Bactericidal Effects of Diode Laser Irradiation on Enterococcus faecalis Using Periapical Lesion Defect Model

Photodynamic Therapy With Resveratrol and an Nd:YAG Laser for Enterococcus faecalis Elimination

BACKGROUND/AIM

Enterococcus faecalis is the leading cause of endodontic treatment failures. Despite various conventional disinfection approaches, microorganisms often persist in root canals. Photodynamic therapy (PDT) is an adjunct antimicrobial strategy employing a nontoxic photosensitizer (PS) and light source. This study evaluated the antimicrobial effect of PDT using an Nd:YAG laser and resveratrol (RSV) with or without pigment, and confirmed that RSV is nontoxic as a PS.

MATERIALS AND METHODS

We employed laser irradiation at a 3W output power, using RSV and red pigment as the PS, on an E. faecalis bacterial solution. Subsequently, colony-forming units were quantified. The impact of RSV on osteoblasts was measured using an MTT assay.

RESULTS

E. faecalis counts declined after laser irradiation. The combined application of laser irradiation with RSV, red pigment, or both showed a reduction compared to no irradiation and control groups without RSV and red pigment. The 50% cytotoxic concentration against osteoblast cells from mice incubated with RSV for 48 h was 162 μM. The value with RSV and laser was 201 μM and that with RSV and red pigment was 199 μM. The value with RSV, laser and red pigment was 357 μM.

CONCLUSION

The combination of Nd:YAG laser irradiation and RSV as the PS with pigment was efficacious for E. faecalis elimination without inducing any toxic effects on osteoblasts. This combination holds potential as a root canal irrigation strategy.

5-Aminolevulinic Acid and Red Led in Endodontics: A Narrative Review and Case Report

The present study aims to discuss the main factors involving the use of 5-aminolevulinic acid together with red LED light and its application in endodontic treatment through a narrative review and a case report. Persistence of microorganisms remaining on chemical-mechanical preparation or intracanal dressing is reported as the leading cause of failure in endodontics. Photodynamic therapy has become a promising antimicrobial strategy as an aid to endodontic treatment. Being easy and quick to apply, it can be used both in a single session and in several sessions, as well as not allowing forms of microbial resistance. 5-aminolevulinic acid in combination with red LED light has recently been studied in many branches of medicine, with good results against numerous types of bacteria including Enterococuss faecalis. The case report showed how bacterial count of CFU decreased by half (210 CFU/mL), after 45 min of irrigation with a gel containing 5% of 5-aminolevulinic acid compared to the sample before irrigation (420 CFU/mL). The subsequent irradiation of red LED light for 7 min, the bacterial count was equal to 0. Thus, it is concluded that the use of 5-aminolevulinic acid together with red LED light is effective in endodontic treatment.

Disinfection of Infected Artificial Dental Periapical Lesions with Diode Laser: An In Vitro Study

Background

Periapical lesions are primarily caused by infections in the root canals. The objective of this study was to assess the antibacterial effectiveness of diode laser during root canal treatment in artificial models of infected periapical lesions.

Material/Methods

One hundred twenty-two extracted premolar single-rooted teeth were inserted into methyl methacrylate artificial models of periapical lesions, and bacterial solutions of Enterococcus faecalis (ATCC 29212) and Streptococcus mitis (ATCC 49456) were then applied to the models. The respective diameters of lesions in the artificial models represented 3 different subgroups based on lesion size. The laser protocol used for endodontic disinfection had a power output of 1.5 W and a wavelength of 810 nm. The impact on cell viability was evaluated by flow cytometry.

Results

Disinfection with laser did not differ between microorganisms (P=0.137), and laser irradiation with a longer duration had better disinfecting action for both microorganisms (P<0.001). Compared with larger lesions, smaller lesions had a higher percentage of dead cells for both microorganisms (P<0.001). The percentage of dead cells in the treatment groups was significantly higher than in the control group (P<0.001).

Conclusions

Laser treatment had a poor, almost negligible effect on elimination of bacterial cells in large periapical lesions. Application of a laser might serve as an adjuvant method to standard irrigation with sodium hypochlorite.

Photodynamic Therapy with Pyoktanin Blue and Diode Laser for Elimination of Enterococcus faecalis

BACKGROUND/AIM

Enterococcus faecalis is responsible for most cases of endodontic treatment failure. Despite various conventional disinfection methods, root canals are not completely free of microorganisms. Photodynamic therapy (PDT) is a new antimicrobial strategy that involves the use of a non-toxic photosensitizer (PS) and a light source. The aim of this study was to evaluate the antimicrobial effect of PDT using diode laser and pyoktanin blue (PB) and confirm the nontoxicity of PB as a PS.

MATERIALS AND METHODS

Laser irradiation with an output power of 3 W was performed with PB as the PS to a bacterial solution containing E. faecalis. Then, the number of colony-forming units was counted. PB cytotoxicity was also assessed by the MTT assay.

RESULTS

E. faecalis counts were reduced after laser irradiation, laser irradiation with PB, or the combination thereof compared to the control, non-irradiation or water. The 50% cytotoxic concentration value for adult human dermal fibroblasts incubated with PB for 1 min was 108 μg/ml.

CONCLUSION

Diode laser irradiation in combination with PB as the PS is efficacious for the elimination of E. faecalis without toxic effects to human dermal fibroblasts. This strategy might be useful for root canal irrigants.

Yolk-structured multifunctional up-conversion nanoparticles for synergistic photodynamic-sonodynamic antibacterial resistance therapy

The worldwide increase in bacterial antibiotic resistance has led to a search for alternative antibacterial therapies. The present study reports the development of yolk-structured multifunctional up-conversion nanoparticles (UCNPs) that combine photodynamic and sonodynamic therapy for effective killing of antibiotic-resistant bacteria. The multifunctional nanoparticles (NPs) were achieved by enclosing hematoporphyrin monomethyl ether (HMME) into its yolk-structured up-conversion core and covalently linked rose bengal (RB) on its silica (SiO₂) shell. Excitation of UCNPs with near-infrared (NIR) light that has improved penetration depth for photodynamic therapy (PDT) enabled the activation of HMME and RB and thus the generation of singlet oxygen (¹O₂). The SiO₂ layer, which improved the biocompatibility of the UCNPs, surrounded the yolk structure, with a cavity space which had a high efficiency of loading photosensitizers. Synergistic PDT and sonodynamic therapy (SDT) improved the photosensitizer utilization rate. As a result, a greater inhibition rate was observed when antibiotic-resistant bacteria were treated with a combined therapy (100%) compared with either the PDT (74.2%) or SDT (70%) alone. Our data indicate that the multifunctional NPs developed in this study have the potential for use in the clinical synergistic PDT-SDT treatment of infectious diseases caused by antibiotic-resistant bacteria.

Comparative Evaluation of Different Modes of Laser Assisted Endodontics in Primary Teeth: An In vitro Study

INTRODUCTION

The presence of bacteria in root canals has been considered to be responsible for endodontic treatment failure, even in case of primary teeth. The use of lasers can be a valuable addition in removing bacterial load in areas where traditional methods may fail to succeed. Methods like direct laser irradiation of canals, Laser Activated Irrigation (LAI) with sodium hypochlorite (NaOCl) and Photodynamic Therapy (PDT) seem to be a promising alternative for disinfection.

AIM

This study was designed to compare the efficacy of latest advancements in disinfection techniques using diode laser namely direct laser irradiation, photodynamic therapy and laser activated irrigation using sodium hypochlorite.

MATERIALS AND METHODS

Sixty freshly extracted primary teeth either single or multi-rooted teeth with two third of their root length intact were collected. Instrumentation was completed to size 30 H-file. Teeth were randomly divided into Group 1- Direct Laser- irradiation, Group 2 - Photodynamic therapy; Group 3- Laser activated irrigation with 2.5% NaOCl. The tooth specimens were inoculated with Enterococcus faecalis. The bacterial colonies were counted preoperatively. Laser irradiation was performed for all groups in accordance to the groups each tooth belonged to. Postoperatively the bacterial colonies were counted. One-way Analysis was applied to compare bacterial count at baseline and post-test between three groups. Tukey's post-hoc test was applied for pairwise comparison between groups. Paired t-test was applied to compare the mean baseline bacterial count with post-test mean bacterial count.

RESULTS

The results obtained with all the three groups postoperatively were highly significant (p-value<0.001). Statistically significant difference between results of Group 1 and Group 2 and also between Group 1 and Group 3 was found (p-value≤ 0.001). However, no statistical difference between Group 2 and Group 3 was found (p-value- 0.96).

CONCLUSION

Disinfection strategies using diode laser by techniques gives promising results. Techniques like laser activated irrigation and photoactivated disinfection are better than direct laser irradiation in eliminating Enterococcus feacalis.

Effect of Diode Laser on Bacteria Beyond the Apex in Relation to the Size of the Apical Preparation - An In-Vitro Study

INTRODUCTION

Microorganisms causing periapical infection are usually difficult to eradicate after conventional endodontic treatment or even in retreatment resulting in poor outcomes. So the purpose of the study was to assess whether disinfection of root canal with laser had any effect on bacteria in the periapex region.

AIM

The aim of the present study was to evaluate the effects of a diode laser when activated in root canals with varying apical diameters, on the bacteria present beyond the apex of the teeth.

MATERIALS AND METHODS

Total 30 intact single rooted teeth were taken and decoronated to standardize the root to a length of 12mm. They were divided into three groups depending on last file size used for instrumentation at apex i.e., size 30, 40 and 50 respectively. The samples were then mounted on test tubes such that roots of teeth were in contact with fresh broth of Escherichia coli (ATCC 25922) and left for incubation. Later a diode laser (Ezlase 940, Biolase) was used for disinfection of root canals of the samples. Following this the bacterial inoculums from each test tube were cultured and CFU were obtained from which the mean log values were obtained. Statistical analysis was done using Kruskal Wallis ANOVA test to compare mean CFU in three groups. Mann-Whitney U test with Bonferroni correction was used to compare inter-group differences.

RESULTS

There was statistically significant difference in mean log values of CFU in all the three study groups. Inter-group comparisons showed that, Group A had significantly lower mean CFUs than Group B and C respectively.

CONCLUSION

The study showed that intracanal irradiation with diode laser had an effect on the bacteria present beyond the apex, and it was influenced by the size of the apical preparation i.e., smaller apical size led to a greater reduction in the bacterial count.

The role of lasers in the treatment of peri-implant diseases: A review

We reviewed the indexed literature regarding the efficacy of laser therapy in the treatment of peri-implantitis (PI). Databases were searched using combinations of the following keywords: peri-implantitis, bone loss, photodynamic therapy, laser, and light-activated disinfection. Titles and abstracts of publications from these search results were screened to determine which studies fulfilled the eligibility criteria. Full texts of relevant studies were read and independently assessed against the eligibility criteria. The resulting 28 studies described the role of lasers in the treatment of PI. The erbium:yttrium–aluminum-garnet laser can be used to sterilize implant surfaces without damaging them. Likewise, the carbon dioxide laser can disinfect implant surfaces and enhance the bone-to-implant contact around previously infected sites. Photodynamic therapy exhibits high target specificity and can destroy pathogens associated with the etiology of PI. Laser therapy can significantly reduce levels of clinical markers of peri-implant tissue inflammation (i.e., bleeding upon probing and clinical attachment loss) without jeopardizing the integrity of the implant or alveolar bone. In conclusion, laser therapy as an adjunct to conventional mechanical debridement therapy can be used effectively for the treatment of PI.

Can Antimicrobial Photodynamic Therapy (aPDT) Enhance the Endodontic Treatment?

In order to achieve a long-lasting effect, one of the main goals in root canal treatment is to eliminate the endodontic bacteria. Conventional chemomechanical debridement is considered as the basic treatment in root canal therapy, but adjunctive techniques such as antimicrobial photodynamic therapy (aPDT) can also be helpful. The aim of this study was to evaluate reports in the scientific literature that used different photosensitizers (PSs) for bacterial reduction. The literature search was conducted using databases including PubMed, Scopus, and Google Scholar with the keywords "photodynamic therapy," "antimicrobial photodynamic therapy," or "photoactivated disinfection" and "endodontic," "Enterococcus faecalis," or "root canal treatment," from 2000 to 2015. By evaluating different studies, it was concluded that aPDT should be applied in combination with conventional mechanical debridement and irrigants. However, it is also important to note that the success rate is critically dependent on the type of the PS, output power of the laser used, irradiation time, pre-irradiation time, and type of tips used.

Photodynamic Antimicrobial Chemotherapy for Root Canal System Asepsis: A Narrative Literature Review

Aim. The aim of this comprehensive literature review was to address the question: Does photodynamic therapy (PDT) improve root canal disinfection through significant bacterial reduction in the root canal system? Methodology. A comprehensive narrative literature review was performed to compare PDT effect with sodium hypochlorite as the comparative classical irrigant. Two reviewers independently conducted literature searches using a combination of medical subject heading terms and key words to identify relevant studies comparing information found in 7 electronic databases from January 2000 to May 2015. A manual search was performed on bibliography of articles collected on electronic databases. Authors were contacted to ask for references of more research not detected on the prior electronic and manual searches. Results. The literature search provided 62 titles and abstracts, from which 29 studies were related directly to the search theme. Considering all publications, 14 (48%) showed PDT to be more efficient in antimicrobial outcome than NaOCl (0.5-6% concentration) used alone and 2 (7%) revealed similar effects between them. Toluidine blue and methylene blue are the most used photosensitizers and most commonly laser has 660 nm of wavelength with a 400 nm diameter of intracanal fiber. Conclusions. PDT has been used without a well-defined protocol and still remains at an experimental stage waiting for further optimization. The level of evidence available in clinical studies to answer this question is low and at high risk of bias.

Comparison of the bactericidal efficacy of photodynamic therapy, 2.5% sodium hypochlorite, and 2% chlorhexidine against Enterococcous faecalis in root canals; an in vitro study

BACKGROUND

Enterococcus faecalis has been widely used as a valuable microbiological pathogen for in vitro studies due to its ability to successfully colonize the root canal in a biofilm-like style, invade dentinal tubules, and resist endodontic treatment procedures.The aim of this study was to compare the bactericidal efficacy of photodynamic therapy (PDT), 2% chlorhexidine, 2.5% NaOCl, and combination of PDT and 2.5% NaOCl against E. faecalis.

MATERIALS AND METHODS

Sixty single-rooted teeth had their canals contaminated with E. faecalis in brain heart infusion broth and were incubated for 48 hours.The canals were then subjected to 2% chlorhexidine, 2.5% NaOCl, PDT (red light emitting diode 625 nm+ Toludine Blue) and PDT + 2.5% NaOCl. Controls consisted of no treatment (positive control) and without inoculation of bacterium (negative control). Following treatment, the canal contents were sampled with sterile paper points.The samples were dispersed in transport medium, serially diluted, and cultured on blood agar to determine the number of colony forming units (CFU). Data were analyzed by Mann-Whitney U test at 5% significance level. The significance level for all analyses was set at P <.05.

RESULTS

Combination of PDT and 2.5% NaOCl achieved maximum reduction in recovered viable bacteria, no viable bacteria was observed after treatment of PDT + 2.5% NaOCl.

CONCLUSION

Combination of PDT and 2.5% NaOCl simultaneously is effective in the elimination of E. faecalis from dentinal tubules under the conditions of this study.

Photodynamic inactivation of Candida albicans mediated by a low density of light energy

Shorter times and lower energies of application of light sources are desirable to use photodynamic antimicrobial chemotherapy (PACT) to the clinical control of candidiasis, especially among babies and children. Light energies ranging from 39.5 to 100 J/cm(2) were previously applied to kill Candida albicans by PACT. The present study evaluated the efficacy of a combination of 0.05 mg/mL toluidine blue O (TBO) and a short time of application (60 s) and a low density of light energy (18 J/cm(2)) of a red light-emitting diode (LED) in killing C. albicans planktonic cells. Standard suspensions of C. albicans were randomly assigned for four treatment groups: control (L-P-), LED alone (L+P-), TBO alone (L-P+), and PACT (L+P+). After treatments, serial dilutions of suspensions were prepared and streaked on Sabouraud dextrose agar to determine colony-forming units of C. albicans per milliliter (CFU/mL). The results were analyzed by ANOVA and Tukey's post-hoc test (P < 0.05). PACT significantly reduced CFUs of C. albicans in comparison to other three treatments. Our results demonstrated a fungicidal effect of PACT mediated by a shorter time of application of LED on C. albicans planktonic cells. Further in vivo studies are needed to elucidate the efficacy of PACT to treat human fungal infections.

pH and Antimicrobial Activity of Portland Cement Associated with Different Radiopacifying Agents

Objective. The aim of this study was to evaluate the antimicrobial activity and pH changes induced by Portland cement (PC) alone and in association with radiopacifiers. Methods. The materials tested were pure PC, PC + bismuth oxide, PC + zirconium oxide, PC + calcium tungstate, and zinc oxide and eugenol cement (ZOE). Antimicrobial activity was evaluated by agar diffusion test using the following strains: Micrococcus luteus, Streptococcus mutans, Enterococcus faecalis, Pseudomonas aeruginosa, and Candida albicans. After 24 hours of incubation at 37°C, inhibition of bacterial growth was observed and measured. For pH analysis, material samples (n = 10) were placed in polyethylene tubes and immersed in 10 mL of distilled water. After 12, 24, 48, and 72 hours, the pH of the solutions was determined using a pH meter. Results. All microbial species were inhibited by the cements evaluated. All materials composed of PC with radiopacifying agents promoted pH increase similar to pure Portland cement. ZOE had the lowest pH values throughout all experimental periods. Conclusions. All Portland cement-based materials with the addition of different radiopacifiers (bismuth oxide, calcium tungstate, and zirconium oxide) presented antimicrobial activity and pH similar to pure Portland cement.