Hard tissue debris removal from the mesial root canal system of mandibular molars with ultrasonically and laser-activated irrigation: a micro-computed tomography study

Comparative effects of the conventional, ultrasonic, and laser-activated irrigation on penetration depth of three photosensitizers in the root canal system

OBJECTIVES

This study compared the effects of conventional, ultrasonic, and laser-activated irrigation (LAI) on penetration depth of three photosensitizers (PSs) in the root canal system.

MATERIALS AND METHODS

In this in vitro, experimental study, 120 extracted anterior teeth were decoronated such that the remaining root length was standardized at 12 mm. After root canal instrumentation with the ProTaper rotary system and irrigation with 5.25% NaOCl, the roots were assigned to 12 groups for the application of toluidine blue (TB), curcumin, and phycocyanin PSs combined with the LAI using erbium laser with 0.4 mm and 0.6 mm tips, ultrasonic activation, and conventional irrigation. The specimens were sectioned apicocoronally, and the dye penetration depth was quantified in the coronal, middle, and apical thirds under a stereomicroscope at x20 magnification. Data were analyzed by the Kruskal-Wallis and Dunn test (alpha=0.05).

RESULTS

The effects of irrigation technique, PS type, and their interaction on dye penetration depth were significant at the apical, middle, and coronal thirds (P < 0.0001). TB + LAI with 0.4- and 0.6-mm laser tips showed the highest penetration depth while phycocyanin + LAI or conventional irrigation showed the lowest penetration depth at all areas. Dye penetration depth was the highest in the coronal, and the lowest in the apical third.

CONCLUSION

The LAI technique with erbium laser (0.4- and 0.6-mm tips) enhanced the penetration depth of TB. The tested irrigation techniques had no significant efficacy for enhancement of the penetration depth of curcumin and phycocyanin.

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.

Cleaning Efficiency of Different Irrigation Techniques in Simulated Severely Curved Complex Root Canal Systems

INTRODUCTION

To compare the biofilm-mimicking hydrogel removal efficiency of laser-activated irrigation (LAI) with five other irrigation techniques in simulated curved root canals with lateral canals.

METHODS

Three-dimensional-printed root canal models (60°-curvature, radius 5 mm; dimension 25/.06) with a total length of 20 mm and lateral canals in all directions at 2, 5, and 8 mm (diameter 0.2 mm) from the apex were filled with a colored biofilm-mimicking hydrogel. The following protocols (each 3 × 20 seconds continuous irrigation with distilled water 3 ml/20 seconds; n = 20) were carried out: conventional needle irrigation; manual agitation ([MA], gutta-percha point 25/.06); EndoActivator (=sonically-activated irrigation EndoActivator, 25/.04); EDDY (=sonically-activated irrigation EDDY [SAI-E]; 25/.04); ultrasonically-activated irrigation and LAI (Erbium-doped Yttrium Aluminum Garnet laser; P400FL tip at canal entrance; 25 pps, 50 mJ, 300 μs). Standardized photos were taken with a microscope and the removal of the hydrogel was determined as a percentage for the entire system, the main canal and the lateral canals. Statistical analysis was performed using analysis of variance and Scheffé test (P = .05).

RESULTS

LAI (89.3% ± 5.9%) showed the greatest hydrogel removal followed by SAI-E (65.5% ± 3.3%) and ultrasonically-activated irrigation (59.1% ± 4.7%), with significant differences between these groups (P < .05). Needle irrigation, MA, and sonically-activated irrigation EndoActivator performed equally (P > .05) and obtained the significantly lowest values (P < .05). LAI and SAI-E showed the significantly best hydrogel removal from the main canal (P < .05). At all three levels, LAI removed significantly more hydrogel from the lateral canals than all other techniques (P < .05).

CONCLUSIONS

LAI was superior to other techniques in both the entire system and the lateral canals in removing the hydrogel. SAI-E achieved comparable results in the main canal.

Effect of preparation size on the removal of accumulated hard-tissue debris from the mesial root canal system of mandibular molars using SWEEPS technology

OBJECTIVES

This study assessed the influence of preparation size on the efficacy of shock wave-enhanced emission photoacoustic streaming (SWEEPS) and conventional irrigation (CI) on removal of accumulated hard tissue debris (AHTD) from isthmus-containing mandibular molars using micro-computed tomographic analysis.

MATERIALS AND METHODS

Sixty extracted mandibular molars with two mesial canals connected by an isthmus were selected. Canals were shaped with Mtwo instruments (VDW, Munich, Germany) up to sizes 25/.06, 40/.04 or 40/.06 (n = 20), and specimens were distributed into 2 final irrigation groups (n = 10): SWEEPS and CI. Roots were scanned at a resolution of 10.5 µm before and after preparation and final irrigation. Data sets were co-registered, and the percentage reduction of AHTD calculated for each specimen was statistically compared using analysis of variance with a of 5% significance level.

RESULTS

The preparation size did not significantly influence the percentage reduction of AHTD (p < 0.05), whereas the final irrigation technique had a significant effect on debris removal (p < 0.05). A significant reduction of AHTD was achieved after final irrigation in all groups (p < 0.05); however, SWEEPS was associated with a significantly greater percentage reduction of debris than CI (p < 0.05). None of the specimens presented a completely clean isthmus.

CONCLUSIONS

Removal of AHTD was not significantly affected by the preparation size. SWEEPS was associated with significantly less debris than CI.

CLINICAL RELEVANCE

SWEEPS performed significantly better than CI regarding the removal of AHTD from isthmus-containing mandibular molars irrespective of the preparation size.

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.

Assessment of Irrigant Agitation Devices in Simulated Closed and Open Root Canal Systems

INTRODUCTION

The in vitro efficacy of irrigant activation devices has not been contrasted to their safety. This was attempted in this study using apically closed versus patent simulated root canal systems in epoxy resin models, with the latter featuring a simulated periapical lesion.

METHODS

All 72 models had 2 joining canals connected by an isthmus, which was filled with dentin debris. The simulated periapical lesion was filled with colored gelatin in the 36 respective models. Canals were irrigated with 1.3% sodium hypochlorite. Samples were divided into 4 subgroups per system (n = 9): conventional irrigation, sonic low (EndoActivator; Dentsply Sirona, Charlotte, NC) and high frequency (EDDY; VDW, Munich, Germany), and ultrasonic agitation of the irrigant (always applying 3 cycles of 20 seconds). The total cleared surface areas (mm²) in the simulated isthmus and periapical lesion were compared between systems and devices using parametric tests (P < .05).

RESULTS

The cleaning of the isthmus was more effective in the apically open compared with the closed systems and was also significantly influenced by the agitation method (P < .001). In the closed systems, EDDY and ultrasonic agitation achieved the significantly (P < .05) best cleaning of the isthmus. In the open systems, ultrasonic agitation showed the single best result (P < .05). EDDY caused by far the highest and ultrasonic agitation the lowest dissolution of the gelatin in the simulated periapical lesion.

CONCLUSIONS

Under the conditions of this study, ultrasonic agitation of a previously administered sodium hypochlorite irrigant was more laterally targeted and thus safer and more effective than sonic agitation methods.

Comparative effects of SWEEPS technique and antimicrobial photodynamic therapy by using curcumin and nano-curcumin on Enterococcus faecalis biofilm in root canal treatment

OBJECTIVES

This study aimed to compare the antimicrobial effects of the shock wave enhanced emission photoacoustic streaming (SWEEPS) technique and Antimicrobial photodynamic therapy (aPDT) with curcumin and nano-curcumin photosensitizers on Enterococcus faecalis (E. faecalis) biofilm in root canals of extracted teeth.

MATERIALS AND METHODS

This experimental study was conducted on extracted single-rooted human teeth. The teeth were decoronated at the cementoenamel junction, the root canals were instrumented with BioRace system, and their apices were sealed. Smear layer was removed, and the teeth were autoclave-sterilized. E. faecalis strains were cultured in sterile brain heart infusion (BHI) and a bacterial suspension with 0.5 McFarland standard concentration was prepared. The root canals were inoculated with the bacterial suspension and incubated at 37 °C for 4 weeks. The teeth were then divided into 12 groups (curcumin, nano-curcumin, curcumin + LED, nano-curcumin + LED, curcumin + SWEEPS, nano-curcumin + SWEEPS, curcumin + LED + SWEEPS, nano-curcumin + LED + SWEEPS, SWEEPS, positive control and negative control). The number of colony forming units (CFUs) was counted and analyzed by one-way ANOVA and Tukey's test.

RESULTS

A significant difference was noted in colony count among the groups (P<0.001). LED alone had the lowest and nano-curcumin + LED + SWEEPS had the highest root canal cleaning efficacy. SWEEPS along with curcumin, nano-curcumin, and LED significantly decreased the bacterial count compared with other groups (P<0.05).

CONCLUSION

Application of the SWEEPS technique with curcumin and nano-curcumin as photosensitizer activated by LED in aPDT improved the reduction of E. faecalis in root canals.

Effectiveness of Different Final Irrigation Procedures on Enterococcus faecalis Infected Root Canals: An In Vitro Evaluation

This study aimed to evaluate the antibacterial effect of three final irrigation protocols and to compare their ability to remove the smear layer and debris from the root canal. Methods: Sixty-three single-rooted human teeth were inoculated with Enterococcus faecalis for 14 days. The teeth were divided into a positive control group (N = 3) and three treatment groups (N = 20) as follows: final irrigation with saline solution (control group), irrigation with 5.25% NaOCl ultrasonically activated with EndoUltra (EU), standard needle irrigation with Qmix 2in1 (Qx) and irrigation with 5.25% NaOCl activated using SiroLaser Blue (SB). The bacterial load was evaluated by analyzing the colony-forming units (CFU/mL). Selected specimens were split longitudinally and examined using scanning electron microscopy in order to determine the presence of a smear layer and debris. Statistical analyses were performed using one-way ANOVA and the Kruskal−Wallis rank-sum test. Results: Activation of NaOCl with EndoUltra or SiroLaser Blue was superior at reducing intracanal bacteria relative to standard needle irrigation with Qmix 2in1 solution (p < 0.05). Even though SiroLaser Blue showed the best results for removing the smear layer and debris, no significant differences were detected between the groups (p > 0.05). Conclusions: Final irrigation with 5.25% NaOCl ultrasonically activated using EndoUltra or SiroLaser Blue demonstrated a higher efficacy in bacterial reduction than standard needle irrigation with Qmix 2in1.

Present status and future directions - irrigants and irrigation methods

Irrigation is considered the primary means of cleaning and disinfection of the root canal system. The purpose of this review was to set the framework for the obstacles that irrigation needs to overcome, to critically appraise currently used irrigants and irrigation methods, to highlight knowledge gaps and methodological limitations in the available studies and to provide directions for future developments. Organization of bacteria in biofilms located in anatomic intricacies of the root canal system and the difficulty to eliminate them is the main challenge for irrigants. Sodium hypochlorite remains the primary irrigant of choice, but it needs to be supplemented by a chelator. Delivery of the irrigants using a syringe and needle and activation by an ultrasonic file are the most popular irrigation methods. There is no evidence that any adjunct irrigation method, including ultrasonic activation, can improve the long‐term outcome of root canal treatment beyond what can be achieved by instrumentation and syringe irrigation. It is necessary to redefine the research priorities in this field and investigate in greater depth the penetration of the irrigants, their effect on the biofilm and the long‐term treatment outcome. New studies must also focus on clinically relevant comparisons, avoid methodological flaws and have sufficiently large sample sizes to reach reliable conclusions. Future multidisciplinary efforts combining the knowledge from basic sciences such as Chemistry, Microbiology and Fluid Dynamics may lead to more effective antimicrobials and improved activation methods to bring them closer to the residual biofilm in the root canal system.

Effect of Chemical Debridement and Irrigant Activation on Endodontic Treatment Outcomes: An Updated Overview

Chemical debridement is considered one of the most important steps during root canal treatment to target unreached areas and provide thorough disinfection of the canals. The efficiency of this step efficiency can be increased using different agitation and irrigation techniques/devices. This comprehensive review aimed to summarize the effect of various irrigant activation and agitation techniques/devices on endodontic treatment outcomes. Using mechanical active irrigation, which enables the activation or agitation of the irrigating solution, is beneficial in root canal treatment by increasing the efficiency of delivering the irrigant up to working length and ensuring isthmus cleanliness. However, considerable variation was noticed between the protocols used in each technique with a lack of well-designed randomized clinical trials to focus on the long-term outcome. Moreover, a low level of evidence was noticed regarding the effectiveness of certain activation techniques over others. Therefore, each study needs to be carefully weighed before using its results and embracing its conclusion. Future studies need to focus more on the antimicrobial effect of each technique and its effect on the healing of apical periodontitis. Also, recent advances, such as multisonic and laser activation, are promising tools that need more clinical investigations to show their efficiency.

Removal of accumulated hard tissue debris from mesial root of mandibular molars evaluated using micro-CT - a systematic review and network meta-analysis

Aim The aim of this systematic review and network meta-analysis was to identify the best irrigant activation technique (IAT) for the removal of accumulated hard tissue debris (AHTD) from the mesial root of mandibular molars evaluated using micro-CT studies.Methods The research question was based on the PICO format. Four electronic databases - PubMed, Scopus, Embase and Web of Science - were searched for articles up to June 2020. Selected articles were assessed for bias using the Joanna Briggs Institute Critical appraisal tool. The network meta-analysis using a fixed-effects model and SUCRA ranking were performed. The quality of the evidence was assessed using the CINeMA framework.Results Eleven studies were included for qualitative synthesis while seven were included for quantitative synthesis. The risk of bias of all included articles was low. The results based on SUCRA values revealed the IAT shock wave-enhanced emission photoacoustic streaming (100%) resulted in the greatest reduction of the volume of AHTD from mesial roots of mandibular molars. Ranking of the other IATs was as follows: photon-induced photoacoustic streaming (87%), laser-activated irrigation (79.3%), XP EndoFinisher (71.2%), ultrasonically activated irrigation (59.6%), apical negative pressure (42.3%), EasyClean (37.4%), EDDY (26.2%), EndoActivator (24.2%), self-adjusting file (11.6%) and needle irrigation (11.3%).Conclusion None of the IATs rendered the root canals completely free of AHTD. The laser-activated irrigation groups fared better than all other interventions in reducing AHTD from the mesial roots of mandibular molars. The confidence rating ranged from low to high for indirect evidence and moderate to high for mixed evidence. Results must be interpreted with caution due to the laboratory nature of the included studies.

Deficiencies in Root Canal Fillings Subsequent to Adaptive Instrumentation of Oval Canals

Simple Summary

Employing a chemo-mechanical preparation, one of the primary procedural phases in endodontic therapy is carefully removing debris, pulp tissue, and bacteria from the root canal system. The cross-sectional root canal shapes comprise circular, oval, long oval, flattened, or irregular. The frequency of oval root canals in the apical third of human teeth is around 25 to 50%. Motorised endodontic files leave almost 60% of the oval root canal perimeter unaffected by their instrumentation, thus resulting in faulty obturation that is required to prevent reinfection and to restrict the passage of microorganisms and toxins to and from the periapical tissue.

Abstract

The purpose of this study was to explore the influence of instrumentation and the potential for debris deposition using XP-endo shaper plus (XP-SP) and full-sequence SAF (F-SAF) on the adaption of thermoplastic root canal fillings in oval canals. Following the manufacturer’s instructions, ninety human permanent mandibular incisors with a single oval canal 6 mm from the apex (verified using pre-operative CBCT scanning) were instrumented with XP-SP and F-SAF. Obtura III Max apparatus was used for root canal obturation without the use of a root canal sealer. The roots were then sectioned 6 mm from the apex and examined with a digital stereomicroscope at x25 magnification to assess the root canal fillings. The F-SAF was associated with a significantly higher (p < 0.01) percentage of entire adaptation of the root fillings (76%) compared to the XP-SP (57%). Furthermore, the XP-SP group was also associated with higher (p < 0.01) defective obturation with debris at 17% and with voids at 26%. However, the F-SAF had lower percentages of defective obturations (7% with debris and 17% with voids). The quality of obturation of oval canals instrumented using full-sequence SAF was better.

Three-dimensional morphologic classifications and analysis of canal isthmuses in permanent molars

PURPOSE

To investigate the three-dimensional morphology of isthmuses in molars according to their boundary characteristics using micro-computed tomography (micro-CT).

METHODS

Micro-CT reconstructed images of 248 molars were evaluated. Isthmuses were classified into four types based on the boundary characteristics: isthmus with roof, isthmus with floor, band-shaped isthmus, and isthmus without boundary. The tooth and root with isthmuses, the number and location of the isthmuses in the root, and the canal configurations were recorded. The maximum of the major diameter of all canal cross-sections in one isthmus (d_max), the minor diameter of the canal in same cross-section (d_min), the distance between the d_max cross-section and apex (D_m-a), isthmus length (L_i), and distance from the isthmus ending cross-section to apex (D_e-a) were measured and analysed with a significance threshold set to 5%.

RESULTS

Isthmuses were present in 75.4% specimens. The four types of isthmuses were found in various molars and roots. Their distribution in different root locations and canal configurations was significantly different. The d_max, d_min, L_i, and D_e-a were analysed according to different molars and different isthmus types; their respective median values were 2.508 mm, 0.07 mm, 3.09 mm, and 3.96 mm.

CONCLUSION

The three-dimensional classification of isthmuses according to the boundary characteristics provides a comprehensive picture of the isthmus in molars. Their corresponding distributions in different molars, location in roots, and canal configurations will be helpful in predicting the type of isthmus based on the tooth position and canal configurations.

Effectiveness of photon-initiated photoacoustic streaming in root canal models with different diameters or tapers

Background

This study aimed to compare the use of photon-initiated photoacoustic streaming (PIPS) and conventional needle irrigation (CNI) in conjunction with different concentrations of sodium hypochlorite (NaOCl) to remove Enterococcus faecalis (E. faecalis) suspended bacteria and biofilms from root canal systems with different diameters or tapers.

Methods

Artificial root canal samples (n = 480) were randomly divided into three groups (n = 160/group). The canals were prepared to fit file sizes #10/.02, #25/.02, or #25/.06. The size #10/.02 group was incubated for seven days. The size #25/.02 or #25/.06 group was incubated for 2 days. A stable biological model of E. faecalis infection was established. The root canals were washed with distilled water or with 1%, 2%, or 5.25% NaOCl combined with CNI or PIPS. Bacterial suspensions and biofilms were assessed using an ATP assay kit and fluorescence microscopy. Image-Pro Plus was used to analyse the average fluorescence intensity to determine the most suitable root canal irrigation solution.

Results

In the CNI and PIPS groups, the ATP value of the 5.25% NaOCl subgroup was the lowest, followed by that of the 2% and 1% NaOCl subgroups. The ATP value of the distilled water subgroup was the highest (P < 0.05). When the root canal taper was 0.02, the ATP value of the #10/.02 + PIPS group was significantly lower than that of the #25/.02 + CNI group (P < 0.05). The average fluorescence intensity of the #10/.02 + PIPS group was lower than that of the #25/.02 + CNI group (P < 0.05). When the apical diameter was #25, the ATP value of the 0.02 taper in the PIPS group was lower than that of the 0.06 taper in the CNI group (P < 0.05), and the average fluorescence intensity of the 0.02 taper + PIPS group was lower than that of the 0.06 taper + CNI group (P < 0.05). PIPS combined with 2% and 5.25% NaOCl effectively improved the long-term antibacterial effect after irrigation and re-culture for 6 h.

Conclusions

Compared with CNI, PIPS has greater ability to remove bacteria in root canals with a small preparation diameter and a small taper. PIPS with 2% and 5.25% NaOCl exhibited superior antibacterial and bacteriostatic effects.

Comparison of Needle, Ultrasonic, and Laser Irrigation for the Removal of Calcium Hydroxide from Mandibular Molar Root Canals

Objective: This study aimed to compare the efficacy of conventional needle irrigation (CI), ultrasonically activated irrigation (UAI), photon-induced photoacoustic streaming (PIPS), and shock wave-enhanced emission photoacoustic streaming (SWEEPS) in removing calcium hydroxide [Ca(OH)₂] from root canals of mandibular molars using microcomputed tomography. Background: Various adjunctive irrigation strategies have been recommended to improve the removal of Ca(OH)₂. No reports have evaluated the SWEEPS laser-activated method for the removal of Ca(OH)₂ from root canals of mandibular molars. Materials and methods: Forty mandibular molars were instrumented and filled with Ca(OH)₂. Four irrigation groups (CI, UAI, PIPS, and SWEEPS) were established. The volume of root canals and Ca(OH)₂ and the Ca(OH)₂ volume reduction percentage (%Rd) were calculated. Data were analyzed by one-way analysis of variance and Kruskal-Wallis analysis of variance. Results: The residual Ca(OH)₂ in the apical third was higher than that in the cervical and middle thirds in all groups (p < 0.05). Comparison of the %Rd of Ca(OH)₂ in mesial canals revealed that PIPS and SWEEPS removed more Ca(OH)₂ than CI and UAI in the cervical third (p < 0.05). The middle third of the mesial canals and the cervical and middle thirds of the distal canals did not show significant differences among groups (p > 0.05). Significant differences in the %Rd of Ca(OH)₂ were noted between CI and other groups in the apical third of mesial and distal canals (p < 0.05). No group demonstrated complete removal of Ca(OH)₂. Conclusions: UAI and laser-activated irrigation significantly improved Ca(OH)₂ removal in the apical third of mesial and distal canals. No agitation technique could completely remove Ca(OH)₂.

Effect of tip insertion depth and irradiation parameters on the efficacy of cleaning calcium hydroxide from simulated lateral canals using Er:YAG laser- or ultrasonic-activated irrigation

Background/purpose

Laser-activated root canal irrigation (LAI) with an Er:YAG laser is considered more effective than other irrigation methods, whereas the effectiveness of LAI in cleaning lateral canals far from the laser tip remains unclear. This study aimed to compare the efficacy of removing calcium hydroxide [Ca(OH)₂] paste from lateral canals using LAI or ultrasonic-activated irrigation (UAI), and to examine the effect of tip insertion depth and laser irradiation parameters on cleaning efficacy.

Materials and methods

Radiopaque Ca(OH)₂ paste (Calcipex II) was injected into lateral canals 6 mm from the root apex in 192 J-shaped simulated root canal models. LAI (Erwin AdvErl; 30 or 70 mJ; 10 or 20 pulses per second; laser tip R200T or R600T) and UAI (ENAC SE10; output setting: 3) were performed 3 times for 20 s. The laser tip was placed at 8–0 mm coronal to the lateral canal location. The volume of Ca(OH)₂ paste before and after the experiment was measured using micro-CT (SMX-100CT).

Results

The Ca(OH)₂ removal rate by LAI was significantly higher than UAI at all tip insertion depths. Ca(OH)₂ removal rate in LAI was significantly lower at the 8 mm position compared with other positions (P < 0.05). When the tip insertion depth was fixed at this position, Ca(OH)₂ removal rate increased significantly when pulse energy and tip diameter were increased (P < 0.05).

Conclusion

LAI removed Ca(OH)₂ paste from lateral canals away from the tip more effectively than UAI. Increasing the pulse energy and tip diameter improved the removal efficiency.

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.

Evaluation of smear layer and debris removal by stepwise intraoperative activation (SIA) of sodium hypochlorite

OBJECTIVES

To evaluate the efficacy of a stepwise intraoperative activation (SIA) of irrigants during and after the instrumentation compared with that of a conventional activation (CA) performed only after the instrumentation to remove smear layer and debris using different activation devices.

MATERIALS AND METHODS

A total of 70 single-rooted teeth were divided into a control group (no activation, n = 10) and two different experimental groups according to the irrigant activation protocol used: group 1 (CA), in which sodium hypochlorite was activated only after the use of the last mechanical file, and group 2 (SIA), in which activation was performed during and after the instrumentation. The two groups were divided into 3 subgroups according to the activation device used (n = 10): passive ultrasonic irrigation (PUI, subgroup a), EndoActivator (EA, subgroup b), and EDDY (subgroup c). The roots were split longitudinally and observed using scanning electron microscopy (SEM) to evaluate the presence of debris and smear layer, and the results were statistically analyzed.

RESULTS

All activation protocols and devices were more effective than control group in removing smear layer and debris from all root canal thirds (P < 0.05), except for CA-EA (group 1b) in the apical third. In the apical third, SIA was found to be more effective than CA (P < 0.05) to remove smear layer and residual debris when PUI was used, to remove the smear layer when EA was used (P < 0.05), and to remove residual debris when EDDY was used (P < 0.05). PUI and EDDY removed statistically more smear layer and debris than EA in the apical third (P < 0.05).

CONCLUSIONS

The SIA technique improved the smear layer and debris removal from the apical third and debris removal from the coronal third, and PUI and EDDY were more effective than EA in the apical third.

CLINICAL RELEVANCE

The stepwise intraoperative activation (SIA) technique may increase smear layer and debris removal.

Activated Irrigation vs. Conventional non-activated Irrigation in Endodontics - A Systematic Review

Objective:

Irrigant activation has been claimed to be beneficial in in vitro and clinical studies. This systematic review aims to investigate the clinical efficiency of mechanically activated irrigants and conventional irrigation.

Methods:

A literature search (PROSPERO registration number: CRD42018112595) was undertaken in PubMed, Cochrane and hand search. The inclusion criteria were clinical trials, in vivo/ex vivo on adult permanent teeth involving an active irrigation device and a control group of conventional irrigation. The exclusion criteria were studies done in vitro, animals and foreign language. Adult patients requiring endodontic treatment of permanent dentition and irrigant activation during the treatment were chosen as the participants and intervention respectively.

Results:

After removal of duplicates, 89 articles were obtained, and 72 were excluded as they did not meet the selection criteria. 6 devices (EndoVac, EndoActivator, Ultrasonic, MDA (manual dynamic agitation), CUI (Continuous Ultrasonic Irrigation) and PUI (Passive Ultrasonic Irrigation)) and 6 variables of interest (Post-operative pain, periapical healing, antibacterial efficacy, canal and/or isthmus cleanliness, debridement efficacy and delivery up to working length) were evaluated in the 17 included articles. The risk of bias and quality of the selected articles were moderate. Results showed that mechanical active irrigation reduces post-operative pain. It improved debridement, canal/isthmus cleanliness. It also improved delivery of irrigant up to working length. Bacterial count was more with active irrigation, though not significant. There is no effect on long-term periapical healing.

Conclusion:

It may be concluded that mechanical active irrigation devices are beneficial in reducing post-operative pain and improving canal and isthmus cleanliness during Endodontics.

Efficacy of the photon-initiated photoacoustic streaming combined with different solutions on Enterococcus faecalis in the root canals

This study aimed to evaluate the efficacy of different irrigation solutions used in photon-initiated photoacoustic streaming (PIPS) or conventional needle irrigation (CNI) for eradication of Enterococcus faecalis from artificial root canals. Altogether, 240 artificial root canal samples were included. The models were split and incubated for 2 days to allow formation of E. faecalis biofilm. The models were randomly divided into two groups (n = 120): CNI and laser-activated irrigation (LAI). Each group was divided into six subgroups according to different irrigation solutions: distilled water, 1% sodium hypochlorite (NaOCl), 2% NaOCl, 5.25% NaOCl, MTAD, and chlorhexidine, respectively. After irrigation, half of the samples (n = 10) were assessed immediately, and the other half of the samples (n = 10) were incubated for 6 hr. Bacterial suspensions were obtained from all samples before and after irrigation, and after incubation, and were quantified adenosine 5'-triphosphate (ATP) assay kit. The biofilms were examined using fluorescent microscopy and analyzed by Image Pro Plus software. Significant reduction of ATP, average fluorescence density after irrigation, and growth after incubation was obtained in LAI group than in CNI group (p < .05). LAI can improve bacteriostasis effect of 2% NaOCl (p < .05). PIPS improved the antibacterial effect of the 2% NaOCl used in root canal therapy.

Relationship between canal morphology and isthmus in mesio-buccal roots of maxillary first molars in 9- to 12-year-old children: An in-vivo cone-beam computed tomography analysis

OBJECTIVES

This study aims to analysis the distribution of root canal isthmuses (RCIs), and its relationship with canal morphology in the mesio-buccal roots of maxillary first molars in children aged 9-12 in a Chinese sub-population.

METHODS

494 healthy, untreated maxillary first molars with fully developed mesio-buccal roots were examined. Cone-beam computed tomography (CBCT) scans were acquired as part of diagnosis and treatment plannings unrelated to the present study. The images were evaluated to identify the canal morphology of mesio-buccal roots according to Vertucci's classification. A map-reading strategy was used to identify RCIs.

RESULTS

In mesio-buccal roots, the most common canal morphology was type Ⅳ (38.5 %). The frequency of type I (1.6 %) was much lower than adults. RCIs were found in 92.5 % mesio-buccal roots. The RCIs which began in the cervical third and ended in the middle third (CT-MT) (31.0 %) had the highest frequency. In type III, the RCIs which began and ended in the middle third (MT-MT) (30.3 %) were most common. For type V, 30.8 % RCIs began in the cervical third and ended in the apical third (CT-AT). No significant differences were found between sexes and sides (P > 0.05).

CONCLUSIONS

For children aged 9-12, the frequency of type I canals was much lower in mesio-buccal roots of maxillary permanent first molars, while the frequency of RCIs was higher than adults, especially in the apical third. The distribution of RCIs had its own characteristics in each canal type, closely related to the structures.

Penetration depth of irrigants into root dentine after sonic, ultrasonic and photoacoustic activation

AIM

To compare penetration depths of endodontic irrigants into the dentinal tubules of extracted teeth when using several activation methods.

METHODOLOGY

The root canals of 90 extracted human teeth were prepared to size 40, .06 taper. The straight and round-shaped root canals were distributed randomly into six groups, and final irrigation was performed with EDTA and sodium hypochlorite as follows: (I) manual dynamic activation, (II) Ultrasonic, (III) Sonic, (IV) PIPS (photon-induced photoacoustic streaming, (V) SWEEPS (shock-wave enhanced emission photoacoustic streaming) and (0) control without final irrigation or activation. Subsequently, methylene blue was inserted into the canals and activated according to the groups (I-V). Teeth were sectioned horizontally, imaged under a light microscope, and dye penetration depths were measured in six sections per tooth and 24 points on a virtual clock-face per section. Data were analysed statistically by nonparametric tests for whole teeth and separately for coronal, middle and apical thirds.

RESULTS

Penetration of dye into the dentinal tubules was lowest for the controls. Median penetration depths amounted to 700-900 μm for groups I-V with differences in the apical thirds between group I and the other test groups. Minimum penetration depths were significantly greater for PIPS in the apical thirds (P ≤ 0.046).

CONCLUSIONS

Greater penetration depths occurred in the apical thirds for ultrasonic, sonic and laser-induced activation compared to manual dynamic activation. PIPS was associated with deeper penetration of irrigants. The novel SWEEPS mode did not increase irrigant penetration.

Micro-CT evaluation of sonically and ultrasonically activated irrigation on the removal of hard-tissue debris from isthmus-containing mesial root canal systems of mandibular molars

AIM

To evaluate the efficacy of sonically and ultrasonically activated irrigation on removal of accumulated hard-tissue debris (AHTD) in mesial root canal systems of mandibular molars using micro-computed tomographic (micro-CT) analysis.

METHODOLOGY

Forty mesial roots of mandibular molars with two independent canals joined apically by an isthmus (Vertucci type II) were selected. The root canals were instrumented using Reciproc R25 instruments, and specimens were scanned at a resolution of 10.5 μm. Subsequently, n = 10 roots were assigned to each of the four final irrigation groups such that the group means and variances were almost identical: sonically activated irrigation with EndoActivator (EA) or EDDY (ED), ultrasonically activated irrigation (UAI) and manual irrigation without activation (MI). The final irrigation procedures were performed using a total of 5 mL 1% NaOCl and 5 mL 15% EDTA per canal over 5 min with activation time of 4 × 20 s. Reconstructed data sets were coregistered, and the mean percentage reduction of AHTD after final irrigation was compared statistically between groups using analysis of variance at a significance level set at 5%.

RESULTS

A significant reduction of AHTD was achieved after final irrigation in all groups (P < 0.05), ranging from 44.1% to 66.8%. The vol% of debris after irrigation was 3.7 ± 1.9% for EA, 3.3 ± 2.3% for ED, 2.1 ± 1.6% for UAI and 4.4 ± 2.3% for MI, with no significant difference between groups (P > 0.05).

CONCLUSIONS

None of the final irrigation protocols completely removed AHTD from mesial root canal systems in extracted human mandibular molars. Sonically and ultrasonically activated irrigation performed no better compared to manual irrigation.

Amplification of pressure waves in laser-assisted endodontics with synchronized delivery of Er:YAG laser pulses

When attempting to clean surfaces of dental root canals with laser-induced cavitation bubbles, the resulting cavitation oscillations are significantly prolonged due to friction on the cavity walls and other factors. Consequently, the collapses are less intense and the shock waves that are usually emitted following a bubble’s collapse are diminished or not present at all. A new technique of synchronized laser-pulse delivery intended to enhance the emission of shock waves from collapsed bubbles in fluid-filled endodontic canals is reported. A laser beam deflection probe, a high-speed camera, and shadow photography were used to characterize the induced photoacoustic phenomena during synchronized delivery of Er:YAG laser pulses in a confined volume of water. A shock wave enhancing technique was employed which consists of delivering a second laser pulse at a delay with regard to the first cavitation bubble-forming laser pulse. Influence of the delay between the first and second laser pulses on the generation of pressure and shock waves during the first bubble’s collapse was measured for different laser pulse energies and cavity volumes. Results show that the optimal delay between the two laser pulses is strongly correlated with the cavitation bubble’s oscillation period. Under optimal synchronization conditions, the growth of the second cavitation bubble was observed to accelerate the collapse of the first cavitation bubble, leading to a violent collapse, during which shock waves are emitted. Additionally, shock waves created by the accelerated collapse of the primary cavitation bubble and as well of the accompanying smaller secondary bubbles near the cavity walls were observed. The reported phenomena may have applications in improved laser cleaning of surfaces during laser-assisted dental root canal treatments.