Search Results (105)

To address severe PCD tool wear during the milling of high-volume-fraction SiC_p/Al composites, a synergistic milling process coupling pulsed laser pretreatment with ultrasonic vibration was proposed. Five-factor, four-level orthogonal experiments were conducted on 70 vol.% SiC_p/Al composites to investigate the effects of milling speed, feed per tooth, cutting depth, laser power, and ultrasonic amplitude on milling forces and tool wear, and a tool wear prediction model was established. The results showed that the factors influencing tool wear, in descending order, were feed per tooth, cutting depth, milling speed, laser power, and ultrasonic amplitude. Appropriate laser power and ultrasonic amplitude reduced cutting loads and suppressed tool wear. The model achieved a coefficient of determination of 0.7887 and was statistically significant overall. The optimal parameter combination was 50 m/min, 0.02 mm/z, 0.1 mm, 60 W, and 3.5 μm, under which the tool wear loss was 1.0 mg, representing a reduction of 61.54% compared with the maximum-wear condition. The main wear modes of the PCD tool included rake-face grooving and fatigue spalling, flank-face abrasive wear, and cutting-edge micro-chipping. These findings provide a useful reference for the precision milling of SiC_p/Al composites. Full article

Aluminum honeycomb structures are widely used in the aeronautical, aerospace, marine, and automotive industries due to their excellent stiffness-to-weight ratio. However, machining these structures remains highly challenging because their thin, highly flexible cell walls are susceptible to plastic deformation and geometric defects. To overcome these limitations, this study proposes an innovative machining approach that combines longitudinal-torsional ultrasonic vibration-assisted machining (LT-UVAM) with a 55-tooth CZD10 cutting tool. A three-dimensional finite element model was developed using Abaqus/Explicit 2017 to simulate the dynamic interactions between the cutting tool and the honeycomb cell walls during the milling process. Following experimental validation on a high-speed machining center, the model was employed to investigate the effects of cutting and vibration parameters on the machining performance. The results demonstrate that longitudinal-torsional ultrasonic vibration coupling significantly reduces the cutting forces, resulting in a 26% to 42% reduction in the axial force component (Fz). Furthermore, vibration assistance effectively limits cell wall deflection, reducing the stress levels by up to 60% in the thinnest walls while maintaining them below the critical Euler buckling load. Furthermore, an ultrasonic vibration frequency of 22.5 kHz almost completely eliminates plastic deformation, while a vibration amplitude of 25 µm significantly reduces tool wear by promoting intermittent tool–workpiece contact, thereby facilitating chip evacuation. Ultimately, the LT-UVAM process produces finer and more uniform chips, leading to improved machining quality, enhanced dimensional accuracy, and extended tool life. Full article

Anxiety disorders and chronic stress are the most common types of mental disorder. According to the WHO, more than 359 million people worldwide suffered from these conditions in 2021. The function of mastication and the masticatory muscles undergo significant changes under the influence of a disturbed psychoemotional state. This manifests as their parafunctional activity, accompanied by increased tone and damage to elements of the dentofacial system, including increased tooth wear, chipping, cracks, and fractures. Attention to this problem is growing annually among researchers in both dental and neurological fields. This is evidenced by a wide range of therapeutic and preventive interventions aimed at correcting chronic stress, muscle hypertonia, and pathology of the dentofacial system. Despite the aforementioned measures, it is often only possible to slow down the pathological process rather than completely resolve it. This is because knowledge regarding the biology and pathophysiology of how chronic stress affects muscle activity remains limited. Understanding such mechanisms and establishing precise interrelationships could help identify targets for effective therapeutic interventions and eliminate the problem. This review of the literature systematizes information on how chronic stress and various autonomic stimuli affect changes in the functional activity of the masticatory muscles and the pathology of hard dental tissues. Full article

Large overhang milling cutters face challenges, including poor cutting stability and surface quality when machining deep-cavity parts in aerospace and other industries. The combined interactions between overhang and process parameters significantly influence machining performance and the tool wear mechanism. In this study, the coupled effects of tool overhang length and feed per tooth on milling force, surface topography, chip morphology, and tool wear mechanism were systematically investigated under typical large overhang conditions. The tool stiffness decreased with increasing overhangs; the feed force decreased by approximately 32.4%~49.48%; and the chip morphology changed from continuous bands to fractures. The feed force increased by approximately 25.11%~67.34% with increasing the feed per tooth, resulting in reduced surface quality and accelerated tool wear. The novelty of this work lies in quantitatively revealing the coupling mechanism between overhang length and feed rate in large overhang milling, providing a theoretical basis for process optimization. The findings are directly applicable to the optimization of machining parameters for deep-cavity components such as aero-engine casings and optical mold cavities, where tool overhang is a critical factor affecting productivity and surface integrity. This study provides a theoretical foundation and experimental reference for optimizing process parameters when milling titanium alloy with long-overhang milling cutters. Full article

Cermet tools possess favorable mechanical and tribological properties and are widely adopted for machining hard-to-cut materials. However, their performance can further be enhanced with different cooling and lubrication techniques. In this study, the tool wear mechanisms of cermet tools during hard turning of AISI 4340 alloy steel are investigated under dry and minimum quantity lubrication (MQL) environments to identify the prevalent causes of tool failure through comprehensive analysis of tool wear progression, chip temperature, and chip morphological analysis. The results revealed that the application of MQL exhibited prolonged and stable steady-state tool wear progression with retained cutting-edge geometry, thus demonstrated 30.27% improvement in tool life compared to dry cutting. On the contrary, a rapid increase in tool wear due to excessive friction and higher thermal load is noticed with dry cutting in the absence of any heat-dissipating medium. Chip temperature measurements supported these observations, as chip temperature increases sharply from 358 °C (with a fresh tool) to about 1090 °C (with a worn tool) under a dry environment. Conversely, with MQL, the corresponding increase was in the range between 294 °C and 843 °C with a fresh and worn tool, respectively. Chip analysis revealed a serrated type of chip morphology. Dry cutting exhibited intensified feed marks, indicative of severe tool–chip friction, whereas MQL demonstrated smoother morphology with closely spaced saw-tooth patterns. Tool wear mechanisms indicate abrasion, adhesion, and edge chipping as dominant wear mechanisms under both environments; however, in the absence of any lubricant, these mechanisms were more intensified with higher crater formation. Full article

This study examines how variations in cutting parameters and end mill rake-angle affect chip-temperature in the cutting zone. This study describes a method involving end mills with varying rake angles to measure the temperature of chips in the cutting zone during the dry rough milling of magnesium alloys. The chip temperature is determined by infrared spectroscopy. The influence of milling parameters (i.e., cutting speed, feed per tooth, and depth-of-cut) on the maximum chip temperature was analyzed. Box plots, bar charts, and 2D graphs are used to display the chip temperatures. We address issues that come up while recording a signal with an average emissivity coefficient value and how to resolve them. The tests yielded chip temperatures that were not higher than 366 °C. Thus, for a variety of machining parameters, the dry roughing milling procedure using carbide tools with different rake angles can be deemed safe. The proposed approach to detecting the chip temperature and processing findings constitutes a novel and efficient way for evaluating safety in the dry milling of magnesium alloys. Full article

Due to the unique microstructure and mechanical heterogeneity of austenitic stainless steel made via wire arc additive manufacturing (WAAM), its machinability differs significantly from that of rolled material. Accordingly, this study systematically investigates the influence of milling strategies on key process responses (cutting forces, surface roughness, vibration displacement, and temperature) to reveal the mechanisms of machining parameters during the milling of WAAM-fabricated austenitic stainless steel. The material used in this study is ER321 austenitic stainless steel. During deposition, the fusion zone cools more slowly than the transition zone; consequently, the fusion zone exhibits a hardness approximately 20 HV_0.1 lower than that of the transition zone. Surface roughness is primarily reduced by decreasing the primary feed per tooth. However, when the primary feed per tooth is small, ploughing is induced, which not only increases surface roughness by 25% but also causes abnormal increases in temperature and vibration displacement. Nevertheless, ploughing has little effect on the total milling force, and the feed per tooth shows a positive correlation with the total milling force. Tool run-out and an increase in the uncut chip thickness lead to a positive correlation between the radial depth of cut and the key process responses. Moreover, ploughing also occurs when the radial depth of cut is small. The axial depth of cut has almost no effect on the machining process. Moreover, a small-diameter mill leads to severe ploughing, and at a high table feed, climb milling leads to cutter offset. Full article

Background. Implant dentistry is an important treatment option for patients requiring prosthetic rehabilitation after tooth loss. This study reports the evaluation of immediately loaded, immediately placed implants in fresh extraction sockets. Methods. Fifty-two partially edentulous patients (27 females and 25 males with mean age of 53.6 years), were treated with 112 Galimplant^® implants placed immediately into fresh sockets for prosthodontic rehabilitation. All implants were loaded immediately. Clinical and radiographic parameters related to both the implants and the prosthodontic restorations were followed for 10 years. Results. Nine patients (17.3%) had a history of periodontitis, 26.9% were smokers, and 21.1% presented with chronic systemic conditions. The outcomes demonstrated an implant survival and success rate of 97.1%, indicating that immediately placed implants with immediate loading can achieve and maintain successful osseointegration. Three implants were lost during the healing period. The mean marginal bone loss was 1.09 ± 0.75 mm. Mucositis affected 21.4% of implants, and peri-implantitis was observed in 11.6% of implants. Fourteen implants (7.1%) were associated with technical complications, including screw loosening and ceramic chipping. Conclusions. The clinical findings of this study indicate favorable long-term outcomes for immediately loaded implants placed in fresh extraction sockets. Both implants and prosthetic restorations demonstrated a success rate of over 92.9% during the observation period. Full article

Background and Clinical Significance: Advanced periodontitis with severe vertical bone loss and grade III mobility is usually managed by extraction and implant placement. Digital workflows and modern regenerative techniques have opened the possibility of preserving teeth that would traditionally be considered for extraction. This report describes a digitally guided modified intentional replantation (MIR) protocol applied to a maxillary tooth with severe periodontal involvement and unfavourable prognosis. Case Presentation: A 68-year-old male, non-smoker, with a history of heart transplantation under stable medical control, presented with generalized Stage IV, Grade C periodontitis. Tooth 21 showed >75% vertical bone loss, probing depths ≥ 9 mm, bleeding on probing, and grade III mobility. After non-surgical therapy and periodontal stabilization, a CAD/CAM-assisted MIR procedure was planned. Cone-beam computed tomography (CBCT) and a 3D-printed tooth replica were used to design a surgical guide for a new recipient socket. The tooth was atraumatically extracted, stored in chilled sterile saline, and managed extraorally for approximately 10 min. Apicoectomy and retrograde sealing with Biodentine^® were performed, followed by immediate replantation into the digitally prepared socket, semi-rigid splinting, and guided tissue regeneration using autologous bone chips, xenograft (Bio-Oss^®), enamel matrix derivative (Emdogain^®), and a collagen membrane (Bio-Gide^®). A conventional orthograde root canal treatment was completed within the first month. At 12 months, tooth 21 exhibited grade 0 mobility, probing depths of 3–4 mm without bleeding on probing, and stable soft tissues. Standardized periapical radiographs and CBCT showed radiographic bone fill within the previous defect and a continuous periodontal ligament-like space, with no signs of ankylosis or root resorption. The tooth was fully functional and asymptomatic. Conclusions: In this medically complex patient, digitally guided MIR allowed preservation of a tooth with severe periodontal involvement and poor prognosis, achieving favourable short-term clinical and radiographic outcomes. While long-term data and larger series are needed, MIR may be considered a tooth-preserving option in carefully selected cases as an alternative to immediate extraction and implant placement. Full article

The study investigated the material removal process during precision milling of AZ91D magnesium alloy. A high-speed camera enabling high-frequency image recording was used to observe the cutting zone. In effect, it was possible to observe the mechanism of the chip formation process at different stages of the cutting flutes performance. Experiments were conducted with different feeds per tooth in order to detect the occurrence of ploughing. Results showed that the both cutting flutes of the end mill did not perform in a uniform manner. Material was predominantly removed by first flute, as a result of which chips formed by this flute were much larger than those generated by the other flute. Nevertheless, the shearing process proceeded effectively even at low feed values. Results also showed that large burrs were formed when machining was conducted with low feed per tooth, which confirmed a significant contribution of plastic deformation to burrs formation. An increase in feed per tooth, however, made it possible to minimize the phenomenon of burrs formation. Full article

The dental pulp is a dynamic connective tissue essential for tooth vitality, sensory function, immune defense, and reparative dentinogenesis. Conventional endodontic procedures, while effective in eradicating infection, often result in a non-functional, devitalized tooth, highlighting the need for biologically based regenerative approaches. The emergence of three-dimensional (3D) culture systems has transformed pulp biology and endodontic research by providing physiologically relevant microenvironments that better reproduce the dentino-pulp interface, vascular and neural networks, and immune interactions. This review synthesizes current advances in 3D dental pulp modeling, from scaffold-based and hydrogel systems to spheroids, organoids, bioprinted constructs, and microfluidic “tooth-on-a-chip” platforms. Each system’s composition, biological relevance, and translational potential are critically examined with respect to odontogenic differentiation, angiogenesis, neurogenesis, and inflammatory response. Applications in disease modeling, biomaterial screening, and regenerative endodontics are highlighted, showing how these models bridge fundamental biology and therapeutic innovation. Finally, we discuss key challenges including vascularization, innervation, standardization, and clinical translation, and propose integrative strategies combining bioprinting, stem-cell engineering, and organ-on-chip technologies to achieve functional pulp regeneration. Overall, 3D pulp models represent a paradigm shift from reductionist cultures to bioinstructive, patient-relevant platforms that accelerate the development of next-generation endodontic therapies. Full article

Objectives: This study aimed to compare the 5-year cumulative survival rates and clinical outcomes of zirconia and lithium disilicate restorations in both tooth- and implant-supported prostheses, focusing on survival, technical and biological complications, as well as patient-reported satisfaction. Materials and Methods: A retrospective cohort of 200 patients treated with either zirconia (n = 100) or lithium disilicate (n = 100) fixed restorations between 2020 and 2024 was analyzed. Only cases with a minimum follow-up of 5 years were included. Clinical parameters (fracture, chipping, retention loss, secondary caries, peri-implant complications), radiographic outcomes (marginal bone loss, periapical stability), and patient satisfaction (VAS scores for esthetics and function) were evaluated. Kaplan–Meier survival analysis and subgroup analyses (anterior/posterior, tooth-/implant-supported) were performed. Results: At 5 years, the cumulative survival rate was 94.0% for zirconia and 89.0% for lithium disilicate (p = 0.210). Technical complications were lower with zirconia (14.0% vs. 21.0%, p = 0.182), including fewer fractures (6.0% vs. 12.0%, p = 0.126). Chipping (5.0% vs. 7.0%) and debonding (3.0% vs. 2.0%) showed no significant differences. Biological outcomes were comparable: secondary caries (7.0% vs. 11.0%, p = 0.332), endodontic issues (4.0% vs. 6.0%, p = 0.516), peri-implant mucositis (9.0% vs. 12.0%, p = 0.495) and peri-implantitis (3.0% vs. 5.0%, p = 0.470). Radiographically, periapical stability was preserved in most cases (93.0% vs. 89.0%, p = 0.317), and the mean marginal bone loss was slightly lower with zirconia (0.46 ± 0.25 mm vs. 0.53 ± 0.30 mm, p = 0.148). Patient-reported outcomes were favorable in both groups, with esthetic VAS scores of 8.6 vs. 8.2 (p = 0.072) and functional scores of 8.4 vs. 8.0 (p = 0.085). Zirconia was rated higher in posterior/implant-supported cases, while lithium disilicate was preferred in anterior restorations. Conclusions: Both zirconia and lithium disilicate restorations demonstrated favorable long-term outcomes, with zirconia trending toward superior mechanical reliability in posterior and implant-supported restorations, and lithium disilicate excelling in esthetic performance, particularly in anterior regions. Material selection should be guided by clinical indication, occlusal load distribution, and esthetic requirements. Full article

The current study focuses on axial ultrasonic vibration-assisted micro-milling as an advanced technique to improve the machining performance of Ti6Al4V, a material whose difficult-to-cut properties present a significant barrier to manufacturing the high-quality micro-components essential for aerospace and biomedical applications. A full factorial design was employed to evaluate the influence of feed-per-tooth (f_z), axial depth-of-cut (a_p), and ultrasonic vibration on cutting forces, surface roughness, burr formation, and tool wear. Experimental results demonstrate that ultrasonic assistance significantly reduces cutting forces by 20.09% and tool wear by promoting periodic tool–workpiece separation and improving chip evacuation. However, it increases surface roughness due to the formation of uniform micro-dimples, which may enhance tribological properties. Burr dimensions were primarily governed by feed-per-tooth, with higher feeds minimizing burr size. The study provides actionable insights into optimizing machining parameters for cutting Ti6Al4V, highlighting the trade-offs between force reduction, surface texture, and burr control. These findings contribute to advancing ultrasonic-assisted micro-milling for industrial applications, namely aerospace and biomedical applications requiring high precision and extended tool life. Full article

Inconel 718 is a Ni-based superalloy with excellent corrosion resistance, heat resistance, high-temperature strength and high creep resistance. It is also known to be a difficult-to-machine material. Conventional machining methods have not only low machining efficiency, but also high cost and low versatility using CBN and ceramic tools, so cost reduction and highly efficient machining by substituting relatively inexpensive cemented carbide tools are required. Some results on the tool life in milling for intermittent cutting for Inconel 718 superalloy have been reported, and the tool life has been considered a problem. Therefore, there is a need to clarify the basic characteristics of milling, such as tool wear and adhesion conditions, and to identify long tool life and highly efficient cutting conditions in order to achieve highly efficient milling of Inconel 718 superalloy. In this study, the milling of Inconel 718 superalloy was conducted using an end mill with a constant depth of cut, and milling efficiency was defined as the table feed rate of the milling machine in mm/min. The tool wear, welding condition, and surface roughness of the workpiece were evaluated according to the combination of cutting speed and feed rate per edge, with a milling efficiency of 800 mm/min. The experimental results showed that with the combination of a cutting speed of 10.33 m/min and feed rate of 0.4 mm/tooth, and the combination of 20.65 m/min and 0.4 mm/tooth, when there was a lower cutting speed and higher feed rate per edge, less weld detachment occurred, less progression of flank wear, and less chipping occurred, and the tool edge was more stable. It was also confirmed that, by keeping the cutting speed constant and increasing the feed rate per edge, both long tool life and highly efficient milling were possible under the above conditions. Full article

Background and Objectives: Periodontitis is a common chronic inflammatory disease and a leading cause of tooth loss worldwide. Traditional diagnostic methods, such as probing and radiographic assessment, are retrospective and fail to detect ongoing disease activity. In recent years, salivary biomarkers and oral microbiome profiling have emerged as promising tools for earlier detection and precision-based management. The aim of this review is to synthesize current evidence on salivary and microbiome-derived biomarkers in periodontitis and to evaluate their translational potential in diagnostics and therapy. Materials and Methods: A narrative review was performed using PubMed, Scopus, and Web of Science to identify studies published between 2020 and 2025. Search terms included periodontitis, salivary biomarkers, oral microbiome, dysbiosis, and precision therapy. Priority was given to systematic reviews, meta-analyses, and translational studies that addressed diagnostic or therapeutic applications. Eligible publications included English-language original studies and reviews reporting on the diagnostic or therapeutic relevance of salivary or microbiome biomarkers in periodontitis. Results: Salivary biomarkers such as cytokines, matrix metalloproteinases (MMPs), oxidative stress markers, microRNAs, and extracellular vesicles (EVs) show consistent associations with disease activity and treatment outcomes. Oral microbiome studies reveal that both classical pathogens and community-level dysbiosis contribute to disease risk. Translational advances include chairside immunoassays, biosensors, lab-on-a-chip devices, and artificial intelligence (AI)-driven analyses. Biomarker-guided therapies—such as microbiome modulation, natural bioactive compounds, host-response modulation, and smart biomaterials—are being evaluated with increasing frequency in translational studies. Conclusions: By integrating salivary and microbiome biomarkers with novel diagnostic technologies and emerging therapies, this review complements existing systematic evidence and offers a translational roadmap toward precision periodontology. Full article