A new method to measure the mechanical properties of rotary endodontic Ni-Ti files: Measurement of 6-axis force/torque and automatic root canal preparation.

The purpose of this study was to develop a new instrument to measure the mechanical properties of rotary endodontic Ni-Ti files (ProTaper Gold F2, ProTaper Ultimate F2, and HyFlex EDM Onefile), and to evaluate the overall utility of the device. The instrument was capable of analyzing the 6-axis force/torque generated by the files during cyclic dynamic movement in a metal curved artificial root canal, and doing automatic cyclic dynamic filing in a resin root canal with a preset vertical force limit by adopting a negative feedback mechanism. By analyzing the 6-axis force/torque, we were able to estimate the position and contact points of the files in the curved root canal. ProTaper Gold showed the highest force/torque in all directions. HyFlex EDM had the highest hysteresis ratio, centering ratio value and NCF (number of cycles to fatigue fracture), while the lowest vertical force.

Dorsal roof flap rhinoplasty: Updated results and a new classification of nasal dorsal deformity.

BACKGROUND: The dorsal roof flap (DRF) technique was developed as a modification of the retractable roof method, which is a variant of dorsal preservation (DP). OBJECTIVE: The paper aims to present new results of the DRF technique and dorsal deformity analysis created for the technique. METHODS: A total of 57 primary rhinoplasty patients treated with DRF technique between 2022-2023 years were included in the study. A dorsal deformity classification based on the anticipated amount of dorsal reduction, nasal bone shape, and hump content was used. According to the classification, the noses were categorized into 3 types. All data were obtained from patient records, computed tomography views, and pre-and postoperative photographs. Aesthetic and functional results were assessed pre-and postoperatively using a visual analog scale (VAS) (0-10, 0 points means very poor). RESULTS: The mean follow-up period was 10.1 ± 3.9 months. 23 cases were type 1, 14 were type 2, and 20 were type 3. The anticipated amount of dorsal reduction in type 1 was 2-4 mm, 5-7 mm in type 2, and 8-10 mm in type 3 deformity. Of the total, 27 cases had a V-shaped nasal bone and 30 had an S-shaped. The hump composition was cartilaginous in 13 cases and bone and cartilage in 44 cases. Pre- and postoperative aesthetic and functional VAS scores were significantly different (p ≤ 0.001). No complications and therefore no revisions were observed during the follow-up period. CONCLUSION: It is a versatile method to reshape the nasal dorsum and minimize the revisions associated with dorsal preservation when used in appropriate cases.

Dynamic modeling of human error in industrial maintenance through structural analysis and system dynamics.

Human error constitutes a significant cause of accidents across diverse industries, leading to adverse consequences and heightened disruptions in maintenance operations. Organizations can enhance their decision-making process by quantifying human errors and identifying the underlying influencing factors, thereby mitigating their repercussions. Consequently, it becomes crucial to examine the value of human error probability (HEP) during these activities. The objective of this paper is to determine and simulate HEP in maintenance tasks at a cement factory, utilizing performance shaping factors (PSFs). The research employs the cross-impact matrix multiplication applied to classification (MICMAC) analysis method to evaluate the dependencies, impacts, and relationships among the factors influencing human error. This approach classifies and assesses the dependencies and impacts of different factors on HEP, occupational accidents, and related costs. The study also underscores that PSFs can dynamically change under the influence of other variables, emphasizing the necessity to forecast the behavior of human error over time. Therefore, this paper utilizes the MICMAC method to analyze the interdependencies, relationships, and impact levels among different variables. These relationships are then utilized to optimize the implementation of the system dynamics (SD) method. An SD model is employed to forecast the system's behavior, and multiple scenarios are presented. By considering the HEP value, managers can adjust organizational conditions and personnel to ensure acceptability. The paper also presents various scenarios related to HEP to assist managers in making informed decisions.

Towards active health: A study on the relationship between physical activity and body image among college students.

Aims: Active health is a new concept, model, and system for maintaining a state of whole-person health. In the context of the increasing severity of college students' mental health, it is of great significance to explore the relationship between physical activity and college students' body image based on an active health perspective. Methods: A survey was conducted among 853 college students in Zhejiang province using the physical activity rating scale, body image scale, sense of acquisition of sports body shaping scale and social adjustment scale. Using SPSS25.0 and Amos 24.0 software for data processing and analysis. Results: (1) There is a significant positive correlation between physical activity, body image, sense of acquisition of sports body shaping, and social adjustment. There is a significant positive correlation between physical activity and body image among college students; The sense of acquisition of sports body shaping a significant mediating role between physical activity and the promotion of college students' body image. The effects of physical activity on body image were mainly achieved through the following three mediating pathways: (1) physical activity → sense of acquisition of sports body shaping → body image, the mediating effect value of this pathway was 0.18, which accounted for 31.6 % of the total effect, with a confidence interval of [0.08, 0.28], (2) physical activity → social adaptation → body image, the mediating effect value of this pathway was 0.09, which accounted for 15.8 % of the total effect of 15.8 %, with a confidence interval of [0.03, 0.15], and (3) physical activity → sense of acquisition of sports body shaping → social adaptation → body image, a pathway with a mediated effect value of 0.09, accounting for 15.8 % of the total effect, with a confidence interval of [0.01, 0.17]. Conclusions: Physical activity is an important factor in promoting the body image of college students, and there is a chain intermediary effect between physical activity and body image. School sport has its own disciplinary value and unique strengths in advancing the development of body image in adolescents, and the significant mediating effects of sense of acquisition of sports body shaping and social adaptation in this process provide theoretical support for the body image turn to move from theory to practice in the field of school sport.

Composition Tuning of Semi-Open Cell Carriers via Phase Freeze-Shrink Self-Molding.

Extracellular matrix (ECM)-mimicking microsized cell carriers featuring a semi-isolated chamber facilitate the study of cellular heterogeneity as well as intercellular communication. However, the semiopen shaping of the designated gel mixture remains unattainable with current methods. We report an oil-phase freeze-shrink self-molding mechanism for generating size- and composition-tunable cradle-shaped microgels (microcradles) from water-in-oil droplets. The universality of this shape transition principle is demonstrated with six types of polysaccharides dispersed in a poly(ethylene glycol) diacrylate (PEGDA) or methacrylate gelatin (GelMA) matrix. By doping the microcradles with the major ECM component, hyaluronic acid sodium, we demonstrate a label-free selective culture of CD44 receptor-rich cells and the formation of cell spheroids within 3 days. This cryo-induced cradle-shaping strategy enables the functionalization of microcarriers for selective cell culture, thereby allowing them to be used for intercellular communication, drug delivery, and the construction of structural units for osteogenesis and 3D printing.

Design of a mixed material moderator in a beam-shaping assembly for proton accelerator-based boron neutron capture therapy.

Boron Neutron Capture Therapy is being promoted with the development of accelerator neutron sources, and many new accelerator-based BNCT facilities are being built. In Particle Accelerator Facility project of Sun Yat-sen University, we plan to build a terminal for BNCT research based on an 8 MeV, CW 3 mA proton accelerator. In this paper, we present a beam-shaping assembly for this proton accelerator with such low 24 kW beam power, using composite moderator materials composed of five elements: Mg, Al, F, O, and Li. The calculation result of FLUKA with ENDF/B and JENDL libraries shows that the epithermal neutron beam flux is 1.57×109n/cm2/s with the CW 3 mA proton beam. The fast neutron component and the gamma ray component under free-air condition are 1.49×10-13Gy∙cm2 and 8.12×10-14Gy∙cm2 respectively, in line with IAEA-TECDOC-1223 design recommendations. The thermal analysis shows that the maximum temperature of beryllium target is 706.5 K, and the structure materials of BSA do not melt.

Ultra-high-cardinality geometric shaping in the finite SNR regime.

Four-dimensional (4D) constellations with up to 131 072 points (17 bit/4D-sym) are designed for the first time using geometric shaping. The constellations are optimized in terms of mutual information (MI) and generalized MI (GMI) for the additive white Gaussian noise (AWGN) channel, targeting a forward error correction (FEC) rate of 0.8 at finite signal-to-noise ratios. The presented 15-17 bit constellations are currently the highest-performing constellations in the literature, having a gap to the AWGN capacity as low as 0.17 dB (MI) and 0.45 dB (GMI) at 17 bit/4D-sym. For lower cardinalities, our constellations match or closely approach the performance of previously published optimized constellations. We also show that (GMI-)optimized constellations with a symmetry constraint, optimized for a FEC rate of 0.8, perform nearly identical to their unconstrained counterparts for cardinalities above 8 bit/4D-sym. A symmetry constraint for MI-optimized constellations is shown to have a negative impact in general. The proposed procedure relies on a Monte-Carlo-based approach for evaluating performance and is extendable to other (nonlinear) channels. Stochastic gradient descent is used for the optimization algorithm for which the gradients are computed using automatic differentiation. This article is part of the theme issue 'Celebrating the 15th anniversary of the Royal Society Newton International Fellowship'.

Effect of several nickel-titanium rotary systems on stress distribution in mandibular molars under occlusal forces: a finite element analysis.

This study assessed the stress distribution under occlusal forces in mandibular molars after utilizing several nickel-titanium rotary systems and identified potential root fracture patterns through finite element analysis (FEA). Five three-dimensionally printed mandibular molars were used, with one tooth left unshaped and the remaining four shaped using ProTaper Gold (Dentsply, Tulsa Dental Specialties, Tulsa, OK), Reciproc Blue (VDW, Munich, Germany), XP-endo Shaper (FKG Dentaire, La Chaux-de-Fonds, Switzerland), and Hyflex EDM (Coltene/Whaledent, Altst€atten, Switzerland) rotary systems. Subsequently, micro-CT scans were performed on the teeth, and representative FEA models were generated. Two distinct loadings, vertical and oblique, were applied, and stress parameters including von Mises stress, maximum principal stress, and minimum principal stress were recorded and compared across groups. Although stress values in both loading conditions correlated with volume increases post-shaping, the stress distribution patterns indicative of potential fractures were comparable across groups. Stresses under oblique loads were observed to be higher than those under vertical loads. Several rotary systems, based on the volumetric changes they induce in dental hard tissues, may elevate stress values throughout the tooth, leading to root fractures in regions where stress concentration occurs. Conservative root canal shaping leads to a lower overall stress concentration. In mandibular molars, oblique forces have a more destructive effect compared to vertical forces.

Government controls, non-government reactions: Private radio manufacturing and the development of amateur radio in China (1912-1949).

As in most countries, the Republic of China's development of amateur radio benefited from the appeal of the amateur radio medium as well as characteristics of its technology, and it was also impacted by external factors such as war. Against a background of tradition, newly formed, but extremely strong, popular scientific beliefs fueled conflicts between state power and folk forces which played a key role in China's amateur radio development. In this study we will explore the tensions between the Chinese government's concerns for national security and distrust of folk radio research, and the rising, public demand for amateur radio. We consider how negotiations between state power and folk forces happen, and what further factors influence the construction and development of radio technology. Our analysis adopts the constructivist approach of Social Shaping of Technology (SST) theory, which focuses on the role of social factors in processes of co-construction and negotiation in technological development. We identify the folk forces, represented by the interaction between private enterprises and amateurs, as well as state power, as two of the main social factors that influenced the development of radio technology in China. From 1912 to 1937, the Chinese government was suspicious of amateur radio activities, and as a result, they instituted policies unfavorable to its development. In contrast, the Yamei Radio Co. Ltd. led the private radio manufacturing enterprises in promoting the development of amateur radio and the popularization of related technologies. In tandem, radio amateurs assisted in the promotion and technological innovation of Yamei products. From 1937 to 1949, with the government's semi-supportive and semi-skeptical attitude, amateur radio associations did make some progress. Benefiting from the early work performed by private enterprises, these associations grew into a new folk force to challenge government control, and they continued to promote the popularization and development of radio technology. Our study illuminates complex relationship among government control, non-governmental reaction, and technological development in a specific context. When there is a conflict, folk forces have the ability to mobilize against policy-driven obstacles, thus to counterbalance government control. This study not only provides a new case for SST research, but it also adds to our understanding of China's radio technology, amateur radio, and radio manufacturing industry.

Microbial hub signaling compounds: natural products disproportionally shape microbiome composition and structure.

Microbiomes are shaped by abiotic factors like nutrients, oxygen availability, pH, temperature, and so on, but also by biotic factors including low molecular weight organic compounds referred to as natural products (NPs). Based on genome analyses, millions of these compounds are predicted to exist in nature, some of them have found important applications e.g. as antibiotics. Based on recent data I propose a model that some of these compounds function as microbial hub signaling compounds, i.e. they have a higher hierarchical influence on microbiomes. These compounds have direct effects e.g. by inhibiting microorganisms and thereby exclude them from a microbiome (excluded). Some microorganisms do not respond at all (nonresponder), others respond by producing themselves NPs like a second wave of information molecules (message responder) influencing other microorganisms, but conceivably a more limited spectrum. Some microorganisms may respond to the hub compounds with their chemical modification (message modifiers). This way, the modified NPs may have themselves signaling function for a subset of microorganisms. Finally, it is also likely that NPs act as food source (C- and/or N-source) for microorganisms specialized on their degradation. As a consequence, such specialized microorganisms are selectively recruited to the microbiota.

Efficient Redirection of Trapped Broad-Band Fluorescence from Substrates into Free Space Using c-Si Metasurfaces.

Fluorescent dye films on transparent substrates are essential for OLEDs, flexible displays, X-ray detection, and wireless optical communications. However, their efficiency is often hampered by fluorescence trapping due to total internal reflection (TIR) and waveguiding. This study tackles this longstanding challenge by reconceptualizing the integration of dye films with nanoantenna metasurfaces. Traditional methods involve directly spin-coating films onto c-Si metasurfaces on quartz substrates, resulting in edge luminescence and weak inner signals. We present a straightforward, adjustable approach by integrating dye films on the opposite side of quartz substrates, reaching a 2.5-fold photoluminescence enhancement and improving the uniformity of the emission compared to the conventional methods. These gains stem from redirecting a significant portion of leaked fluorescence light trapped inside the substrate into free space, surpassing TIR conditions through in-plane diffraction orders of the metasurfaces across the full RGB spectrum. Our findings facilitate the design of more efficient luminescent devices.

Discrete Illumination-Based Compressed Ultrafast Photography for High-Fidelity Dynamic Imaging.

Compressed ultrafast photography (CUP) can capture irreversible or difficult-to-repeat dynamic scenes at the imaging speed of more than one billion frames per second, which is obtained by compressive sensing-based image reconstruction from a compressed 2D image through the discretization of detector pixels. However, an excessively high data compression ratio in CUP severely degrades the image reconstruction quality, thereby restricting its ability to observe ultrafast dynamic scenes with complex spatial structures. To address this issue, a discrete illumination-based CUP (DI-CUP) with high fidelity is reported. In DI-CUP, the dynamic scenes are loaded into an ultrashort laser pulse train with controllable sub-pulse number and time interval, thus the data compression ratio, as well as the overlap between adjacent frames, is greatly decreased and flexibly controlled through the discretization of dynamic scenes based on laser pulse train illumination, and high-fidelity image reconstruction can be realized within the same observation time window. Furthermore, the superior performance of DI-CUP is verified by observing femtosecond laser-induced ablation dynamics and plasma channel evolution, which are hardly resolved in the spatial structures using conventional CUP. It is anticipated that DI-CUP will be widely and dependably used in the real-time observations of various ultrafast dynamics.

3D-Printed MOF Monoliths: Fabrication Strategies and Environmental Applications.

Metal-organic frameworks (MOFs) have been extensively considered as one of the most promising types of porous and crystalline organic-inorganic materials, thanks to their large specific surface area, high porosity, tailorable structures and compositions, diverse functionalities, and well-controlled pore/size distribution. However, most developed MOFs are in powder forms, which still have some technical challenges, including abrasion, dustiness, low packing densities, clogging, mass/heat transfer limitation, environmental pollution, and mechanical instability during the packing process, that restrict their applicability in industrial applications. Therefore, in recent years, attention has focused on techniques to convert MOF powders into macroscopic materials like beads, membranes, monoliths, gel/sponges, and nanofibers to overcome these challenges.Three-dimensional (3D) printing technology has achieved much interest because it can produce many high-resolution macroscopic frameworks with complex shapes and geometries from digital models. Therefore, this review summarizes the combination of different 3D printing strategies with MOFs and MOF-based materials for fabricating 3D-printed MOF monoliths and their environmental applications, emphasizing water treatment and gas adsorption/separation applications. Herein, the various strategies for the fabrication of 3D-printed MOF monoliths, such as direct ink writing, seed-assisted in-situ growth, coordination replication from solid precursors, matrix incorporation, selective laser sintering, and digital light processing, are described with the relevant examples. Finally, future directions and challenges of 3D-printed MOF monoliths are also presented to better plan future trajectories in the shaping of MOF materials with improved control over the structure, composition, and textural properties of 3D-printed MOF monoliths.

In situ shaping of intricated 3D bacterial cellulose constructs using sacrificial agarose and diverted oxygen inflow.

Bacterial cellulose (BC) is gathering increased attention due to its remarkable physico-chemical features. The high biocompatibility, hydrophilicity, and mechanical and thermal stability endorse BC as a suitable candidate for biomedical applications. Nonetheless, exploiting BC for tissue regeneration demands three-dimensional, intricately shaped implants, a highly ambitious endeavor. This challenge is addressed here by growing BC within a sacrificial viscoelastic medium consisting of an agarose gel cast inside polydimethylsiloxane (PDMS) molds imprinted with the features of the desired implant. BC produced with and without agarose has been compared through SEM, TGA, FTIR, and XRD, probing the mild impact of the agarose on the BC properties. As a first proof of concept, a PDMS mold shaped as a doll's ear was used to produce a BC perfect replica, even for the smallest features. The second trial comprised a doll face imprinted on a PDMS mold. In that case, the BC production included consecutive deactivation and activation of the aerial oxygen stream. The resulting BC face clone fitted perfectly and conformally with the template doll face, while its rheological properties were comparable to those of collagen. This streamlining concept conveys to the biosynthesized nanocelluloses broader opportunities for more advanced prosthetics and soft tissue engineering uses.

Subsurface Spectroscopy of Thermal Degradation Inside an Inert Plastic Bonded Explosive (PBX) Simulant Using Feedback-Assisted Wavefront Shaping.

We characterize the subsurface thermal degradation of an inert analog of high-explosive molecular crystals (Eu:Y(acac)3(DPEPO)) (EYAD) embedded inside of a plastic bonded explosive simulant using feedback-assisted wavefront shaping-based fluorescence and Raman spectroscopies. This technique utilizes wavefront shaping to focus pump light inside a heterogeneous material onto a target particle, which significantly improves its spectroscopic signature. We find that embedding the EYAD crystals in the heterogeneous polymer results in improved thermal stability, relative to bare crystal measurements, with the crystal remaining fluorescent to >612 K inside of the heterogeneous material, while the bare crystal's fluorescence is fully quenched by 500 K. We hypothesize that this improvement is due to the polymer restricting the effects of EYAD melting, which occurs at 400 K and is the primary mechanism for spectroscopic changes in the temperature range explored.

Glide Path in Endodontics: A Literature Review of Current Knowledge.

The introduction of nickel-titanium rotary instruments revolutionized shaping procedures as they were able to produce a well-tapered preparation while reducing operator fatigue. The major drawback of rotary instruments was the high risk of fracture due to bending and torsional stress. Thus, the creation of a glide path has been advocated and recommended by most rotary instrument manufacturers. The aim of the present review is to summarize existing knowledge on glide path preparation and identify areas where further research is needed. The primary goal is to provide a comprehensive overview of the techniques and instruments used in glide path preparation, highlighting their advantages and limitations. The secondary goal is to explore the effect of glide path creation on the overall success of endodontic treatment, particularly in terms of reducing procedural errors and improving treatment outcomes. An online search on PubMed, ScienceDirect, UCLA, and Scopus databases was conducted, and 116 articles were identified. Eligible articles were divided into nine categories based on what they researched and compared. The categories included centering ability and/or root canal transportation, cyclic fatigue resistance, glide path and shaping time, tortional stress resistance, apical extrusion of debris and/or bacteria, defects in dentine walls, file separation, postoperative pain assessment, and scouting ability and performance. Establishing a glide path reduces root canal transportation, especially with rotary methods. Reciprocating and heat-treated files offer higher fatigue resistance and shorter preparation time. Instruments with shorter pitch lengths have greater torsional strength. Preparation and coronal preflaring reduce apical debris and bacteria. Glide paths do not affect dentine microcracks, file separation, or defects but reduce immediate postoperative pain and improve cutting ability. Randomized trials are needed to assess their impact on treatment outcomes.

Helical Micropillar Processed by One-Step 3D Printing for Solar Thermal Conversion.

Solar thermal utilization has broad applications in a variety of fields. Currently, maximizing the photo-thermal conversion efficiency remains a research hotspot in this field. The exquisite plant structures in nature have greatly inspired human structural design across many domains. In this work, inspired by the photosynthesis of helical grass, a HM type solar absorber made in graphene-based composite sheets is used for solar thermal conversion. The unique design promoted more effective solar energy into thermal energy through multiple reflections and scattering of solar photons. Notably, the Helical Micropillar (HM) is fabricated using a one-step projection 3D printing process based on a special 3D helical beam. As a result, the solar absorber's absorbance value can reach 0.83 in the 400-2500 nm range, and the surface temperature increased by ≈128.3% relative to the original temperature. The temperature rise rate of the solar absorber reached 22.4 °C min-1, demonstrating the significant potential of the HM in practical applications of solar thermal energy collection and utilization.

Neural activity shaping in visual prostheses with deep learning.

Objective.The visual perception provided by retinal prostheses is limited by the overlapping current spread of adjacent electrodes. This reduces the spatial resolution attainable with unipolar stimulation. Conversely, simultaneous multipolar stimulation guided by the measured neural responses-neural activity shaping (NAS)-can attenuate excessive spread of excitation allowing for more precise control over the pattern of neural activation. However, defining effective multipolar stimulus patterns is a challenging task. Previous attempts focused on analytical solutions based on an assumed linear nonlinear model of retinal response; an analytical model inversion (AMI) approach. Here, we propose a model-free solution for NAS, using artificial neural networks (ANNs) that could be trained with data acquired from the implant.Approach.Our method consists of two ANNs trained sequentially. The measurement predictor network (MPN) is trained on data from the implant and is used to predict how the retina responds to multipolar stimulation. The stimulus generator network is trained on a large dataset of natural images and uses the trained MPN to determine efficient multipolar stimulus patterns by learning its inverse model. We validate our methodin silicousing a realistic model of retinal response to multipolar stimulation.Main results.We show that our ANN-based NAS approach produces sharper retinal activations than the conventional unipolar stimulation strategy. As a theoretical bench-mark of optimal NAS results, we implemented AMI stimulation by inverting the model used to simulate the retina. Our ANN strategy produced equivalent results to AMI, while not being restricted to any specific type of retina model and being three orders of magnitude more computationally efficient.Significance.Our novel protocol provides a method for efficient and personalized retinal stimulation, which may improve the visual experience and quality of life of retinal prosthesis users.

Excitonic van der Waals Metasurfaces for Resonant Wavefront Shaping at Deep Subwavelength Thickness Scale.

Dielectric phase gradient metasurfaces have emerged as promising candidates to shrink bulky optical elements to subwavelength thickness scale based on dielectric meta-atoms. These meta-atoms strongly interact with light, thus offering excellent phase manipulation of incident light. However, to fulfill 2π phase control using meta-atoms, the metasurface thickness, to date, is limited to the order of 102 nm. Here, we present the thickness scaling down of phase gradient metasurfaces to <λ/20 by using excitonic van der Waals metasurfaces. High-refractive-index enabled by exciton resonances and symmetry-breaking nanostructures in the patterned layered tungsten disulfide (WS2) corporately enable quasibound states in the continuum in WS2 metasurfaces, which consequently yield complete phase regulation of 2π with the thickness down to 35 nm. To illustrate the concept, we have experimentally demonstrated beam steering, focusing, and holographic display using WS2 metasurfaces. We envision our results unveiling new venues for ultimate thin phase gradient metasurfaces.

Confocal laser scanning evaluation of the influence of ledges on root canal disinfection.

The aim was to analyse the influence of an apical ledge on root canal disinfection. Forty-four single-rooted teeth were micro-CT scanned and inoculated with Enterococcus faecalis. In Group S shaping was performed with ProTaper Next (PTN) up to X3 at working length (WL). In Group L an apical ledge was created with K-Files #40 and shaping completed up to PTN X3. NaOCl 5% and EDTA 10% irrigant solutions were alternated. Confocal laser scanning microscope (CLSM) and viability staining were used to analyse the proportions of dead (red) and live (green) bacteria and penetration ability inside dentinal tubules. Data were analysed with the Mann-Whitney test with Bonferroni correction (p < 0.05). In Group L the amount of red fluorescence resulted significantly lower, and penetration ability was decreased in the apical and middle portion (p < 0.05). The presence of an apical ledge may negatively influence the disinfection both in the apical and middle third.