Comparative Safety of Needle, EndoActivator, and Laser-Activated Irrigation in Overinstrumented Root Canals

Evaluation of irrigant extrusion following the use of different root canal irrigation techniques: A systematic review and meta-analysis

This systematic review investigates whether different irrigation techniques have different effects on irrigant extrusion from mature tooth apices. Articles published between January 2000 and January 2022 were searched in six electronic databases (MEDLINE, Embase, Google Scholar, Web of Science, Scopus and Cochrane) using appropriate keywords. Overall, 2265 articles were screened by their titles and abstracts. Fifty-six full-text articles were selected based on the inclusion criteria. Of them, 17 in vitro studies were included in the systematic review and meta-analysis. The meta-analysis was conducted using the random-effects inverse variance method. The results showed that the negative pressure technique caused a lesser amount (p = 0.00) and frequency (p = 0.00) of extrusion than the open-ended needle irrigation. Sonic and ultrasonic activation caused less amount of extrusion than both open-ended (p = 0.00 or p = 0.01) and closed-ended needle (p = 0.00) irrigation.

Kök kanal geometrisinin ve iğne tipinin apikalden irrigan taşmasına etkisi: ex vivo çalışma

Objective: The aim was to evaluate the effect of root canal geometry on the amount of apical extrusion of irrigant, by testing different tapers and needle types. Materials and Method: Forty-three extracted single-rooted human mandibular premolar teeth were accessed. Experimental groups were instrumented to produce increasing amounts of taper in each successive group: Group 1 (#25/.02), Group 2 (#25/.04), Group 3 (#25/.06), and Group 4 (#25/.08) (n=43, each). Irrigation was done sequentially by using a 30-G open-ended flat needle, 30-G close-ended side-vented needle, and 27-G open-ended beveled needle. Flat and side-vented needles were each placed 3 mm short of the apex, while the beveled needle was placed as far as possible in the canal without binding. Extruded irrigant was collected in preweighed foam cubes. Statistical significance was set at p<0.05. Results: An increase in canal taper led to a decrease in the amount of extruded irrigant for the flat needle (p<0.05; Groups 1 and 2 versus 3 and 4) and side-vented needle (p<0.05; Groups 1 and 2 versus 4), but no significant effect was found for the beveled needle. The amount of extruded irrigant was greater with the flat than with the side-vented needle at all tapers and with the beveled needle at most tapers (p<0.05). The side-vented needle was generally associated with the least amount of extrusion. Conclusion: Given a constant needle insertion depth, the amount of apically extruded irrigant decreased as canal taper increased. The greatest and least amounts of extrusion were generally observed with the flat and side-vented needle, respectively.

A critical analysis of research methods and experimental models to study irrigants and irrigation systems

Irrigation plays an essential role in root canal treatment. The purpose of this narrative review was to critically appraise the experimental methods and models used to study irrigants and irrigation systems and to provide directions for future research. Studies on the antimicrobial effect of irrigants should use mature multispecies biofilms grown on dentine or inside root canals and should combine at least two complementary evaluation methods. Dissolution of pulp tissue remnants should be examined in the presence of dentine and, preferably, inside human root canals. Micro-omputed tomography is currently the method of choice for the assessment of accumulated dentine debris and their removal. A combination of experiments in transparent root canals and numerical modeling is needed to address irrigant penetration. Finally, models to evaluate irrigant extrusion through the apical foramen should simulate the periapical tissues and provide quantitative data on the amount of extruded irrigant. Mimicking the in vivo conditions as close as possible and standardization of the specimens and experimental protocols are universal requirements irrespective of the surrogate endpoint studied. Obsolete and unrealistic models must be abandoned in favour of more appropriate and valid ones that have more direct application and translation to clinical Endodontics.

Use of electromagnetic stimulation on an Enterococcus faecalis biofilm on root canal treated teeth in vitro

Root canal disinfection is of utmost importance in the success of the treatment, thus, a novel method for achieving root canal disinfection by electromagnetic waves, creating a synergistic reaction via electric and thermal energy, was created. To study electromagnetic stimulation (EMS) for the disinfection of root canal in vitro, single rooted teeth were instrumented with a 45.05 Wave One Gold reciprocating file. Specimens were sterilized and inoculated with Enterococcus faecalis ATCC 29,212, which grew for 15 days to form an established biofilm. Samples were treated with 6% sodium hypochlorite (NaOCl), 1.5% NaOCl 1.5% NaOCl with EMS, 0.9% saline with EMS or 0.9% saline. After treatments, the colony forming units (CFU) was determined. Data was analyzed by Wilcoxon Rank Sums Test (α = 0.05). One sample per group was scored and split for confocal laser scanning microscopy imaging. There was a significant effect with the use of NaOCl with or without EMS versus 0.9% saline with or without EMS (p = 0.012 and 0.003, respectively). CFUs were lower when using 0.9% saline with EMS versus 0.9% saline alone (p = 0.002). Confocal imaging confirmed CFU findings. EMS with saline has an antibiofilm effect against E. faecalis and can potentially be applied for endodontic disinfection.

Characteristics of Bubble Oscillations During Laser-Activated Irrigation of Root Canals and Method of Improvement

BACKGROUND AND OBJECTIVES

Laser-activated irrigation of dental root canals is being increasingly used as its efficacy has been shown to be superior compared with conventional techniques. The method is based on laser-initiated localized fluid evaporation and subsequent rapid bubble expansions and collapses, inducing microfluid flow throughout the entire volume of the cavity. The irrigation efficacy can be further improved if optimally delayed "SWEEPS" double laser pulses are delivered into the canal. This study aims to show that the irrigation efficacy, as measured by the induced pressure within the canal, is related to the double pulse delay, with the maximal pressure generated at an optimal delay. The second aim is to find a method of determining the optimal delay for different cavity dimensions and/or laser parameters.

STUDY DESIGN/MATERIALS AND METHODS

Experiments were made in transparent models of root canals where Er:YAG laser (λ = 2.94 μm, pulse duration t_p  = 25 or 50 microseconds, and pulse energies up to E_L  = 40 mJ) was used with a combination of cylindrical and conical fiber-tip geometries (diameters 400 and 600 µm). High-speed photography (60,000 fps) and average pressure measurements inside the canal were used for process characterization.

RESULTS

The results show that a pressure amplification of more than 1.5 times occurs if the laser pulse delay approximately coincides with the bubble oscillation time. Correlations between normalized oscillation time and canal diameter for a wide range of laser pulse energies (R²  = 0.96) and between the average pressure within the canal and the bubble oscillation periods (R²  = 0.90) were found. A relationship between the bubble oscillation time and the diameter of the treated cavity was found depending on the bubble oscillation time in an infinite fluid reservoir.

CONCLUSIONS

The bubble oscillation time within a constrained volume can be determined based on the known oscillation time in infinite space, which offers a fast and simple solution for optimization of the laser parameters. These findings enable determination of optimal conditions for shock wave generation, and improvement of root canal irrigation at the same dose of laser energy input, leading to improved treatment efficacy and safety. Lasers Surg. Med. © 2020 The Authors. Lasers in Surgery and Medicine published by Wiley Periodicals, Inc.