Efficacy of instrumentation techniques and irrigation regimens in reducing the bacterial population within root canals

Ex vivo analysis of the debris remaining in flattened root canals of vital and nonvital teeth after biomechanical preparation with Ni-Ti rotary instruments

The purpose of this study was to assess the presence of apical debris remaining in the apical third of flattened root canals of vital and nonvital teeth after biomechanical preparation with Ni-Ti rotary instruments. Fresh-extracted human mandibular incisors were used in this study. The teeth had clinical indication for extraction and were submitted to cold pulp vitality testing and radiographic examination. Eighteen teeth were selected and randomly assigned to two groups (n=9), according to the clinical diagnosis, i.e., pulp vitality or pulp necrosis. The canals were instrumented with the ProTaper NiTi rotary system in the following sequence: S1 - up to the middle third; SX - at the cervical third; S2- up to the apical third; and S1, F1, F2, F3 - at the working length. The canals were irrigated with 1% sodium hypochlorite, dried and were submitted to the histological processing. Sections from the apical third were analyzed by an optical microscope (X40) that was coupled to a computer where the images were captured and analyzed using specific softwares. A grid was placed over these images to assess the total canal area and the areas with debris. Mann-Whitney U-test showed no statistically significant difference (p>0.05) between the teeth with pulp vitality (6.49 ± 3.39) and those with pulp necrosis (5.95 ± 2.22). It may be concluded that the clinical condition of pulp tissue did not interfere with the amount of debris remaining in the apical third of flattened root canals prepared with Ni-Ti rotary instruments.

Chlorhexidine Gluconate

The aim of root canal treatment is to eliminate bacteria from the infected root canal and to prevent reinfection. Biomechanical cleaning and shaping greatly reduces the number of bacteria. Nevertheless, due to anatomical complexity of the root canal system, residues and bacteria cannot be removed completely. Therefore, various substances have been used during canal preparation to remove debris, necrotic tissue, bacteria and smear layer. The most common irrigant of choice is sodium hypochlorite (NaOCI): it is an effective antimicrobial agent and tissue solvent. However, NaOCI can be toxic. Chlorhexidine gluconate (CHX) is a broad-spectrum antimicrobial agent. As a root canal irrigant and intracanal medicament, CHX has an antibacterial efficacy comparable to that of NaOCI, and is effective against resistant bacterial strains. CHX may result in residual antimicrobial activity of the dentine surface after prolonged exposure of the root canal to CHX. CHX also has a low grade of toxicity. In this review CHX will be discussed in detail.

Effect of rotary or manual instrumentation, with or without a calcium hydroxide/1% chlorhexidine intracanal dressing, on the healing of experimentally induced chronic periapical lesions

OBJECTIVE

To evaluate the healing of experimentally induced chronic periapical lesions in dogs at 30, 75, and 120 days after root canal instrumentation with rotary NiTi files or manual K-files, with or without a calcium hydroxide/1% chlorhexidine paste intracanal dressing.

STUDY DESIGN

The second, third, and fourth mandibular premolars and the second and third maxillary premolars of 5 dogs (12 to 18 months of age, weighing 8 to 15 kg) were selected for treatment (a total of 82 root canals). After pulp removal, the root canals were left exposed to the oral cavity for 7 days to allow microbial contamination, after which the root canals were sealed with ZOE cement until periapical lesions were confirmed with radiography. Group I and II teeth were instrumented with manual K-files using the crown-down technique. In group III and IV teeth, NiTi rotary files were used. The apical delta was perforated by using #20 to #30 K-files at the length of the tooth, thus creating a standardized apical opening. The apical stop was enlarged to size 70, with 2.5% sodium hypochlorite irrigation at each file change. Teeth in groups II and IV were dressed with calcium hydroxide (Ca(OH) 2 )/1% chlorhexidine (CHX) paste for 15 days before root filling. Group I and III teeth did not receive an intracanal dressing. The access openings of the teeth were permanently restored with silver amalgam condensed on a glass ionomer cement base. Pairs of standardized periapical radiographs were taken at the beginning of the treatment (0 days) and at 30, 75, and 120 days after filling.

RESULTS

There was no significant difference in the rate of radiographic healing of the periapical lesions between manual and rotary instrumentation. Radiographs taken at 120 days showed that the treatment with Ca(OH) 2 /1% CHX paste resulted in a significant reduction in mean size of the periapical lesions in comparison to single-session treatment. These findings were also true for histologic observations.

CONCLUSION

The findings support the hypothesis that, regardless of the instrumentation technique (manual or rotary), the use of an intracanal dressing is important in the endodontic treatment of dog's teeth with experimentally induced chronic periapical lesions.

Influence of irrigant needle depth in removing bioluminescent bacteria inoculated into instrumented root canals using real-time imaging in vitro

AIM

To test the hypothesis that the mechanical efficacy of irrigation in reducing bacteria in the root canal is dependent on depth of placement of the irrigation needle.

METHODOLOGY

The root canals of 30 permanent cuspids were instrumented to apical size 60 using a crown-down technique. A suspension of the bioluminescent reporter strain Pseudomonas fluorescens 5RL was inoculated into each canal of sterilized teeth. Emission of bioluminescence (photons s(-1)) from each tooth was quantified on four sequential occasions using luminometry and bioluminescence imaging: (i) background, (ii) after inoculation, (iii) after irrigating the inoculated teeth with 3 mL of a nonantimicrobial irrigant delivered either 1 mm (group 1, n = 15) or 5 mm (group 2, n = 15) from working length (WL) using a 28G safety-ended irrigating needle, (iv) after an additional 3 mL irrigation (total 6 mL). Intragroup and intergroup comparisons were made using Wilcoxon matched pairs and Mann-Whitney tests, respectively.

RESULTS

In group 1, there was a mean log10 decrease in bacteria of 0.68 +/- 0.26 after 3 mL of irrigant compared with 1.19 +/- 0.48 after 6 mL (P < 0.001); in group 2 the mean log10 decrease was 0.58 +/- 0.28 after 3 mL of irrigant compared with 0.69 +/- 0.35 after 6 mL (P < 0.02) (Wilcoxon matched pairs). Using 3 mL of irrigant, needle depth did not have a significant effect on reduction of intracanal bacteria (P = 0.407), but the effect became significant when 6 mL of irrigant was used (P < 0.002) (Mann-Whitney tests).

CONCLUSIONS

The mechanical efficacy of 6 mL of irrigant in reducing intracanal bacteria was significantly greater when delivered 1 mm compared with 5 mm from WL.

Antimicrobial effect of ozonated water on bacteria invading dentinal tubules

Ozone is known to act as a strong antimicrobial agent against bacteria, fungi, and viruses. In the present study, we examined the effect of ozonated water against Enterococcus faecalis and Streptcoccus mutans infections in vitro in bovine dentin. After irrigation with ozonated water, the viability of E. faecalis and S. mutans invading dentinal tubules significantly decreased. Notably, when the specimen was irrigated with sonication, ozonated water had nearly the same antimicrobial activity as 2.5% sodium hypochlorite (NaOCl). We also compared the cytotoxicity against L-929 mouse fibroblasts between ozonated water and NaOCl. The metabolic activity of fibroblasts was high when the cells were treated with ozonated water, whereas that of fibroblasts significantly decreased when the cells were treated with 2.5% NaOCl. These results suggest that ozonated water application may be useful for endodontic therapy.

Real-Time Imaging and Quantification of Bioluminescent Bacteria in Root Canals In Vitro

The detection of microorganisms in root canals is generally limited to qualitative or semiquantitative methods. We describe a new and nondestructive in vitro method to quantify root-canal bacteria over sequential treatment procedures using real-time imaging in conjunction with the bioluminescent reporter strain Pseudomonas fluorescens 5RL. Induced bacterial photon emission can be monitored by sensitive optical photonic imaging and luminometry, providing images as well as spatial and quantitative measurements. Bioluminescence imaging and luminometry determined that the lower limit of detection of bacteria in root canals occurred between 2 x 10(2) and 2 x 10(3) cells, with high correlation between cell counts and detection devices (r > or = 0.981). A preliminary study assessed the efficacy of sequential irrigation procedures to remove 5 x 10(6) bacteria from root canals (n = 5; apical size 60) using a 28-gauge, endodontic needle positioned 1 mm from working length; 9.2% +/- 3.1% and 8% +/- 3.6% of bacteria remained after 3 and 6 ml irrigation, respectively (p = 0.03), corresponding to approximately 4 x 10(5) bacteria remaining after 6 ml. This method can be used to study the efficacy of sequential endodontic treatment procedures in removing bacteria from root canals.

Association of Enterococcus faecalis with different forms of periradicular diseases

Data from culture studies have revealed that Enterococcus faecalis is occasionally isolated from primary endodontic infections but frequently recovered from treatment failures. This molecular study was undertaken to investigate the prevalence of E. faecalis in endodontic infections and to determine whether this species is associated with particular forms of periradicular diseases. Samples were taken from cases of untreated teeth with asymptomatic chronic periradicular lesions, acute apical periodontitis, or acute periradicular abscesses, and from root-filled teeth associated with asymptomatic chronic periradicular lesions. DNA was extracted from the samples, and a 16S rDNA-based nested polymerase chain reaction assay was used to identify E. faecalis. This species occurred in seven of 21 root canals associated with asymptomatic chronic periradicular lesions, in one of 10 root canals associated with acute apical periodontitis, and in one of 19 pus samples aspirated from acute periradicular abscesses. Statistical analysis showed that E. faecalis was significantly more associated with asymptomatic cases than with symptomatic ones. E. faecalis was detected in 20 of 30 cases of persistent endodontic infections associated with root-filled teeth. When comparing the frequencies of this species in 30 cases of persistent infections with 50 cases of primary infections, statistical analysis demonstrated that E. faecalis was strongly associated with persistent infections. The average odds of detecting E. faecalis in cases of persistent infections associated with treatment failure were 9.1. The results of this study indicated that E. faecalis is significantly more associated with asymptomatic cases of primary endodontic infections than with symptomatic ones. Furthermore, E. faecalis was much more likely to be found in cases of failed endodontic therapy than in primary infections.

The Effects of Chlorhexidine Gluconate (0.12%) on the Antimicrobial Properties of Tooth-Colored ProRoot Mineral Trioxide Aggregate

The purpose of this in vitro study was to determine whether the substitution of 0.12% chlorhexidine gluconate for sterile water as a mixing agent would enhance the antimicrobial activity of tooth-colored ProRoot mineral trioxide aggregate (MTA) against Actinomyces odontolyticus (ATCC17982), Fusobacterium nucleatum (ATCC2586), Streptococcus sanguis (ATCC10556), Enterococcus faecalis (ER3/2S), Escherichia coli (SM10lambdapir), Staphylococcus aureus (ATCC6538), Pseudomonas aeruginosa (UME), and Candida albicans (ATCC10261). Two wells of 5-mm diameter were made in triplicate agar plates inoculated with standardized suspensions of each microorganism. MTA (33 mg) mixed with chlorhexidine (12 microl) or sterile water (12 microl) was placed to fill each well. Plates were incubated at 37 degrees C as required for microbial growth. A blinded, independent observer measured zones of inhibition. All MTA samples inhibited microbial growth regardless of mixing agent. MTA/chlorhexidine showed significantly larger zones of inhibition (p < 0.0002, paired t test). In conclusion, substituting 0.12% chlorhexidine gluconate for water enhanced the antimicrobial activity of tooth-colored ProRoot MTA.

Treatment Outcome in Endodontics—The Toronto Study. Phase II: Initial Treatment

The 4- to 6-yr outcome of initial (first-time) endodontic treatment was assessed for Phase II of the "Toronto Study." In total, 442 teeth were treated by using flared preparation and vertical compaction of warm gutta-percha or step-back preparation and lateral compaction. With 126 teeth excluded (discontinuers: deceased and relocated patients), 163 dropouts, and 31 extracted, 122 (48% recall) were examined for outcome: "healed" (no apical periodontitis [AP], signs, symptoms) or "diseased" (AP, signs, or symptoms). Phase II was analyzed separately and combined with Phase I (n = 242), using Chi-square and Fisher's exact tests (p < or = 0.05). The healed rate (combined sample, 85%) differed significantly for preoperative AP (absent, 93%; present, 79%), treatment technique (flared preparation and vertical compaction, 90%; step-back preparation and lateral compaction, 80%), gender (females, 90%; males, 79%), number of roots (1-92%; > or = 2-81%), and root-filling length (adequate, 87%; inadequate, 77%). Logistic regression revealed increased risk of disease for preoperative AP (odds ratio = 3.3) and technique (odds ratio = 2.3). This study confirmed AP and highlighted treatment technique as the main predictors of outcome in initial treatment.

The LightSpeed system

This article describes the use of an innovative, engine-driven, rotary, root canal preparation instrument. The geometric design of this nickel-titanium instrument is totally different from currently marketed manual or engine-driven stainless steel or nickel-titanium instruments. The thin, taperless, noncutting shafts of LightSpeed instruments maximize the flexibility of the nickel-titanium alloy, particularly in the larger sizes. The three different methods for using the LightSpeed cutting heads and three different methods for using the LightSpeed system are described. LightSpeed instruments enable larger apical preparations in curved canals with less coronal flaring than is possible with most other techniques.

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.

Endodontic treatment performed by Flemish dentists. Part 2. Canal filling and decision making for referrals and treatment of apical periodontitis

AIM

To gather information on root-canal treatment carried out by dentists working in Flanders (Belgium).

METHODOLOGY

A questionnaire reported in a previous study was also used to gather information on canal medicaments, canal filling, and in decision making for referrals and treatment of apical periodontitis.

RESULTS

Calcium hydroxide as an interappointment dressing was used by 69.7% of the respondents. Approximately one-third of the respondents did not use any intracanal medicament. Caustic products used for pulp tissue fixation were used by 66.8% of the respondents. Cavit (48.2%) and glass-ionomer (31.3%) were the temporary coronal-filling materials used most often, followed by zinc oxide-eugenol and IRM(R). Cold lateral condensation of gutta-percha was the filling technique most used by the respondents (65.8%). Single-cone gutta-percha placement (16%), paste techniques (4.9%) and silver points (3.9%) were still used. Resin-based sealers were used most often (88.6%). Paraformaldehyde containing sealers such as Endomethasone and N2 were used infrequently. Approximately half of the practitioners were satisfied with their canal-filling technique, others felt that they could do better (43.0%); 0.7% were not satisfied. In cases with apical periodontitis, the size of periapical lesions and/or the presence of a root filling influenced the choice of endodontic treatment. The most common reasons for referral of endodontic cases were: retrieval of silver points, surgery, and post removal.

CONCLUSIONS

The results of this study indicate that techniques and methods used for canal medication and canal filling were acceptable for the majority of the respondents. Re-treatment was underestimated as a treatment option.

In vitro evaluation of different chemical agents for the decontamination of gutta-percha cones

This study evaluated the effectiveness of three disinfectants used in Dentistry for decontamination of gutta-percha cones. Sixty gutta-percha cones were contaminated with standardized pure cultures of five species of microorganisms (Enterococcus faecalis ATCC 29212, Staphylococcus aureus ATCC 25923, Candida albicans ATCC CBS-ICB/USP 562, Bacillus subtilis spores ATCC 6633 and Streptococcus mutans ATCC 25175). The cones were treated with 10% polyvinylpyrrolidone-iodine aqueous solution (PVP-I; Groups 1 and 2), 5.25% aqueous sodium hypochlorite (Groups 3 and 4) and paraformaldehyde tablets (Group 5). All chemical agents were efficient for the cold sterilization of gutta-percha cones in short time periods.