Impact of root canal disinfection on the bacteriome present in primary endodontic infection: A next generation sequencing study

AIM

To investigate the bacteriome present in teeth with primary endodontic infection (PEI) and apical periodontitis (AP) and to determine quantitatively and qualitatively the impact of chemomechanical preparation (CMP) using 2.5% sodium hypochlorite NAOCl on the bacteriome found in PEI with AP using the Illumina MiSeq platform.

METHODOLOGY

Thirty-six paired samples from 18 patients were successfully sequenced and analysed. Samples were collected at two sampling times: before (s1) and after (s2) CMP using 2.5% NaOCl. The DNA was extracted from s1 and s2 samples and quantified using quantitative PCR (qPCR). All 36 samples were sequenced using the Illumina MiSeq platform. Raw V3-V4 amplicon sequencing data were processed with the DADA2 pipeline to generate amplicon sequence variants (ASVs). Alpha diversity metrics representing abundance (Chao1) and diversity and evenness (Shannon, Simpson) were computed. The paired-sample Wilcoxon's test was used to compare alpha diversity metrics and qPCR counts between s1 and s2. The PERMANOVA method (with 999 permutations) was applied to compare community composition between sample types (s1 versus s2) and between patient IDs. ALDEx2 (ANOVA-like differential expression tool for high-throughput sequencing data) to investigate differentially abundant taxa between s1 and s2. A paired-sample Wilcoxon's test was used to compare alpha diversity metrics and qPCR counts between s1 and s2.

RESULTS

The qPCR counts were significantly higher in s1 compared to s2 (p = .0007). The Chao1 index indicated no difference in alpha diversity (p < .7019); whereas Shannon (p = .0056) and Simpson (p = .02685) indexes showed higher values in s2. The PERMANOVA test using Adonis2 showed a significant effect of sample time on community composition (R2 = .0630, p = .012). Patient ID also showed a significant effect on community composition (R2 = .6961, p = .001). At the genus level, Dialister, Mogibacterium, Prevotella, and Olsenella were differentially enriched at s1, while Actinomyces, Stenotrophomonas_unclassified, Enterococcus_unclassified, and Actinomyces_unclassified were differentially enriched in s2.

CONCLUSION

The bacteriome present in teeth with PEI with AP is complex and diverse. CMP using 2.5% NaOCl showed a high quantitatively and qualitatively disinfectant impact on the bacteriome present in PEI with AP.

The Efficiency of Erbium Lasers in the Removal of Root Canal System and Surface Biofilms: A Systematic Review and Meta-Analysis

Background: Studies have shown positive effects of erbium lasers in removal of biofilms. A review article was required with quantitative data for confirmation of their effects, but there is still no a comprehensive study reviewing their effects based on the root canal and implant surface. This systematic review and meta-analysis was conducted to evaluate the efficiency of erbium lasers in removal of the root canal system and surface biofilms. Methods: Studies were searched with keywords in databases of PubMed, Scopus, Europe PMC, Cochrane Central, Embase, and Web of Science and screened by referees. Data were included based on mean ± standard deviation and size of control and laser groups. Effect sizes were assessed as standardized mean differences and calculated for each study and for the root and dental surface. Laser characteristics and bacteria were considered as moderators. Results: Nineteen articles in the current study comprised 565 samples (283 control samples and 282 laser samples). The analyses showed the significant effects of erbium lasers on bacterial biofilms on the implant surface [-0.496, 95% confidence interval, CI (-0.720 to -0.273); I2 = 26.94; p = 0.029; Q = 13.28] and root canal [-0.551, 95% CI (-0.656 to -0.445); I2 = 23.89; p = 0.031; Q = 10.46]. Results showed that highest efficiency lasers were obtained at higher wavelengths of 2940 nm, 75-100 mJ energy, and 100-150 μsec and <50-Hz pulses. Conclusions: Erbium lasers can be used to remove biofilms on dental implant surfaces and root canal systems and are safe options for untouchable sites in the root canal.

The effect of photodynamic therapy in controlling the oral biofilm: A comprehensive overview

Several resistance mechanisms are involved in dental caries, including oral biofilms. An accumulation of bacteria on the surface of teeth is called plaque. Periodontitis and gingivitis are caused by dental plaque. In this review article, we aimed to review the studies associated with the application of photodynamic therapy (PDT) to prevent and treat various microbial biofilm-caused oral diseases in recent decades. There are several studies published in PubMed that have described antimicrobial photodynamic therapy (APDT) effects on microorganisms. Several in vitro and in vivo studies have demonstrated the potential of APDT for treating endodontic, periodontal, and mucosal infections caused by bacteria as biofilms. Reactive oxygen species (ROS) are activated in the presence of oxygen by integrating a nontoxic photosensitizer (PS) with appropriate wavelength visible light. By causing irreversible damage to microorganisms, ROS induces some biological and photochemical events. Testing several wavelengths has been conducted to identify potential PS for APDT. A standard protocol is not yet available, and the current review summarizes findings from dental studies on APDT.

The efficacy of antimicrobial photodynamic therapy in the disinfection of coronal and radicular dentine of primary teeth: A systematic review and meta-analysis

BACKGROUND

Optimal endodontic disinfection by means of conventional root canal treatment of primary teeth remains a challenge. Recently, antimicrobial photodynamic therapy (aPDT) has been proposed as an adjunct to conventional endodontic treatment for microbial disinfection. The purpose of this review is to critically appraise and synthesize the currently-available evidence about the antimicrobial efficacy of aPDT (antimicrobial photodynamic therapy) when used as an adjunct to traditional root canal therapy.

MATERIALS AND METHODS

The focused question was ''In primary teeth needing root canal treatment (participants), is adjunct aPDT (intervention) more effective in disinfecting coronal and radicular dentine (outcomes) than root canal treatment alone (control)?'. The electronic research databases PubMED/Medline, ISI Web of Knowledge, Embase and CENTRAL (Cochrane Central Register of Controlled Trials) using relevant keyword phrases including 'antimicrobial photodynamic therapy', 'primary teeth', 'deciduous teeth', and 'endodontic treatment'. Original studies that described endodontic treatment of primary teeth or dentine using aPDT in comparison to conventional endodontic treatment were included. Case reports, reviews and other non-comparative studies were excluded. The literature search and quality assessment were carried out by two reviewers independently.

RESULTS

Ultimately, 9 studies were included in this review. Overall, majority of the studies concluded that adjunct aPDT improves the antimicrobial efficacy of conventional root canal therapy. However, several sources of bias were found in the studies.

CONCLUSION

Within the limitations of the studies, it is concluded that aPDT is a suitable adjunct to improve the disinfection of conventional root canal treatment. However, future studies should focus on the clinical outcomes, in relation to the reduction of microbial counts to ascertain the efficacy of aPDT in disinfection of primary dentine.

The role of the light source in antimicrobial photodynamic therapy

Antimicrobial photodynamic therapy (APDT) is a promising approach to fight the growing problem of antimicrobial resistance that threatens health care, food security and agriculture. APDT uses light to excite a light-activated chemical (photosensitiser), leading to the generation of reactive oxygen species (ROS). Many APDT studies confirm its efficacy in vitro and in vivo against bacteria, fungi, viruses and parasites. However, the development of the field is focused on exploring potential targets and developing new photosensitisers. The role of light, a crucial element for ROS production, has been neglected. What are the main parameters essential for effective photosensitiser activation? Does an optimal light radiant exposure exist? And finally, which light source is best? Many reports have described the promising antibacterial effects of APDT in vitro, however, its application in vivo, especially in clinical settings remains very limited. The restricted availability may partially be due to a lack of standard conditions or protocols, arising from the diversity of selected photosensitising agents (PS), variable testing conditions including light sources used for PS activation and methods of measuring anti-bacterial activity and their effectiveness in treating bacterial infections. We thus sought to systematically review and examine the evidence from existing studies on APDT associated with the light source used. We show how the reduction of pathogens depends on the light source applied, radiant exposure and irradiance of light used, and type of pathogen, and so critically appraise the current state of development of APDT and areas to be addressed in future studies. We anticipate that further standardisation of the experimental conditions will help the field advance, and suggest key optical and biological parameters that should be reported in all APDT studies. More in vivo and clinical studies are needed and are expected to be facilitated by advances in light sources, leading to APDT becoming a sustainable, alternative therapeutic option for bacterial and other microbial infections in the future.

Effect of antimicrobial photodynamic therapy on the reduction of bacteria and virulence factors in teeth with primary endodontic infection

OBJECTIVE

To evaluate the effectiveness of supplemental photodynamic therapy for improving the bacterial removal and the levels of lipopolysaccharide (LPS) and lipoteichoic acid (LTA) by conducting a clinical trial.

METHODOLOGY

Twenty-four root canals with pulp necrosis and periapical lesion were selected and randomly divided into conventional group using endodontic treatment with chemo-mechanical preparation (CMP) alone (n = 12) and a group using antimicrobial photodynamic therapy (aPDT) after CMP (n = 12). The samples were collected before and after CMP (conventional group) and after photodynamic therapy (aPDT group). A photosensitizer (0.005% methylene blue) was applied to the root canal for 3 minutes after CMP, whereas aPDT was performed by using a red laser with a power of 30Mw and energy density of 9J/cm² for 90 s per root canal. Culture technique was performed to determine the bacterial colony forming units. LPS and LTA levels were quantified by using limulus amoebocyte lysate (LAL) assay and enzyme-linked immunosorbent assay (ELISA), respectively.

RESULTS

All samples showed growth of viable bacteria on Fastidious Anaerobe Agar (FAA), with an average of 5.19 × 10⁵ CFU/ mL. CMP was effective in decreasing viable bacteria (p < 0.05), whereas there was a significant decrease (p < 0.05) in the samples treated with aPDT compared to those submitted to CMP. LPS and LTA were detected in all initial samples, with mean values of 20.561 EU/mL and 430.91 pg/mL, respectively. Both CMP and aPDT groups significantly decreased the levels of LPS and LTA (p < 0.05), with a statistical difference between the groups regarding aPDT (p < 0.05).

CONCLUSION

Photodynamic therapy as an adjunct to CMP proved to be effective in improving root canal disinfection and reducing the LPS and LTA levels in teeth with primary endodontic infection.

Clinical applications of antimicrobial photodynamic therapy in dentistry

Given the emergence of resistant bacterial strains and novel microorganisms that globally threaten human life, moving toward new treatment modalities for microbial infections has become a priority more than ever. Antimicrobial photodynamic therapy (aPDT) has been introduced as a promising and non-invasive local and adjuvant treatment in several oral infectious diseases. Its efficacy for elimination of bacterial, fungal, and viral infections and key pathogens such as Streptococcus mutans, Porphyromonas gingivalis, Candida albicans, and Enterococcus faecalis have been investigated by many invitro and clinical studies. Researchers have also investigated methods of increasing the efficacy of such treatment modalities by amazing developments in the production of natural, nano based, and targeted photosensitizers. As clinical studies have an important role in paving the way towards evidence-based applications in oral infection treatment by this method, the current review aimed to provide an overall view of potential clinical applications in this field and summarize the data of available randomized controlled clinical studies conducted on the applications of aPDT in dentistry and investigate its future horizons in the dental practice. Four databases including PubMed (Medline), Web of Science, Scopus and Embase were searched up to September 2022 to retrieve related clinical studies. There are several clinical studies reporting aPDT as an effective adjunctive treatment modality capable of reducing pathogenic bacterial loads in periodontal and peri-implant, and persistent endodontic infections. Clinical evidence also reveals a therapeutic potential for aPDT in prevention and reduction of cariogenic organisms and treatment of infections with fungal or viral origins, however, the number of randomized clinical studies in these groups are much less. Altogether, various photosensitizers have been used and it is still not possible to recommend specific irradiation parameters due to heterogenicity among studies. Reaching effective clinical protocols and parameters of this treatment is difficult and requires further high quality randomized controlled trials focusing on specific PS and irradiation parameters that have shown to have clinical efficacy and are able to reduce pathogenic bacterial loads with sufficient follow-up periods.

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.

Cytocompatibility and antimicrobial activity of a novel endodontic irrigant combining citric acid and chlorhexidine

OBJECTIVES

This study aimed to evaluate the antibacterial ability and cytocompatibility of a new irrigant solution for endodontic treatment composed of 10% citric acid (CA) and 1% chlorhexidine (CHX).

METHODS

Thirty-five extracted single-canal human teeth were selected and de-crowned. Canal systems (n = 7/group) were infected with Enterococcus faecalis for 4 weeks and subject to irrigation with 1% CHX; 10% CA; irrigating solution 10% CA associated with 1% CHX (CACHX); 2.5% NaOCl or sterile water (control). Microbiological samples were collected immediately and 18 h after irrigation (enriched samples). The canals were filled with culture medium post irrigation to verify the bacterial presence/absence qualitatively and quantitatively through colony counting (log₁₀ CFU/mL). A multiparametric assay was performed after exposure of human periodontal ligament fibroblasts (HPdLF) to the test solutions. The Kruskal-Wallis test with Dunn´s post-test and Fisher's exact test were employed at the 95% confidence level to compare differences among groups.

RESULTS

All tested solutions were cytocompatible with human periodontal ligament fibroblasts. No difference was observed on antibacterial activity between 1% CHX, 10% CA, CACHX and 2.5% NaOCl (p > 0.05). Eighteen hours after irrigation, CACHX samples were the only that did not present E. faecalis in the root canal system.

CONCLUSIONS

The demonstrated good in vitro biocompatibility and elimination of E. faecalis suggest a potential use of 10% CA associated with 1% CHX as a solution for microbiological control during endodontic treatment.

CLINICAL RELEVANCE

Irrigants play an essential role during endodontic therapy. This irrigating solution, based on the association of 10% citric acid with 1% chlorhexidine, seems viable for clinical procedures.

Nature and Prevalence of Bacterial Taxa Persisting after Root Canal Chemomechanical Preparation in Permanent Teeth: A Systematic Review and Meta-analysis

INTRODUCTION

Culture-independent molecular studies have shown a broad spectrum of bacterial taxa that persist after chemomechanical procedures (CMP). Therefore, this study systematically reviewed these reports to explore the prevalence of bacteria in post-instrumentation samples of root canals from permanent teeth, especially of as-yet-uncultivated/difficult-to-culture bacteria.

METHODS

Electronic databases were searched from 2007 to January 2021. Clinical studies using culture-independent molecular methods to identify species-level taxa before and after CMP were included. Studies were critically appraised using the Joanna Briggs Institute Prevalence Critical Appraisal Checklist and the funnel plot analysis. The meta-analysis was performed on the prevalence of as-yet-uncultivated/difficult-to-culture bacterial taxa using RStudio.

RESULTS

A total of 3781 titles were screened, but only 20 studies were included. The most frequent species in post-instrumentation samples were Streptococcus spp., Leptotrichia buccalis, Fusobacterium nucleatum, and Capnocytophaga ochracea. The detection frequency of some species increased after CMP, including mainly Firmicutes members such as streptococci, Enterococcus faecium, Selenomonas noxia, and Solobacterium moorei. The prevalence (confidence interval) of difficult-to-culture species was as follows: Dialister invisus, 17% (7%-29%); Solobacterium moorei, 14% (8%-23%); Bacteroidaceae [G-1] bacterium HMT 272, 13% (5%-23%); and Filifactor alocis, 11% (3%-23%).

CONCLUSIONS

The prevalence of as-yet-uncultivated/difficult-to-culture bacterial taxa in post-instrumentation samples was low. The persistent species belonged mainly to the phylum Firmicutes, and streptococci were the major members. Future larger clinical studies on the composition of the whole bacterial community that persist after CMP are still necessary for a better understanding of bacterial interactions and their clinical significance in the treatment outcome.

Protocol for the clinical practice of photodynamic therapy in endodontics: assessment of guideline quality using the AGREE II instrument

BACKGROUND

The choice of parameters in Photodynamic Therapy for endodontic treatment, such as wavelength, energy, application time, and number of sessions can vary based on the characteristics of the procedure and the patient. Providing information supported by scientific evidence in an accessible way to clinicians who are unfamiliar with the literature is necessary. Thus, this study aimed to synthesize a clinical protocol for the use of photodynamic therapy in endodontics in permanent teeth.

METHODS

Protocols with high methodological quality were identified using a literature search and the Appraisal of Guidelines Research and Evaluation Instrument (AGREE II), a validated tool for assessing quality. The recommendations of these studies were synthesized and submitted to a group of experts for evaluation and adaptation, and consensus was assessed using the Delphi methodology.

RESULTS

The analysis of the literature on the application of antimicrobial photodynamic therapy in endodontics showed that clinical trials with good levels of evidence and clinical recommendations have been reported previously, with two studies identified as having a clinical recommendation level of A1A and an evidence level of A.

CONCLUSION

The written protocol was considered to be satisfactory and as having appropriate content validity during the second round of evaluation by the experts. The studies included in this research were predominantly explanatory in nature, highlighting the need for pragmatic designs to increase the degree of clinical applicability.

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.

Virulence of Lactobacillus spp. misidentified as Enterococcus faecalis from children's carious dentine

Objective: This study aimed to search for Enterococcus faecalis in children's deep carious dentine and characterize their virulence traits.Material and Methods: Eight isolates from 15 carious molars identified by 16S rDNA species-specific PCR as E. faecalis were included. These eight isolates were subject to identification by MALDI-TOF and characterized regarding: (i) bacterial aggregation and biofilm formation on polystyrene and glass, with/without saliva, as single or dual-species (associated to Streptococcus mutans); (ii) environmental pH measurement before and after 24 h incubation; (iii) acidogenicity; (iv) gelatinase production; (v) macrophage adherence; and (vi) toxicity towards Caenorhabditis elegans. Statistical analyses were performed using two-way ANOVA/Tukey or Fisher's exact tests.Results: All isolates initially identified as E. faecalis by PCR were correctly identified as Lactobacillus by MALDI-TOF, being designated as Lactobacillus misidentified as Enterococcus (LME). These isolates produced biofilm in the presence of saliva and in the dual-species assays. Bacterial aggregation was only observed in the dual-species model. After 24 h, environmental pH dropped from 7.5 to 4.5 for seven of eight isolates, and to 4.0 in all dual-species models. LME isolates were acidogenic, none of them produced gelatinase or adhered to macrophages, but all presented toxicity towards C. elegans.Conclusions: No E. faecalis were identified in the children's caries lesions. All LME isolates presented important virulence traits, including biofilm formation and high acidogenicity, which cause enamel demineralization, that might increase the risk of dental caries in children carrying LME. Thus, the correct identification and in-depth virulence characterization of microorganisms isolated from dental caries are important to understand the dynamics of this disease.

How can biophotonics help dentistry to avoid or minimize cross infection by SARS-CoV-2?

Biophotonics is defined as the combination of biology and photonics (the physical science of the light). It is a general term for all techniques that deal with the interaction between biological tissues/cells and photons (light). Biophotonics offers a great variety of techniques that can facilitate the early detection of diseases and promote innovative theragnostic approaches. As the COVID-19 infection can be transmitted due to the face-to-face communication, droplets and aerosol inhalation and the exposure to saliva, blood, and other body fluids, as well as the handling of sharp instruments, dental practices are at increased risk of infection. In this paper, a literature review was performed to explore the application of Biophotonics approaches in Dentistry focusing on the COVID-19 pandemic and how they can contribute to avoid or minimize the risks of infection in a dental setting. For this, search-related papers were retrieved from PubMED, Scielo, Google Schoolar, and American Dental Association and Centers for Disease Control and Prevention databases. The body of evidence currently available showed that Biophotonics approaches can reduce microorganism load, decontaminate surfaces, air, tissues, and minimize the generation of aerosol and virus spreading by minimally invasive, time-saving, and alternative techniques in general. However, each clinical situation must be individually evaluated regarding the benefits and drawbacks of these approaches, but always pursuing less-invasive and less aerosol-generating procedures, especially during the COVID-19 pandemic.

Adjunctive use of antimicrobial photodynamic therapy in the surgical treatment of periapical lesions: a case series

BACKGROUND

Antimicrobial photodynamic therapy (aPDT) is being used in endodontics to improve orthograde root canal disinfection as an adjunct to standard treatments. Conversely, evidence concerning the application of aPDT in retrograde endodontic surgery is limited. Thus, the aim of the present study was to provide additional data regarding the use of aPDT in the surgical endodontic treatment of periapical lesions.

METHODS

A total of 25 consecutive patients presenting teeth with periapical radiolucency eventually associated with clinical signs and symptoms of apical periodontitis were included. Following access flap completion, osteotomy, mechanical debridement, root apical third resection, and preparation of the root-end cavity, aPDT was applied to decontaminate the surgical site using phenothiazine chloride dye at a concentration of 10 mg/mL and irradiation with a hand-held 100-mW diode laser with a wavelength of 660 ± 10 nm. At the latest follow-up visit, healing was evaluated as successful, uncertain, or failure according to well-established clinical and radiological criteria.

RESULTS

Overall, 31 periapical lesions were treated with aPDT. Healing proceeded uneventfully. The mean follow-up time was 36.19 months, with times ranging from 12 to 85 months. A total of 25 (80.65%) cases were classified as successful, 5 (16.13%) as uncertain, and only one (3.22%) as failure. Irrespective of the treatment outcome, all treated teeth were still functional, with no symptoms reported by the patients.

CONCLUSION

aPDT as an adjunctive treatment modality in the surgical endodontic treatment of periapical lesions showed promising medium-term results associated with preservation of all diseased teeth.

Effects of Antimicrobial Photodynamic Therapy on Organic Solution and Root Surface In Vitro

Antimicrobial photodynamic therapy (a-PDT) is attracting attention as a new form of dental treatment. While it is primarily applied to produce an antibacterial effect, it decreases lipopolysaccharide (LPS) and protease activity. Here, we evaluated differences in the antibacterial activity of a-PDT on three types of bacteria and the effects on the organic substances (i.e., albumin and LPS). Furthermore, we investigated the effects of a-PDT on root surfaces. A FotoSan630® and toluidine blue were used to perform a-PDT in this study. We measured its antimicrobial activity against Porphyromonas gingivalis, Streptococcus mutans, and Enterococcus faecalis. Antimicrobial testing revealed strong antimicrobial action and P. gingivalis, E. faecalis, and S. mutans were almost undetectable after 50, 120, and 100 s, respectively. In organic resolution tests, albumin was significantly decreased from 1 min after a-PDT application onward, while LPS significantly decreased at 5 min after the application. The root surfaces after a-PDT were confirmed to be cleaner than the controls without suffering any damage. Depending on the bacterial species, a-PDT exhibited antimicrobial activity against various types of bacteria and sensitivity differed. Moreover, we reported that a-PDT resolves protein and LPS, enabling the formation of a healthy root surface without any damage.

Efficacy of antimicrobial photodynamic therapy administered using methylene blue, toluidine blue and tetra 2-mercaptopyridine substituted zinc phthalocyanine in root canals contaminated with Enterococcusaecalis

BACKGROUND

Traditional chemomechanical treatment procedures are an indispensable part of endodontic treatment, however, additional treatment approaches such as antimicrobial photodynamic therapy (aPDT) may also be recommended for the elimination of residual microorganisms. In this study, the disinfection efficiency of aPDT performed using methylene blue (MB), toluidine blue (TB), and tetra 2-mercaptopyridine substituted zinc phthalocyanine (TM-ZnPc) was compared in the roots contaminated with Enterococcus faecalis (E. faecalis).

MATERIALS AND METHODS

Forty-nine teeth with a single root and canal were included in this study. The roots were sterilized, and inoculated with E. faecalis. The roots were kept in an incubator for 30 days to form the biofilm. Forty-five teeth were prepared up to the F3 file of the ProTaperNext system under 2.5 % NaOCL irrigation. The samples were divided into three groups according to the type of used photosensitizer (PS) (n = 15); MB (313 μM), TB (327 μM), and TM-ZnPc (6μM). All PSs were irradiation with a light-emitting diode (LED) lamp (630 nm, 2-4 mW/cm²) for the 60 s. Two microbiological samples of the intracanal content were taken (one before and one immediately after additional aPDT in all groups) using sterile paper points. The colony-forming units per milliliter (CFU/mL) were calculated after 24 h of incubation at 37 °C.

RESULTS

After all aPDT protocols, intracanal bacterial load decreased significantly compared to the amount after chemomechanical preparation (P < 0.05). No significant difference in the reduction in intracanal bacterial load was found between the PSs (P < 0.05).

CONCLUSIONS

In the current study, the aPDT protocol performed with TM-ZnPc provided similar antimicrobial efficacy, although it was used at a lower concentration compared to MB and TB. Therefore, the use of TM-ZnPc in intra-canal disinfection in endodontics seems promising.

Potassium iodide enhances the photobactericidal effect of methylene blue on Enterococcus faecalis as planktonic cells and as biofilm infection in teeth

OBJECTIVE

To explore the effectiveness, biosafety, photobleaching and mechanism of antimicrobial photodynamic therapy (aPDT) using methylene blue (MB) plus potassium iodide (KI), for root canal infections.

METHODS

Different combinations and concentrations of MB, KI and 660 nm LED light were used against E. faecalis in planktonic and in biofilm states by colony-forming unit (CFU), confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM). Human gingival fibroblasts (HGF) were used for safety testing by Cell Counting Kit-8 (CCK8) and fluorescence microscopy (FLM). The photobleaching effect and mechanisms were analyzed.

RESULTS

KI could not only enhance MB aPDT on E. faecalis in both planktonic and biofilm states even in a hypoxic environment, but also produced a long-lasting bactericidal effect after end of the illumination. KI could accelerate photobleaching to reduce tooth staining by MB, and the mixture was harmless for HGFs. Mechanistic studies showed the generation of hydrogen peroxide and free iodine, and iodine radicals may be formed in hypoxia.

CONCLUSION

aPDT with MB plus KI could be used for root canal disinfection and clinical studies are worth pursuing.

Adjunctive antimicrobial photodynamic therapy to conventional chemo-mechanical debridement of infected root canal systems: A systematic review and meta-analysis

BACKGROUND

To investigate the efficacy of antimicrobial photodynamic therapy (aPDT) adjunctive to conventional chemo-mechanical debridement of root canal system in patients with endodontic infections.

METHODS

A meta-analysis was done according to the Cochrane Collaboration recommendations and PRISMA statement. Two independent reviewers performed an extensive literature search on electronic databases of MEDLINE, EMBASE, and SCOPUS up to January 2019. The search strategy was done from the following terms: antimicrobial photodynamic therapy OR photo-activated disinfection AND root canal therapy OR endodontic therapy OR root canal infection OR endodontic infection. The I² test was used for determine the inter-study heterogeneity. Publication bias assessment carried out on the studies using the Egger's regression test.

RESULTS

Sensitivity analysis of 10 randomized clinical trials (RCTs) revealed differences in microbial load reduction (0.143, 95% CI [0.06, 0.30], P = 0.000) in favor of aPDT plus conventional chemo-mechanical debridement. A high degree of heterogeneity (P = 0.000; Q- value = 154.74; I² = 94.18%) was noticed among photosensitizer and light parameters. Subgroup analysis demonstrated the absence of heterogeneity in RCTs, with low risk of bias for microbial load reduction gain. No evidence of publication bias was determined.

CONCLUSIONS

Although the aPDT parameters may vary from one RCT to the next, all studies found a reduction in microbial load with adjunctive use of aPDT; however, further high-quality RCTs focused on the standardized aPDT parameters are needed.

Photodynamic therapy in endodontics

Photodynamic therapy (PDT) is a treatment modality that was initiated in 1900; however, it was not until the last decade that PDT regained attention for its several favourable features during the treatment of microbial infections in endodontics. Recently, several papers advocated its use for root canal treatment. The concept of photodynamic inactivation requires microbial exposure to either exogenous or endogenous photosensitizer molecules, followed by visible light energy, typically wavelengths in the red/near-infrared region that cause the excitation of the photosensitizers resulting in the production of singlet oxygen and other reactive oxygen species that react with intracellular components and consequently produce cell inactivation and death. Recently, PDT has been suggested as a promising effective adjunct to standard antimicrobial intracanal cleaning and shaping for the treatment of periapical lesions. Current publications tested PDT in terms of bacterial load reduction in vivo, in vitro and ex vivo, showing promising results. The purpose of this article was to review the existing literature on PDT in the endodontic field regarding its mechanism of action, photosensitizers and light sources, limitations and clinical procedures. Although positive results have been demonstrated in vitro, there are considerably fewer in vivo investigations. In conclusion, more in vivo studies are needed on the use of antimicrobial PDT in root canal treatment.

Comparison of final disinfection protocols using antimicrobial photodynamic therapy and different irrigants after single-file reciprocating instrumentation against intracanal bacterial biofilm - An in vitro study

BACKGROUND

The aim of the study was to compare the efficacy of antimicrobial photodynamic therapy (aPDT) with irrigation protocols that include sodium hypochlorite (NaOCl), ethylenediaminotetraacetic acid (EDTA) or QMiX (combined irrigant: EDTA, chlorhexidine, detergent) solution after single-file reciprocating root canal instrumentation.

METHODS

The study sample included 68 extracted mandibular human single canal teeth. The canals were inoculated with bacterial suspension made of wild strain of Enterococcus faecalis. After 17 days of incubation, the samples were assigned to experimental groups according to the final disinfection protocol and a control group. The root canals in all groups were, firstly, instrumented with Wave One Gold reciprocating system. Then the canals were disinfected as follows: Group 1. 2.5% NaOCl and EDTA followed by the application of the aPDT; Group 2. 2.5% NaOCl, EDTA and 2.5% NaOCl; Group 3. 2.5% NaOCl and QMIX solution; Group 4. 2.5% NaOCl and EDTA. In the control group, the canals were irrigated with saline solution. Microbiological samples were collected at baseline, after single-file instrumentation and after the final disinfection protocols. The samples were plated onto Mitis Salivarius agar plates for incubation. The colony forming units (CFUs) were counted, and the final number was determined based on the dilution factor.

RESULTS

Reciprocating single-file instrumentation reduced CFUs significantly in all groups (p<0.05). No significant difference between Group 1 and Group 2 was observed (p=0.178). Irrigation with the QMiX was more efficient than the aPDT (p=0.02).

CONCLUSIONS

The aPDT used after irrigation with NaOCl and EDTA demonstrated similar antimicrobial efficacy as conventional irrigation with NaOCl.