reduction in the cultivable bacterial populations in infected root canals by a chlorhexidine-based antimicrobial protocol

The present clinical study was conducted to assess the bacterial reduction after chemomechanical preparation using 0.12% chlorhexidine digluconate solution as an irrigant and the additive antibacterial effect of intracanal dressing with calcium hydroxide (Ca(OH)(2)) associated with 0.12% chlorhexidine digluconate gel. According to stringent inclusion/exclusion criteria, 13 teeth with primary intraradicular infections and chronic apical periodontitis were selected and followed in the study. Bacterial samples were taken at the baseline (before treatment) (S1), after chemomechanical preparation using chlorhexidine (CHX) as an irrigant (S2), and after a 7-day dressing with Ca(OH)(2)/CHX paste (S3). Cultivable bacteria recovered from infected root canals at the three stages were counted and identified by means of 16S ribosomal RNA gene sequencing analysis. At S1, all canals were positive for bacteria, with the mean number of 3.5 taxa per canal (range, 2-9). At S2, 7 cases (53.8%) still harbored cultivable bacteria, with a mean number of 1.7 taxon per canal (range, 1-4). At S3, only one case (7.7%) was positive for the presence of bacteria. The great majority of taxa found in posttreatment samples were gram-positive bacteria. A significantly high reduction in bacterial counts was observed between S1 and S2 and S1 and S3 (p<0.001). Also, significant differences were observed for comparisons involving S2 and S3 samples with regard to both quantitative bacterial reduction (p=0.014) and number of cases yielding negative cultures (p=0.01). It was concluded that chemomechanical preparation with 0.12% CHX solution as an irrigant significantly reduced the number of intracanal bacteria but failed to render the canal free of cultivable bacteria in about one half of the cases. Application of a 7-day intracanal dressing with Ca(OH)(2)/CHX paste further increased significantly the number of cases yielding negative cultures.     

Effectiveness of castor oil extract on Escherichia coli and its endotoxins in root canals

This in vitro study sought to evaluate the effectiveness of castor oil extract used as an irrigating solution on Escherichia coli and its endotoxins in root canals. Sixty single-rooted teeth were prepared (using castor oil extract as irrigating solution) and divided into five groups (n = 12): Group 1 samples were treated with calcium hydroxide (Ca(OH)2), Group 2 samples were treated with polymyxin B, Group 3 samples were treated with Ca(OH)2 and 2% chlorhexidine gel (CHX), and Group 4 samples were treated with castor oil extract. A control group used physiological saline solution as an irrigant. Canal content samples were collected at four different times: immediately after instrumentation, seven days after instrumentation, after 14 days of intracanal medication, and seven days after removal of intracanal medication. A plating method was used to assess antimicrobial activity and the quantification of endotoxins was evaluated by the chromogenic Limulus lysate assay. Data were submitted to ANOVA and a Dunn test (a = 5%). Irrigation with castor oil extract decreased E. coli counts but had no effect on the level of endotoxins. Samples taken seven days after removal of medication revealed a significant reduction in endotoxin levels in Groups 3 and 4. Compared to the saline solution irrigation, castor oil extract decreased microorganism counts in root canals immediately after canal preparation. None of the medications used completely eliminated endotoxins in the root canal.     

Effect of root canal procedures on endotoxins and endodontic pathogens

BACKGROUND/AIMS: The purpose of this study was to determine the amount of endotoxin (lipopolysaccharide) and cultivable bacteria in human necrotic root canals before (S1) and after chemo-mechanical preparation using chlorhexidine (CHX) gel as auxiliary chemical substance (S2), and after 7 days of intracanal dressing (S3) in order to evaluate the anti-endotoxin and antimicrobial effects of endodontic procedures. METHOD: Twenty-four teeth were selected for the present study. Chemo-mechanical preparation was performed using 2% CHX gel and three different intracanal medicaments [CaOH2 paste; 2% CHX gel; and CaOH2 + 2% CHX gel]. A quantitative chromogenic Limulus amoebocyte lysate assay was used to measure the amount of endotoxin. Aerobic and anaerobic techniques were used to isolate and identify bacteria, and to determine the bacterial reduction by counting colony-forming units (CFU). RESULTS: Endotoxins and bacteria were present in 100% of the initial samples, with endotoxin concentration ranging from 62.93 to 214.56 UE/ml and CFU ranging from 4 x 10(5) to 2.6 x 10(6). After chemo-mechanical preparation a mean endotoxin reduction of 44.4% was found. Eight (33.3%) root canals were still positive by culture analysis with a mean reduction of bacteria (CFU) of 99.96%. After 7 days of intracanal dressing, endotoxin concentration decreased by only 1.4% compared with S2, and residual bacteria were recovered by culture analysis in 13 cases (54.1%). No significant difference was found among different intracanal medicaments. CONCLUSION: Relatively high values of endotoxin were still present in the root canal after chemo-mechanical preparation although the majority of bacteria were eliminated. No improvement was achieved by 7 days of intracanal dressing.     

Bacterial reduction in infected root canals treated with 2.5% NaOCl as an irrigant and calcium hydroxide/camphorated paramonochlorophenol paste as an intracanal dressing

This clinical study investigated the bacterial reduction after instrumentation using 2.5% sodium hypochlorite (NaOCl) as an irrigant and further interappointment dressing with a calcium hydroxide (Ca(OH)(2))/camphorated paramonochlorophenol (CPMC) paste. Eleven teeth with primary intraradicular infections and chronic apical periodontitis selected according to stringent inclusion/exclusion criteria followed in the study. Bacterial samples were taken before treatment (S1), after chemomechanical preparation using hand NiTi files and 2.5% NaOCl (S2), and following a 7-day medication with a Ca(OH)(2) paste in CPMC (S3). Cultivable bacteria recovered from infected root canals at the three stages were counted and identified by means of 16S rRNA gene sequencing analysis. At S1, all cases harbored bacteria, with a mean number of 2.8 taxa per canal (range, 1-6). At S2, 6 of 11 (54.5%) of the cases yielded positive cultures, with one to three species per canal. At S3, only one case (9.1%) was positive for the presence of bacteria, with Propionibacterium acnes as the only taxon isolated. A significantly high reduction in bacterial counts was observed between S1 and S2, and S1 and S3. Significant differences were also observed for comparisons involving S2 and S3 samples with regard to both quantitative bacterial reduction (p = 0.029) and number of culture-negative cases (p = 0.03). It was concluded that chemomechanical preparation with 2.5% NaOCl as an irrigant significantly reduced the number of bacteria in the canal but failed to render the canal free of cultivable bacteria in more than one-half of the cases. A 7-day intracanal dressing with Ca(OH)(2)/CPMC paste further significantly increased the number of culture-negative cases.     

Comparative analysis of endodontic pathogens using checkerboard hybridization in relation to culture

Background/Aim:  The purpose of this study was to detect bacterial species and to quantify the total number of bacteria from samples of infected root canals before (S1) and after chemo-mechanical preparation using 2% chlorhexidine (CHX) gel as auxiliary chemical substance (S2) and after 7 days of intracanal dressing (S3) to compare microbial changes.
Method:  Twenty-four teeth were selected for this study. Chemo-mechanical preparation was performed using 2% CHX gel, then three different intracanal medicaments [M1: Ca(OH)₂ paste; M2: 2% CHX gel; and M3: Ca(OH)₂ paste plus 2% CHX gel] were used for 7 days. Checkerboard DNA–DNA hybridization was performed to detect 40 bacterial species. Aerobic and anaerobic culture techniques were used to determine the bacterial community by counting the colony-forming units (CFU).
Results:  The species most frequently identified by checkerboard in S1 were: Fusobacterium nucleatum ssp . polymorphum , Treponema socranskii ssp. socranskii , Parvimonas micra and Enterococcus faecalis. In S2 and S3 a total of eight different species were identified; and only one of them was gram-positive ( E. faecalis ). Microorganisms were not identified after use of M2 for 7 days. The quantification obtained on agar plates ranged from 4 × 10⁵ to 2.6 × 10⁶ CFU/ml in S1, mean CFU was reduced by 99.96% in S2, and there was no statistical difference between the CFU in S2 and S3.
Conclusion:  The antibacterial effect of the mechanical preparation supplemented by the use of an antibacterial auxiliary substance greatly reduced the microorganisms in the main root canal.     

Influence of antimicrobial solutions in the decontamination and adhesion of glass-fiber posts to root canals

Objective

This study evaluated the effect of root canal disinfectants on the elimination of bacteria from the root canals, as well as their effect on glass-fiber posts bond strength.

Material and Methods

Fifty-three endodontically treated root canals had post spaces of 11 mm in length prepared and contaminated with E. faecalis. For CFU/ml analysis, eight teeth were contaminated for 1 h or 30 days (n=4). Teeth were decontaminated with 5% NaOCl, 2% CHX, or distilled water. As control, no decontamination was conducted. After decontamination, sterile paper points were used to collect samples, and CFU/ml were counted. For push-out, three groups were evaluated (n=15): irrigation with 2.5% NaOCl, 2% CHX, or sterile distilled water. A bonding agent was applied to root canal dentin, and a glass-fiber post was cemented with a dual-cured cement. After 24 h, 1-mm-thick slices of the middle portion of root canals were obtained and submitted to the push-out evaluation. Three specimens of each group were evaluated in scanning electron microscopy (SEM). Data were analyzed with one-way ANOVA and Dunnett’s T3 test (α=0.05).

Results

The number of CFU/ml increased from 1 h to 30 days of contamination in control and sterile distilled water groups. Decontamination with NaOCl was effective only when teeth were contaminated for 1 h. CHX was effective at both contamination times. NaOCl did not influence the bond strength (p>0.05). Higher values were observed with CHX (p<0.05). SEM showed formation of resin tags in all groups.

Conclusion

CHX showed better results for the irrigation of contaminated root canals both in reducing the bacterial contamination and in improving the glass-fiber post bonding.     

The antibacterial activity of chlorhexidine digluconate against Streptococcus mutans biofilms follows sigmoidal patterns

The aim of this study was to determine the pattern of the antibacterial activity of chlorhexidine digluconate (CHX) against mature Streptococcus mutans biofilms. Streptococcus mutans biofilms were formed on saliva‐coated hydroxyapatite discs and then treated with 0–20% CHX, once, three times, or five times (1 min per treatment) during the period of mature biofilm formation (beyond 46 h). After the treatments, the colony‐forming unit (CFU) counts of the treated biofilms were determined. The pH values of the spent culture medium were also determined to investigate the change in pH resulting from the antibacterial activity of CHX. The relationships between the concentration of CHX and the CFU counts and the concentration of CHX and culture medium pH, relative to the number of treatments performed, were evaluated using a sigmoidal curve‐fitting procedure. The changes in CFU counts and culture medium pH followed sigmoidal curves and were dependent on the concentration of CHX (R² = 0.99). The sigmoidal curves were left‐shifted with increasing number of treatments. Furthermore, the culture‐medium pH of the treated biofilms increased as their CFU counts decreased. The lowest CHX concentration to increase culture‐medium pH above the critical pH also decreased as the number of treatments increased. These results may provide fundamental information for selecting the appropriate CHX concentrations to treat S. mutans biofilms.     

Proportion of Healed Teeth With Apical Periodontitis Medicated With Two Percent Chlorhexidine Gluconate Liquid: A Case-Series Study

IntroductionChlorhexidine gluconate (CHX) is a potential intracanal medicament, but data on healing after its use are lacking. Previously we reported on bacterial sampling in 22 teeth with apical periodontitis medicated with CHX. This study assessed healing in those teeth.MethodsCanals were instrumented and medicated with 2% CHX liquid for 7–15 days and subsequently irrigated and filled. Bacterial samples were taken before and after instrumentation, after medication and before root filling, and enumerated by culture and vital microscopy. After 2–4 years, subjects were examined clinically and radiographically by assigning Periapical Index scores by independent calibrated examiners. Outcome was dichotomized as healed or disease.ResultsWith 2 teeth extracted, 1 deceased subject, and 2 nonrespondents, 16 of 17 examined teeth (94%) were healed without association with bacterial sampling results. The proportion of healed teeth in this study did not differ significantly (Fisher exact test; P = .20) from that in a historical control (90%).ConclusionsThe results suggested a comparable outcome after medication with 2% CHX liquid and calcium hydroxide.     

In vitro evaluation of the effectiveness of irrigants and intracanal medicaments on microorganisms within root canals

AIM: To evaluate in vitro the effectiveness of sodium hypochlorite (NaOCl), chlorhexidine (CHX) and five intracanal medicaments on microorganisms within root canals. METHODOLOGY: Ninety-six human single-rooted extracted teeth were used. After removing the crowns, canal preparation was completed and the external root surfaces were coated with epoxy resin. Following sterilization, the teeth were contaminated with Candida albicans and Enterococcus faecalis, and were incubated at 37 +/- 1 degrees C for 7 days. The teeth were divided according to the irrigant solution or intracanal medicament: group 1, sterile physiologic solution (SPS) and calcium hydroxide (Ca(OH)2) paste; group 2, SPS and camphorated paramonochlorophenol (CPMC); group 3, SPS and tricresol formalin; group 4, SPS and CaOH2 + CPMC paste; group 5, SPS and PMC furacin; group 6, 2.5% NaOCl without intracanal medication; group 7, 2.0% CHX without intracanal medication and group 8, SPS without intracanal medication (control group). Microbiological samples were collected with sterile paper points, and bacterial growth was determined. The data were submitted to the analysis of variance (anova, P = 0.05). RESULTS: For C. albicans, groups 3 and 8 were statistically less effective than groups 1, 2, 4 and 5 (Kruskal-Wallis (K-W) = 65.241; gl = 7; P = 0.001). For E. faecalis, groups 6 and 8 were statistically less effective than groups 1-4 and 7 (K-W = 61.048; gl = 7; P = 0.001). CONCLUSIONS: Ca(OH)2 + CPMC paste was the most effective intracanal medicament for the elimination of the two microorganisms; 2.0% CHX solution was more effective than 2.5% NaOCl against E. faecalis.     

Outcome of Endodontic Retreatment Using 2 Root Canal Irrigants and Influence of Infection on Healing as Determined by a Molecular Method: A Randomized Clinical Trial

IntroductionThis study compared the clinical and radiographic outcome of endodontic retreatment of teeth with apical periodontitis using either 1% sodium hypochlorite (NaOCl) or 2% chlorhexidine digluconate (CHX) as the irrigant. The influence of residual infection detected by a molecular method on the outcome was also examined.MethodsFifty-two root-filled teeth with apical periodontitis were randomly assigned into 2 groups according to the irrigant used during retreatment. Root canal microbiological samples taken before (S1) and after (S2) preparation using either NaOCl or CHX irrigation and after calcium hydroxide medication (S3) were subjected to 16S ribosomal RNA gene-based real-time quantitative polymerase chain reaction (qPCR) to quantify total bacteria. The periapical status was scored using the periapical index and dichotomized as healed (<3) or not healed (≥3) at the 1- and 4-year follow-up.ResultsForty-five (NaOCl, n = 20; CHX, n = 25) and 33 teeth (NaOCl, n = 16; CHX, n = 17) were available at the 1- and 4-year follow-up, respectively. After 1 year, 65% in the NaOCl group and 64% in the CHX group healed, with no differences between them (P > .05). At the later follow-up, the corresponding figures were 81% and 82%, respectively (P > .05). Canals that yielded qPCR-negative results in S3 had a higher healing rate (79%) than qPCR-positive canals (45%, P < .05). The mean bacterial load increased from S2 to S3 in half of the unhealed cases (P < .05). All S3-positive canals containing <3.12 × 10³ bacterial cell counts healed. Increasing the apical level of the root canal filling influenced the outcome (P < .05).ConclusionsNo significant differences in the clinical outcome between 1% NaOCl and 2% CHX were found. Bacterial persistence at the time of filling as detected by qPCR significantly affected the outcome.     

Effects of instrumentation, irrigation and dressing with calcium hydroxide on infection in pulpless teeth with periapical bone lesions

AIM: The aim of this study was to evaluate the fate of microorganisms in root canals of teeth with infected pulps and periapical bone lesions with and without the use of calcium hydroxide medication. METHODOLOGY: Endodontic samples were cultured and microorganisms were counted and identified in 43 teeth before (sample 1) and after (sample 2) treatment during the first visit and before (sample 3) and after (sample 4) treatment during the second visit. In the first visit teeth were instrumented and half of the teeth were filled with a thick slurry of calcium hydroxide in sterile saline. The other teeth were obturated with gutta-percha and AH-2 6 sealer. After 4 weeks the teeth with calcium-hydroxide were accessed again and after microbiological sampling they were obturated with gutta-percha and AH-26 sealer. RESULTS: The mean total colony forming unit (CFU) counts of positive samples dropped significantly as a result of canal preparation during the first visit from 1.0 x 10(6) to 1.8 x 10(3) (between samples 1 and 2) but increased to 9.3 x 10(3) in the period between the two visits (sample 2 and 3). There was no difference in mean total CFU counts of positive samples between the end of the first (sample 2) and the end of the second visit (sample 4). The most frequently isolated species were Prevotella intermedia, Capnocytophaga spp.. Actinomyces odontolyticus. Propionibacterium acnes and Peptostreptococcus micros. CONCLUSIONS: Although a calcium hydroxide paste was placed in the prepared canals, the number of positive canals had increased in the period between visits. However, the number of microorganisms had only increased to 0.93% of the original number of CFU (sample 1). It is concluded that a calcium hydroxide and sterile saline slurry limits but does not totally prevent regrowth of endodontic bacteria.     

Comparative effects of different chlorhexidine mouth-rinse formulations on volatile sulphur compounds and salivary bacterial counts

AIM: To compare five different commercial mouth rinses with chlorhexidine (CHX) with respect to their anti-halitosis effect and anti-microbial activity on salivary bacterial counts, following a standardised research protocol. And secondly, to validate the study model proposed in the evaluation of patients suffering from halitosis. PATIENTS AND METHODS: Ten volunteers, with a healthy oral status, were enrolled in a double-blind, cross-over design, using sterile saline as negative control and five CHX-containing mouth rinses: 0.12% CHX alone (CHX+NO), plus alcohol (CHX+ALC), plus 0.05% cetylpiridinium chloride (CHX+CPC), plus sodium fluoride (CHX+NaF), and 0.05% CHX plus 0.05% CPC, plus 0.14% zinc lactate (CHX+Zn). The levels of whole-mouth volatile sulphur compounds (VSCs) were measured by means of a sulphide monitor at baseline, 1 and 5 h after rinsing with the assigned product. Baseline measurements also included an organoleptic assessment and the recording of the tongue-coating index. Aerobic and anaerobic salivary bacterial counts were also obtained by collecting unstimulated saliva samples at the same evaluation times, and processed by culturing techniques. Analysis of variance was used to evaluate whether significant differences existed among groups, at each evaluation point, or in changes between evaluations. RESULTS: No significant differences were detected at baseline, with VSC levels ranging between 190 and 227 parts per billion (p.p.b.) After rinsing, VSC levels were reduced with all products (except saline), after 1 h. Significant differences at 1 h were detected (p=0.04), corresponding to a lower amount of p.p.b. (109) in (CHX+Zn) as compared with the other groups (except CHX+NO). At 5 h, VSC levels were lower for CHX+CPC and CHX+Zn (155 and 169, respectively), while the other groups showed levels higher than 220 p.p.b. With respect to aerobic salivary bacterial counts, CHX+CPC demonstrated the lowest percentage of survival (6% after 1 h and 18% after 5 h). For anaerobic bacterial counts, again CHX+CPC demonstrated the lowest percentage of survival (10% at 1 h and 23% at 5 h), together with CHX+ALC (18% of survival at 5 h). However, salivary counts and VSCs were only significantly correlated at baseline, but not after treatment. CONCLUSION: Important differences can be expected from different CHX formulations, in relation to both their anti-halitosis effect and anti-microbial activity in saliva. Formulations that combine CHX and CPC achieved the best results, and a formulation combining CHX with NaF resulted in the poorest.     

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。     

Effects of photodynamic therapy, 2 % chlorhexidine,triantibiotic mixture,propolis and ozone on root canals experimentally infected with <Emphasis Type="Italic">Enterococcus faecalis</Emphasis>: an in vitro study

The aim of this study was to evaluate the antibacterial effect of photodynamic therapy (PDT), 2 % chlorhexidine (CHX). The teeth were contaminated with 0.1 mL Enterococcus faecalis (3 × 10⁸ cell/mL) and randomized into eight treatment groups: Group 1 (2.5 % NaOCl); Group 2 (PDT); Group 3 (2 % CHX); Group 4 (TAM); Group 5 (propolis), Group 6 (ozone), Group 7 (positive control) and Group 8 (negative control). Following treatment, the canal content was sampled. The samples were cultured in triplicate on blood agar plates to determine the number of colony forming units (CFU)/mL. The teeth were analyzed by SEM to determine the percentage of area with contamination and debris. The group with the lowest CFU/mL count was the ozone group, which obtained similar values to the PDT group. SEM images showed that 2.5 % NaOCL group showed the lowest percentage of contaminated area. Applications of PDT, 2 % CHX, TAM, propolis and ozone showed antibacterial potential similar to 2.5 % NaOCL.     

Growth inhibitory activity of gutta-percha points containing root canal medications on common endodontic bacterial pathogens as determined by an optimized quantitative in vitro assay

Gutta-percha points containing calcium hydroxide, zinc oxide (ZnO), a mixture of ZnO and chlorhexidine (ZnO/CHX), iodine-polyvinylpyrrolidone (ZnO/J-PVP), or a mixture of CHX and J-PVP and ZnO (ZnO/CHX/J-PVP) were tested for their ability to inhibit growth of pure cultures of bacterial species commonly involved in endodontic infections (Peptostreptococcus micros, Streptococcus intermedius, Enterococcus faecalis, and Porphyromonas gingivalis). To quantitate growth inhibition, an in vitro assay was established that controlled for important parameters of root canal infection. Approximately 10(7) bacteria per assay were suspended in diluted human serum and co-incubated with the gutta-percha points in an anaerobic atmosphere for up to 2 wk. Aliquots used for determination of colony counts were taken on days 0, 1, 2, 4, 7, and 14 of incubation. As judged by colony-forming unit reduction kinetics and final counts, calcium hydroxide had better growth inhibitory activity than ZnO/CHX, ZnO/J-PVP, and ZnO alone for all bacteria tested except Peptostreptococcus micros. The combination of CHX and J-PVP with ZnO did not render results different from those of ZnO/CHX or ZnO/J-PVP. The results of this study support the introduction of standardized assays for testing antibacterial properties of root canal medications under conditions that more closely resemble those encountered in endodontal infections.     

Antibacterial effectiveness of peracetic acid and conventional endodontic irrigants

This study evaluated the in vitro antibacterial activity of conventional and experimental endodontic irrigants against Enterococcus faecalis. The following substances were evaluated by direct contact test: 2.5% sodium hypochlorite (NaOCl); 2% chlorhexidine (CHX); 1% peracetic acid. After different contact periods (30 s, 1, 3, and 10 min), a neutralizing agent was applied. Serial 10-fold dilutions were prepared and plated onto tryptic soy agar (TSA) and the number of colony-forming units per milliliter (CFU/mL) was determined. Sterile saline was used as a negative control. Both 2.5% NaOCl and 2% CHX eliminated E. faecalis after 30 s of contact. Peracetic acid reduced the bacterial counts by 86% after 3 min and completely eliminated E. faecalis after 10 min. These results allow us to conclude that 1% peracetic acid is effective against E. faecalis, despite its slower action compared with 2.5% NaOCl and 2% CHX.     

Antimicrobial substantivity of bovine root dentin exposed to different chlorhexidine delivery vehicles

Root canal dentin acquires antimicrobial substantivity after exposure to chlorhexidine gluconate (CHX) for 1 wk. Therefore development of a vehicle for delivery of CHX as an intracanal medication is desirable. This in vitro study assessed the efficacy of two CHX delivery vehicles, a controlled-release device and a gel, to affect antimicrobial substantivity of bovine root dentin. Sixty bovine incisor root specimens were prepared with standardized length (10 mm) and canal diameter (3.3 mm), and coated externally with nail polish. Specimens were divided into four equal groups and their canals medicated for 7 days with either: (i) an experimental controlled-release device containing 25% CHX that was immersed in sterile saline; (ii) 2% CHX gel; or (iii) Ca(OH)2 paste. Sterile saline was used as the positive control. After medication, the canals of the specimens were inoculated with Enterococcus faecalis for 21 days. Root canal dentin samples ranging in depth from 0.1 to 0.45 mm were then obtained using sterile round burs of ascending diameter. Each dentin sample was placed in a separate test tube containing Brain Heart Infusion broth and incubated for 24 h. The optical density (OD) of the broth was then measured spectrophotometrically at 540 nm. The positive control showed significantly higher mean OD values (one-way ANOVA and Tukey's Studentized Range Test; p < 0.001) than the three test groups. The CHX controlled-release device group showed significantly lower OD values than the Ca(OH)2 group; however only at dentin depths up to 0.2 mm. In contrast, the CHX gel group consistently showed significantly lower OD values than both the CHX controlled-release device and Ca(OH)2 groups. These results suggest that bovine root canals medicated with 2% CHX gel for 7 days acquire antimicrobial properties for at least 21 days.     

Effects of chemomechanical preparation with 2.5% sodium hypochlorite and intracanal medication with calcium hydroxide on cultivable bacteria in infected root canals

This clinical study was conducted to assess the bacterial reduction after chemomechanical preparation with 2.5% NaOCl as an irrigant and the additive antibacterial effect of intracanal dressing with calcium hydroxide. According to stringent inclusion criteria, 11 teeth with primary intraradicular infections and chronic apical periodontitis were selected and monitored in the study. Bacterial samples were taken at the baseline (before treatment) (S1), after chemomechanical preparation with 2.5% NaOCl as an irrigant (S2), and after a 7-day dressing with a calcium hydroxide paste in glycerin (S3). Cultivable bacteria recovered from infected root canals at the 3 stages were counted and identified by means of 16S rRNA gene sequencing analysis. At S1, all canals were positive for bacteria, with the mean number of 2.8 taxa per canal (range, 1-6). At S2, 5 cases (45.5%) still harbored cultivable bacteria, with 1 or 2 species per canal. At S3, bacteria were cultured from 2 cases (18.2%), with 1 species per positive case. There was no indication that any specific bacterial taxon was more resistant to treatment. A significant reduction in bacterial counts was observed between S1 and S2, and S1 and S3. However, no statistically significant difference was observed for comparisons involving S2 and S3 samples with regard to the number of cases yielding negative cultures (P = .18) or quantitative bacterial reduction (P = .19). It was concluded that the whole antibacterial protocol used in this study significantly reduced the number of bacteria in the canal and rendered most canals free of cultivable bacteria.