Picosecond Ultrasonics in Magnetic Topological Insulator MnBi2Te4.

MnBi2Te4 is a magnetic topological insulator with layered A-type antiferromagnetic order. It exhibits a rich layer- and magnetic-state dependent topological phase diagram; however, much about the coupling between spin, charge, and lattice remains to be explored. In this work, we report that MnBi2Te4 is an excellent acoustic phonon cavity by realizing phonon frequency combs using picosecond ultrasonics. With the generated acoustic phonon wavepackets, we demonstrate that the timing and phase of acoustic echoes can be used to detect the presence of stacking faults between van der Waals layers buried deep within the crystal. Furthermore, by implementing this nondestructive ultrafast optical measurement in conjunction with time-resolved magneto-optical Kerr effect experiments, we uncover that out-of-plane vibrations in MnBi2Te4 do not couple to the magnetic order, i.e. there is no appreciable magnetostriction. Our work points out how a well-developed technique can probe the structural defects and phonon pulse engineering in layered topological insulators.

An ultrasound-based ensemble machine learning model for the preoperative classification of pleomorphic adenoma and Warthin tumor in the parotid gland.

OBJECTIVES: The preoperative classification of pleomorphic adenomas (PMA) and Warthin tumors (WT) in the parotid gland plays an essential role in determining therapeutic strategies. This study aims to develop and validate an ultrasound-based ensemble machine learning (USEML) model, employing nonradiative and noninvasive features to differentiate PMA from WT. METHODS: A total of 203 patients with histologically confirmed PMA or WT who underwent parotidectomy from two centers were enrolled. Clinical factors, ultrasound (US) features, and radiomic features were extracted to develop three types of machine learning model: clinical models, US models, and USEML models. The diagnostic performance of the USEML model, as well as that of physicians based on experience, was evaluated and validated using receiver operating characteristic (ROC) curves in internal and external validation cohorts. DeLong's test was used for comparisons of AUCs. SHAP values were also utilized to explain the classification model. RESULTS: The USEML model achieved the highest AUC of 0.891 (95% CI, 0.774-0.961), surpassing the AUCs of both the US (0.847; 95% CI, 0.720-0.932) and clinical (0.814; 95% CI, 0.682-0.908) models. The USEML model also outperformed physicians in both internal and external validation datasets (both p < 0.05). The sensitivity, specificity, negative predictive value, and positive predictive value of the USEML model and physician experience were 89.3%/75.0%, 87.5%/54.2%, 87.5%/65.6%, and 89.3%/65.0%, respectively. CONCLUSIONS: The USEML model, incorporating clinical factors, ultrasound factors, and radiomic features, demonstrated efficient performance in distinguishing PMA from WT in the parotid gland. CLINICAL RELEVANCE STATEMENT: This study developed a machine learning model for preoperative diagnosis of pleomorphic adenoma and Warthin tumor in the parotid gland based on clinical, ultrasound, and radiomic features. Furthermore, it outperformed physicians in an external validation dataset, indicating its potential for clinical application. KEY POINTS: • Differentiating pleomorphic adenoma (PMA) and Warthin tumor (WT) affects management decisions and is currently done by invasive biopsy. • Integration of US-radiomic, clinical, and ultrasound findings in a machine learning model results in improved diagnostic accuracy. • The ultrasound-based ensemble machine learning (USEML) model consistently outperforms physicians, suggesting its potential applicability in clinical settings.

Ultrasonic activation of adhesive systems increases bond strength and intratubular penetration of resin cement in root dentin subjected to radiation therapy.

OBJECTIVE: This study aimed to evaluate the effect of ultrasonic activation of etch-and-rinse and self-etch adhesive systems on the bond strength of resin cement to irradiated root dentin. MATERIALS AND METHODS: Eighty human maxillary anterior teeth were distributed into 8 groups (n = 10), according to the type of adhesive system used (etch-and-rinse and self-etch), the ultrasonic activation of the adhesive systems, and the dentin condition (irradiated or non-irradiated - 70 Gy). Endodontic treatment was performed followed by fiberglass post-space preparation. After fiberglass posts' luting, the roots were transversely sectioned on dentin discs and submitted to the push-out bond strength test (0.5 mm/min). The fractured specimens were analyzed under a stereomicroscope and Scanning Electron Microscope (SEM) for failure mode classification. One of the dentin discs was analyzed under SEM to evaluate the characteristics of the adhesive interface. RESULTS: Irradiated specimens had lower bond strength than non-irradiated specimens (P < 0.0001). Ultrasonic activation of both adhesive systems increased the bond strength of the resin cement to irradiated dentin (P < 0.0001). Radiotherapy significantly affected the failure mode in the middle (P = 0.024) and apical thirds (P = 0.032) (adhesive failure). CONCLUSION: Non-irradiated specimens had a more homogeneous adhesive interface. When ultrasonically activated, both adhesive systems showed a greater number of resinous tags, regardless of the dentin condition. CLINICAL RELEVANCE: Ultrasonic activation of adhesive systems is a feasible strategy to enhance fiberglass posts retention in oncological patients.

Feasibility Study for Monitoring an Ultrasonic System Using Structurally Integrated Piezoceramics.

This paper presents a new approach to monitoring ultrasonic systems using structurally integrated piezoceramics. These are integrated into the sonotrode at different points and with different orientations. The procedure for integrating the piezoceramics into the sonotrode and their performance is experimentally investigated. We examine whether the measured signal can be used to determine the optimal operating frequency of the ultrasonic system, if integrating several piezoceramics enables discernment of the current vibration shape, and if the piezoceramics can withstand the high strains caused by the vibrations in a frequency range of approximately 20-25 kHz. The signals from the piezoceramic sensors are compared to the real-time displacement at different points of the sonotrode using a 3D laser scanning vibrometer. To evaluate the performance of the sensors, different kinds of excitation of the ultrasonic system are chosen.

Quantitative Ultrafast Magnetoacoustics at Magnetic Metasurfaces.

Femtosecond (fs) time-resolved magneto-optics is applied to investigate laser-excited ultrafast dynamics of one-dimensional nickel gratings on fused silica and silicon substrates for a wide range of periodicities Λ = 400-1500 nm. Multiple surface acoustic modes with frequencies up to a few tens of GHz are generated. Nanoscale acoustic wavelengths Λ/n have been identified as nth-spatial harmonics of Rayleigh surface acoustic wave (SAW) and surface skimming longitudinal wave (SSLW), with acoustic frequencies and lifetimes being in agreement with theoretical calculations. Resonant magnetoelastic excitation of the ferromagnetic resonance (FMR) by SAW's third spatial harmonic, and, most interestingly fingerprints of the parametric resonance at 1/2 SAW frequency have been observed. Numerical solutions of Landau-Lifshitz-Gilbert (LLG) equation magnetoelastically driven by complex polychromatic acoustic fields quantitatively reproduce all resonances at once. Thus, our results provide a solid experimental and theoretical base for a quantitative understanding of ultrafast fs-laser-driven magnetoacoustics and tailoring the magnetic-grating-based metasurfaces at the nanoscale.

Data-driven Identification of Parametric Governing Equations of Dynamical Systems Using the Signed Cumulative Distribution Transform.

This paper presents a novel data-driven approach to identify partial differential equation (PDE) parameters of a dynamical system. Specifically, we adopt a mathematical "transport" model for the solution of the dynamical system at specific spatial locations that allows us to accurately estimate the model parameters, including those associated with structural damage. This is accomplished by means of a newly-developed mathematical transform, the signed cumulative distribution transform (SCDT), which is shown to convert the general nonlinear parameter estimation problem into a simple linear regression. This approach has the additional practical advantage of requiring no a priori knowledge of the source of the excitation (or, alternatively, the initial conditions). By using training data, we devise a coarse regression procedure to recover different PDE parameters from the PDE solution measured at a single location. Numerical experiments show that the proposed regression procedure is capable of detecting and estimating PDE parameters with superior accuracy compared to a number of recently developed machine learning methods. Furthermore, a damage identification experiment conducted on a publicly available dataset provides strong evidence of the proposed method's effectiveness in structural health monitoring (SHM) applications. The Python implementation of the proposed system identification technique is integrated as a part of the software package PyTransKit [1].

Evaluation of pulp tissue dissolving efficiency of sodium and calcium hypochlorite solutions activated by ultrasonics and laser: an in vitro study.

OBJECTIVES: This study aimed to compare the tissue dissolving capacities of sodium and calcium hypochlorite [NaOCl and Ca(OCl)2] solutions applied without activation or with two irrigant activation methods. MATERIALS AND METHODS: One hundred and eight dentin cavities were prepared. Preweighed tissue pieces were placed in these dentin cavities, and samples were divided into nine groups of twelve. In groups 1, 2, and 3, NaOCl was used with non-activation (NA), passive ultrasonic (PUA), and laser activation (LA). With the same techniques, Ca(OCl)2 was used in groups 4, 5, and 6, and distilled water was used in groups 7, 8, and 9. The weight loss of tissue samples was calculated and analyzed using Two-way ANOVA and Duncan tests. RESULTS: Distilled water groups showed no tissue dissolution in any conditions. NaOCI and Ca(OCI)2 showed statistically similar dissolving effectiveness when used with the same technique. Activated groups dissolved significantly greater tissue than non-activated ones, the highest in LA. CONCLUSIONS: Ca(OCI)2 can be an alternative to NaOCl; for both, the first choice of activation may be the LA.

Segmentation of process-related contaminations on two-piece abutments using pixel-based machine learning: a new quantification approach?

PURPOSE: A reference method for quantifying contaminations on two-piece abutments manufactured using CAD/CAM has not yet been established. In the present in vitro study, a pixel--based machine learning (ML) method for detecting contamination on customized two-piece abutments was investigated and embedded in a semiautomated quantification pipeline. MATERIALS AND METHODS: Forty-nine CAD/CAM zirconia abutments were fabricated and bonded to a prefabricated titanium base. All samples were analyzed for contamination by scanning electron microscopy (SEM) imaging followed by pixel--based ML and thresholding (SW) for contamination detection; quantification was performed in the postprocessing pipeline. Wilcoxon signed-rank test and Bland-Altmann plot were applied to compare both methods. The contaminated area fraction was recorded as a percentage. RESULTS: There was no statistically significant difference between the percentages of contamination areas (median = 0.004) measured with ML (median = 0.008) and with SW (median = 0.012), asymptotic Wilcoxon test: P = 0.22. The Bland-Altmann plot demonstrated a mean difference of -0.006% (95% confidence interval [CI] from -0.011% to 0.0001%) with increased values from a contamination area fraction of > 0.03% for ML. CONCLUSION: Both segmentation methods showed comparable results in evaluating surface cleanliness; pixel-based ML is a promising assessment tool for detecting external contaminations on zirconia abutments. Further studies are required to investigate the clinical performance of this tool.

Elastic moduli and refractive index of γ-Ge3N4.

Germanium nitride, having cubic spinel structure, γ-Ge3N4, is a wide band-gap semiconductor with a large exciton binding energy that exhibits high hardness, elastic moduli and elevated thermal stability up to approximately 700°C. Experimental data on its bulk and shear moduli (B0 and G0, respectively) are strongly limited, inconsistent and, thus, require verification. Moreover, earlier first-principles density functional calculations provided significantly scattering B0 values but consistently predicted G0 much higher than the so far available experimental value. Here, we examined the elasticity of polycrystalline γ-Ge3N4, densified applying high pressures and temperatures, using the techniques of laser ultrasonics (LU) and Brillouin light scattering (BLS) and compared with our extended first-principles calculations. From the LU measurements, we obtained its longitudinal- and Rayleigh wave sound velocities and, taking into account the sample porosity, derived B0 = 322(44) GPa and G0 = 188(7) GPa for the dense polycrystalline γ-Ge3N4. While our calculations underestimated B0 by approximately 17%, most of the predicted G0 matched well with our experimental value. Combining the LU- and BLS data and taking into account the elastic anisotropy, we determined the refractive index of γ-Ge3N4 in the visible range of light to be n = 2.4, similarly high as that of diamond or GaN, and matching our calculated value. This article is part of the theme issue 'Exploring the length scales, timescales and chemistry of challenging materials (Part 1)'.

Antimicrobial effectiveness of ultrasonic irrigation in root canal treatment: a systematic review of randomized clinical trials and meta-analysis.

OBJECTIVE: The objective of this systematic review and meta-analysis (SRM) was to answer the question as to whether the use of ultrasonic irrigation (UI) results in better antimicrobial activity in root canal disinfection compared to conventional irrigation (CI). METHODS: A literature search was performed in the main scientific databases, carried out until October 2021. The eligibility criteria were randomized clinical trials (RCTs). Two meta-analyses were conducted using R software with the "META" package. The mean difference (MD) and odds ratio (OR) measure of effect were calculated. The fixed effect model was applied with a 95% confidence interval. The Cochrane collaboration scale was used to assess risk of bias and the GRADE tool to assess the quality of evidence. RESULTS: A total of 1782 records were screened, and 12 studies meeting the criteria were included in this review. A low risk of bias was observed for most domains, except allocation concealment that was considered unclear. The certainty of evidence was classified as moderate in the OR meta-analyses and low in the MD meta-analyses. Ultrasonic irrigation resulted in a better antimicrobial effect in both meta-analyses, MD 1.42 [1.60; 1.23] p < 0.0001, I2 = 80%; and OR 3.86 [1.98; 7.53] p< 0.0001, I2 = 28.7%. CONCLUSION: Within the limitations of this SRM, UI presented better antimicrobial efficacy than CI. CLINICAL RELEVANCE: UI should be used by clinicians as it promotes better antimicrobial efficacy in patients undergoing endodontic treatment.

Effectiveness of a new endodontic irrigation system for removing smear layer and dissolving simulated organic matter.

OBJECTIVES: The study aimed to evaluate the potential for the dissolution of organic tissue in areas of simulated complexity and cleaning of root canal walls of the new iVac® endodontic irrigation system. MATERIAL AND METHODS: Thirty mandibular premolars were evaluated by scanning electron microscopy before and after biomechanical preparation. Then, they were distributed according to the final irrigation protocol into groups with conventional irrigation, ultrasonic agitation with metallic insert (UA), and iVac® system, and new photomicrographs were obtained. For tissue dissolution analysis, glass capillaries filled with catgut were attached to the cervical and apical thirds of twenty-one prototyped upper incisors. They were weighed before and after the previously mentioned irrigation protocols. The data were statistically compared with a significance level of 5%. RESULTS: The final irrigation provided greater cleaning of the root canal walls in the cervical, middle, and apical thirds of the root canals (P < 0.05), with no statistically significant difference between UA and iVac®, regardless of the analyzed thirds. Both ultrasonic irrigation protocols dissolved a significantly greater volume than the conventional irrigation protocol (P < 0.05), with no difference between the two protocols (P < 0.05). CONCLUSIONS: The iVac® system showed root canal wall cleaning and tissue dissolution similar to UA with a metallic insert, and both were superior to conventional irrigation. CLINICAL RELEVANCE: The new irrigation system iVac is more effective than conventional irrigation and has similar root canal wall cleaning and tissue dissolution to UA.

Acoustic Backscatter Communication and Power Transfer for Batteryless Wireless Sensors.

Sensors for industrial and structural health monitoring are often in shielded and hard-to-reach places. Acoustic wireless power transfer (WPT) and piezoelectric backscatter enable batteryless sensors in such scenarios. Although the low efficiency of WPT demands power-conserving sensor nodes, backscatter communication, which consumes near-zero power, has not yet been combined with WPT. This study reviews the available approaches to acoustic WPT and active and passive acoustic through-metal communication. We design a batteryless and backscattering tag prototype from commercially available components. Analysis of the prototypes reveals that low-power hardware poses additional challenges for communication, i.e., unstable and inaccurate oscillators. Therefore, we implement a software-defined receiver using digital phase-locked loops (DPLLs) to mitigate the effects of oscillator instability. We show that DPLLs enable reliable backscatter communication with inaccurate clocks using simulation and real-world measurements. Our prototype achieves communication at 2 kBs-1 over a distance of 3 m. Furthermore, during transmission, the prototype consumes less than 300 µW power. At the same time, over 4 mW of power is received through wireless transmission over a distance of 3 m with an efficiency of 2.8%.

Adapting the Time-Domain Synthetic Aperture Focusing Technique (T-SAFT) to Laser Ultrasonics for Imaging the Subsurface Defects.

Traditional ultrasonic testing uses a single probe or phased array probe to investigate and visualize defects by adapting certain imaging algorithms. The time-domain synthetic aperture focusing technique (T-SAFT) is an imaging algorithm that employs a single probe to scan along the test specimen in various positions, to generate inspection images with better resolution. Both the T-SAFT and phased array probes are contact methods with limited bandwidth. This work aims to combine the advantages of the T-SAFT and phased array in a noncontact way with the aid of laser ultrasonics. Here, a pulsed laser beam is employed to generate ultrasonic waves in both thermoelastic and ablation regimes, whereas the laser Doppler vibrometer is used to acquire the generated signals. These two lasers are focused on the test specimen and, to avoid the plasma and crater influence in the ablation regime, the transmission beam and reception beam are separated by 5 mm. By moving the test specimen with a step size of 0.5 mm, a 1D linear phased array (41 and 43 elements) with a pitch of 0.5 mm was synthesized, and three side-drilled holes (Ø 8 mm-thermoelastic regime, Ø 10 mm and Ø 2 mm-ablation regime) were introduced for inspection. The A-scan data obtained from these elements were processed via the T-SAFT algorithm to generate the inspection images in various grid sizes. The results showed that the defect reflections obtained in the ablation regime have better visibility than those from the thermoelastic regime. This is due to the high-amplitude signals obtained in the ablation regime, which pave the way for enhancing the pixel intensity of each grid. Moreover, the separation distance (5 mm) does not have any significant effect on the defect location during the reconstruction process.

Nonlinear Optical Absorption in Nanoscale Films Revealed through Ultrafast Acoustics.

Herein we describe a novel spinning pump-probe photoacoustic technique developed to study nonlinear absorption in thin films. As a test case, an organic polycrystalline thin film of quinacridone, a well-known pigment, with a thickness in the tens of nanometers range, is excited by a femtosecond laser pulse which generates a time-domain Brillouin scattering signal. This signal is directly related to the strain wave launched from the film into the substrate and can be used to quantitatively extract the nonlinear optical absorption properties of the film itself. Quinacridone exhibits both quadratic and cubic laser fluence dependence regimes which we show to correspond to two- and three-photon absorption processes. This technique can be broadly applied to materials that are difficult or impossible to characterize with conventional transmittance-based measurements including materials at the nanoscale, prone to laser damage, with very weak nonlinear properties, opaque, or highly scattering.

Coherent Phononics of van der Waals Layers on Nanogratings.

Strain engineering can be used to control the physical properties of two-dimensional van der Waals (2D-vdW) crystals. Coherent phonons, which carry dynamical strain, could push strain engineering to control classical and quantum phenomena in the unexplored picosecond temporal and nanometer spatial regimes. This intriguing approach requires the use of coherent GHz and sub-THz 2D phonons. Here, we report on nanostructures that combine nanometer thick vdW layers and nanogratings. Using an ultrafast pump-probe technique, we generate and detect in-plane coherent phonons with frequency up to 40 GHz and hybrid flexural phonons with frequency up to 10 GHz. The latter arises from the periodic modulation of the elastic coupling of the vdW layer at the grooves and ridges of the nanograting. This creates a new type of a tailorable 2D periodic phononic nanoobject, a flexural phononic crystal, offering exciting prospects for the ultrafast manipulation of states in 2D materials in emerging quantum technologies.

Value of the Hyomental Distance Measured With Ultrasound in Forecasting Difficult Laryngoscopy in Newborns.

PURPOSE: Preoperative evaluations of difficult airways are imperative, especially in newborns. The hyomental distance is a reliable index for predicting difficult airways in adults. However, few studies have evaluated the value of the hyomental distance for predicting difficult airways in newborns. It is unclear whether the hyomental distance forecasts a restricted or difficult view when using direct laryngoscopy. We intended to develop an effective system for predicting difficult tracheal intubation in newborns. DESIGN: A prospective observational clinical study. METHODS: Newborns aged 0 to 28 days undergoing oral endotracheal intubation with direct laryngoscopy for elective surgery under general anesthesia were enrolled. The hyomental distance and hyoid level tissue thickness were assessed by ultrasound. Other parameters, such as the mandibular length and sternomental distance, were also evaluated before anesthesia. The glottic structure view under laryngoscopy was graded according to the Cormack-Lehane classification. The patients with Grade 1 and 2 laryngeal views were assigned to Group E. Those with Grade 3 and 4 views were assigned to Group D. FINDINGS: A total of 123 newborns were recruited for our study. The incidence of poor visualization of the larynx during laryngoscopy in our study was 10.6%. The multifactor logistic regression results showed that the hyomental distance was a powerful predictor of difficult laryngoscopy (OR = 0.16, 95% CI 0.03-0.74, P = .019). The curve with the highest sensitivity and specificity and the maximum area under the curve (AUC) was the hyomental distance. The receiver operating characteristic (ROC) curve for the hyomental distance suggested that the best cut-off value was less than equal to 2.74 cm, with an AUC of 0.80 (95% CI 0.64-0.95). CONCLUSIONS: It is noninvasive and feasible to accurately measure the hyomental distance with ultrasound in newborns, and the results are reliable. We believe that the hyomental distance measured with ultrasound could be used as a marker for predicting difficult laryngoscopy in newborns.

The efficacy of the adjunct use of subgingival air-polishing therapy with erythritol powder compared to conventional debridement alone during initial non-surgical periodontal therapy.

AIM: To assess the efficacy of the adjunct use of a subgingival erythritol powder air-polishing device (EPAP) in comparison to conventional subgingival instrumentation alone during initial non-surgical periodontal therapy. MATERIALS AND METHODS: Twenty-one patients with generalized Stages 2 and 3 grade B periodontitis were included in this single centre, single blinded, split-mouth, randomized clinical trial. Teeth on the control side were treated with conventional hand and ultrasonic instrumentation, while those on the contralateral test side was treated using EPAP as adjunct to conventional subgingival instrumentation with hand and ultrasonic instruments. Three months after initial instrumentation, persisting pockets of ≥4 mm were re-treated, in both control and test sides, again with the respective treatment approach-subgingival instrumentation alone on control, and subgingival instrumentation + EPAP on test side. Clinical parameters such as probing pocket depth (PPD), bleeding on probing, and relative attachment level were recorded at baseline and 3 and 6 months following the initial instrumentation. Subgingival plaque samples were collected at baseline, immediately post surgery, as well as at 1 week, 1 month, 3 months, and 6 months after initial instrumentation. RESULTS: In the test group after 6 months, a significantly larger number of initially deep pockets (PPD ≥ 5.5 mm) were reduced to shallow (PPD ≤ 3.4 mm), and a larger attachment gain was observed. No statistically significant microbiological differences could be found between test and control group. CONCLUSIONS: The results of the present study indicate that the adjunct use of subgingival airflow therapy with EPAP during initial non-surgical periodontal therapy might be beneficial in initially deep pockets (PPD ≥ 5.5 mm).

Latest diagnostic performance of different ultrasonic features for biliary atresia.

BACKGROUND: Early diagnosis of biliary atresia (BA) is an important clinical challenge. PURPOSE: To summarize the latest diagnostic performance of different ultrasonic (US) features for BA. MATERIAL AND METHODS: MeSH terms "biliary atresia" and "ultrasonography" and related hyponyms were used to search PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials. Eligible articles were included and data were retrieved. The methodologic quality was assessed by version 2 of the Quality Assessment of Diagnostic Accuracy Studies tool. Estimated sensitivity and specificity of each US feature were calculated by Stata 14.0. RESULTS: Fifty eligible studies on 5622 patients were included. Respective summary sensitivity and specificity were 77% (95% CI=69-84) and 98% (95% CI=96-99) for triangular cord sign (TCS) in 32 studies, 86% (95% CI=78-92) and 86% (95% CI=72-94) for shear wave elastography (SWE) in seven studies, 75% (95% CI=65-83) and 92% (95% CI=86-95) for gallbladder and biliary system abnormality (GBA) in 25 studies, and 81% (95% CI=69-90) and 79% (95% CI=67-87) for hepatic artery (HA) enlargement in seven studies. The overall US features from 11 studies yielded a summary sensitivity of 84% (95% CI=72-92) and specificity of 86% (95% CI=77-92). CONCLUSION: TCS and GBA were the two most widely accepted US features currently used for differential diagnosis of BA. The newly developed SWE was an objective and convenient method with good diagnostic performance. HA enlargement can be used as an auxiliary sign.

Micro-CT evaluation of four final irrigation protocols on hard-tissue debris removal from mesial roots of mandibular molars containing isthmus.

OBJECTIVES: To evaluate by means of microcomputed tomography (micro-CT), the efficacy of four final irrigation protocols in the removal of hard-tissue debris (HTD) in mesial roots of mandibular molars containing isthmus. MATERIALS AND METHODS: Forty standardized mesial roots of extracted mandibular molars presenting isthmus were selected. The root canals were prepared and randomly divided into 4 groups (n = 10): EA, EndoActivator (Dentsply Sirona); EC, Easy Clean (Easy Dental Equipment, Belo Horizonte, Brazil); XPF, XP-Endo Finisher (FKG Dentaire, La Chaus-de Fonds, Switzerland); and PUI, passive ultrasonic irrigation using Irrisafe tip (Satelec Acteon, Merignac, France). Each final irrigation protocol was performed in two cycles (60 s), using, respectively, 2.5% sodium hypochlorite and 17% EDTA. Micro-CT scans were obtained pre-operatory, post-preparation, and post-irrigation. The percentage of HTD reduction was calculated. Data was analyzed statistically (ANOVA and Kruskal-Wallis, significance set at 5%). RESULTS: The percentage of HTD reduction was greatest for the XPF group (77.92%), followed by EA (62.92%), PUI (47.48%), and EC (32.65%). Statistical differences (p < .05) were found between XPF and EC only. A significant difference (p < .05) was found between XPF and EC in all thirds and between PUI and EC in the middle third. CONCLUSIONS: XPF, EA, and PUI were similarly effective in HTD reduction. However, none of the evaluated protocols was able to completely remove all the debris. CLINICAL RELEVANCE: Final irrigation protocols aim to clean the canal complexities that are not addressed by the shaping procedures. Micro-CT allowed to assess the removal of hard-tissue debris in the isthmus and canals of mandibular molars.

Comparison of the efficacy of three different supplementary cleaning protocols in root-filled teeth with a bioceramic sealer after retreatment-a micro-computed tomographic study.

OBJECTIVE: The present study evaluated the efficacy of three different supplementary cleaning protocols on the removal of bioceramic-based root canal filling materials from oval-shaped canals. MATERIALS AND METHODS: A total of 36 human mandibular premolars were instrumented and obturated with gutta-percha and iRoot SP using the single-cone technique. Retreatment was performed with ProTaper Universal retreatment files. The samples were randomly divided into the following supplementary cleaning protocols: conventional syringe irrigation (CSI), passive ultrasonic irrigation (PUI), and XP-endo Finisher R (XPR). The samples underwent micro-CT scanning to quantify the amount of residual filling materials after retreatment and after performing the cleaning protocols. The volume of filling material removal was analyzed by one-way analysis of variance and post hoc Bonferroni and Games-Howell tests (P < 0.05). RESULTS: There were significant differences in the amount of root canal filling material removal in every comparison group (P < 0.05). The XPR removed significantly more residual filling materials (P < 0.01) followed by PUI and CSI (P < 0.05). Similar efficacy was found in the total root canal and all root thirds. CONCLUSIONS: The additional use of XP-endo Finisher R and passive ultrasonic irrigation effectively removed the bioceramic-obturated root filling materials from the oval-shaped canals. However, none of the techniques completely removed the filling materials. CLINICAL RELEVANCE: The XP-endo Finisher R and passive ultrasonic irrigation exhibited greater efficacy compared with syringe irrigation in the reduction of residual filling materials after retreatment in root-filled teeth with a bioceramic sealer.