Assessment of multispecies biofilm growth on root canal dentin under different radiation therapy regimens.

OBJECTIVES: To assess the growth of a multispecies biofilm on root canal dentin under different radiotherapy regimens. MATERIALS AND METHODS: Sixty-three human root dentin cylinders were distributed into six groups. In three groups, no biofilm was formed (n = 3): NoRT) non-irradiated dentin; RT55) 55 Gy; and RT70) 70 Gy. In the other three groups (n = 18), a 21-day multispecies biofilm (Enterococcus faecalis, Streptococcus mutans, and Candida albicans) was formed in the canal: NoRT + Bio) non-irradiated + biofilm; RT55 + Bio) 55 Gy + biofilm; and RT70 + Bio) 70 Gy + biofilm. The biofilm was quantified (CFUs/mL). Biofilm microstructure was assessed under SEM. Microbial penetration into dentinal tubules was assessed under CLSM. For the biofilm biomass and dentin microhardness pre- and after biofilm growth assessments, 45 bovine dentin specimens were distributed into three groups (n = 15): NoRT) non-irradiated + biofilm; RT55 + Bio) 55 Gy + biofilm; and RT70 + Bio) 70 Gy + biofilm. RESULTS: Irradiated specimens (70 Gy) had higher quantity of microorganisms than non-irradiated (p = .010). There was gradual increase in biofilm biomass from non-irradiated to 55 Gy and 70 Gy (p < .001). Irradiated specimens had greater reduction in microhardness after biofilm growth. Irradiated dentin led to the growth of a more complex and irregular biofilm. There was microbial penetration into the dentinal tubules, regardless of the radiation regimen. CONCLUSION: Radiotherapy increased the number of microorganisms and biofilm biomass and reduced dentin microhardness. Microbial penetration into dentinal tubules was noticeable. CLINICAL RELEVANCE: Cumulative and potentially irreversible side effects of radiotherapy affect biofilm growth on root dentin. These changes could compromise the success of endodontic treatment in oncological patients undergoing head and neck radiotherapy.

Effect of using diode laser on Enterococcus faecalis and its lipoteichoic acid (LTA) in chronic apical periodontitis.

The purpose of this study was to evaluate the effect of diode laser irradiation on Enterococcus faecalis (E. faecalis) and its lipoteichoic acid (LTA). Ninety-six freshly extracted single-rooted teeth were divided into six groups, n = 8 per group. Groups 1, 2, 3, and 4 as laser group (810 nm PILOT™ Diode Laser, 400 µm fiber diameter, continuous mode, 30 s time) with powers at 1.0 W, 1.5 W, 2.0 W, and 2.5 W respectively. Group 5 or positive control group (3 ml of 1% sodium hypochlorite (NaOCl) irrigation) and group 6 or negative control group (3 ml of normal saline (0.9% NaCl) irrigation). Root canal samples were collected before and after receiving laser irradiation and irrigation solution. Cultivable bacteria were determined by counting the colony (CFU/ml). Evaluation of temperature on the external root surface of teeth was done with K type thermocouple using laser at different powers. Enzyme-linked immunosorbant assay (ELISA) was performed to measure the LTA levels and the correlations between E. faecalis count, LTA levels, and rise in temperature were observed using Pearson's correlation test. E. faecalis LTA was subjected to laser irradiation and its structural damage was examined by thin layer chromatography (TLC). Compared with the control groups, all laser groups showed a decreased colony counts and decreased LTA levels with statistically significant difference (p Ë‚ 0.05). The bactericidal effect and LTA reduction of laser was better at 2.5 W power. Laser at 2.5 W power had temperature rise of more than 7 °C which is beyond the safe thermal threshold level. No statistically significant correlation was found between E. faecalis count, levels of LTA, and rise in external root surface temperature (p Ëƒ 0.05). TLC results showed a structural damage in the glycolipid moiety of E. faecalis LTA. Diode laser can effectively reduce the E. faecalis count and its LTA levels.

Bactericidal efficacy of three parameters of Nd:YAP laser irradiation against Enterococcus faecalis compared with NaOCl irrigation.

The success of endodontic treatment depends on the thorough removal of microorganisms from the root canal system. The search for new ways to eliminate the microorganisms is therefore justified. Nd:YAP is a laser that uses yttrium aluminum perovskite, doped with neodymium crystal, as active laser medium. We used the Nd:YAP laser in an in vitro experiment to evaluate the bactericidal effect of three parameters of Nd:YAP laser-activated irrigation on biofilms of Enterococcus faecalis in root canals. The canals of 45 extracted human single-root teeth were prepared on a #35 Mtwo instrument and contaminated with E. faecalis for 14 days. Forty infected single-root teeth were then randomly divided into four groups according to the irrigation agitation protocols as follows: 5.25% sodium hypochlorite (NaOCl), Nd:YAP laser (180 mJ) + NaOCl, Nd:YAP laser (280 mJ) + NaOCl, and Nd:YAP laser (360 mJ) + NaOCl. The remaining bacteria were counted immediately using the cell count method. Teeth were firstly spilt and one half examined by scanning electron microscopy (SEM). The other half involved examination of bacterial colonization in dentinal tubules using confocal laser scanning microscopy (CLSM). Nd:YAP laser (280 mJ) + NaOCl and Nd:YAP laser (360 mJ) + NaOCl completely removed the E. faecalis biofilms from the root canal walls and made it the cleanest among the treatment groups. Bacterial reductions in the treatment groups for dentinal tubules are presented in a descending order as follows: Nd:YAP laser (360 mJ) (53.7%), Nd:YAP laser (280 mJ) (51.5%) > Nd:YAP laser (180 mJ) (45.3%) > 5.25% NaOCl (31.9%) > control (19.3%) (p < 0.05). Nd:YAP laser of 280 mJ and 360 mJ showed effective bactericidal effect in removing E. faecalis biofilm from the root canal walls and dentinal tubules.

Effects of prolonged exposure to moderate static magnetic field and its synergistic effects with alkaline pH on Enterococcus faecalis.

Static magnetic field (SMF) has been shown to biologically affect various microorganisms, but its effects on Enterococcus faecalis, which is associated with multiple dental infections, have not been reported yet. Besides, Enterococcus faecalis was found to be resistant to the alkaline environment provided by a major dental antimicrobial, calcium hydroxide. Therefore, the antibacterial activity of prolonged exposure to moderate SMF (170 mT) and its possible synergistic activity with alkaline pH (pH = 9) were evaluated in the study. The ability to form a biofilm under these conditions was examined by crystal violet assay. Real-time quantitative PCR was performed to evaluate the relative expression of stress (dnaK and groEL) and virulence (efaA, ace, gelE and fsrC) related genes. As the results indicated, cell proliferation was inhibited after 120 h of SMF exposure. What's more, the combined treatment of SMF and alkaline pH showed significantly improved antimicrobial action when compared to single SMF and alkaline pH treatment for more than 24 h and 72 h respectively. However, the ability to form a biofilm was also enhanced under SMF and alkaline pH treatments. SMF can induce stress response by up-regulating the expression of dnaK and elevate virulence gene expression (efaA and ace). These responses were more significant and more genes were up-regulated including groEL, gelE and fsrC when exposed to SMF and alkaline pH simultaneously. Hence, combination of SMF and alkaline pH could be a promising disinfection strategy in dental area and other areas associated with Enterococcus faecalis infections.

Bactericidal effect of a diode laser on Enterococcus faecalis in human primary teeth-an in vitro study.

BACKGROUND: In recent years, the diode laser (810 nm) has been used for root canal disinfection, which plays an important role in endodontic therapy. This study was undertaken to evaluate the disinfecting ability of a diode laser in experimentally infected root canals of primary teeth. METHODS: Human retained mandibular primary anterior teeth without apical foramen resorption were selected and contaminated with Enterococcus faecalis for 21 days. The specimens were randomly divided into four groups: the negative group (no treatment), positive group (5.25% NaOCl), diode laser group (diode laser), and diode-NaOCl group (diode laser combined with NaOCl). The disinfecting abilities of the treatments were measured by the numbers of bacteria, scanning electron microscopy and confocal laser microscopy (live-dead staining). RESULTS: Eighty teeth were selected. After irradiation and irrigation, the elimination of bacteria and the smear layer in the laser groups and positive group were significantly superior, compared with the negative group (p < 0.01). In the diode-NaOCl group, bacterial reduction reached nearly 100% on the surfaces of root canals; live bacteria were rarely observed, even in deeper dentinal tubules. CONCLUSION: Use of a diode laser, especially in combination with NaOCl, was effective for disinfecting infected root canals of primary teeth.

Antimicrobial Potential of Laser Diode in Infected Dentin.

AIM: To evaluate the antibacterial effect of diode laser, associated or not with 2.5% sodium hypochlorite (NaOCl), against Enterococcus faecalis. MATERIALS AND METHODS: Eighty dentin blocks were obtained from single-rooted human teeth and sterilized. Seventy were inoculated with 0.01 mL of fresh bacterial inoculum (within 24 hours of preparation from pure culture) standardized to 1 McFarland turbidity. Contaminated blocks were incubated for 7 days at 37°C in humid conditions. Ten uncontaminated samples were incubated at 37°C during the contamination period to serve as a negative control group, while 10 of the infected specimens served as a positive control group. The dentin blocks were randomly divided into eight experimental groups (n = 10 each) according to the method of decontamination: 2.5% NaOCl alone; 2.5% NaOCl + photodynamic therapy (PDT) with methylene blue/660 nm laser at 18 J for 180 seconds; 2.5% NaOCl + PDT with methylene blue/660 nm laser at 8 J for 80 seconds; methylene blue alone; PDT alone with methylene blue/660 nm laser at 18 J for 180 seconds; PDT alone with methylene blue/660 nm laser at 8 J laser for 80 seconds; positive control group; and negative control group. Microbial growth was evaluated by culture medium turbidity and microbial concentration was analyzed by UV spectrophotometry (adjusted to read at wavelength l = 600 nM). RESULTS: Root canals treated with laser alone at 18 J for 180 seconds had higher bacterial contamination compared with groups in which NaOCl was used, with or without laser irradiation at 18 J for 180 seconds (p < 0.05). CONCLUSION: Photodynamic therapy with a 660 nm diode laser effectively reduced E. faecalis contamination. These findings can guide development of further studies in search of better alternatives for endodontic treatment. CLINICAL RELEVANCE: Chemical and mechanical root canal preparation plays an essential role in reducing microbial burden. However, microorganisms present in areas not mechanically reachable by endodontic instruments. As an alternative to fix this problem, the laser can be applied.

Determining the optimal dose of 1940-nm thulium fiber laser for assisting the endodontic treatment.

Insufficient cleaning, the complex anatomy of the root canal system, inaccessible accessory canals, and inadequate penetration of irrigants through dentinal tubules minimizes the success of the conventional endodontic treatment. Laser-assisted endodontic treatment enhances the quality of conventional treatment, but each laser wavelength has its own its own limitations. The optimal parameters for the antibacterial efficiency of a new wavelength, 1940-nm Thulium Fiber Laser, were firstly investigated in this study. This paper comprises of two preliminary analyses and one main experimental study, presents data about thermal effects of 1940-nm laser application on root canal tissue, effective sterilization parameters for bacteria, Enterococcus faecalis, and finally the antibacterial effectiveness of this 1940-nm Thulium Fiber Laser irradiation in single root canal. Based on these results, the optimal parameter range for safe laser-assisted root canal treatment was investigated in the main experiments. Comparing the antibacterial effects of four laser powers on an E. faecalis bacteria culture in vitro in 96-well plates showed that the most effective group was the one irradiated with 1 W of laser power (antibacterial effect corresponding to a log kill of 3). After the optimal laser power was determined, varying irradiation durations (15, 30, and 60 s) were compared in disinfecting E. faecalis. Laser application caused significant reduction in colony-forming unit values (CFU) compared with control samples in the 17% ethylenediaminetetraacetic acid (EDTA) group. The results of bacteria counts showed that 1 W with 30 s of irradiation with a 1940-nm thulium fiber laser was the optimal dose for safely achieving maximal bactericidal effect.

Effectiveness of repeated photodynamic therapy in the elimination of intracanal Enterococcus faecalis biofilm: an in vitro study.

The study aimed to investigate the effectiveness of photodynamic therapy in the elimination of intracanal Enterococcus faecalis biofilm and to analyse how a repeated light irradiation, replenishment of oxygen and photosensitiser affect the results of the photodynamic disinfecting protocol. After chemomechanical preparation, 46 single-rooted human teeth were infected with a clinical strain of E. faecalis and incubated for a week in microaerobic conditions. The experimental procedures included groups of single application of photodynamic therapy, two cycles of PDT, irrigation with 5.25% NaOCl solution and negative and positive control. The number of residing bacterial colonies in the root canals was determined based on the CFU/ml method. In the group of preparations irrigated with NaOCl, bacterial colonies were not observed. A single PDT eliminated 45% of the initial CFU/ml. Repeated PDT eradicated 95% of the intracanal bacterial biofilm. Photodynamic therapy has a high potential for the elimination of E. faecalis biofilm. There is a safe therapeutic window where photoinduced disinfection can be used as an adjuvant to conventional endodontic treatment, which remains the most effective.

[Bactericidal effects and smear layer removal of Er:YAG-laser radiation against Enterococcus faecalis in root canals].

OBJECTIVE: To evaluate the cleaning ability of Er:YAG laser against Enterococcus faecalis in root canals.
 Methods: The single-rooted human teeth were sterilized and inoculated with Enterococcus faecalis and were randomly assigned into 2 groups. A group of teeth was irrigated with saline during root canal preparation while another group with NaClO. After mechanical preparation, the two groups were randomly divided into 3 subgroups according to the different treatments: Samples, laser radiation, and calcium hydroxide intracanal medication for 7 days. Bactericical effects were compared among groups. Root canal walls and dental tubules were observed under scanning electron microscope.
 Results: Er:YAG laser was the most efficient way for anti-bacteria among the groups (P<0.05), but there was no significant difference between the 2 laser groups (P>0.05). Meanwhile the smear laser was efficiently removed by laser compared with other treatments, and the laser could open the dentinal tubules.
 Conclusion: Er:YAG laser can be effectively used for root canal disinfection without NaClO and Ca(OH)2.

The efficacy of photon-initiated photoacoustic streaming and sonic-activated irrigation combined with QMiX solution or sodium hypochlorite against intracanal E. faecalis biofilm.

The aim of the study was to assess the antibacterial efficacy of photon-initiated photoacoustic streaming (PIPS) using an Er:YAG laser and sonic-activated irrigation combined with QMiX irrigant or sodium hypochlorite against Enterococcus faecalis intracanal biofilm. Root canals of 91 human extracted single-canal teeth were instrumented, sterilized, contaminated with E. faecalis and incubated for 15 days. The infected teeth were then randomly distributed into six experimental groups: G1: PIPS/Er:YAG laser (wavelength 2940 nm, pulse energy 20 mJ, 15 Hz, pulse duration 50 µs, energy density 2.06 J/cm(2), 3 × 20 s) with the QMiX irrigant; G2: PIPS/Er:YAG laser-activated 2.5 % NaOCl; G3 sonic-activated irrigation (EndoActivator system) for 60 s with the QMiX irrigant; G4 sonic-activated irrigation for 60 s with 2.5 % NaOCl; G5 30-gauge needle irrigation with the QMiX irrigant; G6 30-gauge needle irrigation with 2.5 % NaOCl. The positive control group was rinsed with sterile saline solution. The root canals were sampled by flushing with saline solution at baseline and after the treatments, serially diluted and cultured. The number of bacteria in each canal was determined by plate count. The presence and the absence of E. faecalis in root canals were demonstrated by polymerase chain reaction (PCR), and the pattern of the bacteria colonization was visualized by scanning electron microscopy. There was significant reduction in the bacterial population for all groups (p < 0.001). The best antibacterial efficacy was recorded after sonic-activated irrigation with both NaOCl (99.999 %) and QMiX (99.999 %) and after PIPS with QMiX (99.999 %), which were more effective than conventional irrigation with NaOCl (99.998 %) and the PIPS with the NaOCl (99.966 %). Also, the PIPS with QMiX solution provided the highest number of sterile samples (five). There was no difference in the bacteria reduction between the active irrigation techniques, regardless of the irrigant used. Although the laser activation did not improve the antimicrobial action of the NaOCl nor QMiX, the fact that it generated the greatest number of sterile samples warrants further investigation.

Which is the most effective disinfection method in primary root canals: Conventional or newly developed ones?

BACKGROUND: The aim of the study was to evaluate the antimicrobial activity of the-potassium-titanyl-phosphate--the KTP laser and ozone in of primary root canals. MATERIALS AND METHODS: Sixty primary incisor teeth were selected. The specimens were inoculated with 10 mL Enterococcus faecalis (E. faecalis). Groups: The KTP laser (1,5 W); gaseous ozone (150 s); sodium hypochlorite (NaOCl); saline group. Sterile paper points used to sample bacteria from the canals to tubes containing 5 mL of brain heart infusion broth. Then, 10 mL suspension was incubated in culture media for 24 h. Data were analyzed statistically using Kruskal-Wallis and Mann-Whitney U-test. RESULTS: There were statistically significant differences between all groups (P<0.05). Complete sterilization was achieved in the 2.5% NaOCl group. The number of bacteria were significantly reduced in experimental groups in comparison to the saline group. CONCLUSION: The KTP laser and ozone application provided a significant antibacterial effect in primary root canals; however, 2.5% NaOCl was superior.

Are silicone-supported [C60]-fullerenes an alternative to Ru(II) polypyridyls for photodynamic solar water disinfection?

Different photosensitizing materials manufactured by immobilizing (0.5-3.0 g m(-2)) tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) (RDP(2+)), [C60]-fullerene, or 1-(4-methyl)-piperazinylfullerene (MPF) on porous neutral (pSil) or surface-modified anionic (pSil(-)) poly(dimethylsiloxane) are compared on the grounds of their singlet molecular oxygen ((1)O2) production and photodynamic solar water disinfection capability. The C60-based sensitizers display a broad weak absorption in the visible and strong absorption in the UV, while absorption of light by RDP(2+) supported on pSil is strong in both the UV and blue regions. The (1)O2 emission lifetimes (τ(Δ)) determined for RDP(2+) and MPF on porous silicone materials under air are similar (40-50 µs) and correspond to the decay of (1)O2 generated by sensitizers dissolved in the polymer support. In contrast, τ(Δ) measured for C60 in pSil is similar to that observed for MPF or RDP(2+) when immobilized at low loading on pSil, but dramatically increases up to 5 ms if C60 aggregates are formed in the porous material as evidenced by microscopy evaluation. The photosensitizing properties of the dyes, together with their electrical charge and the overall charge of the porous silicone-based materials, lead to highly different sunlight-driven bacteria inactivation efficiencies, as tested with waterborne E. faecalis. RDP/pSil provides efficient disinfection by photosensitization unlike MPF/pSil, which leads to reduced bacteria inactivation rates due to poorer (1)O2 production. C60/pSil and MPF/pSil(-) materials, despite their (1)O2 photogeneration, show unsuccessful waterborne bacteria inactivation due to the negative surface charge of fullerene aggregates in contact with water, and to the net negative charge of the pSil(-), respectively.

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.

The use of optical fiber in endodontic photodynamic therapy. Is it really relevant?

This study analyzed the necessity of use of an optical fiber/diffusor when performing antimicrobial photodynamic therapy (PDT) associated with endodontic therapy. Fifty freshly extracted human single-rooted teeth were used. Conventional endodontic treatment was performed using a sequence of ProTaper (Dentsply Maillefer Instruments), the teeth were sterilized, and the canals were contaminated with Enterococcus faecalis 3 days' biofilm. The samples were divided into five groups: group 1--ten roots irradiated with a laser tip (area of 0.04 cm(2)), group 2--ten roots irradiated with a smaller laser tip (area of 0.028 cm(2)), and group 3--ten teeth with the crown, irradiate with the laser tip with 0.04 cm(2) of area. The forth group (G4) followed the same methodology as group 3, but the irradiation was performed with smaller tip (area of 0.028 cm(2)) and G5 ten teeth with crown were irradiated using a 200-mm-diameter fiber/diffusor coupled to diode laser. Microbiological samples were taken after accessing the canal, after endodontic therapy, and after PDT. Groups 1 and 2 showed a reduction of two logs (99%), groups 3 and 4 of one log (85% and 97%, respectively), and group 5 of four logs (99.99%). Results suggest that the use of PDT added to endodontic treatment in roots canals infected with E. faecalis with the optical fiber/diffusor is better than when the laser light is used directed at the access of cavity.

An in vitro study on the efficacy of hydrogen peroxide mediated high-power photodynamic therapy affecting Enterococcus faecalis biofilm formation and dispersal.

OBJECTIVE: Biofilms are involved in failure of root canal treatment due to their high resistance to antimicrobial agents, which make their removal as a big challenge. The present study aims at utilizing hydrogen peroxide (HP) plus high frequency laser reinforced antimicrobial photodynamic therapy (a-PDT) as a complementary therapy against Enterococcus faecalis (E. faecalis) at planktonic and biofilm stages. MATERIALS AND METHODS: E. faecalis at planktonic and biofilm stages was treated with the photosensitizer HP, followed by no irradiation or irradiation with a power of 2.5 W (ʎ = 980 nm). The cell viability, anti-biofilm, anti-metabolic potential, and temperature changes were evaluated. RESULTS: The combination of HP and 980 nm diode laser intensely boosted antibacterial and anti-biofilm efficacy compared with either component alone, affirming HP reinforcement as a bacteriostatic agent. The maximum effect on biofilm occurs in 5.25% sodium hypochlorite (NaOCl) group. During laser irradiations, the mean of temperature changes remains below 5.6 °C. CONCLUSIONS: It could be concluded that the HP could improve anti-biofilm efficacy as a photosensitizer in a-PDT.

Evaluation of the bactericidal effect of Nd:YAG, Er:YAG, Er,Cr:YSGG laser radiation, and antimicrobial photodynamic therapy (aPDT) in experimentally infected root canals.

BACKGROUND AND OBJECTIVE: In recent years, various laser systems have been introduced into the field of laser-assisted endodontic therapy. The aim of this study was to evaluate the bactericidal effect of Nd:YAG, Er:YAG, Er,Cr:YSGG laser radiation, and antimicrobial photodynamic therapy (aPDT) in experimentally infected root canals compared with standard endodontic treatment of 5.25% sodium hypochlorite (NaClO) irrigation. MATERIALS AND METHODS: Two hundred and twenty infected root canals from extracted human teeth (contaminated with Enterococcus faecalis ATCC 4083 for 4 weeks) were randomly divided into five experimental groups (Nd:YAG, Er:YAG + 5.25% NaClO + 0.9% normal saline + distilled water (Er:YAG/NaClO/NS/DW), Er:YAG + 0.9% normal saline + distilled water (Er:YAG/NS/DW), Er,Cr:YSGG, and aPDT) and two control groups (5.25% NaClO as positive control and 0.9% normal saline (NS) as negative control). The numbers of bacteria on the surface of root canal walls and at different depths inside dentinal tubules before and after treatment were analyzed by means of one-way analysis of variance (one-way ANOVA). The morphology of bacterial cells before and after treatment was examined by scanning electron microscopy (SEM). RESULTS: After treatment, the bacterial reductions in the experimental groups and the positive control group were significantly greater than that of the negative control group (P < 0.001). However, only Er:YAG/NaClO/NS/DW group showed no bacterial growth (the bacterial reduction reached up to 100%) on the surface of root canal walls or at 100/200 µm inside the dentinal tubules. CONCLUSIONS: All the laser radiation protocols tested, especially Er:YAG/NaClO/NS/DW, have effective bactericidal effect in experimentally infected root canals. Er:YAG/NaClO/NS/DW seems to be an ideal protocol for root canal disinfection during endodontic therapy.

Decontamination efficacy of photon-initiated photoacoustic streaming (PIPS) of irrigants using low-energy laser settings: an ex vivo study.

AIM: To assess ex vivo, the antibacterial effectiveness of photon-initiated photoacoustic streaming (PIPS) of irrigants using an Er:YAG laser equipped with a newly designed, stripped and tapered tip in extracted teeth with infected root canals. METHODOLOGY: One hundred and forty-eight single-rooted extracted teeth were prepared to a size 25, 0.06 taper. The specimens were sterilized, and all teeth except ten (negative control group) were inoculated with Enterococcus faecalis and incubated in a CO(2) chamber at 37 °C for 15 days in Eppendorf tubes filled with trypticase soy broth medium changed every 2 days. Infected teeth were then randomly divided into four test groups (n = 32 for each): pulsed erbium/YAG laser at nonablative settings for 30 s with sterile bi-distilled water (Group A) or 5% sodium hypochlorite (NaOCl) (Group B); without laser-activated sterile bi-distilled water irrigation for 30 s (Group C) or 5% NaOCl irrigation for 30 s (Group D); the positive control group received no treatment in infected teeth (n = 10). Colony-forming units (CFUs) were counted from bacteriologic samples taken before (S1) and after treatment (S2). Data were analysed by Kruskal-Wallis and post hoc Dunn's multiple comparison tests. RESULTS: CFU counts were significantly lower in 5% NaOCl groups with or without laser activation than in sterile bi-distilled water without laser activation group (P < 0.001). Moreover, there was a significant difference between bi-distilled water groups with or without laser activation (P < 0.001). Sodium hypochlorite with laser activation group had the greatest CFU reduction, which was significantly greater than that evident in bi-distilled water groups with or without laser activation (P < 0.001). There were no significant differences between 5% NaOCl groups with or without laser activation (P > 0.05). None of the four groups generated negative samples predictably. CONCLUSIONS: Under the conditions of this ex vivo study, there were no significant differences in bacterial reduction between the laser and NaOCl or NaOCl alone groups. [Correction added after online publication, 18th April 2012: The following statement has been deleted: 'Thus, the use of a laser did not improve microbial killing over and above use of NaOCI alone.'].

Evaluation of Nd:YAG and Er:YAG irradiation, antibacterial photodynamic therapy and sodium hypochlorite treatment on Enterococcus faecalis biofilms.

AIM: To compare the antimicrobial efficacy of two-high power lasers (Nd:YAG and Er:YAG) and two commercial antimicrobial photodynamic therapy (aPDT) systems with that of sodium hypochlorite (NaOCl) action on Enterococcus faecalis biofilms grown on dentine discs. METHODOLOGY: Enterococcus faecalis biofilms were grown on dentine discs in a microtiter plate, incubated for 24 h and subjected to the following treatments: aPDT (Denfotex and Helbo system), Er:YAG laser irradiation (2940 nm, 50 mJ or 100 mJ, 15 Hz, 40 s), Nd:YAG laser irradiation (1064 nm, 2 W, 15 Hz, 40 s) and immersion in 2.5% (w/v) NaOCl for 1, 5, 10 and 30 min. Surviving bacteria were harvested, and the number of CFU per disc was determined by plate counting. RESULTS: Significant reductions (anova, P ≤ 0.05) in viable counts were observed for aPDT (Helbo) (2 log(10) reduction), Er:YAG irradiation using 100 mJ pulses (4.3 log(10) reduction) and all NaOCl treatments (>6 log(10) reduction). NaOCl (2.5%) for 5 min effectively eliminated all bacteria. aPDT (Denfotex), Er:YAG irradiation using 50 mJ pulses and Nd:YAG treatment caused a reduction in the viable counts of <1 log(10) unit; these results were not significantly different from the untreated controls. CONCLUSION: Within the limitations of this particular laboratory set-up, NaOCl was the most effective in E. faecalis biofilm elimination, while Er:YAG laser treatment (100 mJ pulses) also resulted in high reductions in viable counts. The use of both commercial aPDT systems resulted in a weak reduction in the number of E. faecalis cells. Nd:YAG irradiation was the least effective.

Bactericidal effects of two parameters of Er:YAG laser intracanal irradiation: ex-vivo study.

The success of endodontic treatment depends on the complete elimination of microorganisms from the root canal system, thus the search for new procedures to eliminate them is justified. The aim of this study was to assess bacterial reduction after intracanal irradiation with the Er:YAG laser. The canals of 70 extracted human maxillary canines were prepared up to file #40 using 1% NaOCl, irrigated with 17% EDTA, and then washed with physiological solution activated by ultrasound. The roots were sterilized by autoclaving, inoculated with 10 µl of a suspension containing 1.5 × 10(8) CFU/ml of Enterococcus faecalis ATCC 29212 and incubated at 37°C for 72 h. The canals were irradiated with the Er:YAG laser using two energy settings: 60 mJ and 15 Hz, and 100 mJ and 10 Hz. The remaining bacteria were counted immediately and 48 h after laser irradiation. The results showed a high bacterial reduction at both time points. With 60 mJ and 15 Hz there was an immediate reduction of 99.73% and the reduction was 77.02% after 48 h, and with 100 mJ and 10 Hz there was an immediate reduction of 99.95% and the reduction was 84.52% after 48 h. Although the best results were observed with 100 mJ of energy, the difference between the two settings was not statistically significant. The count performed 48 h after irradiation showed that E. faecalis were able to survive, and can grow even from small numbers.

Comparison of two diode lasers on bactericidity in root canals--an in vitro study.

This in vitro study compares two 810-nm and 940-nm diode lasers on bacterial kill in root canals of extracted human teeth and shows the clinical relevance of different treatment modalities. Ninety root canals of single-rooted human teeth were prepared up to ISO 70, steam sterilized, and assigned to two test groups (810 nm, 940 nm) and one control group. Following an initiatory experiment in which access opening of root canals and surrounding cavity were excluded from irradiation in the main experiment, 60 teeth were inoculated with 2 µl of either Escherichia coli or Enterococcus faecalis suspension. Laser irradiation was performed, additionally including access opening of root canals and surrounding cavity in the laser treatment. Excluding access opening of root canals and surrounding cavity from the laser treatment, the diode laser achieved an average bacterial reduction of Escherichia coli of 76.06% (810 nm) and 68.15% (940 nm), while including access cavities showed an average bacterial reduction of Escherichia coli of 97.84% (810 nm) and 98.83% (940 nm) and an average bacterial reduction of Enterococcus faecalis of 98.8% (810 nm) and 98.66% (940 nm). Diode laser wavelengths are effective in endodontic therapy. It seems to be clinically relevant that additional irradiation of the access cavity produces significantly better bactericidal results.