Search Results (184)

The reverse circulation pneumatic down-the-hole (DTH) drilling system employs percussive drilling to achieve high efficiency and strong adaptability across diverse rock formations. However, its cutting removal efficiency remains suboptimal. To enhance reverse circulation performance, a comprehensive understanding of airflow and solid particle dynamics at the borehole bottom is essential. This study investigates rock cutting transportation and distribution under varying drilling parameters and evaluates reverse circulation flow ratio using a Computational Fluid Dynamics (CFD) multiphase flow model, coupled with finite volume analysis of the reverse circulation bit. Simulation results reveal that increasing the input gas flow rate (Q), reducing the equivalent particle diameter (D), and minimizing the borehole enlargement ratio (E) significantly improve cutting removal efficiency, with optimal values identified for each parameter. Additionally, solid volume fraction contours at the borehole bottom indicate that the arrangement of spherical teeth influences the flow field. Optimal values for rock cutting density (ρ), rate of penetration (ROP), and rotational speed (N) were also determined to maximize reverse circulation flow ratio. The Genetic Algorithm–Least Squares Support Vector Machine (GA-LSSVM) method was used to train the response surface data and construct a predictive model, which was then further optimized using Particle Swarm Optimization (PSO) to determine accurate parameter settings. These findings provide operational insights into optimizing drilling parameters to advance efficient drilling performance. Full article

Marine deposits in western Europe provide insight into the interplay between the warm Tethys and cooler Boreal domains, offering a climatic context for the radiation of Early Jurassic species. Reconstructions of temperature for the Hettangian and Sinemurian periods are scarce, with inferred marine temperatures of 15–20 °C based on δ¹⁸O values, which are lower than those of subsequent Jurassic stages. This emphasizes the necessity for supplementary data in order to enhance our comprehension of the climatic dynamics that characterized the Early Jurassic period. This study analyses 75 invertebrate samples, including 53 specimens of Gryphaea arcuata, from Early Sinemurian marine sediments in the Fresville quarry, Normandy, France. The present study employs a multi-proxy approach, utilizing δ¹³C and δ¹⁸O values in conjunction with Sr and Mg contents, to assess the processes of fossil diagenesis, marine productivity, and seawater temperatures. Significant post-depositional alteration was observed in the geochemical compositions of 22 bivalve shells assigned to the genera Pseudolimea, Plagiostoma, and Chlamys, which were originally composed of aragonite, except for the outer layer, which is made of calcite. However, the low-Mg calcite shells of Gryphaea arcuata, which are renowned for their diagenetic resistance, retained the majority of their isotopic integrity. The results of the statistical analyses indicate that there was minimal late pervasive diagenesis involving meteoric waters at Fresville. This is in accordance with the typical decrease in δ¹³C, δ¹⁸O values, and Sr and Mg contents that such processes would otherwise cause. Published isotopic data from Sinemurian marine fossils (plesiosaur and shark teeth) were used to estimate seawater δ¹⁸O (~−1‰ VSMOW) and surface temperatures (~24 °C). The calculated benthic temperatures of Gryphaea (17 °C) correspond to habitats at depths of about 50 m. These findings suggest a positive hydrological balance and euhaline conditions in a humid tropical climate context. Full article

Background and Objectives: In recent decades the prevalence of dental caries has continued to increase despite widespread access to modern dental care. This study aimed to evaluate the diagnostic relevance of differentiating healthy, carious, and restored dental structures using intraoral scans—a non-irradiating imaging technique. Materials and Methods: A cross-sectional reliability (diagnostic agreement) study was carried out. All 36 examiners underwent pre-calibration on the ICDAS scores recordings. They filled in ICDAS files for each randomly assigned patient through three different methods: clinical examinations and three-dimensional digital models obtained with two different intraoral scanners. Cohen’s weighted kappa test and Prevalence and Biased Adjusted Kappa (PABAK) were utilized to evaluate agreements. A corresponding p-value for agreement was computed for each agreement coefficient. Results: When ICDAS values recorded using intraoral scanners were compared for examiners with different experience levels, there was an inter-rater substantial agreement for all teeth (PABAK = 0.688; CI 95% = 0.344–0.894), but also for anterior teeth only, as well as for smooth surfaces only. Regardless of the examiner’s clinical experience, PABAK inter- and intra-rater agreement on fillings identification on three-dimensional digital models obtained by intraoral scanning were at least moderate in most cases. Conclusions: Three-dimensional digital models offer reliable diagnostic information, especially for experienced clinicians, supporting their use as a standardized tool in routine practice to obtain an accurate, dynamic view of patients’ caries status, although limitations such as controlled study conditions and variability in scanning algorithms across systems must also be acknowledged in daily dental diagnostics. Full article

Among gearbox faults, gear tooth faults are dominant. Although the traditional vibration spectrum analysis method is the mainstream diagnostic method, it has limitations such as sensitivity to environmental noise and high sensor deployment cost. Based on the influence of the meshing stiffness of the faulty gear on the dynamic transmission error of the gear, this study innovatively proposes to use the transmission error to diagnose and identify typical gear tooth faults. This paper first calculates the time-varying stiffness of typical faulty gear teeth based on the potential energy method, and analyzes the influence of various faults and environmental noise on the dynamic transmission error signal and vibration signal by establishing a six-degree-of-freedom gear transmission dynamics model. Then, a gear transmission experimental platform is built to synchronously collect the vibration acceleration and transmission error data of the gearbox. The convolutional neural network is used to classify the data under different sample lengths and different noise intensities. The results show that the transmission error signal under the same conditions has a higher gear fault diagnosis accuracy. The proposed method can not only improve the accuracy and anti-interference of gear fault diagnosis but also reduce the deployment cost of signal acquisition, providing a new paradigm for gear condition monitoring. Full article

Background: Clear aligner therapy (CAT) represents a biomimetic orthodontic approach that uses flexible thermoplastic materials to reproduce the physiological tooth movement and mechanical load distribution of natural tissues. While these materials promote oral hygiene and aesthetic comfort, their long-term biological impact on the caries process remains uncertain. This retrospective study aimed to evaluate changes in the number of decayed teeth (ΔD) before and after clear aligner treatment and to identify duration-dependent risk factors. Methods: This retrospective study included 362 patients (279 females, 83 males) treated with Invisalign^® aligners between 2020 and 2024. Baseline and post-treatment panoramic radiographs were analyzed to determine decayed tooth counts. Age, sex, and total aligner count were recorded. Non-parametric tests, multivariable regression, and ROC analysis were used to assess predictors of ΔD. Results: The mean number of decayed teeth increased slightly from 3.54 ± 2.76 to 3.83 ± 2.93 (p < 0.001). Longer treatment duration was independently associated with caries progression (β = +0.0088 per tray, p = 0.0037), and each 10-tray increment increased the odds of new decay by 55% (OR = 1.55, 95% CI: 1.26–1.90). ROC analysis identified ≥42 trays as a clinically relevant threshold (AUC = 0.67). Conclusions: Clear aligner therapy demonstrated a statistically significant yet clinically small increase in caries incidence, primarily related to treatment duration. As a biomimetic orthodontic approach that integrates mechanical and biological dynamics, extended clear aligner use may alter biofilm–surface interactions and salivary conditions over time. Therefore, preventive strategies–such as professional fluoride applications, strict cleaning protocols, and shorter recall intervals–should be emphasized for long-duration treatments to preserve the biological benefits of this biomimetic system. Full article

Background/Objectives: Orthodontically induced bone remodeling is a complex process, driven by the interaction between osteoblasts, osteoclasts and various biochemical mediators, in response to mechanical forces applied to the teeth. Monitoring this process can be achieved by identifying biomarkers in gingival crevicular fluid (GCF), a dynamic and non-invasive method. Laser therapy, widely used in other medical fields for bio-stimulation and surgery, does not yet benefit from a standardized protocol in orthodontics. The aim of this study was to evaluate the advantages of using laser therapy during orthodontic treatment by analyzing osteocalcin (OC) in gingival crevicular fluid (GCF). Methods: Based on the inclusion and exclusion criteria, we selected 30 patients who presented dentoalveolar disharmony with crowding, who benefited from fixed orthodontic treatment, using edgewise brackets with the same slot size for all subjects. Laser therapy was performed randomly on one hemiarch (HL), right or left, for each patient, randomly chosen at time T0, after activation of the orthodontic appliance. On the other side, the control hemiarch (HC), the same protocol was followed, but without active light. Laser therapy was performed with a dental laser, with a power of 12 watts, setting the periodontology working mode. GCF was collected at baseline, before activation of the orthodontic appliance (time T0) and 14 days after its activation (time T1) from the control hemiarch (HC) and laser hemiarch (HL). Determination of OC levels, as a marker of bone apposition, was performed by the enzyme-linked immunosorbent assay (ELISA) method. To evaluate laser therapy, OC levels were assessed comparatively between HL and HC. Results: Comparing OC values at times T0 and T1 for HL, we obtained a statistically significant difference (p < 0.0001). No statistically significant difference was detected when comparing OC values in HC between T0 and T1 (p = 0.2422). A statistically significant difference was observed between HC and HL at T1 (p < 0.0001). Conclusions: The higher OC levels observed in the hemiarches where laser therapy was applied, compared to the controls, demonstrate its effectiveness as an adjuvant in bone remodeling during orthodontic treatment. Full article

Anti-climbing energy absorbers (AEAs) are often installed at the ends of subway vehicles to prevent climbing in the event of a head-on collision or rear-end collision, thereby improving safety performance. To reduce the air resistance of the vehicle during operation, the AEA is usually wrapped with the GFRP head cover. However, the collision behavior of the head cover during a collision requires further research. The effects of mechanical properties of cutting anti-climbing energy absorbers (CAEAs) on the collision behavior of glass fiber reinforced polymer (GFRP) head covers for subway vehicles are investigated in this study. Firstly, the force–displacement curve of the CAEA was obtained through a dynamic impact test, and the finite element (FE) model of the CAEA with a GFRP head cover was constructed and verified. Subsequently, the effects of the four mechanical characteristics of the CAEA (i.e., initial peak crushing force (IPCF), platform force, compaction force, and eccentric height difference) on the collision behavior of the GFRP head cover were systematically analyzed. The results show that the increase in IPCF improves the energy absorption of CAEA, but that damage and stress concentration of the head cover at the moving end also occur. The increase in platform force induced the premature fracture of the GFRP head cover. The collision behavior of the head cover reaches a critical value when the compaction force is between 2500 and 3000 kN. Increasing the eccentric height difference between the anti-climbing teeth weakens the cutting energy absorption efficiency of CAEA and changes its deformation mode. This study can provide important insights into the design and optimization of anti-climbing energy absorbers for subway vehicles, and has important engineering value for improving the durability of the head cover and the collision safety of the vehicle. Full article

The premium electric-vehicle market demands exceptionally quiet transmissions because the absence of engine masking makes gearbox noise more perceptible. Virtual NVH (noise, vibration, and harshness) evaluation requires coupling elastic deformation, gear–tooth contact, and vibration transmission through bearings and housing within a single environment. This study develops an integrated workflow in MSC ADAMS for predicting the NVH behavior of a 23/81-tooth helical gear pair. Finite element-based flank stiffness is imported, and a nonlinear contact model is applied to flexible teeth. Baseline simulation at 50 Nm and 200 rpm yields a static transmission error (TE) of 7.5 µm and a dynamic peak-to-peak TE of 0.7 µm, with the fundamental mesh tone at 77 Hz. Increasing tip relief by +0.10 mm lowers RMS TE by 31% and the first mesh order by 3.1 dB while raising the flank pressure from 1.65 GPa to 1.88 GPa. The workflow efficiently supports early-stage gear-noise optimization prior to the development of physical prototypes. Full article

The placement of miniscrews in orthodontics enhances dental and skeletal movements with reduced need for patient cooperation but may lead to complications such as incorrect positioning or damage to adjacent teeth. Computer-assisted surgery techniques have shown improved accuracy and reduced risks. This study aimed to compare the accuracy of the X-Guide^® dynamic navigation system with the freehand method for orthodontic miniscrew insertion and to assess the influence of screw position and side on accuracy. The main hypothesis was that the X-Guide^® system would yield superior accuracy in the primary variable (3D apical deviation) compared to the freehand technique. Secondary hypotheses were that the X-Guide^® system would also demonstrate superior accuracy in the secondary parameters (3D entry deviation, angular deflection, apical depth, and 2D entry deviation) and that screw position and side would not significantly affect any of the outcomes. An in vitro, randomized, and blinded experimental design was used with 10 maxillary models divided into two groups: experimental (X-Guide^®) and control (freehand). In each model, six miniscrews were planned using cone beam computed tomography (CBCT): three were inserted freehand and three with navigation. A trained novice clinician performed all insertions. Post-placement CBCT scans were used to compare 3D deviations between planned and actual positions. Wilcoxon signed-rank tests and Friedman’s ANOVA were applied. In conclusion, the results supported the main hypothesis regarding the primary variable: the X-Guide^® system significantly improved miniscrew placement accuracy in terms of 3D apical deviation, even when used by a novice operator. However, the results partially rejected the secondary hypotheses related to precision, showing a significant improvement in 3D entry deviation with dCAS, but not in angular deflection or 2D measured parameters. Furthermore, the results supported the secondary hypothesis regarding screw position, which did not affect the outcomes. Nevertheless, with dCAS, a significantly greater deviation was found on the right side for 3D entry deviation, 2D entry deviation, and angular deflection. Full article

Background/Objectives: Non-syndromic tooth agenesis (NSTA) is a congenital condition that causes the absence of one or more teeth without accompanying systemic abnormalities, which significantly affects quality of life. Genetic factors, including mutations in several specific genes, contribute to the pathogenesis of NSTA. This study investigates a novel EVC2 mutation in a patient with NSTA and explores its potential pathogenic mechanism, with the aim of enriching the spectrum of pathogenic genes. Methods: Whole-exome sequencing (WES) was performed on peripheral blood samples from a patient diagnosed with NSTA. Bioinformatics analysis was utilized to identify the mutation and assess its potential impact on protein structure and function. Molecular dynamics simulations were conducted to analyze structural alterations in the EVC2 protein. The binding affinity between EVC2, EVC, and Smoothened (SMO) was to determine the effect of mutation on protein–protein interaction. Protein localization and expression were analyzed using immunofluorescence and Western blotting. Reverse transcription quantitative PCR (RT-qPCR) was employed to evaluate downstream signaling pathway alterations. Results: A novel EVC2 mutation (c.1657_1660delinsA, p.Glu553_leu554delinsMet) was identified in the proband, and the mutation was maternally inherited. Molecular dynamics simulations revealed that the mutation resulted in a decrease in α-helical content and significant conformational changes in the protein structure. This led to reduced binding affinity between EVC2 and its ligands EVC and SMO, destabilizing the structural integrity of the protein complex. Despite these structural changes, EVC2 protein localization and expression were unaffected. Furthermore, a downregulation of GLI1 and SHH expression was observed, indicating impaired Hedgehog (Hh) signaling. The downregulation of the Hh signaling pathway impairs the tooth development process and may lead to the occurrence of tooth agenesis. Conclusions: A novel EVC2 mutation was identified in a patient with NSTA. Based on molecular dynamics simulations, it is hypothesized that this EVC2 variant could contribute to the pathogenesis of NSTA by impairing the EVC2-EVC-SMO complex formation, which may lead to downregulation of downstream GLI1 and SHH. These findings provide new insights into the molecular mechanisms underlying EVC2-mediated NSTA, suggesting that disruption of Hh signaling may represent a critical pathogenic mechanism. Full article

Background: Pulp canal calcification (PCC) poses a challenge for endodontic treatment, as it obscures the canal and increases the risk of complications. This study aimed to evaluate the accuracy of endodontic access cavity preparation using dynamic navigation (DN) and to compare it with the freehand (FH) technique in teeth with severe PCC. Materials and Methods: Sixty 3D printed maxillary central incisors with simulated severe PCC were divided into two groups and accessed either with a DN system or by the conventional FH technique. Accuracy was evaluated by comparing planned and performed access cavity trajectories on preoperative and postoperative CBCT scans. Preparation time and procedural errors were recorded. Normality was assessed with the Shapiro–Wilk test. The Mann–Whitney U test was used to compare continuous variables. The significance level was set at 0.05. Results: The DN group showed significantly lower apical point 3D deviation (1.25 vs. 1.96 mm, p = 0.001), apical point depth deviation (0.43 vs. 0.88 mm, p < 0.001), and angular deflection (1.93 vs. 5.71 degrees, p < 0.001) than the FH group. The DN group had fewer procedural errors. The endodontic access entry point deviation was comparable between both techniques (p = 0.395). The preparation time was significantly higher in the DN group (204 vs. 108.5 s, p < 0.001). Conclusions: DN significantly improves the accuracy of access cavity preparation in calcified canals compared to the FH approach, reducing the risk of complications. Therefore, DN can be a valuable tool for managing challenging endodontic cases. As guided endodontic access preparation can be more time-consuming, extended treatment appointments may be required. Full article

Introduction: Fluoride varnishes are widely used in caries prevention, but the rate and duration of fluoride ion release differ depending on material composition and environmental factors. Objectives: This systematic review synthesized evidence from in vitro studies on human teeth to identify key factors influencing fluoride release. Methods: A systematic literature search was conducted in July 2025 in PubMed, Scopus, Web of Science, Embase, and the Cochrane Library using the terms “fluoride release” AND “varnish” in titles and abstracts. Study selection followed PRISMA 2020 guidelines, predefined eligibility criteria, and was structured according to the PICO framework. Of 484 retrieved records, 15 studies met the inclusion criteria and were analyzed qualitatively. Results: The primary outcome was the magnitude and duration of fluoride release from varnishes. Most studies reported peak release within the first 24 h, followed by a marked decline, although some formulations (e.g., Clinpro XT and Duraphat) maintained more stable long-term release. Substantial methodological heterogeneity was observed across studies, including differences in sample type, storage medium, pH, temperature, and measurement protocols, which influenced fluoride release dynamics. Reported secondary outcomes included enamel remineralization, changes in surface properties, and antibacterial activity, with bioactive additives such as CPP–ACP and TCP enhancing preventive effects. Acidic conditions consistently increased fluoride release. Conclusions: The magnitude and persistence of fluoride release from varnishes depend on both intrinsic material properties and external environmental conditions. Bioactive additives may prolong fluoride availability and provide additional preventive benefits. Full article

Periodontitis is a common inflammatory disease affecting the supporting structures of teeth. Epigallocatechin-3-gallate (EGCG), a polyphenol found in green tea, is known for its therapeutic properties in various diseases, including periodontitis. This study aims to identify the gene targets of EGCG and investigate its potential in modulating molecular pathways associated with periodontitis. The potential gene targets of EGCG were obtained from the traditional Chinese medicine systems pharmacology database and analysis platform (TCMSP) and SwissTargetPrediction databases, while genes associated with periodontitis were sourced from GeneCards and Gene Expression Omnibus (GEO) datasets. By overlapping the two datasets, ten common target genes were identified. To explore their functional relevance, enrichment analyses such as Gene Ontology (GO) and REACTOME pathway mapping were conducted. Protein–protein interaction (PPI) networks were then generated, and further analyses involving molecular docking and molecular dynamics (MD) simulations were carried out to evaluate the binding affinity and structural stability of EGCG with the selected target proteins. Ten common genes (MMP2, MMP14, BCL2, STAT1, HIF1A, MMP9, MMP13, VEGFA, ESR1, and PPARG) were identified. PPI network and GO and pathway analyses identified the promising hub genes as ESR1, MMP2, MMP9, MMP13, and STAT1 and which highlighted roles in tissue development, extracellular matrix remodeling, and signaling pathways such as interleukin and matrix metalloproteinase activities. Molecular docking and MD simulations revealed strong binding interactions between EGCG and key proteins (ESR1, MMP2, MMP9, MMP13, and STAT1), with favorable binding energies and stable complexes. Among these, ESR1 and MMP13 exhibited the most favorable docking scores and stability in molecular dynamics simulations and MM–PBSA calculations. This study provides valuable insights into the molecular mechanisms of EGCG in periodontitis treatment. The findings suggest that ESR1 and MMP13 are the most promising targets for EGCG, supported by strong binding interactions and stable conformations in simulations. These results offer a foundation for further experimental studies and potential therapeutic applications of EGCG in managing periodontitis. Full article

To address the challenge of predicting lubrication states and reliability caused by the uncertainty of gear materials and structural parameters, a lubrication reliability analysis method considering the randomness of gear parameters is proposed. Firstly, a nonlinear dynamic model of a gear pair is established to derive the dynamic meshing force. The geometric and kinematic analyses are then performed to determine time-varying equivalent curvature radius and entrainment velocity. The minimum film thickness during meshing is further calculated. Considering gear parameters as random variables, a gear lubrication reliability model is formulated. Monte Carlo Simulation method is employed to accurately analyze the dynamic response, dynamic meshing force, equivalent curvature radius, entrainment velocity, probability distribution of minimum film thickness, and gear lubrication failure probability. Additionally, a specialized wear test device is designed to investigate the evolution of tooth surface roughness with wear and to forecast trends in gear lubrication failure probability as wear progresses. The results indicate that the uncertainty in gear parameters have minimal impact on the equivalent curvature radius and entrainment velocity, but significantly affect the dynamic meshing force. The gear speed and root mean square roughness are critical factors affecting lubrication reliability, and the early wear of the teeth enhances the lubrication reliability. The present work provides valuable insights for the design, maintenance, and optimization of high-performance gear systems in practical engineering applications. Full article

Ground engaging tools (GETs) are critical consumable components on mining excavators, and their timely replacement is essential to prevent risks and excessive downtime. This paper presents a monitoring method utilising the modal properties—natural frequencies and mode shapes. The method is applied in a test case to show how the GETs on an excavator bucket could be monitored. Modal analysis and dynamic analysis are conducted with ANSYS to verify the effectiveness of the proposed method. The finite element analysis models are validated by experimental vibration experiments. The results demonstrate a strong correlation between changes in natural frequencies and the conditions of the teeth on the excavator bucket, when comparing the intact to the worn-out condition. In conclusion, the presented method offers a promising approach for real-time monitoring of the GETs on mining excavators and similar equipment. It will contribute to efficient maintenance interventions and enhancing operational efficiency and safety. Full article