Search Results (295)

Tooth development (odontogenesis) is regulated by interactions between epithelial and mesenchymal tissues through signaling pathways such as Bone Morphogenetic Protein (BMP), Wingless-related integration site (Wnt), Sonic Hedgehog (SHH), and Fibroblast Growth Factor (FGF). Mesenchymal stem cells (MSCs) derived from dental tissues—including dental pulp stem cells (DPSCs), periodontal ligament stem cells (PDLSCs), and dental follicle progenitor cells (DFPCs)—show promise for regenerative dentistry due to their multilineage differentiation potential. Epigenetic regulation, particularly DNA methylation, is hypothesized to underpin their distinct regenerative capacities. This study reanalyzed publicly available DNA methylation data generated with Illumina Infinium HumanMethylation450 BeadChip arrays (450K arrays) from DPSCs, PDLSCs, and DFPCs. High-confidence CpG sites were selected based on detection p-values, probe variance, and genomic annotation. Principal Component Analysis (PCA) and hierarchical clustering identified distinct methylation profiles. Functional enrichment analyses highlighted biological processes and pathways associated with specific methylation clusters. Noncoding RNA analysis was integrated to construct regulatory networks linking DNA methylation patterns with key developmental genes. Distinct epigenetic signatures were identified for DPSCs, PDLSCs, and DFPCs, characterized by differential methylation across specific genomic contexts. Functional enrichment revealed pathways involved in odontogenesis, osteogenesis, and neurodevelopment. Network analysis identified central regulatory nodes—including genes, such as PAX6, FOXC2, NR2F2, SALL1, BMP7, and JAG1—highlighting their roles in tooth development. Several noncoding RNAs were also identified, sharing promoter methylation patterns with developmental genes and being implicated in regulatory networks associated with stem cell differentiation and tissue-specific function. Altogether, DNA methylation profiling revealed that distinct epigenetic landscapes underlie the developmental identity and differentiation potential of dental-derived mesenchymal stem cells. This integrative analysis highlights the relevance of noncoding RNAs and regulatory networks, suggesting novel biomarkers and potential therapeutic targets in regenerative dentistry and orthodontics. Full article

Background: Attachments are essential components in clear aligner therapy, enhancing retention and improving the predictability of tooth movements. Mechanical and wear properties of the composite resins used for attachment reproduction are critical to maintaining their integrity and shape over time. This study aimed to evaluate and compare the mechanical properties, thermal behavior, and wear performance of the hybrid composite Aligner Connect (AC) and the flowable resin (Connect Flow, CF). Methods: Twenty samples (ten AC and ten CF) were reproduced. All specimens underwent differential scanning calorimetry (DSC), combustion analysis, flat instrumented indentation, compression stress relaxation tests, and tribological analysis. A 3D wear profile reconstruction was performed to assess wear surfaces. Results: DSC and combustion analyses revealed distinct thermal transitions, with CF showing significantly lower Tg values (103.8 °C/81.4 °C) than AC (110.8 °C/89.6 °C) and lower residual mass after combustion (23% vs. 61%), reflecting reduced filler content and greater polymer mobility. AC exhibited superior mechanical properties, with higher maximum load (585.9 ± 22.36 N) and elastic modulus (231.5 ± 9.1 MPa) than CF (290.2 ± 5.52 N; 156 ± 10.5 MPa). Stress relaxation decrease was less pronounced in AC (18 ± 4%) than in CF (20 ± 4%). AC also showed a significantly higher friction coefficient (0.62 ± 0.060) than CF (0.55 ± 0.095), along with greater wear volume (0.012 ± 0.0055 mm³ vs. 0.0070 ± 0.0083 mm³) and maximum depth (36.88 ± 3.642 µm vs. 17.91 ± 3.387 µm). Surface roughness before wear was higher for AC (Ra, 0.577 ± 0.035 µm; Rt, 4.369 ± 0.521 µm) than for CF (Ra, 0.337 ± 0.070 µm; Rt, 2.862 ± 0.549 µm). After wear tests, roughness values converged (Ra, 0.247 ± 0.036 µm for AC; Ra, 0.236 ± 0.019 µm for CF) indicating smoothened and similar surfaces for both composites. Conclusions: The hybrid nanocomposite demonstrated greater properties in terms of stiffness, load-bearing capacity, and structural integrity when compared with flowable resin. Its use may ensure more durable attachment integrity and improved aligner–tooth interface performance over time. Full article

Line laser measurement, as a typical method of laser triangulation, makes the acquisition of 3D tooth-surface data more accurate, efficient, and informative. Thus, a line laser 3D measurement model of gears is established, and a specialized polyhedral artifact with specific geometric features is invented to determine the pose parameters of the line laser sensor in measuring space. Based on this, a single-spindle gear-measuring instrument is developed and a series of experimental studies are conducted for gears with different module and flank directions in this instrument, including profile deviation, helix deviation, pitch deviation, topological deviation, etc. A comparative experiment with traditional contact measurement methods validates the correctness of the methods mentioned in this paper for the accurate evaluation of tested gears. In further research, the mining and utilization of big data obtained from the line laser 3D measurement of gears will be an important topic. Full article

Background: Charcot–Marie–Tooth (CMT) is a group of inherited diseases impairing the peripheral nervous system. CMT originates from genetic variants that affect proteins fundamental for the myelination of peripheral nerves and survival. Moreover, environmental and humoral factors can impact disease development and evolution. Currently, no therapy is available. Metabolomics is an emerging field of biomedical research that enables the development of novel biomarkers for neurodegenerative diseases by targeting metabolic pathways or metabolites. This study aimed to evaluate the metabolomics profile of CMT disease by comparing patients with healthy individuals. Methods: A total of 22 CMT patients (CMT) were included in this study and were demographically matched with 26 healthy individuals (C). Serum samples were analyzed through Nuclear Magnetic Resonance spectroscopy, and multivariate and univariate statistical analyses were subsequently applied. Results: A supervised model showed a clear separation (R²X = 0.3; R²Y = 0.7; Q² = 0.4; p-value = 0.0004) between the two classes of subjects, and nine metabolites were found to be significantly different (2-hydroxybutyrate, 3-hydroxybutyrate, 3-methyl-2-oxovalerate, choline, citrate, glutamate, isoleucine, lysine, and methyl succinate). The combined ROC curve showed an AUC of 0.94 (CI: 0.9–1). Additional altered metabolic pathways were also identified within the disease context. Conclusion: This study represents a promising starting point, demonstrating the efficacy of metabolomics in evaluating CMT patients and identifying novel potential disease biomarkers. Full article

Repairing veneer defects is the key to ensuring the quality of plywood. In order to improve the maintenance quality and material utilization efficiency during the maintenance process, this paper proposes a bidirectional maintenance method based on gear rack transmission and its related equipment. Based on the working principle, a geometric relationship model was established, which combines the structural parameters of the mold, punch, and gear system. Simultaneously, it solves the problem of motion attitude analysis of conjugate tooth profiles under non-standard meshing conditions, aiming to establish a constraint relationship between stamping motion and structural design parameters. On this basis, a constrained optimization model was developed by integrating multi-objective optimization theory to maximize maintenance efficiency. The NSGA-III algorithm is used to solve the model and obtain the Pareto front solution set. Subsequently, three optimal parameter configurations were selected for simulation analysis and experimental platform construction. The simulation and experimental results indicate that the veneer repair time ranges from 0.6 to 1.8 seconds, depending on the stamping speed. A reduction of 28 mm in die height decreases the repair time by approximately 0.1 seconds, resulting in an efficiency improvement of about 14%. The experimental results confirm the effectiveness of the proposed method in repairing veneer defects. Vibration measurements further verify the system’s stable operation under parametric modeling and optimization design. The main vibration response occurs during the meshing and disengagement phases between the gear and rack. Full article

Reducing gear noise in electric vehicle (EV) drivetrains is crucial due to the absence of internal combustion engine noise, making even minor acoustic disturbances noticeable. Manufacturing parameters significantly influence gear-generated noise, yet traditional analytical methods often fail to predict these complex relationships accurately. This research addresses this gap by introducing a data-driven approach using machine learning (ML) to predict gear noise levels from manufacturing and sensor-derived data. The presented methodology encompasses systematic data collection from various production stages—including soft and hard machining, heat treatment, honing, rolling tests, and end-of-line (EOL) acoustic measurements. Predictive models employing Random Forest, Gradient Boosting (XGBoost), and Neural Network algorithms were developed and compared to traditional statistical approaches. The analysis identified critical manufacturing parameters, such as surface waviness, profile errors, and tooth geometry deviations, significantly influencing noise generation. Advanced ML models, specifically Random Forest, XGBoost, and deep neural networks, demonstrated superior prediction accuracy, providing early-stage identification of gear units likely to exceed acceptable noise thresholds. Integrating these data-driven models into manufacturing processes enables early detection of potential noise issues, reduces quality assurance costs, and supports sustainable manufacturing by minimizing prototype production and resource consumption. This research enhances the understanding of gear noise formation and offers practical solutions for real-time quality assurance. Full article

Background: The rising demand for aesthetic dental treatments has spurred interest in peroxide-free color correctors as alternatives to traditional hydrogen peroxide formulations, which are associated with tooth sensitivity and potential enamel demineralization. This systematic review evaluates the whitening efficacy and safety profile of hydrogen peroxide-free color corrector (HPFCC) products, focusing on color change metrics, enamel and dentin integrity, and adverse effects. Methods: Following PRISMA guidelines, we searched PubMed, Scopus, and Web of Science throughout January 2025 for randomized controlled trials, observational studies, and in vitro experiments comparing HPFCC to placebo or peroxide-based agents. The data extraction covered study design, sample characteristics, intervention details, shade improvement (ΔE00 or CIE Lab), enamel/dentin mechanical properties (microhardness, roughness, elastic modulus), and incidence of sensitivity or tissue irritation. Risk of bias was assessed using the Cochrane tool for clinical studies and the QUIN tool for in vitro research. Results: Six studies (n = 20–80 samples or subjects) met the inclusion criteria. In vitro, HPFCC achieved mean ΔE00 values of 3.5 (bovine incisors; n = 80) and 2.8 (human molars; n = 20), versus up to 8.9 for carbamide peroxide (p < 0.01). Across studies, HPFCC achieved a mean ΔE00 of 2.8–3.5 surpassing the perceptibility threshold of 2.7 and approaching the clinical acceptability benchmark of 3.3. Surface microhardness increased by 12.9 ± 11.7 VHN with HPFCC (p < 0.001), and ultramicrohardness rose by 110 VHN over 56 days in prolonged use studies. No significant enamel erosion or dentin roughness changes were observed, and the sensitivity incidence remained below 3%. Conclusions: These findings derive from one clinical trial (n = 60) and five in vitro studies (n = 20–80), encompassing violet-pigment serums and gels with differing concentrations. Due to heterogeneity in designs, formulations, and outcome measures, we conducted a narrative synthesis rather than a meta-analysis. Although HPFCC ΔE00 values were lower than those of carbamide peroxide, they consistently exceeded perceptibility thresholds while maintaining enamel integrity and causing sensitivity in fewer than 3% of subjects, supporting HPFCCs as moderate but safe alternatives for young patients. Full article

Periodontitis is a chronic, multifactorial inflammatory disease characterized by the progressive destruction of the periodontal supporting tissues, including alveolar bone, potentially resulting in tooth loss. Etiopathogenesis involves a dysbiotic shift in the subgingival microbiota where the presence of pathogenic species such as Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, and Treponema denticola has been documented. This disbalance is combined with an inadequate host immune response, often exacerbated by other systemic comorbidities including diabetes mellitus and cardiovascular diseases. Conventional therapy typically comprises mechanical debridement and adjunctive local or systemic antimicrobials, but emerging antibiotic resistance highlights a need for alternative adjuvant therapeutic strategies. The present descriptive analysis of microbiome and clinical trends study evaluated the adjuvant effects of a clinoptilolite-based zeolite material, namely PMA-zeolite, with professional prophylaxis on clinical and microbiological parameters in patients with chronic periodontitis over a 10-week period. Clinical assessment revealed significant reductions in bleeding on probing (BoP) and periodontal pocket depth (PD), indicating improved inflammatory status. Microbiome profiling demonstrated a marked decrease in key periodontal pathogens, suggesting that PMA-zeolite can help rebalance the oral microbiome. These findings suggest that the combined therapy exhibits promising anti-inflammatory and antimicrobial properties, indicating its role in promoting microbial homeostasis and reducing periodontal inflammation. However, further investigation through larger, controlled clinical trials is needed to validate the efficacy of the therapy. Full article

The gap seal ring is a critical component in high-speed centrifugal pumps. The leakage rate and performance of the pump are sensitive to variation in seal ring parameters. This study investigates the influence of seal ring tooth profile on the leakage flow of pump chambers. Numerical simulation and experimental tests are used to analyze the impact of four different tooth-height labyrinth seal ring structures on the pressure pulsation characteristics of pump leakage chambers. It can be concluded that the use of labyrinth seal rings can significantly reduce the pressure pulsation and leakage rate of pump chambers. For the Case 2 structure with a tooth height of 0.18 mm, the pressure pulsation in the pump chamber can be reduced by a maximum of 22.5%, and the leakage rate can be reduced by 41.1%. For the Case 3 structure with a tooth height of 0.23 mm, the pressure pulsation in the pump chamber can be reduced by a maximum of 30.3%, and the leakage rate can be reduced by 40.6%. The use of labyrinth seal rings significantly reduces the pressure pulsation intensity of the impeller surfaces, which improves the force stability of the high-speed centrifugal pump impeller. This study is helpful in providing theoretical support for the design of labyrinth seal rings in high-speed centrifugal pumps. Full article

Study design: Trends in the utilization of Mandibulo-Maxillary Fixation (MMF) are shifting nowadays from tooth-borne devices over specialized screws to hybrid MMF devices. Hybrid MMF devices come in self-made Erich arch bar modifications and commercial hybrid MMF systems (CHMMFSs). Objective: We survey the available technical/clinical data. Hypothetically, the risk of tooth root damage by transalveolar screws is diminished by a targeting function of the screw holes/slots. Methods: We utilize a literature review and graphic displays to disclose parallels and dissimilarities in design and functionality with an in-depth look at the targeting properties. Results: Self-made hybrid arch bars have limitations to meet low-risk interradicular screw insertion sites. Technical/clinical information on CHMMFSs is unevenly distributed in favor of the SMARTLock System: positive outcome variables are increased speed of application/removal, the possibility to eliminate wiring and stick injuries and screw fixation with standoff of the embodiment along the attached gingiva. Inferred from the SMARTLock System, all four CHMMFs possess potential to effectively prevent tooth root injuries but are subject to their design features and targeting with the screw-receiving holes. The height profile and geometry shape of a CHMMFS may restrict three-dimensional spatial orientation and reach during placement. To bridge between interradicular spaces and tooth equators, where hooks or tie-up-cleats for intermaxillary cerclages should be ideally positioned under biomechanical aspects, can be problematic. The movability of their screw-receiving holes according to all six degrees of freedom differs. Conclusion: CHMMFSs allow simple immobilization of facial fractures involving dental occlusion. The performance in avoiding tooth root damage is a matter of design subtleties. Full article

Gear whine noise is governed not only by intentional microgeometry modifications but also by unavoidable pitch (indexing) deviation. This study presents a workflow that couples a tooth-resolved surface scan with a calibrated pitch-deviation table, both imported into a multibody dynamics (MBD) model built in MSC Adams View. Three operating scenarios were evaluated—ideal geometry, measured microgeometry without pitch error, and measured microgeometry with pitch error—at a nominal speed of 1000 r min⁻¹. Time domain analysis shows that integrating the pitch table increases the mean transmission error (TE) by almost an order of magnitude and introduces a distinct 16.66 Hz shaft order tone. When the measured tooth topologies are added, peak-to-peak TE nearly doubles, revealing a non-linear interaction between spacing deviation and local flank shape. Frequency domain results reproduce the expected mesh-frequency side bands, validating the mapping of the pitch table into the solver. The combined method therefore provides a more faithful digital twin for predicting tonal noise and demonstrates why indexing tolerances must be considered alongside profile relief during gear design optimization. Full article

Background: Charcot-Marie-Tooth (CMT) disease is a hereditary motor and sensory neuropathy that affects foot morphology and gait patterns, potentially leading to abnormal plantar pressure distribution. This systematic review synthesizes the existing literature examining plantar pressure characteristics in CMT patients. Methods: A comprehensive search was conducted across PubMed, Scopus, and Web of Science databases. Risk of bias was assessed using the Newcastle–Ottawa Scale. Results: Six studies comprising 146 patients were included. Four studies employed dynamic baropodometry, and two used in-shoe pressure sensors to evaluate the main plantar pressure parameters. The findings were consistent across different populations and devices, with a characteristic plantar-pressure profile of marked midfoot off-loading with peripheral overload at the forefoot and rearfoot, often accompanied by a lateralized center-of-pressure path and a prolonged pressure–time exposure. These alterations reflect both structural deformities and impaired neuromuscular control. Interventional studies demonstrated a load redistribution of pressure after corrective surgery, though residual lateral overload often persists. Conclusions: Plantar pressure mapping seems to be a valuable tool to identify high-pressure zones of the foot in order to personalize orthotic treatment planning, to objectively monitor disease progression, and to evaluate therapeutic efficacy. Further longitudinal studies with standardized protocols are needed to confirm these results. Full article

Spiral bevel gears are used in a wide range of industries, such as automotive and aerospace, to transfer power between intersecting axes. However, a certain level of vibration is always present in the systems, primarily due to the complex dynamic forces generated during the meshing of the gear teeth affected by the tooth profile. To address these challenges, this research developed a comprehensive dynamic model with eight degrees of freedom, capturing both translational and rotational movements of the system’s components. The study focused on evaluating the effects of two different tooth profile modifications, namely topology and flank modifications, on the vibration characteristics of the system. The system comprised a spiral bevel gear pair with mesh stiffness in forward rotation. The results highlighted that optimizing the tooth profile and minimizing tooth surface deviation significantly reduce vibration amplitudes and improve dynamic stability. These findings not only enhance the performance and lifespan of spiral bevel gears but also provide a robust foundation for the design and optimization of advanced gear systems in industrial applications, ensuring higher efficiency and reliability. In this paper, it was observed that some modifications led to a 68% reduction in vibration levels. Additionally, three modifications helped improve the vibrational behavior of the system, preventing chaotic behavior, which can lead to system failure, and transforming the system’s behavior into periodic motion. Full article

To address poor film pickup, incomplete soil–film separation, and high soil content in conventional residual film recovery machines, this study designed a belt-tooth type residual film recovery machine. Its core component integrates flexible belts with nail-teeth, providing both overload protection and efficient conveying. EDEM simulations compared film pickup performance across tooth profiles, identifying an optimal structure. Based on the kinematics and mechanical properties of residual film, a film removal mechanism and packing device were designed, incorporating partitioned packing belts to reduce soil content rate in the collected film. Using Box–Behnken experimental design, response surface methodology analyzed the effects of machine forward speed, film-lifting tooth penetration depth, and pickup belt inclination angle. Key findings show: forward speed, belt angle, and tooth depth (descending order) primarily influence recovery rate; while tooth depth, belt angle, and forward speed primarily affect soil content rate. Multi-objective optimization in Design-Expert determined optimal parameters: 5.2 km/h speed, 44 mm tooth depth, and 75° belt angle. Field validation achieved a 90.15% recovery rate and 5.86% soil content rate. Relative errors below 2.73% confirmed the regression model’s reliability. Compared with common models, the recovery rate has increased slightly, while the soil content rate has decreased by more than 4%, meeting the technical requirements for resource recovery of residual plastic film. Full article

Background: The behavior of soft tissues following recession type 1 (RT1) and/or non-carious cervical lesions (NCCLs) treated with class V restorations is not well understood. These conditions cause both functional and esthetic issues. Recent studies show that increased cervical thickness can influence gingival tissue response. This suggests that restoration design has a key impact. This study aims to evaluate the effect of tooth shape modification on gingival tissue response and periodontal health with 3D analysis. Methods: Seven patients with buccal gingival recession and NCCL were selected, resulting in 50 treated teeth. Patients underwent class V buccal restorations using the BOVR technique. Three-dimensional evaluation through scanned dental impressions was performed at baseline and at T1 to monitor tissue profile changes in the buccal zenith sagittal plane. The average observation period was 4 months. Following the assessment, linear measurements were calculated according to standard planes. These measurements aimed to monitor transverse and axial tissue modifications. Probing depth, plaque index, and bleeding index were also recorded. Results: Increased tooth thickness led to tissue alteration. Greater composite thickness was significantly associated with an increase in tissue thickness (p ≤ 0.001) and gingival creeping (p ≤ 0.001) at the free gingival margin. Periodontal health remained unaffected, and 50% of the teeth required no additional surgical treatment due to satisfactory outcomes. Conclusions: Class V restorations that increase cervical thickness may promote soft tissue volume gain over a 4-month period without compromising periodontal health. A 4-month observation period is recommended before considering the surgical correction. Full article