Clinical Efficacy of Treatment Procedures in Endodontic Infection Control and One Year Follow-Up of Periapical Healing

Immediate root canal disinfection with ultraviolet light: an ex vivo feasibility study

OBJECTIVE

The study was designed to test application of ultraviolet light to root canal walls, as a mean of complementary immediate disinfection after the use of sodium hypochlorite.

STUDY DESIGN

Root canals were infected ex vivo with Enterococcus faecalis for 48 hours. Non-attached bacteria were washed away, and the remaining attached bacteria were subjected to disinfection, with 5% sodium hypochlorite alone or followed by exposure to ultraviolet light (254 nm, 300 mJ/cm(2)). Root canals were then tested for remaining viable bacteria. Canals were obturated and tested again after 14 days.

RESULTS

Sodium hypochlorite alone achieved negative cultures in only 47% of the cases, but 96% was achieved with sodium hypochlorite followed by ultraviolet light (P < .001). This status was also maintained after 14 days.

CONCLUSIONS

Illumination of root canals with ultraviolet light may be an effective supplementary means to achieve immediate disinfection of infected root canals.

Effects of prolonged exposure to alkaline pH on Enterococcus faecalis survival and specific gene transcripts

INTRODUCTION

The persistence of Enterococcus faecalis in treated root canals has been attributed to its resistance to the high pH of antimicrobial agents used during treatment, but the specific mechanisms are not clear. We investigated the survival and gene expression of E. faecalis maintained in alkaline media.

METHODS

E. faecalis JH2-2 was maintained in media at pH 7, 10, 11 and 12 at either 25 degrees C or 37 degrees C for 1 week (168 h). At 24, 48, 72, 120 and 168 h, cell viability was determined in parallel with real-time quantitative polymerase chain reaction analyses of stress response genes (dnaK, fba, ftsZ, GroEL, napA, pbp5, tsf and tuf).

RESULTS

After 1 week the E. faecalis showed survival levels of 100% in pH 7, 1% in pH 10, 0.001% in pH 11 and 0.00001% in pH 12 media. At 37 degrees C increased levels of gene transcripts occurred between 72 and 120 h in pH 7 media for ftsZ and dnaK, and in pH 10 media for ftsZ, pbp5, dnaK, napA, tsf, fba and GroEL. No increase in transcripts was observed at 37 degrees C in media at pH 11 or pH 12, nor at 25 degrees C in any media.

CONCLUSION

Transcripts of ftsZ, a gene involved in cell division, increased by 37-fold after 120 h at pH 10 at 37 degrees C. Overall, the greatest increase in levels of gene transcripts occurred in cultures maintained in pH 10 media at 37 degrees C. These data may assist in understanding the survival strategies of E. faecalis following prolonged exposure to alkaline pH levels.

Molecular- and Culture-based Comparison of the Effects of Antimicrobial Agents on Bacterial Survival in Infected Dentinal Tubules

The aim of this study was to evaluate the effect of root canal obturation with or without prior calcium hydroxide (Ca(OH)(2)) or 2% chlorhexidine (CHX) on the persistence of bacteria or its DNA in infected dentinal tubules. Canals of 85 extracted teeth were instrumented and inoculated with 10(4) cells/mL of Enterococcus faecalis. Teeth were incubated at 37 degrees C for 21 days and divided into 3 groups of 25 teeth plus controls. Teeth in group 1 were obturated immediately with gutta-percha (GP) and AH-Plus (Maillefer, Dentsply, Tulsa, OK). In group 2, Ca(OH)(2) was placed for 7 days before obturation. In group 3, 10 minutes of irrigation was performed with CHX performed before obturation. After incubation, GP was removed, and dentin specimens were collected and analyzed with culturing and polymerase chain reaction (PCR). No growth occurred in any cultures. By using PCR, E faecalis was detected in fewer roots in group 3 than in groups 1 or 2 (chi(2), p = 0.05); 2% CHX treatment followed by obturation was more effective in removing E faecalis DNA than placement of Ca(OH)(2) or immediate obturation.

Bacteriologic investigation of the effects of sodium hypochlorite and chlorhexidine during the endodontic treatment of teeth with apical periodontitis

OBJECTIVE

This clinical study was undertaken to compare the effectiveness of 2.5% sodium hypochlorite (NaOCl) and 0.12% chlorhexidine digluconate as irrigants in reducing the cultivable bacterial populations in infected root canals of teeth with apical periodontitis.

STUDY DESIGN

According to stringent inclusion/exclusion criteria, 32 teeth with primary intraradicular infections and chronic apical periodontitis were selected and followed in the study. Bacterial samples were taken at the baseline (S1) and after chemomechanical preparation using either NaOCl (n = 16) or chlorhexidine (n = 16) as irrigants (S2). Cultivable bacteria recovered from infected root canals at the 2 stages were counted. Isolates from S2 samples were identified by means of 16S rRNA gene sequencing analysis.

RESULTS

At S1, all canals were positive for bacteria, and the median number of bacteria per canal was 7.32 x 10(5) for the NaOCl group and 8.5 x 10(5) for the chlorhexidine group. At S2, the median number of bacteria in canals irrigated with NaOCl and chlorhexidine was 2.35 x 10(3) and 2 x 10(2), respectively. Six of 16 (37.5%) canals from the NaOCl group and 8 of 16 (50%) canals from the chlorhexidine group yielded negative cultures. Chemomechanical preparation using either solution substantially reduced the number of cultivable bacteria in the canals. No significant difference was observed between the NaOCl and chlorhexidine groups with regard to the number of cases yielding negative cultures (P = .72) or quantitative bacterial reduction (P = .609). The groups irrigated with NaOCl or chlorhexidine showed a mean number of 1.3 and 1.9 cultivable species per canal, respectively. The great majority of isolates in S2 were from gram-positive bacteria, with streptococci as the most prevalent taxa.

CONCLUSIONS

The present findings revealed no significant difference when comparing the antibacterial effects of 2.5% NaOCl and 0.12% chlorhexidine used as irrigants during the treatment of infected canals.

Bacterial reduction and persistence after endodontic treatment procedures

Bacteria that persist after endodontic disinfection procedures may lead to treatment failure. Over 50% of the bacteria found in endodontic infections are as-yet-uncultivated so investigations of bacteria that endure treatment procedures should include techniques that side-step cultivation. This culture-independent study evaluated the bacterial reduction promoted by intracanal disinfection procedures and identified the taxa persisting after treatment. Samples taken from the infected canals of teeth with apical periodontitis before treatment (S1), after instrumentation using NaOCl as irrigant (S2) and after interappointment medication with a calcium hydroxide paste (S3) were subjected to 16S rRNA gene clone library and real-time polymerase chain reaction analyses. The S2 and S3 samples from five of the 15 canals showed negative results. In the other cases, instrumentation and instrumentation/medication promoted a significant reduction (99.67% and 99.85%, respectively) in the number of bacteria when compared to S1 samples. Forty-three distinct bacterial taxa were identified, of which 24 (56%) were as-yet-uncultivated phylotypes. Nineteen of these 43 taxa (including eight as-yet-uncultivated phylotypes) were disclosed in post-treatment samples, with streptococci being the most prevalent taxa. Findings demonstrated that culture-independent methods provide a detailed insight into the effects of intracanal disinfection protocols, helping to define more effective strategies to deal with endodontic bacteria, including as-yet-uncultivated phylotypes.

The antimicrobial effects of root canal irrigation and medication

The role of microorganisms in the development and maintenance of pulpal and periapical inflammation have been well documented. The success of root canal treatment largely depends on the elimination of microbial contamination from the root canal system. Although mechanical instrumentation of root canals can reduce bacterial population, effective elimination of bacteria cannot be achieved without the use of antimicrobial root canal irrigation and medication. This review will discuss the antimicrobial effects of the known root canal irrigants and medicaments and explore future developments in the field.

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.

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.

Antibacterial efficacy of calcium hydroxide intracanal dressing: a systematic review and meta-analysis

AIM

To determine to what extent does calcium hydroxide intracanal medication eliminate bacteria from human root canals, compared with the same canals before medication, as measured by the number of positive cultures, in patients undergoing root canal treatment for apical periodontitis (teeth with an infected root canal system).

METHODOLOGY

CENTRAL, MEDLINE and EMBASE databases were searched. Reference lists from identified articles were scanned. A forward search was undertaken on the authors of the identified articles. Papers that had cited these articles were also identified through the Science Citation Index to identify potentially relevant subsequent primary research.

REVIEW METHODS

The included studies were pre-/post-test clinical trials comparing the number of positive bacterial cultures from treated canals. Data in those studies were independently extracted. Risk differences of included studies were combined using the generic inverse variance and random effect method.

RESULTS

Eight studies were identified and included in the review, covering 257 cases. Sample size varied from 18 to 60 cases; six studies demonstrated a statistically significant difference between pre- and post-medicated canals, whilst two did not. There was considerable heterogeneity among studies. Pooled risk difference was -21%; 95% CI: -47% to 6%. The difference between pre- and post-medication was not statistically significant (P = 0.12).

CONCLUSIONS

Calcium hydroxide has limited effectiveness in eliminating bacteria from human root canal when assessed by culture techniques.

A comparative study on the disinfection potentials of bioactive glass S53P4 and calcium hydroxide in contra-lateral human premolars ex vivo

AIM

To evaluate the effects of bioactive glass S53P4 versus calcium hydroxide when used as dressings in contra-lateral human premolars infected with Enterococcus faecalis ATCC 29212.

METHODOLOGY

Pairs of contra-lateral premolar teeth plus single control premolars were obtained from 23 individuals aged 10-26 years undergoing orthodontic treatment. Root canals of teeth with fully formed apices (nine contra-lateral pairs, seven controls) were instrumented using a size 60 FlexoFiles 2 mm short of canal length. Canals with open apices (six contra-lateral pairs, four controls) were circumferentially instrumented using a FlexoFile. Root canals were rinsed with 1% sodium hypochlorite and 10% citric acid. Teeth were then suspended in tryptic soy broth (TSB) and autoclaved. Positive controls and study teeth were infected with E. faecalis ATCC 29212 for 2 weeks in TSB, while negative controls were kept in sterile TSB. Subsequently, contra-lateral premolars were dressed with bioactive glass S53P4 (BAG) or calcium hydroxide suspensions for 10 days. Dentine samples were obtained from teeth with fully formed apices using ISO-size 70, 80 and 90 FlexoFiles to working length and cultured. Teeth with open apices were fixed, fractured and examined using scanning electron microscopy (SEM).

RESULTS

Calcium hydroxide had a strong antibacterial effect and was significantly more effective than BAG in preventing residual bacterial growth (P < 0.01). SEM analysis revealed apparent substance-specific modes of action.

CONCLUSIONS

Calcium hydroxide was an effective disinfectant in human teeth.

Sensitivity of oral bacteria to 254 nm ultraviolet light

AIM

To explore the sensitivity of bacteria commonly found in root canals to 254 nm ultraviolet (UV) light, either as individual cells or as participants of a bacterial multilayer.

METHODOLOGY

The sensitivity of oral bacteria, as individual cells, to UV light was tested by subjecting plates streaked with bacteria to 254 nm UV, at a fluence of 1-20 mJ cm(-2). An experimental model was designed to produce a bacterial multilayer and to study absorption of UV light by bacteria in an outer layer and its effect on the elimination of bacteria in the inner layer.

RESULTS

Direct exposure to relatively low doses of UV light (2-7 mJ cm(-2)) effectively eliminated all bacterial strains tested. Furthermore, an Enterococcus faecalis strain, partially resistant to a 24 h exposure to calcium hydroxide, was effectively eliminated within several seconds of exposure to UV light (P < 0.001). UV was absorbed by a multilayer of bacteria. When 4 bacterial cells microm(-2) were present in the light path, the UV light dose had to be increased by a factor of x10 to achieve 100% elimination of the bacteria in an inner layer.

CONCLUSIONS

The application of UV light to eliminate endodontic pathogens may be possible. Nevertheless, its absorbance by outer layers of bacteria should be considered and the UV light dose adapted accordingly.