Ex vivo comparison of antibacterial efficacy of conventional chemomechanical debridement alone and in combination with light-activated disinfection and laser irradiation against Enterococcus faecalis biofilm

Antimicrobial efficacy of chitosan versus sodium hypochlorite: A systematic review and meta-analysis

AIM

This meta-analysis aimed to compare the antibacterial efficacy of chitosan/chitosan nanoparticles (Ch/Ch-NPs) versus sodium hypochlorite/chlorhexidine (NaOCl/CHX).

MATERIALS AND METHODS

A search was performed in four electronic databases until December 08, 2023. Studies with missing, unclear, and insufficient data sets were excluded. The included studies were assessed by two independent reviewers using the Joanna Briggs Institute Critical Appraisal Checklist for Quasi-Experimental Studies. The meta-analysis of standardized mean difference was performed using a random effects model. Additionally, funnel plots as well as Egger's regression intercept test were used to evaluate potential publication bias.

RESULTS

A total of 426 samples were used in nine included studies. There was no difference in antibacterial efficacy between Ch/Ch-NPs-NaOCl (SMD: 0.005; 95% CI: -0.844-0.854; p = 0.990). However, the antibacterial efficacy of NaOCl was statistically more effective than Ch/Ch-NPs (SMD: 0.807; 95% CI: 0.015-1.599; p = 0.046) using the bacterial culture method, and Ch/Ch-NPs was statistically higher than NaOCl (SMD: -1.827; 95% CI: -2.720, -0.934; p < 0.000) using confocal laser scanning microscopy.

CONCLUSIONS

Ch/Ch-NPs may be an alternative to NaOCl against Enterococcus faecalis. The methods used in the in vitro studies evaluating the antibacterial efficacy of irrigation solutions against E. faecalis may have had an impact on the results.

A promising approach utilising photothermal energy to disinfect the root canal system: An in vitro investigation

This study aimed to assess root canal disinfection through various irrigation protocols, including a novel photothermal system called 'LEAP'. Mandibular premolars were infected with Enterococcus faecalis and divided into five groups for different treatments: Group 1: standard needle irrigation; Group 2: passive ultrasonic irrigation; Group 3: GentleWave; Group 4: LEAP; and Group 5: Group 1 + Group 4. Microbial counts were measured before (S1) and after disinfection (S2) using colony-forming units (CFU) and confocal laser scanning microscopy (CLSM). Results revealed a significant reduction in bacterial counts for all groups (p < 0.05). While the percentage of dead bacteria near the canal wall (0-50 μm) did not differ significantly, at 50-150 μm, LEAP and SNI + LEAP exhibited significantly higher bacterial reduction than other groups (p < 0.05). The findings indicate that LEAP is comparable to existing irrigation devices in the main root canal and notably superior in tubular disinfection.

The effect of the enzymes trypsin and DNase I on the antimicrobial efficiency of root canal irrigation solutions

The purpose of this study was to evaluate the antibacterial efficacy of using 2.5% NaOCl, 2% chlorhexidine (CHX), Irritrol, and chitosan-coated silver nanoparticles (AgCNPs) alone or in combination with deoxyribonuclease I (DNase I) and trypsin pre-enzyme applications in dentin samples contaminated with Enterococcus faecalis (E. faecalis) by CLSM. 144 dentin blocks with confirmed E. faecalis biofilm formation were divided randomly according to the irrigation protocol (n = 12): NaOCl, CHX, Irritrol, AgCNPs, trypsin before NaOCl, CHX, Irritrol, AgCNPs, and DNase I before NaOCl, CHX, Irritrol, AgCNPs. Dentin blocks were stained with the Live/Dead BacLight Bacterial Viability Kit and viewed with CLSM after irrigation applications. The percentage of dead and viable bacteria was calculated using ImageJ software on CLSM images. At a significance level of p < 0.05, the obtained data were analyzed using one-way Anova and post-hoc Tukey tests. In comparison with NaOCl, CHX had a higher percentage of dead bacteria, both when no pre-enzyme was applied and when DNase I was applied as a pre-enzyme (p < 0.05). There was no difference in the percentage of dead bacteria between the irrigation solutions when trypsin was applied as a pre-enzyme (p > 0.05). AgCNPs showed a higher percentage of dead bacteria when trypsin was applied as a pre-enzyme compared to other irrigation solutions (p < 0.05), while the pre-enzyme application did not affect the percentage of dead bacteria in NaOCl, CHX, and Irritrol (p > 0.05). No irrigation protocol tested was able to eliminate the E. faecalis biofilm. While the application of trypsin as a pre-enzyme improved the antimicrobial effect of AgCNPs, it did not make any difference over other irrigation solutions.

Adjuvant therapy with a 980-nm diode laser in root canal retreatment: randomized clinical trial with 1-year follow-up

The purpose of this study is to assess the laser effect in root canal disinfection and periapical healing of endodontically treated teeth from patients with asymptomatic apical periodontitis. This study was performed as a randomized clinical trial. Thirty patients were selected according to the inclusion/exclusion criteria. Fifteen patients received the root canal retreatment (RCR) combined with 980-nm diode laser irradiation (LI). The canals were irrigated with saline solution and gently dried with paper points, keeping the dentin partially moist. The irradiation was performed using a 320-µm-diameter fiber in helicoidal movements (pulsed mode, power output of 1.5 W, 100 Hz for 20 s). The other 15 patients received the RCR with placebo irradiation (PI). Microbiological samples were taken in three periods: S1, after the filling material removal (baseline); S2, after laser or placebo irradiation (LI or PI); and S3, after the RCR followed by laser or placebo. The samples were submitted to the total microbial and E. faecalis counting. The periapical radiographic healing was analyzed after 3, 6, 9, and 12 months. Microbiological data (CFU/mg) were analyzed by ANOVA and Tukey's test (P < 0.05), and the repair by Mann-Whitney test (P < 0.05). In S2, the laser provided 42.44% microbial reduction and 53.14% of E. faecalis, different from the placebo that had no reduction, and 4.85% for Enterococcus (P < 0.05). In S3, the bacterial counts decreased without differences between groups. No differences in healing were found at 3 months. However, diode laser facilitated the repair from 3- to 12-month follow-up (P < 0.05) and had 45% more healed cases than placebo. Diode laser provided an antimicrobial effect before the biomechanical preparation but was not synergistic in RCR. It improved the periapical healing during follow-up.

Influence of antimicrobial photodynamic therapy with different pre-irradiation times on children's dental biofilm: randomized clinical trial

PURPOSE

Photodynamic therapy (PDT) is effective in reducing pathogenic microorganisms in the oral cavity and in preventing dental diseases. This study evaluated the pre-irradiation time using PDT (diode laser associated with 0.01% methylene blue) to decrease the number of microorganisms in the visible plaque in permanent teeth.

METHODS

This randomized clinical trial included 108 homologous lower permanent first molars (36 and 46) with biofilm from 54 children aged six to 12 years. PDT was performed (0.01% methylene blue photosensitizer/therapeutic laser-InGaAIP), according to the following protocols: Group 1, biofilm collection of the distal area of the lingual surface of 36 µm before PDT; group 2, mesial area of the lingual surface of 36 µm 1 min after PDT; group 3, area of the lingual surface of 46 µm before PDT; and group 4, mesial area of the lingual surface of 46 µm 5 min after PDT.

RESULTS

After statistical analysis, significant differences were observed between the groups (p = 0.000). In groups 2 and 4, the number of bacteria tended to decrease, with a more evident bacterial reduction in group 4.

CONCLUSIONS

Pre-irradiation reduced the number of colony-forming units of mature bacterial biofilms in vivo. A time of 5 min resulted in a greater reduction in the number of colony-forming units.

CLINICAL TRIAL REGISTRATION

ReBEC Identifier: RBR-6bqfp3; Date of Register: March 2nd, 2020. Retrospectively Registered.

Antibacterial Effects of the Novel Blue Laser and Erbium Chromium Laser on Enterococcus Faecalis in Root Canal Dentin with Different Thicknesses

The aim of this study was to investigate the antibacterial effects of 445 nm blue diode lasers and erbium chromium lasers on the biofilm of Enterococcus faecalis in root canal dentin with different thicknesses. Dentin slices with thicknesses of 300, 500, and 1,000 microns were prepared; and after the biofilm formation, they were randomly divided into four groups: group A : Er, Cr:YSGG laser radiation; group B: 445 nm diode laser radiation; group C : laser radiation in three cycles; and control group D: 5 samples of each thickness were selected as a positive control group. Er, Cr:YSGG and diode lasers alone did not significantly reduce the number of bacteria in any of the thicknesses. Only in 1 mm thick sections, the group exposed with the both Er, Cr:YSGG laser and 445 nm diode laser (66%) significantly reduced the number of bacteria. There was a significant difference in a thickness of 0.3 mm compared to a thickness of 1 mm, indicating that these lasers had a better effect at a thickness of 0.3 mm than at 1 mm parts (P-value < 0.008). It seems that these lasers can be used as an adjunct to conventional chemical methods in cleaning infected canals.

Antibacterial Effect of Red Laser Therapy on Enterococcus faecalis Using Different Photosensitizers: An In Vitro Study

Objective

To assess the antibacterial effect of red laser using different photosensitizers such as methylene blue and malachite green on monoradicular premolars contaminated with E. faecalis ATCC 29212.

Methods

This was an in vitro experimental study. Monoradicular premolars (44, 45, 34, and 35) were used, which were treated with ProTaper Next. After instrument change, irrigation, disinfection, and aspiration were performed with 2 ml of 4% NaOCl with a NaviTip 30°G needle (Ultradent, South Jordan, UT, USA). Group 1: RL + MB (red laser associated with methylene blue photosensitizer), group 2: RL + MG (red laser associated with malachite green photosensitizer), and group 3: control (no treatment). The E. faecalis strain was cultured on trypticase soy agar (TSB) (Difco, Detroit, MI, USA) and incubated at 37°C for 24 h. After the incubation period, colony-forming units (CFU/ml) of each group were counted using the plate count method. The ANOVA test was used with a significance level of p < 0.05.

Results

Group 1 had the lowest antibacterial contamination as it averaged only 530 ± 581.3 CFU/ml, while group 2 had the highest contamination with an average of 1990 ± 542.5 CFU/ml. Comparison revealed that there were statistically significant differences between the RL + MB and RL + MG groups (p < 0.001).

Conclusions

Group 1 had the best antimicrobial potential because it presented the lowest contamination in CFU/ml of E. faecalis compared to group 2 and group 3.

A new model for the formation of an Enterococcus faecalis endodontic biofilm with nutritional restriction

An in vitro model for the formation of an Enterococcus faecalis endodontic biofilm under nutritional restriction was established, simulating clinical conditions for the evaluation of antimicrobial substances. Biofilm formation in dentin was standardized using root quarters incubated with E. faecalis ATCC 29212 at 37°C without nutritional changes. Biofilms were evaluated at 7, 14, and 30 days, counting bacterial colony-forming units using conventional culture and verified scanning electron microscopy. Bacterial viability and biovolume were determined with confocal laser microscopy. Colonization of E. faecalis and biofilm formation on the dentinal surface was confirmed after 7 and 14 days, respectively. Microorganism colonization was homogeneous over the entire root surface at each time point, without significant differences in the viability percentage and biovolume. On the contrary, a decrease in viability and an increase in biovolume were observed when the time was increased. Compared with other incubation times, 14 days was found to be the best time for the establishment of the biofilm in terms of biovolume and bacterial viability. This in vitro model for the formation of endodontic biofilm will allow future evaluation of the efficacy of antimicrobial substances with a more adequate clinical approach.

Photodynamic Inactivation of an Endodontic Bacteria Using Diode Laser and Indocyanine Green-Loaded Nanosphere

Apical periodontitis, an inflammatory lesion causing bone resorption around the apex of teeth, is treated by eradicating infectious bacteria from the root canal. However, it has a high recurrence rate and often requires retreatment. We investigated the bactericidal effect of antimicrobial photodynamic therapy (aPDT)/photodynamic antimicrobial chemotherapy (PACT) using indocyanine green (ICG)-loaded nanospheres coated with chitosan and a diode laser on a biofilm of Enterococcus faecalis, a pathogen of refractory apical periodontitis. Biofilm of E. faecalis was cultured in a porcine infected root canal model. ICG solution was injected into the root canal, which was then irradiated with a laser (810 nm wavelength) from outside the root canal. The bactericidal effect was evaluated by colony counts and scanning electron microscopy. The result of the colony counts showed a maximum 1.89 log reduction after irradiation at 2.1 W for 5 min. The temperature rise during aPDT/PACT was confirmed to be within a safe range. Furthermore, the light energy transmittance through the root was at a peak approximately 1 min after the start of irradiation, indicating that most of the ICG in the root canal was consumed. This study shows that aPDT/PACT can suppress E. faecalis in infected root canals with high efficiency.

Biofilm Inactivation using Photodynamic Therapy in Dentistry: a review of literature

Introduction: Photodynamic therapy (PDT) is a therapy involving light and a photosensitising chemical substance, used in conjunction with molecular oxygen in order to elicit cell death (photo-toxicity) and thus ability to kill microbial cells, including bacteria, fungi and viruses. Photodynamic therapy is an alternative method of biofilm disruption and it is considered a new way of microorganism inactivation. It is also an additional procedure to reduce the infection rate in patients, caused by the increasing antimicrobials resistance of bacteria. The aim of this literature review was to evaluate the specific effects and the antibacterial effectiveness of photodynamic therapy using different types of photosensitizers (Erythrosine, Rose Bengal, Toluidine blue, Methylene blue, Ozone, Riboflavin, Curcumin, Chlorhexidine, SAPYR) and a visible light of a specific wavelength for each photosensitizer and to reveal the applications of PDT in periodontics, endodontics, prosthodontics and dental caries. Methods: A research of literature was performed in an attempt to find all the articles published on this topic in the last 10 years. The articles was searched by using a certain combination of different keywords (photodynamic therapy ) and (diode laser ) and (teeth) in PubMed database. Results: A total number of 83 articles were found. After applying inclusion and exclusion criteria, 35 articles were taken into consideration for our study and among them 4 were a manuscript, 3 was a review of literature, 1 was an in vivo evaluation and 27 were in vitro studies. Conclusion: Considering that none of the disinfection methods can completely remove the biofilm, PDT is a therapeutic tool complementary to conventional disinfection, with great applicability in dentistry. PDT showed significantly efficacy in reduction of biofilms. Exposure to light in the presence of a photosensitizing chemical substance helps in the reduction of microbes and the protocols could be recommended for clinical usage, but only together with ‘classic ‘ disinfection.

Influence of an 810-nm Diode Laser on the Temperature Changes of the External Root Surface: An In Vitro Study

Background and Aims:

Rising effects of temperature due to laser use during root canal disinfection may harm periodontium and alveolar bone. Therefore, the aim of this study was to estimate the surface root temperature of lower incisors throughout the application of different power levels and times of an 810-nm diode laser.

Materials and Methods:

Sixty single-rooted extracted human lower incisor teeth were selected and chemomechanical preparation was performed. Specimens were irradiated using 810-nm diode laser at 1.05, 1.5, and 1.95 W power settings and two periods of time 20 and 60s, in a continuous wave (CW) mode, without water spray. Specimens were divided into three main groups (n = 20). Each group was subdivided into two subgroups (n = 10). Then, the peak temperatures at the middle and apical regions of the root surface were registered using a thermocouple.

Results:

Temperature rise of root surface at all the selected output powers was below 7°C. The highest temperature value was obtained in the apical region at 60s when the root canal irradiated at 1.95 W output power.

Conclusion:

Diode laser is safe for use as a root canal disinfectant. Time of exposure to laser irradiation has an effect on the temperature difference at different output powers.

The Influence of Enterococcus faecalis as a Dental Root Canal Pathogen on Endodontic Treatment: A Systematic Review

Endodontic treatment failure may occur due to different causes such as persistence of bacteria, root canals that are poorly cleaned and obturated, improper coronal seal (leakage), and untreated canals (missed canals). The main reason for endodontic failure is the presence of some species of bacteria inside the root canal system such as Enterococcus (E.) faecalis. Those bacteria are more resistant to disinfection agents, causing a persistent intra-radicular or extra-radicular infection.

The current review aims to compile all the current studies concerning Enterococcus faecalis as a dental root canal pathogen that causes endodontic failure. In this systemic review, two databases, PubMed and Google Scholar, were searched using specific inclusion and exclusion criteria. Among 2943 studies, only 11 met the inclusion criteria and were included in the review for further analysis.

The 11 studies give prominence to the high distribution of Enterococcus faecalis within the root canal system. These studies investigated different aspects of Enterococcus faecalis, including its prevalence, resistance mechanisms, characteristics, express survival genes, and treatment.

The compiled data observed that most of the studies highlight Enterococcus faecalis as the primary pathogen associated with endodontic treatment. It has characteristic proprieties that make it capable of escaping disinfection means. Furthermore, clinical trials are required to examine E. faecalis and may provide valuable information about novel microbial detection methods to decrease the number of E. faecalis within the root canal system.