Photon-initiated photoacoustic streaming (PIPS) with an Er: YAG laser has been introduced in root canal treatment to improve irrigation and facilitate the removal of bacteria in the root canal system. This study aimed to compare the antibacterial effectiveness of two different root canal irrigation techniques, conventional needle irrigation (CNI) and PIPS, using 1% sodium hypochlorite (NaOCl), in the treatment of teeth with apical periodontitis. Sixty patients with a total of sixty teeth affected by apical periodontitis were included in this study. The teeth underwent root canal therapy, and after mechanical instrumentation, they were randomly assigned to two groups (n = 30) based on the final irrigation protocol: CNI or PIPS with 1% NaOCl. Bacterial suspensions in the root canals were evaluated using Adenosine 5\'-triphosphate (ATP) assay kit after mechanical instrumentation and after final irrigation. Then, a follow-up was conducted after 7 days. The results revealed that final irrigation significantly reduced ATP values in both the CNI and PIPS groups (P < 0.001). The ATP values after final irrigation was greater in the CNI group compared to the PIPS group (P < 0.001). After a 7-day follow-up, percussion tenderness and fistula were significantly resolved in both groups (P < 0.05). A multivariate linear regression model was used to identify the factors that influence post irrigation ATP values. The analysis demonstrated that pre-operative percussion tenderness (P = 0.006), the presence of a fistula (P < 0.001) and the method used in the final irrigation (P < 0.001) had a significant impact on the ATP value after final irrigation. These results indicate that employing PIPS with 1% NaOCl as the final irrigation protocol exhibited superior antibacterial effectiveness and has the potential to enhance clinical outcomes in the treatment of teeth afflicted with apical periodontitis.

OBJECTIVE: The aim of the present study was to visualize and compare the cavitation effect and fluid dynamics induced by photon-induced photoacoustic streaming (PIPS) using sodium hypochlorite (NaOCl) with different concentrations as irrigant.
METHODS: Forty artificial root canals were prepared using MTWO Niti file up to size #25/.06. The canals were randomly divided into four groups (n = 10/group). High-speed camera was used to visualize and compare the cavitation effect induced by PIPS in the artificial root canals containing saline or NaOCl. Fluid velocity and Reynolds number of saline, 1%-, 2.5%- and 5.25% NaOCl irrigants induced by PIPS in the apical region were calculated using TEMA 2D software while the fluid motions were recorded.
RESULTS: Visualization profile revealed that NaOCl presented a stronger cavitation effect and fluid dynamics than saline during PIPS activation. In the apical region, 1% NaOCl group presented the highest average velocity of 3.868 m/s, followed by 2.5% NaOCl group (3.685 m/s), 5.25% NaOCl group (2.353 m/s) and saline group (1.268 m/s), corresponding to Reynolds number of 1653.173, 1572.196, 995.503 and 477.692. Statistically higher fluid velocity was calculated in 1% and 2.5% NaOCl groups compared to saline group, respectively (p < 0.05).
CONCLUSIONS: The application of NaOCl and its concentration significantly influence the cavitation effect and fluid dynamics during PIPS activation. 1% and 2.5% NaOCl groups presented a more violent fluid motion in the apical region when activated by PIPS.

Objective: The aim of this study was to compare the efficacy of HyFlex EDM (Coltene/Whaledent, Altstätten, Switzerland) and ProTaper Universal Retreatment Nickel-Titanium (NiTi) Systems [The ProTaper Universal Retreatment (PTR), Dentsply Maillefer, Ballaigues, Switzerland] in the removal of the root canal filling materials with or without laser activated irrigation. Materials and methods: The root canals of 60 human mandibular premolars were instrumented with K files up to size 35 at a working length; the step-back procedure was performed in 1 mm increments up to size 50. Next, the teeth were obturated using the lateral compaction technique with gutta-percha and resin-based sealer, and they were randomly divided into two groups (n = 30) according to the retreatment systems: PTR and HyFlex EDM NiTi rotary files. Then, each group was divided into two subgroups (n = 15), laser [photon-induced photo-acoustic streaming (PIPS); Fotona, Ljubljana, Slovenia] activated irrigation and conventional needle irrigation group. Following these procedures, the specimens were evaluated using micro-computed tomography. Results: There was no significant difference between the instrumentation systems regarding the cleaning efficacy (χ2 = 0.754; p = 0.86). Additionally, PIPS method did not have a significant effect on the removal of the filling material compared to conventional needle irrigation. Conclusions: Both instrumentation systems were effective in removing the filling material, but neither was able to remove the filling material completely. PIPS method did not show a significant additional effect regarding the removal of filling material.

UNASSIGNED: The purpose of this in-vitro study was to investigate the effect of irrigation activation methods using different laser parameters on microhardness and push-out bonding strength of root canal dentin. This study evaluates and compares the efficacy of different laser parameters in smear layer removal using the scanning electron microscopic image analysis.
UNASSIGNED: In this in-vitro study, 60 newly extracted human teeth with extraction indications were used. Later, the teeth were randomly divided into three groups (n = 20). In Group 1, irrigation was performed using 2 Er:YAG laser (Fotona Laser AT Fidelis Plus III, Slovenia) with 0.6 W, 15 Hz, and 40 mJ parameters. In Group 2, irrigation was performed at 0.3 W, 15 Hz, and 20 mJ. In Group 3 (control group), conventional syringe irrigation method was performed without activation. After irrigation activation, horizontal sections were taken from the teeth, sections from the coronal, middle, and apical triplets were selected and subjected to the Vicker\'s microhardness test. The Kruskal-Wallis and Wilcoxon signed-rank tests were performed on the obtained data.
UNASSIGNED: There was no statistically significant difference between the control group and the laser group (P > 0.05). As a result of the push-out bonding strength test performed on the coronal and apex regions of laser treated and untreated groups, the values of the coronal region were found to be higher than the apex region, and it was found that the bonding strength of the coronal part of the laser group was increased (P < 0.05). The change in parameters between the laser groups did not produce a statistically significant difference between the groups (P > 0.05).
UNASSIGNED: According to this study the laser group increases the bonding strength without a negative change in microhardness. In this study the further research is needed on this subject.

OBJECTIVE: The objective of this study was to compare antibacterial and smear layer removal efficacy of the erbium:yttrium-aluminium-garnet (Er:YAG) laser irradiation by photon-induced photoacoustic streaming (PIPS), neodymium:yttrium-aluminium-garnet (Nd:YAG), and diode lasers and conventional irrigation agent in primary molar root canals.
BACKGROUND: The selection, application, and activation of the irrigant are important factors affecting the success of the endodontic treatment.
METHODS: Distal root canals of human primary mandibular molar teeth used for antimicrobial efficacy evaluation were first inoculated with Enterococcus faecalis (n = 25). Smear layer removal efficacy was evaluated on the noninoculated specimens (n = 20). The root canals in the first treatment groups were irrigated with a conventional technique using 5% sodium hypochlorite (NaOCl). In the laser groups, the root canals were irradiated with either Nd:YAG (1064 nm) or diode lasers (940 nm) followed by NaOCl irrigation agent. In the fourth groups, the NaOCl irrigation agent was activated with an Er:YAG laser (2940 nm) by PIPS tip using nonablative settings. Antibacterial efficacy was determined by viable counts of E. faecalis after treatments. The treated root canals were examined by scanning electron microscopy to determine the smear layer removal efficacy of treatments.
RESULTS: Statistically significant (p < 0.05) reductions in the number of E. faecalis were achieved in Nd:YAG and diode laser groups and Er:YAG laser by PIPS-activated irrigation groups compared to the NaOCl group. Er:YAG laser by PIPS-activated irrigation resulted in more cleaning of the root canal walls and a higher quantity of open tubules.
CONCLUSIONS: These findings suggest that Er:YAG laser by PIPS-activated irrigation can be considered as an effective irrigant agitation technique in pediatric endodontics.

This study is to investigate the efficacy of different irrigant activation techniques on removal of accumulated hard tissue debris (AHTD) in mesial roots of human mandibular molars. Extracted human mandibular molars with an isthmus between the mesial root canals were selected based on micro-CT (μCT) scans. The mesial canals were instrumented to an apical diameter ISO30 using ProTaper rotary files. Teeth were randomly assigned to three irrigant activation groups (n = 10): ultrasonically activated irrigation (UAI) using a size 20 Irrisafe for 3 × 20 s, laser-activated irrigation (LAI) with an Er:YAG laser (2940 nm) and plain 300 μm fiber tip inside the canal (20 mJ, 20 Hz, 3 × 20 s), and laser-activated irrigation with identical parameters with a 400 μm photon-induced photoacoustic streaming (PIPS) tip held at the canal entrance. All teeth were scanned with μCT before and after instrumentation and after irrigant activation. After reconstruction and image processing, the canal system volume filled with hard tissue debris before and after irrigant activation was calculated. Changes in hard tissue debris volumes were compared between groups using one-way ANOVA. The percentage volume of hard tissue debris (vol%) was significantly lower after irrigant activation in all groups. Although the lowest debris values were observed in the laser groups, no significant differences in the vol% of accumulated hard tissue debris after activation were observed between groups. Accumulated hard tissue debris was reduced significantly in all activation groups. Ultrasonically and laser-activated irrigation regimens performed similarly in this respect. None of the tested methods was able to render the root canal systems free of debris.

BACKGROUND: The aim of this study was to assess the efficacy of lasers in removing filling remnants from oval-shaped canals after retreatment procedures with rotary instruments using micro-computed tomographic imaging.
METHODS: The root canals of 42 mandibular canines were prepared and obturated using the warm vertical compaction technique. Retreatment was performed with rotary instruments, and the specimens were distributed in 3 groups (n = 14) according to the laser device used in a later stage of retreatment procedure: Er:YAG, Er:YAG laser-based photon-induced photoacoustic streaming, and Nd:YAG. The specimens were scanned in a micro-computed tomographic device after root canal filling and each stage of retreatment at a resolution of 13.68 μm. The percentage differences of the remaining filling material before and after laser application within and between groups were statistically compared using the paired sample t test and 1-way analysis of variance test, respectively. Significance level was set at 5%.
RESULTS: Overall, filling residues were located mainly in the apical third and into canal irregularities after the retreatment procedures. After using rotary instruments, the mean percentage volume of the filling remnants ranged from 13%-16%, with no statistical significant difference between groups (P > .05). Within groups, additional laser application had a significant reduction in the amount of the remaining filling materials (P < .05). A comparison between groups showed that Er:YAG laser application after the use of rotary instruments had a significantly higher removal of filling remnants (~13%) than Er:YAG laser-based photon-induced photoacoustic streaming (~4%) and Nd:YAG (~3%) (P < .05).
CONCLUSIONS: None of the retreatment procedures completely removed the filling materials. The additional use of lasers improved the removal of filling material after the retreatment procedure with rotary instruments.

BACKGROUND: Laser-activated irrigation to remove organic debris from canal isthmuses was investigated using x-ray microfocus computed tomographic imaging.
METHODS: A total of 14 extracted human mandibular molars were used. The mesial canals were prepared using a standardized instrumentation protocol. Two groups (n = 7) underwent final irrigation using either standard needle irrigation (SNI) or photon-induced photoacoustic streaming (PIPS). After enlarging canals to 30/.06, canal volumes were reconstructed from micro-computed tomographic scans before and after irrigation to assess removal of organic tissue and inorganic debris by quantitative analysis of the superimposed volumes. Comparisons of the volumes were made using 2-way analysis of variance and Tukey method, with statistical differences considered significant at the alpha = 0.05 level.
RESULTS: Debris removal and an increase in root canal system volume for the laser-activated PIPS group was more significant (P < .001) than for the SNI group (P = .04). Irrigation using PIPS increased the canal volume and eliminated debris from the canal system 2.6 times greater than SNI.
CONCLUSIONS: Eliminating debris from complex canal spaces found in mandibular molars was achieved at a significantly greater level using laser-activated PIPS irrigation compared with SNI.