Bactericidal Effect of Er:YAG Laser-Activated Sodium Hypochlorite Irrigation Against Biofilms of Enterococcus faecalis Isolate from Canal of Root-Filled Teeth with Periapical Lesions

Principle and antimicrobial efficacy of laser-activated irrigation: A narrative review

In the last two decades, the activation of root canal irrigants with pulsed lasers as an adjunct in root canal treatment has become increasingly popular. This narrative review explains the physical basics and the working mechanism of laser-activated irrigation (LAI), explores the parameters influencing LAI efficacy, considers historical evolutions in the field and summarizes laboratory and clinical evidence with emphasis on the antimicrobial action of LAI. Cavitation is the driving force behind LAI, with growing and imploding vapour bubbles around the laser tip causing various secondary phenomena in the irrigant, leading to intense liquid dynamics throughout the underlying root canal. High-speed imaging research has shown that laser wavelength, pulse energy, pulse length and fibre tip geometry are parameters that influence this cavitation process. Nevertheless, this has not resulted in standardized settings for LAI. Consequently, there is significant variability in studies assessing LAI efficacy, complicating the synthesis of results. Laboratory studies in extracted teeth suggest that, with regard to canal disinfection, LAI is superior to conventional irrigation and there is a trend of higher antimicrobial efficacy of LAI compared to ultrasonic activation. Clinical evidence is limited to trials demonstrating similar postoperative pain levels after LAI versus no activation or ultrasonic activation. Clinical evidence concerning the effect of LAI on healing of apical periodontitis as yet is scarce.

Association between the irrigation-agitation techniques and Periapical Healing of large periapical lesions: a Randomized Controlled Trial

OBJECTIVES

The aim of this study was to evaluate the effects of manual dynamic activation (MDA), passive ultrasonic irrigation (PUI), and laser-activated irrigation (shock wave-enhanced emission photoacoustic streaming (SWEEPS)) on the periapical healing of large periapical lesions following nonsurgical root canal treatment.

MATERIALS AND METHODS

A total of fifty-six systemically healthy patients with a mandibular single-rooted tooth with periapical lesions of endodontic origin and a periapical index score of 3 or higher were included in the study. Before the treatment procedures, lesion volumes were determined volumetrically using cone-beam computed tomography (CBCT). Patients were randomized into treatment (MDA, PUI, SWEEPS) and control groups (n = 14). Root canal treatment and irrigation procedures were performed by a calibrated postgraduate operator and completed at one visit. For routine follow-up, clinical and radiographic evaluations were performed by a blinded evaluator using periapical (PA) radiographs according to Molven's criteria at 3, 6, and 9 months. At 12 months, lesion volumes were quantified volumetrically using CBCT (ITK-SNAP). The data were statistically analyzed with the Wilcoxon test. The significance level was set at p < 0.05.

RESULTS

In all groups, the mean lesion volume after treatment was significantly smaller than the mean volume before treatment (p = 0.001). Among the 56 teeth, 11 teeth were 'totally healed', and 39 teeth were 'reduced' on PA radiographs. No 'enlargement' was detected in any group. On CBCT, the lesion volume decreased in the following order: LAI-SWEEPS (86.9%) > PUI (85.4%) > MDA (80.4%) > control (74.5%), with no statistically significant difference (p > 0.05).

CONCLUSIONS

Despite the limitations of the present study, although a greater percentage of healing was observed in the LAI-SWEEPS and PUI groups, irrigation procedures had no statistically significant effect on the healing of periapical lesions with a single root canal at the 12-month follow-up. On the other hand, the outcome may change in multirooted teeth with curved and complex root canal systems.

CLINICAL RELEVANCE

In the short term and in single-canal teeth, advanced irrigation agitation methods such as laser and ultrasonic did not make a difference in healing other than manual irrigation agitation.

Analyses of the Antibiofilm Activity of o-Phenanthroline Monohydrate against Enterococcus faecalis and Staphylococcus aureus and the Mechanisms Underlying These Effects

Enterococcus faecalis and Staphylococcus aureus exhibit robust biofilm formation capabilities, the formation of which is closely linked to pathogenicity and drug resistance, thereby resulting in host infection and treatment failure. o-Phenanthroline monohydrate (o-Phen) and its derivatives demonstrate a wide range of antibacterial and antifungal activities. In this study, we aimed to explore the antibiofilm activity of o-Phen to E. faecalis and S. aureus and provide insights into the molecular mechanisms for combating biofilm resistance. We demonstrated that o-Phen possesses significant antibacterial and antibiofilm properties against E. faecalis and S. aureus, inducing alterations in bacterial morphology, compromising cell membrane integrity, and exhibiting synergistic effects with β-lactam antibiotics at sub-MIC concentrations. The adhesion ability and automatic condensation capacity of, and synthesis of, extracellular polymers by E. faecalis cells were reduced by o-Phen, resulting in the inhibition of biofilm formation. Importantly, transcriptome analysis revealed 354 upregulated and 456 downregulated genes in o-Phen-treated E. faecalis. Differentially expressed genes were enriched in 11 metabolism-related pathways, including amino acid metabolism, pyrimidine metabolism, and glycolysis/gluconeogenesis. Moreover, the oppA, CeuA, and ZnuB genes involved in the ABC transport system, and the PBP1A penicillin-binding protein-coding genes sarA and mrcA were significantly downregulated. The multidrug efflux pump system and membrane permeability genes mdtG and hlyD, and bacterial adhesion-related genes, including adcA and fss2 were also downregulated, while mraZ and ASP23 were upregulated. Thus, o-Phen is anticipated to be an effective alternative drug for the treatment of E. faecalis and S. aureus biofilm-associated infections.

Efficacy of Laser-Activated Irrigation Versus Ultrasonic-Activated Irrigation: A Systematic Review

This study aimed to conduct a systematic review and critical analysis of the evidence pertaining to the efficacy of laser-activated irrigation (LAI) versus ultrasonic-activated irrigation (UAI) in mature permanent teeth. A comprehensive literature search was performed using PubMed and Google Scholar. Additionally, a hand search was performed to identify relevant studies related to UAI and LAI. The search covered all articles published from January 1997 to December 2021. The identified studies were screened for eligibility using the inclusion and exclusion criteria. The included articles were then subjected to data extraction and analysis. The search yielded 1,637 results. Of these, 23 articles were included in this systematic review. All included articles were assessed for the outcomes of antimicrobial efficacy, smear layer, and dentin debris removal. The majority of the articles reported the superiority of LAI over UAI. Within the confines of this systematic review, the current evidence mandates that LAI has superior efficacy over UAI in the elimination of microorganisms, dentin debris, and smear layer from the root canal system.

The evolution of cavitation in narrow soft-solid wedge geometry mimicking periodontal and peri-implant pockets

In periodontology and implantology, laser-induced cavitation has not yet been used to treat biofilm-related problems. In this study we have checked how soft tissue affects the evolution of cavitation in a wedge model representing periodontal and peri-implant pocket geometry. One side of the wedge model was composed of PDMS mimicking soft periodontal or peri-implant biological tissue, the other side was composed of glass mimicking hard tooth root or implant surface, which allowed observations of the cavitation dynamics with an ultrafast camera. Different laser pulse modalities, PDMS stiffness, and irrigants were tested for their effect on the evolution of cavitation in the narrow wedge geometry. The PDMS stiffness varied in a range that corresponds to severely inflamed, moderately inflamed, or healthy gingival tissue as determined by a panel of dentists. The results imply that deformation of the soft boundary has a major effect on the Er:YAG laser-induced cavitation. The softer the boundary, the less effective the cavitation. We show that in a stiffer gingival tissues model, photoacoustic energy can be guided and focused at the tip of the wedge model, where it enables generation of secondary cavitation and more effective microstreaming. The secondary cavitation was absent in severely inflamed gingival model tissue, but could be induced with a dual-pulse AutoSWEEPS laser modality. This should in principle increase cleaning efficiency in the narrow geometries such as those found in the periodontal and peri-implant pockets and may lead to more predictable treatment outcomes.

Biofilm in Endodontics: In Vitro Cultivation Possibilities, Sonic-, Ultrasonic- and Laser-Assisted Removal Techniques and Evaluation of the Cleaning Efficacy

Incomplete and inadequate removal of endodontic biofilm during root canal treatment often leads to the clinical failure. Over the past decade, biofilm eradication techniques, such as sonication of irrigant solutions, ultrasonic and laser devices have been investigated in laboratory settings. This review aimed to give an overview of endodontic biofilm cultivation methods described in papers which investigated sonic-, ultrasonic- and Er:Yag laser-assisted biofilm removal techniques. Furthermore, the effectiveness of these removal techniques was discussed, as well as methods used for the evaluation of the cleaning efficacy. In general, laser assisted agitation, as well as ultrasonic and sonic activation of the irrigants provide a more efficient biofilm removal compared to conventional irrigation conducted by syringe/needle. The choice of irrigant is an important factor for reducing the bacterial contamination inside the root canal, with water and saline being the least effective. Due to heterogeneity in methods among the reviewed studies, it is difficult to compare sonic-, ultrasonic- and Er:Yag laser-assisted techniques among each other and give recommendations for the most efficient method in biofilm removal. Future studies should standardize the methodology regarding biofilm cultivation and cleaning methods, root canals with complex morphology should be introduced in research, with the aim of simulating the clinical scenario more closely.

Efficacy of antimicrobial photodynamic therapy and Er,Cr:YSGG laser-activated irrigation on dentinal tubule penetration of MTA-based root canal sealer: a confocal microscopy study

BACKGROUND

Antimicrobial photodynamic therapy (aPDT) and laser-activated irrigation (LAI) are adjunctive therapies developed to enhance the effectiveness of root canal disinfection. Sealer penetration into dentinal tubules is significant for preventing re-infection, and the sealer's penetration ability is affected by the chemo-mechanical preparation of the root canal. This study aimed to evaluate the efficacy of aPDT and LAI on dentinal tubule penetration of MTA-based root canal sealer.

METHODS

Forty single-rooted mandibular premolars were divided into four groups (n = 10): control, methylene blue 50 mg/L (MB50), curcumin 500 mg/L (C500), and Er,Cr:YSGG and sodium hypochlorite (LAI). The smear removal efficiency of the groups on intraradicular dentin was evaluated with a scanning electron microscope (SEM). Confocal laser scanning microscopy (CLSM) was performed to determine the depth of penetration of MTA Fillapex into dentinal tubules. Data were analyzed statistically.

RESULTS

The maximum penetration depth of the C500 group was significantly higher than that of the other groups in all three levels of root sections (p<0.05). Regarding mean penetration depth, the highest values were obtained from the C500 group. However, there was no statistically significant difference between the C500 and MB50 groups in the middle and coronal thirds of the root (p>0.05). The LAI group showed the lowest penetrated area percentage in the middle and coronal third of the root (p<0.05). The C500 and LAI groups were more effective in removing the smear layer than the control and MB50 groups.

CONCLUSION

aPDT could enhance the penetration of MTA-based root canal sealer into dentin tubules.

Effect of Various Laser-Activated Irrigation Protocols on Endodontic Sealer Penetration into the Dentinal Tubules: A Confocal Laser Scanning Microscopy Study

Objective: To study the effect of various laser-activated irrigation protocols on endodontic sealer penetration into the dentinal tubules. Background data: Laser-activated irrigation is helpful for smear layer removal and thus might increase the penetration of endodontic sealer into the dentinal tubules. Methods: Forty-eight mandibular premolars with straight canals were instrumented and divided into four groups: C-I group, conventional needle irrigation with sodium hypochlorite (NaOCl) followed by ethylenediaminetetraacetic acid (EDTA); Er:YAG-I, Er,Cr:YSGG-I, and Nd:YAP-I groups, NaOCl and EDTA irrigations activated by erbium:yttrium-aluminum-garnet (Er:YAG), erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG), and neodymium:yttrium-aluminum-perovskite (Nd:YAP) lasers, respectively. The cleanness of the treated canals was evaluated by scanning electron microscopy (SEM). Then, canals were obturated with AH-Plus sealer labeled with rhodamine B (0.1%) and combined with gutta-percha. After setting, canals were sectioned at 2, 5, and 8 mm short from the root apex, and the penetration area of the AH-Plus into the dentinal tubules was observed using confocal laser scanning microscopy (CLSM). Results: SEM results indicated that the Er:YAG-I and Er,Cr:YSGG-I lasers were more effective than the Nd:YAP-I and C-I in removing the smear layer. CLSM results indicated that the average AH-Plus penetration areas among the tested groups were in ascending order: C-I < Nd:YAP-I < Er:YAG-I, Er,Cr:YSGG-I (p < 0.05). Conclusions: Laser-activated irrigations significantly increased the penetration of the endodontic sealer into the dentinal tubules, among which Er:YAG-I and Er,Cr:YSGG-I lasers were the most effective and may be considered routine protocols for endodontic treatment.

Bactericidal effect of Er,Cr:YSGG laser irradiation on endodontic biofilm: An ex vivo study

AIM

This ex vivo study aimed to evaluate the of Er,Cr:YSGG laser effectiveness in the decontamination of an endodontic biofilm.

MATERIALS AND METHODS

Seventy-three single rooted human teeth, freshly were chosen. Each tooth was exposed to four associated species in an endodontic biofilm (Enterococcus faecalis, Streptococcus salivarius, Porphyromonas gingivalis, and Prevotella intermedia) and randomly allocated to one of the seven experimental groups. The group 1 (7 teeth) was used to finalize the reliable biofilm-forming technique. The groups 2 and 3 (15 teeth each group) were irradiated with two different Er;Cr:YSGG laser settings (0,75 W - 40 Hz and 4 W - 40 Hz, respectively). The groups 4 and 5 (15 teeth each group) were irrigated with two different solutions and laser irradiated with the same settings (1,5 W - 15 Hz). The group 6 (6 teeth) was the control group treated only with 4 ml 2,5% NaOCl irrigation during 60 s.

RESULTS

The observations of group 2 and 3 specimens showed the ripeness of the biofilm with the presence of Enterococcus faecalis and Streptococcus salivarius in chains but in group 3 thermal edge effects produced by the optic fiber in the canal walls were present. The group 4 specimens observation showed an average cleaning of the root canal walls while on the canal walls of group 5 samples the apical third presented several debris and smear layer and in the centre cracks and melting dentin of the radicular wall were observed.

CONCLUSION

In those experimental conditions, this study, demonstrated that Er,Cr:YSGG laser has a canals decontamination ability when associated to NaOCl irrigation.

Photon-Induced Photoacoustic Streaming Activation of the Postbleaching Antioxidant Application Rapidly Improves Bonding to Pulp Chamber Dentin

Objective: This study explored whether the erbium/yttrium/aluminum/garnet (Er:YAG) laser irradiated through the photon-induced photoacoustic streaming (PIPS) method would impact on the resin bonding to pulp chamber dentin when used to activate bleaching and/or postbleaching antioxidant treatment. Materials and methods: One hundred five dentin samples prepared from freshly extracted human incisors were randomly assigned to seven groups (n = 15): control (no bleaching/antioxidant); CB (conventional bleaching only); MB (modified bleaching only); CB-NI (conventional bleaching+antioxidant with needle irrigation); MB-NI (modified bleaching+antioxidant with needle irrigation); CB-PIPSI (conventional bleaching+antioxidant with PIPS-activated irrigation); and MB-PIPSI (modified bleaching+antioxidant with PIPS-activated irrigation). Bleaching (40% hydrogen peroxide) lasted for 20 min. Modified bleaching groups were irradiated with Er:YAG laser using the PIPS tip (2940 nm, 0.90 W, 30 Hz, 30 mJ/pulse, 50-μsec pulse duration) during the first 60 sec of the procedure. The antioxidant treatment with 10% sodium ascorbate lasted for 60 sec. PIPS-activated antioxidant groups were irradiated with Er:YAG laser using the PIPS tip (2940 nm, 0.30 W, 15 Hz, 20 mJ per pulse, 50-μsec pulse duration) throughout the procedure. After completing the composite restorations, all samples were subjected to 5000 thermocycling and the shear bond strength (SBS) test at a crosshead speed of 1 mm/min. SBS data were analyzed using the Kruskal-Wallis test with Bonferroni correction (α& 0.05). Results: No significant difference was detected among the control, CB-PIPSI, and MB-PIPSI (p > 0.05), which presented a significantly higher SBS compared with the other groups (p < 0.05). Conclusions: Irrespective of the application mode of the initial bleaching, PIPS-activated irrigation of the antioxidant improved SBS to bleached dentin to the level of the control in 1 min. Postbleaching antioxidant treatment combined with the PIPS method might be a promising approach to enable immediate resin restoration of bleached dentin.

The Efficiency of the Er: YAG Laser and PhotonInduced Photoacoustic Streaming (PIPS) as an Activation Method in Endodontic Irrigation: A Literature Review

In the field of endodontics, lasers have been used for a long time for the optimization of Endodontic irrigation in particular. The laser-activated irrigation (LAI) technique is based on the photomechanical effects of the lasers at low settings. They create specific cavitation phenomena and acoustic streaming in intracanal fluids. More recently, a new technique with a Er:YAG laser has been used with sub-ablative energy (20 mJ, 15 Hz) and ultra-short pulses (50 µs). This leads to intracanal cavitation and shockwaves as a result of photoacoustic and photomechanical effects. This phenomenon is called photon-induced photoacoustic streaming (PIPS). PIPS and Laser activated irrigation are described in the literature as a revolutionary and powerful method to activate the irrigant; however, systematic literature on this topic is missing. This review compares the literature on Er:YAG LAI and PIPS on endodontic irrigation with other irrigation methods. An article search was performed on the PubMed database using a series of keywords related to endodontic irrigation, including Er:YAG LAI and PIPS; 59 articles were selected for the review according to the inclusion and exclusion criteria. No in vivo study was found. The Er:YAG LAI and PIPS outperformed other methods in 33 of the 59 articles. There was a great variety in the study designs including bacterial incubation time, laser parameters, irrigation protocols, and irrigating solution used. The evidence suggests that the Er:YAG LAI and PIPS are promising in canal disinfection as well as debris and smear layer removal. However, the large variety in the study methods makes the results less significant. Further studies are needed to better evaluate the efficiency of these techniques, especially in vivo studies.

[Advanced research on root canal therapy for primary teeth]

Primary tooth root canal therapy is a treatment performed on primary teeth diagnosed with pulpitis or periapical periodontitis. This procedure requires perfect instrumentation, disinfection, and filling of root canals to eliminate infection, control inflammation, relieve pain, prevent pathological effects on inherited permanent tooth, and prolong primary tooth preservation. This paper reviews the research history on primary tooth root canal treatment and summarizes the progress on primary tooth root canal treatment, including anatomical morphology, root canal preparation, root canal disinfection, root canal filling, and application of antibiotics.

Er,Cr:YSGG Laser-Activation Enhances Antimicrobial and Antibiofilm Action of Low Concentrations of Sodium Hypochlorite in Root Canals

The onset and persistence of endodontic infections due to residual biofilm after chemical disinfection promotes secondary bacterial infection. Alternative methods to disinfect operated root canals are a matter of great interest. The aim was to evaluate the antibacterial effectiveness of sodium hypochlorite (NaOCl) at low concentrations activated by the Er,Cr:YSGG laser-activated irrigation (LAI) against 10-day-old intracanal Enterococcusfaecalis biofilm. Biofilms were formed inside the root canals and divided into 7 groups (n13): 0.5% NaOCl + Er,Cr:YSGG; Saline + Er,Cr:YSGG; 0.5% NaOCl + syringe irrigation(SI); 2.5% NaOCl + SI; 5% NaOCl + SI; positive and negative controls. Bacterial survivors were counted and specimens visualized under scanning electron and confocal laser scanning microscopy. Treatments with 0.5% NaOCl + Er,Cr:YSGG and 2.5% NaOCl + SI gave a significant reduction in the number of CFU/mm². Moreover, scanning electron microscopy and confocal laser scanning microscopy imaging confirmed and reinforced bacteriological data. Thus, Er,Cr:YSGG LAI proved to be able to improve the intracanal distribution of 0.5% NaOCl after 60 s of activation, reaching the same level of effectiveness than 2.5% NaOCl. This is regarded as of clinical interest, since working with lower concentrations may contribute to reduce undesired effects.

Er,Cr:YSGG Laser-Activated Irrigation and Passive Ultrasonic Irrigation: Comparison of Two Strategies for Root Canal Disinfection

Objective: To compare the antibacterial effectiveness of 0.5% sodium hypochlorite (NaOCl) activated by the Er,Cr:YSGG laser-activated irrigation (LAI) and passive ultrasonic irrigation (PUI) against a 10-day-old intracanal Enterococcus faecalis biofilm. Background: LAI and PUI are regarded as alternative methods to release the irrigant in the inner regions of the root canal system achieving enhanced cleaning ability. Nevertheless, little evidence regarding the activation of low concentrations of NaOCl has been reported. Materials and methods: Seventy-two single-rooted teeth were instrumented, inoculated (E. faecalis ATCC 29212), and incubated for 10 days to allow biofilm formation. Specimens were randomly divided into six groups (n = 12 each): (1) 0.5% NaOCl+Er,Cr:YSGG LAI, (2) saline+Er,Cr:YSGG LAI, (3) 0.5% NaOCl+PUI, (4) saline+PUI, (5) positive control (no treatment), and (6) negative control (no bacteria). The activation time was distributed as follows: 30 sec of activation, followed by a rest phase of 30 sec, and ending with 30 sec of activation. The number of bacterial survivors was determined by plate counting. Results: Both irrigation regimens LAI and PUI reduced the number of colony-forming unit. Moreover, LAI +0.5% NaOCl and the rest of groups significantly differ (p < 0.001 for all comparisons). Conclusions: Er,Cr:YSGG LAI proved to be more effective than PUI in enhancing the antimicrobial activity of 0.5% NaOCl against 10-day-old intracanal E. faecalis biofilms.

Impact of Different Irrigant Agitation Methods on Bacterial Elimination from Infected Root Canals

Activation techniques are essential for root canal disinfection but may result in incomplete removal of bacteria. The aim of our study was to assess the antibacterial action of sonically, ultrasonically and laser-activated irrigation and 5.25% sodium hypochlorite (NaOCl) on Enterococcus faecalis in an infected tooth. Forty-four extracted mandibular premolars were mechanically prepared, sterilized, and inoculated with E. faecalis for 1 week. Bacterial counts after inoculation were evaluated in 4 randomly chosen teeth, remaining root canals were divided into 4 groups. Group A: laser-activated irrigation by photon-induced photoacoustic streaming, Group B: the sonic irrigation by EDDY, Group C: ultrasonic irrigation by EndoUltra, and Group D: 5.25% NaOCl. Colony forming unit (CFU) counts were measured and Kolmogorov-Smirnov, Wilcoxon, Kruskal-Wallis and Mann-Whitney tests were used to determine differences. The mean of CFU was found to significantly decrease in group D, 2110 ± 1015.93 (p < 0.001). Changes in measurement levels followed the same trend over time in groups A 27.40 ± 30.15, B 81.3 ± 85.68 and C 44.40 ± 67.12 (p = 0.141). The average CFU after irrigation in all groups was significantly greater than 0. Within the limitations of this study, all activation techniques were superior to NaOCl 5.25% in reducing E. faecalis from the infected tooth model.

Ultrasonic Irrigant Activation during Root Canal Treatment: A Systematic Review

INTRODUCTION

The aim of this study was to systematically review the evidence on the cleaning and disinfection of root canals and the healing of apical periodontitis when ultrasonic irrigant activation is applied during primary root canal treatment of mature permanent teeth compared with syringe irrigation.

METHODS

An electronic search was conducted of the Cochrane Library, Embase, LILACS, PubMed, SciELO, and Scopus databases using both free-text key words and controlled vocabulary. Additional studies were sought through hand searching of endodontic journals and textbooks. The retrieved studies were screened by 2 reviewers according to predefined criteria. The included studies were critically appraised, and the extracted data were arranged in tables.

RESULTS

The electronic and hand search retrieved 1966 titles. Three clinical studies and 45 in vitro studies were included in this review. Ultrasonic activation did not improve the healing rate of apical periodontitis compared with syringe irrigation after primary root canal treatment of teeth with a single root canal. Conflicting results were reported by the in vitro microbiological studies. Ultrasonic activation was more effective than syringe irrigation in the removal of pulp tissue remnants and hard tissue debris based on both clinical and in vitro studies. Ultrasonic activation groups were possibly favored in 13 studies, whereas syringe irrigation groups may have been favored in 3 studies.

CONCLUSIONS

The level of the available evidence was low, so no strong clinical recommendations could be formulated. Future studies should focus on the antimicrobial effect and healing of apical periodontitis in teeth with multiple root canals.