Search Results (116)

Chemical endodontic irritants can lead to the demineralization of the inorganic tooth structure, its loss of integrity, microhardness changes, erosion, and an increased risk of fractures. We investigated the action of iron oxide nanomagnet particles (IONPs) as an irrigant solution for improving hardness and identifying the concentration of element ions in the root canal. There were six groups in total: a control group (no treatment) and experimental groups (UN: ultrasound agitation normal saline, UI: ultrasound agitation IONPs, MSI: magnetic field and endodontic needle with syringe agitation IONPs, MUI: magnetic field and ultrasound agitation IONPs, and EDTA: ethylenediaminetetraacetic acid). We hypothesized that IONPs with magnetic agitation would preserve microhardness better than EDTA. Vickers hardness testing was used to evaluate microhardness, which was then analyzed using energy-dispersive X-ray spectroscopy (EDS) to investigate the calcium/phosphorus ratio and the presence of iron. The IONP groups exhibit a higher VHN value than the EDTA group (p < 0.05). These results support our hypothesis, indicating that utilizing an IONP irrigant solution with an external magnetic field does not change microhardness but enhances it compared to the EDTA group, suggesting that employing an external magnetic field to deliver nanoparticles to the root canal wall does not affect the properties of the tooth structure compared to conventional instrumentation techniques, which lead to unnecessary loss of root structure. Full article

Caragana korshinskii Kom. (CKB), widely cultivated in Inner Mongolia, China, has potential for silage feed development due to its favorable nutritional characteristics, including a crude protein content of 14.2% and a neutral detergent fiber content below 55%. However, its vascular bundle fiber structure limits the efficiency of lactic acid conversion and negatively impacts silage quality, which can be improved through mechanical crushing. Currently, conventional crushing equipment generally suffers from uneven particle size distribution, high energy consumption, and low processing efficiency. In this study, a layered aggregate model was constructed using the discrete element method (DEM), and the Hertz–Mindlin with Bonding contact model was employed to characterize the heterogeneous mechanical properties between the epidermis and the core. Model accuracy was enhanced through reverse engineering and a multi-particle-size filling strategy. Key parameters were optimized via a Box–Behnken experimental design, with a core normal stiffness of 7.37 × 10¹¹ N·m⁻¹, a core shear stiffness of 9.46 × 10¹⁰ N·m⁻¹, a core shear stress of 2.52 × 10⁸ Pa, and a skin normal stiffness of 4.01 × 10⁹ N·m⁻¹. The simulated values for bending, tensile, and compressive failure forces had relative errors of less than 10% compared to experimental results. The results showed that rectangular hammers, due to their larger contact area and more uniform stress distribution, reduced the number of residual bonded contacts by 28.9% and 26.5% compared to stepped and blade-type hammers, respectively. Optimized rotational speed improved dynamic crushing efficiency by 41.3%. The material exhibited spatial heterogeneity, with the mass proportion in the tooth plate impact area reaching 43.91%, which was 23.01% higher than that in the primary hammer crushing area. The relative error between the simulation and bench test results for the crushing rate was 6.18%, and the spatial distribution consistency reached 93.6%, verifying the reliability of the DEM parameter calibration method. This study provides a theoretical basis for the structural optimization of crushing equipment, suppression of circulation layer effects, and the realization of low-energy, high-efficiency processing. Full article

Purpose: To evaluate the clinical and histological outcomes of patients that receive implant-supported crowns after vacuum plasma surface treatment (VPST) of biomaterials used in socket preservation (SP) and guided bone regeneration (GBR). Materials and methods: This study was designed as a case series. Patients in need of tooth extraction and socket preservation or guided bone regeneration were enrolled. The socket preservation technique was performed after tooth extraction using a heterologous collagen bone graft and a collagen xenomatrix, both activated with vacuum plasma. Meanwhile, a two-stage horizontal ridge augmentation was performed using a customized titanium mesh and a mix of autologous (untreated) and heterologous (treated) bone grafts, along with a treated collagen membrane. ACTILINK Reborn with Universal Vortex Holder (Plasmapp Co., Ltd., Daejeon, Republic of Korea) was used to treat all biomaterials. The outcome measures were implant and prosthesis failures, complications, and histological examination. Soft and hard tissue samples were collected at the time of implant placement only in patients treated with SP. Results: A total of six patients were treated—three with socket preservation and delayed implant placement, and three with staged GBR. No implant or prosthesis failed. One customized titanium mesh broke after plasma treatment, requiring replacement with a pericardium membrane. No other complications occurred. Histological analysis at three months post-surgery revealed well-vascularized newly formed bone at different stages of maturation with integrated bone graft particles, while the soft tissue appeared to be physiologically structured. Conclusion: VPST may enhance the hydrophilicity of biomaterials, supporting favorable healing outcomes in SP and GBR. Further randomized controlled trials with appropriate sample size calculations are needed to confirm these preliminary results. Full article

Background: Alveolar ridge preservation (ARP) following tooth extraction plays a vital role in maintaining ridge dimensions and supporting subsequent implant therapy. Objectives: This study histologically and radiographically evaluates the efficacy of techBiomat bone^®—a deproteinized bovine bone mineral (DBBM)—for alveolar ridge preservation (ARP), comparing the results of bone formation, residual graft particles, and nonmineralized tissue to those of spontaneous healing in human tooth sockets. Methods: A split-mouth study was conducted to evaluate the radiographic and histologic outcomes in human sockets with and without ARP. Results: A significant improvement in bone fill was observed compared to untreated sockets. Radiographically, 87% of the treated sockets demonstrated more than 75% bone fill, whereas only 7% of the untreated sockets did. Histologically, the percentage of new bone formation was greater in treated sockets (42%) than in untreated sockets (25%). The findings also highlighted a lower proportion of nonmineralized tissue in grafted sites, suggesting improved healing over spontaneous healing. The residual graft material in the treated sockets had a moderate resorption rate, with almost complete replacement by the host bone after six months. The use of techBiomat bone^® demonstrated promising results, with a resorption rate conducive to optimal bone regeneration, with less than 9% residual graft material remaining after six months. Conclusions: This study supports the efficacy of techBiomat bone^® graft material for ARP, highlighting its potential in maintaining ridge volume. Further studies with larger sample sizes are needed to confirm these findings. Full article

The influence of machining parameters on the generation of dust particles during the machining of carbon fiber-reinforced polymer (CFRP) composites remains insufficiently understood. These particles, which stay suspended in the air, pose a serious health risk to operators. This study examined the effects of cutting conditions—specifically cutting speed, feed per tooth, and depth of cut—and the impact of delaminations formed during CFRP drilling on the size, shape, and quantity of hazardous dust particles. Experiments were conducted using a commercially available uncoated cemented carbide cutting tool. The analysis of dust particle size and morphology, as well as the evaluation of delamination, was performed using microscopic and tomographic methods. The results demonstrate that reducing the cutting speed led to a decrease in particle size for the investigated CFRP material. Furthermore, it was observed that tool wear results in the generation of smaller particles. Simultaneous delamination during drilling was found to significantly affect the structural integrity of the composite material. Full article

The interaction law between soil and tillage components is the basis for designing and selecting soil tillage components. This paper uses the discrete element method to explore the soil penetration performance of the comb teeth of a pneumatic film-stripping tillage residual film recycler under different structural and working state parameters. The soil particle contact model is set up, the virtual prototype of the comb roller is established, and EDEM (Version 2018, DEM Solutions Company, Edinburgh, UK) discrete element software is applied to simulate the interaction between the comb roller and the soil particles during the residual film recycler’s operation. Simulation and test results show that using a spiral arrangement of tooth comb knives (Alar, 843300, China, Zhongyuan Stainless Steel Bending Manufacturing Co.) can reduce the impact load on the machine, improving the soil disturbance and facilitating the penetration of soil mulch. The composite force on the combing roller increases with comb depth in the soil for a combing roller depth of 6–18 cm. Moreover, the rotational speed varies within the range of 60–120 r/min. The forward speed of the recycling machine significantly affects the soil penetration performance of the comb roller; the power it consumes increases with forward speed. This study can provide a reference for the structural design and optimization of working parameters of future deep tillage machines. Full article

In the process of herringbone gear grinding, excessive grinding force leads to a large increase in grinding specific energy. A large increase in the specific grinding energy can easily lead to an increase in the transient cutting load. It leads to grinding burn, tooth surface crack and other undesirable phenomena, which ultimately affect the surface quality and service performance of the workpiece. This paper is based on the contact mechanics of workpiece materials. The number of dynamic effective abrasive particles is considered. Combined with the mechanism of grinding force, the model is developed. Based on the consideration of the wear characteristics of the grinding wheel and the structure parameters of the gear itself, the grinding force model was modified. The accuracy of grinding force model is improved by dividing the effective contact angle of grinding grains into four cases. The experimental results show that the normal grinding force error reaches 10.73% and the tangential grinding force error reaches 10.34%. The model reveals the grinding mechanism, optimizes grinding parameters and improves grinding efficiency. It provides a new way for high-precision machining of aerospace precision herringbone gear. Full article

The large toothed double-roll crusher, as key crushing equipment for open pit mines, is very necessary to analyse its crushing performance at different feed particle sizes, compressive strengths of coal, and rotation speeds of toothed rollers. Firstly, a toothed double-roll crusher is taken as the research object in this paper; the coupling simulation model of the toothed double-roll crusher based on the DEM-MBD and Ab-T₁₀ breakage model is constructed. The validity of the coupling simulation model is verified through the actual measurement data. On this basis, the crushing performance under variable factors is analysed by integrating comprehensive tests. The results show that the rotation speed of the toothed roller is the main influence factor on the crushing performance of the toothed double-roll crusher when it works at 25~33.3 r/min. With the increase in compressive strength of coal, the productivity decreases, and this phenomenon disappears gradually at 33.3~42 r/min. Further, a 5–20% increase in the large size of the coal particles can improve 10% crushing quality with a discharge size lower than 300 mm and approximately 25% productivity of the toothed double-roll crusher. Finally, the power density is reduced as the mass percentage of large-sized coal particles increases, and this phenomenon is weakened with the increase in the compressive strength of coal. Full article

Background/Objectives: Pulp stones (PSs) are calcified masses, with rounded or oval shapes, ranging from small particles to masses larger than the chamber and/or canals. There are limited data regarding the prevalence of pulp stones in the Iberian population. Our aim was to determine the prevalence of PSs, using CBCT, in an Iberian population, and its association with gender, age, tooth location (arch and hemiarch), dental group, the presence of caries, restorations, alveolar bone loss, and a history of orthodontic treatment. Methods: In total, 300 CBCTs were analyzed, selected from the database of the Dental Clinic of the University of Valencia. A total of 5485 teeth were included. The images were obtained by NewTom equipment and visualized using NNT software 11 by a single calibrated examiner in the axial, sagittal, and coronal planes. The Chi-square test, ANOVA, and t-test were used to analyze the study variables for a significance level of p < 0.05. Results: The prevalence of PSs was 88.3% from the total number of patients assessed and 61.2% from the total number of teeth assessed. No differences were found by gender or age. A significant association was found within tooth groups between arches and hemiarches. The proportion of PSs was 3.7 times higher in teeth with caries, 4.7 times higher in teeth with fillings, and 2.3 times higher in teeth with alveolar bone loss. Conclusions: PSs were more prevalent in molars. The presence of caries, fillings, and bone loss increased the chance of presenting PSs. Maxillary teeth had a higher prevalence of PSs than mandibular teeth. Full article

Periodontitis is a chronic inflammatory condition of the periodontium, which often leads to tooth loss. Recently, statins have emerged as potent anti-inflammatory agents with pleiotropic effects that can potentially outperform conventional periodontal treatments. However, the clinical application of statins is limited by the lack of suitable drug carriers that fit the periodontal region and provide a controlled local drug release. In this study, we address the critical gap in localized periodontal drug delivery and introduce an ultrasound-assisted technique to encapsulate atorvastatin within alginate microparticles (10–400 µm in diameter)—a simple, scalable, and biocompatible solution. While ultrasound is widely used in polymer synthesis, its application in alginate polymerization remains underexplored. To mimic physiological conditions, particles were incubated in artificial saliva at 37 °C, with drug release being analyzed via high-performance liquid chromatography. A methylcellulose-based hydrogel served as a conventional reference product. Results revealed that alginate particles exhibited at least a 10-fold increase in mean dissolution time compared to the methylcellulose gel, indicating superior stability. Increasing atorvastatin concentration extended the time interval needed for 50% of the drug to be released (t_50%) from 1 h to 11 h, maintaining the overall drug diffusion level for several days. Further analysis showed that covalent cross-linking of alginate with divinyl sulfone significantly delayed the initial drug release by 3 h (p < 0.05) due to the additional molecular stabilization. These findings underscore the utility of ultrasonic atomization for the processing of alginate-based formulations. Given the ease of production, biocompatibility, and small size, successfully fabricated alginate particles represent a promising carrier for delivery of statins or other related drugs in clinical dentistry. Full article

In high-temperature geothermal wells, the formation usually has extremely high abrasiveness, hardness, and temperature, which pose severe challenges to drilling tools. Among them, the interaction between the cutter of the drill bit and the rock is the key factor determining the rock-breaking efficiency of PDC (Polycrystalline Diamond Composite) drill bits. To further explore the rock-breaking mechanism of cutters on granite, this study adopts a combination of experimental and simulation methods to conduct systematic research. The results indicate that the specific crushing work increases and then decreases with rising temperature, reaching a minimum of 0.388 J/mm³ at 200 °C. In the temperature range of 300 °C to 500 °C, the specific crushing work is 15% lower than at room temperature. The specific crushing work during instant cooling is 12–25% lower than that during self-cooling, with instant cooling showing higher rock-breaking efficiency. As the rake angle increases, the specific crushing work initially decreases and then increases. The smallest specific crushing work, 0.383 J/mm³, occurs at a rake angle of 10°, where the number of debris and particle size are maximized. With deeper cutting depths, the specific crushing work gradually decreases, resulting in more debris, larger particle sizes, and higher cutter surface temperatures. These findings clarify the variation laws of rock load, cutting tooth distribution, and rock fragmentation state when the PDC bit breaks rocks. A rake angle of 10° can be used as the selection of cutting tooth inclination angle for PDC bit design, providing a theoretical basis for the design and application of PDC bits in high-temperature geothermal drilling and holding significant guiding importance. Considering that increasing the depth of penetration can cause uneven wear of the cutter, the drilling parameters can be controlled under certain conditions to achieve a penetration depth of 2 mm, thereby improving the rock-breaking efficiency and working life of the PDC bit. Full article

The China Bearing Reducer (CBR) is a single-stage cycloid reducer with a compact structure, primarily used in high-precision fields such as robotic joints and Computer Numerical Control (CNC) machine tool turntables, where strict requirements for transmission accuracy are necessary. Tooth modification and manufacturing errors in the cycloid gear are two important factors affecting the transmission accuracy of CBRs. In this paper, the transmission performance of the CBR is studied using a new tooth modification method that considers manufacturing errors. Firstly, the structure of the CBR is introduced, and a new method known as Variable Isometric Sectional Profile Modification (VISPM) is proposed. Secondly, the Tooth Contact Analysis (TCA) model is constructed using the VISPM method, and a method for reconstructing the tooth profile with cycloid tooth profile error based on B-spline curve fitting is proposed. The TCA is carried out with both VISPM and tooth profile error. The influence of the modification parameters on meshing characteristics, such as contact force, contact stress, contact deformation, and transmission error, is analyzed. Thirdly, the optimization of the modification parameters is conducted using Particle Swarm Optimization (PSO) to determine the optimal VISPM and isometric and offset modification (IOM) parameter values. The results indicate that the VSIPM method is superior to the IOM method in enhancing meshing characteristics. A physical prototype of the CBR25 is manufactured using the optimized VISPM and IOM, and the transmission error is tested on an experimental platform. The test results demonstrate that the ETCA method is corrected for cycloid drive analysis. Full article

Universal shade flowable composites have been introduced to mimic tooth structure with reduced color mismatch and reduced chair time and cost. However, the polymerization shrinkage of resin material may lead to sensitivity and restoration failure. The purpose of this study was to compare the polymerization shrinkage of recently introduced universal shade flowable resin-based composites using both wet and dry density methods. Using two measurement methods, ISO 17304 (wet method) and a gas displacement pycnometry system (dry method), the density of the unpolymerized and the polymerized RBCs were measured, and the polymerization shrinkage was calculated from the density difference. Scanning electron microscopy was used to visualize filler particles. The polymerization shrinkage showed significant differences between many materials. In particular, Bulk Base HARD II Medium Flow showed significantly lower polymerization shrinkage than all the other materials. Shrinkages measured by different methods were significantly different in all cases. The wet method measured a smaller shrinkage than the dry method in most cases, but the shrinkage measured for Gracefil LoFlow was larger with the wet method. Shrinkage between universal shade flowable resin-based composites significantly varied based on both material and measurement method. The polymerization shrinkage of resin-based composites is an important factor in biomimetic clinical dentistry, and work must be conducted to measure it accurately and with more standardization. Full article

Deep caries and severe periodontitis cause bone resorption in periodontal tissue, and severe bone resorption leads to tooth loss. Periodontal ligament stem cells (PDLSCs) are important for the healing of defective periodontal tissue. It is increasingly understood that healing of periodontal tissue is mediated through the secretion of trophic factors, particularly exosomes. This study investigated the effects of exosomes from human PDLSCs (HPDLSCs-Exo) on human osteoblast-like cells in vitro and on the healing of rat calvarial bone defects in vivo. HPDLSCs-Exo were isolated and characterized by their particle shape, size (133 ± 6.4 nm), and expression of surface markers (CD9, CD63, and CD81). In vitro results showed that HPDLSCs-Exo promoted the migration, mineralization, and expression of bone-related genes such as alkaline phosphatase (ALP), bone morphogenetic protein 2 (BMP2), osteocalcin (OCN), and osteopontin (OPN) in human osteoblast-like cells. Furthermore, in vivo results showed that more newly formed bone was observed in the HPDLSCs-Exo-treated group than in the non-treated group at the defect sites in rats. These results indicated that HPDLSCs-Exo could promote osteogenesis in vitro and in vivo, and this suggests that HPDLSCs-Exo may be an attractive treatment tool for bone healing in defective periodontal tissue. Full article

Variable flow emitters are used in subsurface drip irrigation to address challenges in soil moisture transport. This study investigates the impact of flow channel structural parameters on the hydraulic performance and anticlogging ability of emitters using computational fluid dynamics (CFD) simulations and experimental tests. The results show that the realizable k–ε turbulence model can be used to simulate the flow field inside the variable flow emitter flow channel. The nRMSE between the measured (q_m) and simulated (q) values of the flow rate is 11.23%, and the relative error between the measured (x_m) and simulated (x) values of the flow index is 4.66%, which gives a high simulation accuracy. A polar analysis shows that the tooth angle (A) has the smallest effect on the effluent flow rate at 0.1 MPa (q_0.1), x, and particle passage rate (η) of the variable flow emitter. Flow channel depth (D), tooth spacing (B), and tooth height (E) have a different order of precedence in the influence of the three indices, which are D > B > E > A, B > E > D > A and E > B > D > A, respectively. The value of η is positively correlated with the mean flow velocity (v) and the mean turbulent kinetic energy (k) in the flow channel, and η tends to increase and then decrease with the increase of x. The retention time of the particles in the flow channel is closely related to the magnitude of v and k. Three multivariate lin ear regression equations (R² = 0.883–0.995) were constructed for q_0.1, x, and η versus the flow channel structural parameters. The optimal design combination of channel structure parameters for different scenarios was determined using the scipy.optimize.minimize function in Python 3.8.0. The research results provide a reference for the optimal design of variable flow emitters. Full article