Search Results (768)

Harvesting energy from human walking offers a promising alternative to batteries for powering wearable devices. However, existing energy harvesters suffer from limited power output. So, a novel non-resonant energy harvester was proposed in this paper. The core mechanism of the harvester integrates three components: a helical twin-rod twist rod, a face gear with dumbbell-shaped holes, and a rotor featuring bevel teeth on its upper surface. This core mechanism can efficiently harvest low-frequency reciprocating motion and convert it into unidirectional rotational motion, thereby enabling highly efficient acquisition of low-frequency energy. It offers advantages such as high energy harvesting efficiency and a simple structure. Then an electromagnetic generator converts this rotational energy into electricity. A prototype of the proposed harvester was developed and tested on a vertical reciprocating motion platform. Experiments investigated the influence of parameters including human input energy and mechanical harvesting structure on output performance of the harvester. Application testing demonstrated that manual pressing at 1 Hz successfully illuminated 120 LEDs. When integrated into a shoe heel and tested with a 60 kg person stepping in place at 2 steps per second, the harvester achieved an RMS output voltage of 18.5 V, an output power of 263.27 mW, and a power density of 4.21 mW/cm³. Overall, this research presents a new approach for designing high-efficiency energy harvesters for human walking applications. Full article

Background: Early detection of dental caries is essential for effective oral health management. Current diagnostic workflows rely heavily on radiographic imaging, which involves infrastructure requirements, workflow coordination, and resource considerations that may limit frequent use in high-throughput or resource-constrained settings. These contextual factors motivate exploration of adjunct screening concepts that could support front-end triage decisions within existing care pathways. This study evaluates, in simulation, whether modeled tooth-percussion response signals contain sufficient discriminative information to justify further translational and managerial investigation. Implementation costs, workflow optimization, and economic outcomes are not evaluated directly; rather, the objective is to assess whether the technical preconditions for a potentially scalable screening concept are satisfied under controlled in silico conditions. Methods: An in silico model of tooth percussion was developed in which enamel, dentin, and pulp/root structures were represented as a simplified layered mechanical system. Impulse responses generated from simulated tapping were used to compute the modeled surface-vibration response (enamel-layer displacement), which served as a proxy for a measurable percussion-related signal (e.g., contact vibration), rather than a recorded acoustic waveform. Carious conditions were simulated through depth-dependent reductions in stiffness and effective mass and increases in damping to represent enamel and dentin demineralization. A synthetic dataset of labeled simulated signals was generated under varying structural parameters and measurement-noise assumptions. Machine-learning models using Mel-frequency cepstral coefficient (MFCC) features were trained to classify healthy teeth, enamel caries, and dentin caries at a screening (triage) level. Results: Under baseline simulation conditions, the classifier achieved an overall accuracy of 0.97 with balanced macro-averaged F1-score (0.97). Misclassifications occurred primarily between healthy and enamel-caries categories, whereas dentin-caries cases were most consistently identified. When measurement noise and structural variability were increased, performance declined gradually, reaching approximately 0.90 accuracy under the most challenging simulated scenario. These results indicate that discriminative information is present within the modeled signals at a screening (triage) level, meaning that higher-risk categories can be distinguished probabilistically rather than with definitive diagnostic certainty. Sensitivity and specificity trade-offs were not optimized in this study, as the objective was to assess separability rather than to define clinical decision thresholds. Conclusions: Within the constraints of the in silico model, simulated tooth-percussion response signals demonstrated discriminative patterns between healthy, enamel caries, and dentin caries categories at a screening (triage) level. These findings establish technical plausibility under controlled simulation conditions and support further investigation of percussion-based screening as a potential adjunct to clinical assessment. From a healthcare management perspective, the present results address a prerequisite question—whether such signals contain sufficient information to justify translational research, rather than demonstrating workflow optimization, cost reduction, or system-level impact. Clinical validation, threshold optimization, and implementation studies are required before managerial or operational benefits can be evaluated. Full article

Background: Apical periodontitis (AP) is a common inflammatory condition of the periapical tissues, most often associated with persistent endodontic infection. Conventional two-dimensional radiography may underestimate AP because of anatomical superimposition and limited sensitivity. Cone-beam computed tomography (CBCT) allows three-dimensional visualization of periapical structures and has been increasingly used in epidemiological research. Objective: This study aimed to evaluate the prevalence and distribution of apical periodontitis, with particular emphasis on apical periodontitis associated with root canal-treated teeth (AP-RCT), in a Saudi subpopulation using CBCT imaging. Methods: This retrospective cross-sectional study analyzed CBCT scans of Saudi patients obtained for routine diagnostic purposes between 2017 and 2021. Apical periodontitis was identified using standardized radiographic criteria requiring the presence of periapical radiolucency in more than one imaging plane. Demographic and clinical variables were recorded. Descriptive statistics were used to estimate prevalence. Associations between demographic factors and AP-RCT counts were evaluated using multivariable negative binomial regression. Regional tooth distribution was analyzed using generalized estimating equation models accounting for within-participant clustering. Results: A total of 320 CBCT scans were analyzed. Apical periodontitis was detected in 231 participants (72.2%) and in 667 teeth (8.3% of examined teeth). Of the affected teeth, 457 (68.5%) were associated with root canal treatment. The mean number of AP-RCT per participant was 1.36 ± 1.81 (median: 1; IQR: 0–2). Multivariable analysis identified age as the only significant predictor of AP-RCT. Compared with individuals aged 21–30 years, higher AP-RCT rates were observed in the 31–40-year and 41–50-year age groups, while participants ≤20 years showed lower rates. Tooth-level analysis demonstrated higher AP-RCT prevalence in maxillary premolars, maxillary molars, and mandibular molars, whereas mandibular anterior teeth showed the lowest prevalence. Conclusions: Apical periodontitis, particularly AP-RCT, was frequently observed in this Saudi subpopulation when assessed using CBCT. Age and tooth location were the primary determinants of disease distribution. These findings provide population-level epidemiological data on the prevalence and anatomical distribution of apical periodontitis in root canal-treated teeth. Clinical Significance: CBCT-based epidemiological assessment enables detailed evaluation of the distribution of apical periodontitis in dentate populations and may assist in characterizing disease patterns in anatomically complex regions, without implying comparative diagnostic accuracy or treatment outcome assessment. Full article

Zirconia is a material that mimics human teeth and has been extensively studied and applied. This study investigated the surface modifications of dental zirconia induced by two UV-C wavelengths (222 and 254 nm). A total of 72 zirconia specimens were prepared and divided into groups for irradiation at varying distances (1, 6, 12 cm) and durations (40, 120, 480 and 1440 min), with three specimens retained as untreated controls. Surface changes were assessed by measuring colour difference (ΔE) and water contact angle, and by analyzing surface morphology and elemental composition using SEM and EDX, and XRD was employed to determine the crystalline structure. The results showed that both wavelengths induced clinically perceptible colour changes (ΔE > 2.0), with the most pronounced effect at 6 cm for 222 nm and 1 cm for 254 nm. WCA decreased significantly with irradiation time, showing a linear correlation with log(time), and 222 nm irradiation yielded lower WCA than 254 nm. While SEM revealed no morphological changes, both UV treatments significantly increased the Zr/O ratio compared to the control. XRD tests confirmed that UV-C irradiation does not damage the zirconium oxide crystal structure. It is concluded that both UV-C wavelengths can alter the colour and enhance the wettability of zirconia; these modifications are particularly relevant for dental restorative applications, specifically in the fabrication of anterior tooth crowns, where achieving a natural tooth-like appearance is desired. Full article

Background/Objectives: In humans, diseases such as oral cancer may require surgical amputation of the jaw. This severe disruption causes impairments in eating, swallowing, and speech, leading to a significant decline in quality of life. In contrast, newts, a group of urodele amphibians, can regenerate their jaws even in adulthood. This study explored how adult newts reconstruct lower jaws after substantial loss and clarified how this process contributes to rapid functional recovery when feeding becomes impossible. Methods: Adult Japanese fire-bellied newts (Cynops pyrrhogaster) underwent surgical amputation of the anterior half of their lower jaws. Regeneration was monitored for 64 weeks using histological analyses of bone, cartilage, and dental tissues and micro-computed tomography (micro-CT)-based osteomorphometry to quantify structural changes in the regenerating lower jaw. Results: Histological observations and osteomorphometry revealed the following: epithelial coverage of the amputation margin; ectopic cartilage formation, growth, and regression; bone resorption at the amputation margin prior to bone regeneration; anterior extension of the lower jaw bone along the original dentition position, followed by its thickening; and dental lamina invagination with tooth germ formation. Through these processes, the lower jaw bone, Meckel’s cartilage, and dentition were restored by 64 weeks post-amputation to their pre-amputation states. Conclusions: This study delineates the full sequence of lower jaw regeneration in adult newts, demonstrating complete restoration of bone, cartilage, and teeth after substantial lower jaw loss. These findings provide a detailed framework for understanding urodele jaw regeneration and may inform future strategies for promoting jaw reconstruction in humans. Full article

Background and Objectives: The regeneration of the pulp–dentin complex represents an alternative to conventional root canal treatment, aiming to preserve tooth biology and function. Cell-free regenerative endodontic therapy (CF-RET) exploits endogenous stem cells from the periapical region without ex vivo cell manipulation. Despite growing interest, the biological mechanisms, clinical indications, and predictability of CF-RET remain not clearly defined. This structured narrative review aimed to update a previous review by analyzing recent human studies on CF-RET. Materials and Methods: This review was conducted using the PRISMA 2020 guidelines to guide transparent reporting of the literature search and study selection process and was registered in PROSPERO (CRD420251075131). In vitro and in vivo human studies published between January 2017 and December 2024 investigating CF-RET were included, while studies involving cell transplantation, non-human models, case reports, and reviews were excluded. Study selection, data extraction, and quality assessment using the QuADS tool were performed, and the evidence was synthesized using a qualitative narrative approach. Results: Sixty-four studies were included. In vitro studies reported favorable effects of growth factors, exosomes, and biomimetic scaffolds on stem cell viability, migration, proliferation, odontogenic differentiation, and angiogenesis, while neurogenic differentiation was less consistently investigated. Scaffold composition, microstructure, and rheological properties were also considered. In vivo studies mainly focused on immature teeth with incomplete root development and demonstrated positive clinical and radiographic outcomes, including root development and canal diameter reduction. Conclusions: The current evidence supports the biological potential of CF-RET as a regenerative approach; however, substantial heterogeneity, the limited number of clinical studies and the absence of standardized protocols preclude definitive conclusions, highlighting the need for further well-designed translational and clinical investigations considering clinical applicability. Full article

Background/Aims: The Mediterranean killifish, Aphanius fasciatus (Valenciennes, 1821), is a small euryhaline and eurytherm cyprinodont. While its ecology and role as a bioindicator are well known, its anatomy remains poorly understood. This study aimed to provide the first detailed description of the digestive tract of A. fasciatus, from the oropharyngeal cavity to the rectum. Methods: An anatomical and morphological approach supported by light microscopy was applied to examine oral, pharyngeal, and intestinal structures in adult specimens. Results: The jaws bear tricuspids incisiform teeth, whereas the pharynx has caniniform teeth. The tongue forms a muscular thickening of the oral floor and aids swallowing. The oropharyngeal tract and esophagus lead to a dilated anterior intestinal region resembling a primitive stomach, with mucosal folds and mucus-secreting epithelium, but lacking gastric glands. This chamber functions mainly for food storage, absorption, and preparation rather than true gastric digestion. The intestine extends to the rectum, showing sexual dimorphism: females have a relaxed anus, males a more toned and folded structure. Conclusions: These findings provide essential baseline information for comparison with other experimental models and reinforce the suitability of A. fasciatus as a reliable model for anatomical and functional studies. Full article

This Finite Element Analysis (FEA) study examined the stability of Polyetheretherketone (PEEK) miniscrews and tissue response in the posterior maxilla under varying angulations. A Cone beam computed tomography (CBCT)-derived three-dimensional model of the fully dentate maxilla was generated, featuring anatomical structures (teeth, periodontal ligament (PDL), alveolar bone) and orthodontic components (brackets, transpalatal arch, archwires). PEEK miniscrews were positioned bilaterally in the regions of the second premolar-first molar and first molar-second molar. A force of 100 g was applied perpendicular to the archwire. Four insertion angulations (45°, 70°, 90°, and 110°) were simulated. FEA revealed a consistent posterior displacement pattern: crowns tipped distally and buccally, while roots moved mesially, with intrusion. The first molar’s PDL peaked at 110°. Cortical bone stress was greatest in molars (1.41 × 10⁵ Pa at 70–110°). Cancellous bone stress peaked under 70° loading in the second molar (1.25 × 10⁵ Pa). PEEK miniscrews exhibited minimal deformation and low interfacial stress, confirming stable anchorage across all angles. Posterior PEEK miniscrews demonstrated excellent stability across all insertion angles, with 70° providing optimal biomechanical efficiency for intrusion. The first molar’s PDL experienced the highest stress concentrations at extreme angles. These findings offer clinical guidance for miniscrew placement to achieve effective intrusion while maintaining tissue safety. Full article

Background: Regenerative endodontic treatment (RET) has emerged as a biologically based alternative to traditional apexification for managing immature permanent teeth with pulp necrosis. By promoting tissue ingrowth and continued root development, RET aims not only to eliminate infection but also to reinforce structurally compromised roots. Although its clinical use has expanded, evidence regarding the long-term predictability and durability of RET remains limited, as most published studies provide only short- or mid-term follow-up. Case presentation: This report describes two pediatric cases involving regenerative procedures performed on three immature permanent maxillary incisors, each followed for more than six years. The first case involved a 7-year-old girl who developed pulp necrosis in a maxillary lateral incisor after acute dental trauma. Management followed a regenerative protocol using triple antibiotic paste (ciprofloxacin, metronidazole, and minocycline) as intracanal medication and mineral trioxide aggregate as the coronal barrier. The second case concerned an 8-year-old girl presenting with chronic infection and sinus tracts affecting both maxillary central incisors. These teeth were treated using a regenerative approach with calcium hydroxide as the intracanal medicament and Biodentine as the sealing material. Clinical, radiographic, and cone beam computed tomography evaluations demonstrated complete symptom resolution and periapical healing but incomplete progressive apical closure. All treated teeth developed a calcified apical barrier, and outcomes remained stable throughout the extended follow-up period. Conclusions: While inherently limited by the nature of case reports, these findings support RET as a reliable and durable therapeutic option for necrotic immature permanent teeth, including cases in which conventional apexification has not been successful. Full article

Conventional glass ionomer cement (GIC) is a reaction product formulated from glass powders and polycarboxylic acid aqueous solution. This material has garnered significant attention in restorative dentistry due to its favorable properties, including chemical adhesion to tooth structure, biocompatibility, and sustained fluoride release, coupled with its minimal pulp irritation. However, its low mechanical strength, high brittleness, and susceptibility to cracking limit its use in stress-bearing areas of teeth. To expand the clinical application scope of GIC and develop an “ideal” dental restorative material, enhancing traditional GIC is necessary. This narrative review summarizes the main strategies for enhancing GIC, covering modifications to both the powder and liquid components. The key findings indicate that incorporating reinforcing fillers into the powder or modifying the polyacid chemistry can significantly improve mechanical properties such as compressive, tensile, and flexural strength. Additionally, some modifications help maintain or enhance fluoride release. However, the translation of many laboratory-based improvements to clinical practice requires further validation. In conclusion, while numerous promising enhancement routes exist, future development should focus on synergistic approaches and rigorous clinical evaluation to advance towards high-performance, durable restorative materials. Full article

A twin-screw multiphase pump is essential equipment for the transfer of gas-liquid multiphase mixtures in oil and gas operations. This work addresses rotor deformation in real applications by correcting the rotor profile using the arc transition approach, eliminating teeth tips, mitigating local stress concentration, and reducing the danger of rotor deformation. Simultaneously, in conjunction with the oil and gas mixed transportation requirements of the Changqing Oilfield, the MPC208-67 twin-screw mixed transportation pump was engineered, and the essential structural specifications were established. This paper employs the Mixture multiphase flow model and the SST k-ω turbulence model to simulate the internal flow field of the pump in Changqing Oilfield, aiming to examine the impact of high-gas-content conditions on the pump’s performance and ensure it aligns with design specifications. The modeling findings indicate that the pressure in the pump progressively rises along the axial direction and remains constant within the chamber. As the void fraction of the medium increases, the pressure differential between the inlet and exit of the rotor fluid domain progressively diminishes, resulting in high-velocity fluid emerging in the interstice between driving and driven rotors. The simultaneous increase in rotational speed elevates the overall fluid velocity while diminishing the pressure value. Under rated conditions, the output pressure and flow rate of the planned multiphase pump achieve 1.8 MPa and 300 m³/h, respectively, thereby fully satisfying the design specifications. This work employs the response surface approach to optimize multi-objective performance parameters, including leakage and pressurization capacity, to enhance the pump’s operational performance under high gas content situations. The optimization results indicate a 17.87% reduction in pump leakage, an 8.86% rise in pressurization capacity, and a substantial enhancement in pump performance. Full article

High-speed miniature rotary actuators are critical components in compact, high-performance systems. However, conventional electromagnetic micromotors face a prominent trade-off between miniaturization and output performance, which restricts their applicability in highly integrated devices. To address this challenge, a novel high-speed rotary piezoelectric ultrasonic motor is proposed. The proposed motor consists of a titanium alloy metal body with offset driving teeth, piezoelectric ceramic plates, two conical rotors, a compression spring, an output shaft, and a fastening sleeve. Four PZT-8 plates are bonded to the periphery of the metal body and excited to generate in-plane bending vibration modes; these vibrations are then transformed into unidirectional rotary motion through the periodic contraction and expansion of the offset driving teeth and frictional contact with the rotors. The operating principle and structural parameters of the proposed motor were analyzed and optimized using finite element analysis (FEA), including modal, harmonic response, and transient analyses. A prototype was fabricated to evaluate its mechanical properties. The stator has a compact size of 12 mm × 12 mm × 4 mm and a mass of 2.3 g. Experimental results demonstrate that under an excitation voltage of 350 V_p-p at the resonant frequency of 28.6 kHz, the motor achieves a maximum rotational speed of 4720 rpm and a maximum stall torque of 0.36 mN·m. With its simple structure, compact size, lightweight design, and excellent output performance, the proposed ultrasonic motor provides a solution for compact high-speed rotary actuation. Full article

During a taxonomic revision on Caridina of East and Southeast Asia, a group of amphidromous and anchialine Caridina species, i.e., Caridina serratirostris, C. celebensis, C. rubella, C. troglodytes, C. magnovis, C. rintelenorum, and C. henriettae, widely distributed in the Indo-Pacific region has been found to exhibit distinct and unique morphological characters, e.g., rostra moderately long and straight, armed with many dorsal teeth, at least six of them on the carapace; telson terminating in a posteromedian projection; stylocerite long, reaching to or beyond the end of the basal segment of the antennular peduncle; and preanal carina with a spine, and with slender walking legs. Genetically, the group forms a monophyletic clade, either alone or together with the genus Marosina. The clade is well-separated from other species/species groups of Caridina. By taking a conservative taxonomic approach, the genus Marosina is thus redefined to accommodate members of the C. serratirostris species group. The revised genus Marosina can be separated from the typical Caridina species (represented by Caridina typus species group) by the structure of the endopod of the male first pleopod, which does not have an appendix interna, and the long stylocerite, which reaches to or beyond the end of the basal segment of the antennular peduncle, and the high number of postorbital teeth on the carapace. The paper provides a revised diagnosis of Marosina, with a key to all species assigned to it. Diagnosis, taxonomic remarks, habitat, and distribution information for all species are provided. The ecology, biogeography, and conservation of the genus are briefly discussed. Full article

This study focuses on the design and control system of a rotating nozzle for 3D construction printers. The development of a rotating nozzle is motivated by the need to enhance control over extrusion direction and material alignment, thereby improving the mechanical performance of printed structures by the use of non-circular nozzles. The typical 3D construction printer is equipped only with a stationary circular nozzle, which prevents the use of a non-circular nozzle due to the printer’s lack of a rotational mechanical system. This, in turn, limits the opportunity to enhance mechanical properties such as tensile and compressive strengths effectively. The proposed design is developed through computer-aided design (CAD) software, and the printer’s configuration is adjusted for integration of the rotational mechanism’s control system. This design includes a full description of the rotational mechanism and integration steps for the 3D printer. Besides the main motor of the 3D printer, an additional motor is installed next to the nozzle and controlled by a new axis (parameter), which is added into the G-code. A new axis, called “U”, is responsible for the rotation of the nozzle itself. For the development of this axis design, the cosine law is applied. The calculation is based on the three consecutive points in the G-code to obtain an accurate degree of rotation for the nozzle. The effectiveness of the system was confirmed by evaluating the compressive strength depending on printhead type. Based on testing results, one trowel printhead had the highest flexural strength of 5 MPa, and a trapezoidal printhead with teeth had the highest compressive strength of 8 MPa, compared to a circular default nozzle head with 6 MPa and 2 MPa for compressive and flexural strengths, respectively. The new optimized nozzle design is implemented in existing 3D printers, which allows it not only to develop its capability in the printing process but also to make sustainable contributions in the 3D construction industry. Full article

Early enamel lesions result from pH imbalance in the oral cavity, causing subsurface de-mineralization. Resin infiltration has emerged as a minimally invasive treatment option that can halt lesion progression, filling and stabilizing enamel while improving esthetics and microhardness. Raman spectroscopy provides rapid, non-destructive analysis of enamel by detecting molecular vibrations that reflect its chemical composition and structural changes. It allows efficient characterization and depth profiling of dental tissues and materials. Raman spectra also enable quantitative assessment of compositional and structural alterations within enamel. This study aimed to assess the penetration depth of two experimental infiltration materials and a commercial resin within incipient demineralization enamel lesions using Raman spectroscopy. Artificial enamel lesions were created on three extracted human teeth. The samples were treated with a commercial resin infiltrate and two experimental resin infiltrates, with a modified recipe, following the manufacturer’s protocol. Each tooth was sectioned into a 1 mm thick disk. Raman spectra were recorded at sequential depths across both the control (untreated) and infiltrated surfaces of each disk. Characteristic peaks corresponding to infiltrate’s organic matrix and enamel’s phosphate and carbonate groups were employed for assessing penetration depth. Full article