Search Results (566)

Stress shielding (SS) after cementless total hip arthroplasty arises from the stiffness mismatch between conventional Ti-6Al-4V femoral stems (110 GPa) and cortical bone (10–30 GPa). The β-type Ti-33.6Nb-4Sn (TNS) alloy femoral stem addresses this limitation through a continuous Young’s modulus gradient (~70 GPa proximally to ~40 GPa distally) achieved by localized heat treatment of a single homogeneous alloy. This review synthesizes a translational research program encompassing material characterization, finite element modeling (FEM), preclinical animal studies, and prospective clinical follow-up of up to seven years. FEM demonstrated favorable proximal micromotion well below the osseointegration threshold, with physiological proximal stress concentration concordant with clinical outcomes. At seven years, SS grade distribution was significantly lower in the TNS group than in Ti-6Al-4V controls, with SS frequency reduced in Gruen Zones 2, 3, and 6, and no stem-related failures; however, third-degree SS was still observed in 11 of 34 evaluable cases (32%), indicating that modulus-gradient optimization alone is insufficient to fully prevent SS. TNS alloy is currently the only β-type titanium alloy clinically applied in joint prostheses. Remaining challenges include stem geometry optimization, additive manufacturing-based porous structures, and dual-energy X-ray absorptiometry-based bone density quantification. Future directions encompass long-term follow-up, cyclic fatigue FEM simulations, and expansion to fracture fixation devices and dental implants. Full article

The long-term stability of dental implants is limited by multiple factors, including peri-implant infection, impaired osseointegration, and poor soft tissue sealing. Compared with conventional passive surface modification strategies, piezoelectric materials can convert mechanical energy into local electrical signals under occlusal loading, cell traction, or ultrasonic stimulation. With the aid of defect engineering, heterostructure construction, and co-catalytic design, these materials can also induce the generation of reactive oxygen species and reactive nitrogen species, thereby enabling on-demand antibacterial activity. This review systematically summarizes the bioelectric basis of bone tissue and clarifies how piezoelectricity and piezocatalysis may be used in dental implant surface engineering. Their applications are discussed in terms of antibiofilm and antibacterial activity, osteogenesis and osseointegration, osteoimmunomodulation, soft tissue healing, and temporally programmed therapy. In addition, this review also discusses issues that remain unresolved, such as polymer-based composite systems, realistic activation windows, evaluation standards, device–material integration, and multi-omics validation. Overall, piezoelectric surface engineering is evolving from a single osteogenesis-oriented strategy into an integrated platform that coordinates infection control, immune remodeling, and osseointegration. However, the actual effectiveness of its clinical application still needs to be determined through more rigorous mechanism analysis, long-term stability assessment, biosafety assessment, and standardized preclinical research. Full article

The aim of this study was to evaluate the influence of artificial saliva ageing and cyclic hydrothermal loading on the mechanical properties of dental composite materials. Two commercial composites (Filtek Z550 and Filtek Ultimate Flow) and two experimental materials representing flow-type and hybrid composites were investigated. SENB specimens were prepared in accordance with ASTM E399, together with flat specimens intended for impact strength testing using the Dynstat method. All samples were aged in artificial saliva for approximately one month at 37 ± 1 °C, and subsequently, half of the specimens were subjected to thermocycling in the temperature range of 10–65 °C for 10,000 cycles. Static mechanical tests, including three-point bending (TFS), biaxial flexural strength (BFS), and compression strength (CS), were performed before and after thermocycling. In addition, impact strength and fracture toughness expressed by the stress intensity factor K_IC were determined. The results were analyzed in terms of the residual work of fracture (WOF), while the durability of the materials was evaluated using Weibull distribution parameters. The experimental analysis was complemented by SEM observations of the microstructure. The obtained results demonstrated a pronounced deterioration of mechanical properties after hydrothermal loading. The average impact strength after artificial saliva ageing reached 11.69 J/mm² for Filtek Z550, 11.57 J/mm² for Ex-hyb(P), 16.39 J/mm² for Filtek Ultimate Flow, and 10.27 J/mm² for Ex-flow(P), whereas after thermocycling, these values decreased to 5.38 J/mm², 8.86 J/mm², 4.55 J/mm², and 4.39 J/mm², respectively. A similar trend was observed for the fracture toughness parameter KIC, which decreased considerably after thermocycling for all investigated materials. The analysis of the residual work of fracture revealed the influence of thermocycling on the energy-related parameters of the composites. In the case of TFS, the average WOF decreased, among others, from 13.65·10⁻³ J to 1.90·10⁻³ J for Filtek Ultimate Flow and from 4.76·10⁻³ J to 2.37·10⁻³ J for Filtek Z550. For BFS, a noticeable decrease in WOF was also observed, particularly for Ex-flow(P) and Filtek Ultimate Flow. In the compression tests (CS), the changes were less unambiguous, and some materials exhibited an increase in WOF after thermocycling. Furthermore, changes in the scale and shape parameters of the Weibull distribution were identified, indicating degradation of composite durability under hydrothermal loading. The results confirmed that cyclic hydrothermal loading exerts a greater influence on impact strength and fracture toughness than on static flexural strength. While all investigated materials exhibited degradation, the extent of changes was material-dependent, and compression behaviour showed non-uniform responses. Weibull analysis confirmed reduced reliability and increased heterogeneity of the composites after ageing, indicating that hydrothermal fatigue is a dominant factor governing long-term mechanical deterioration of dental resin-based composites. Full article

This study focuses on streamlining the manufacturing process for milling dental prosthetic components from biopolymer materials in order to achieve the best possible surface roughness. Various combinations of cutting parameters were systematically tested in experiments, and their impact on the final surface roughness of the material was analyzed. The study provides a comprehensive view of how variations in cutting speed, feed per tooth and cutting depth affect the final surface quality. The results show that the appropriate configuration of cutting parameters can significantly improve surface roughness, reducing the need for additional finishing and increasing production efficiency. The findings provide valuable information for the manufacture of polymer-based dental prosthetic components, support process optimization, and contribute to the development of accurate and reproducible computer-aided design and computer-aided manufacturing (CAD/CAM) manufacturing procedures. A full factorial design of experiments (DoE) approach was applied to evaluate the influence of cutting speed, feed per tooth, and cutting depth on the resulting surface roughness. The results confirmed that feed per tooth represented the most influential machining parameter affecting the resulting Ra values. The optimized cutting conditions resulted in the lowest surface roughness and improved process stability compared to manufacturer-recommended machining conditions. Full article

Additive manufacturing using vat photopolymerization (VPP) resin materials has gained attention for fabricating dental prostheses; however, the effects of material type and build angle on their properties remain unclear. We compared the mechanical properties of two filler-containing VPP hybrid resins, SprintRay Ceramic Crown (CC) and OnX Tough 2 (OT), with those of a conventional polymethyl methacrylate (PMMA) disc material, and evaluated the influence of build angle on surface characteristics, dimensional accuracy, and mechanical performance. Specimens were fabricated using a DLP system at build angles of 0°, 45°, and 90°. Vickers hardness, surface morphology and roughness, dimensional deviations, flexural strength, elastic modulus, and fracture energy were assessed according to relevant standards. CC exhibited significantly higher hardness and elastic modulus than PMMA and OT, whereas OT showed the highest fracture energy. Surface morphology and roughness were strongly affected by build angle, with 45° producing distinct periodic patterns and increased roughness. Dimensional evaluation revealed a tendency toward overbuilding, particularly in the vertical direction at 45°. Flexural properties were also influenced by build angle, with 45° generally providing favorable performance. Both material composition and build angle affect VPP-fabricated dental resin performance, highlighting the importance of appropriate material and processing selection for clinical applications. Full article

This study evaluated and compared the mechanical performance of conventionally milled zirconia and two additively manufactured zirconia ceramics fabricated using Lithography-based Ceramic Manufacturing (LCM) technology for potential use in load-bearing dental restorations. A total of 150 zirconia specimens were prepared and allocated into three material groups: milled zirconia and LCM-printed zirconia (LithaCon 3Y 210 and LithaCon 3Y 230), each subdivided into non-aged (control, C) and thermocycled aged (A) conditions (n = 25 per condition). Specimens were standardized using CAD and fabricated by milling or LCM printing. Flexural strength was assessed using a three-point bending test in accordance with ISO 6872:2024, nanoindentation hardness was measured with a Berkovich indenter following ISO 14577-1:2015, and surface roughness was evaluated using optical profilometry per ISO 21920-2:2021. Flexural strength showed no significant differences among groups, while hardness and surface roughness varied significantly. LCM zirconia demonstrated comparable flexural strength to milled zirconia, although milled materials exhibited higher hardness. The 210A group showed the most favorable overall mechanical profile, warranting further investigation of long-term performance. Full article

In this study, the structural, thermal, and mechanical properties of nanocomposites obtained by adding zinc oxide (ZnO) nanoparticles (NPs), produced by phyto-mediated synthesis using Dianthus chinensis plant extract, to a PMMA-based photopolymer resin at different ratios (0.05%, 0.10%, 0.15%, 0.20%, and 0.25%, by weight) were evaluated. The prepared composite resins were produced in different test geometries using a DLP (digital light processing)-based 3D printer (Asiga Ultra). Following the structural characterization of ZnO nanoparticles, tensile, compressive, and flexural mechanical tests were performed on the resulting composites, as well as FTIR, TGA, DSC, and DMA analyses. The FTIR results showed that ZnO NPs were physically integrated into the matrix. TGA and DSC analyses revealed that the addition of ZnO NPs, particularly at an addition rate of 0.15%, increased thermal stability. DMA analyses showed an increase in storage modulus and glass transition temperature as the addition rate increased. In mechanical tests, the highest modulus of elasticity and maximum strength values were obtained at additive ratios of 0.10–0.15%. The highest tensile strength (55.31 MPa) and compressive strength (388.53 MPa) were obtained at ZnO contents of 0.10–0.15 wt%, while the maximum flexural strength reached 125.94 MPa at 0.15 wt% ZnO. In addition, the storage modulus increased from 1.469 × 10⁹ Pa for the control resin to 1.872 × 10⁹ Pa for the composite containing 0.15 wt% ZnO, indicating improved stiffness and thermomechanical stability. The stress–strain curves show that improvements in ductility and deformation capacity of the material are achieved at these additive ratios. The findings demonstrate that green-synthesized ZnO nanoparticles are an effective and sustainable additive material for improving the mechanical and thermal performance of DLP-based photopolymer dental resins. Full article

Background: Biofilm formation and associated tooth demineralization are key factors influencing the clinical performance of dental materials. Methods: This study compared the antibiofilm and demineralization preventive effects of two zinc-modified glass ionomer cements (Zn-GICs) with a conventional GIC. Disk-shaped specimens of Caredyne Restore (CR), ChemFil Rock (CFR), and Ketac Molar (KM) (n = 6) were evaluated in a multi-species biofilm model using an oral biofilm reactor. Early biofilm formation was analyzed by scanning electron microscopy (after 2 h and 4 h), bacterial accumulation and water-insoluble glucan (WIG) production were quantified (after 12 h). For demineralization assessment, restored human enamel and dentin specimens (n = 6) including an additional resin-based control group (Dura Seal, DS) were subjected to a 14-day biofilm challenge and lesion depth was measured using swept-source optical coherence tomography and confocal microscopy. Results: CR showed significantly lower bacterial accumulation and WIG production than the other materials (p < 0.05). CFR demonstrated lower bacterial levels than KM (p < 0.05), whereas no significant differences were observed between CFR and KM in WIG production (p > 0.05). CR produced the shallowest enamel and dentin lesions, whereas DS exhibited the deepest (p < 0.05); however, no statistically significant differences were observed between CFR and KM in lesion depth (p > 0.05). Conclusions: CR demonstrated superior biofilm suppression and reduced demineralization, whereas CFR showed limited differences compared with the conventional GIC. Full article

Understanding the differences between synthetic and natural hydroxyapatite under conditions that mimic the oral environment, particularly the demineralization and remineralization processes of dental enamel, is essential for assessing their suitability as enamel models in biomineralization studies. The present study aims to systematically compare the structural, chemical, and morphological properties of well-crystallized synthetic carbonated hydroxyapatite (CHA) and natural non-biogenic hydroxyapatite (HA) before and after exposure to solutions with demineralizing and remineralizing activity. Two highly informative surface characterization techniques—X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM)—were employed to examine the resulting surface changes. In addition, powder X-ray diffraction and infrared analyses were used to characterize the initial samples. Demineralization was induced using a lactic acid-based solution, while remineralization was performed through a two-step treatment involving polycarboxybetaine followed by artificial saliva. The results show that natural HA contains an additional fluorapatite phase and a wider range of trace elements (Na, F, Si), leading to a more complex structure. During demineralization, synthetic CHA exhibits more pronounced surface changes and faster dissolution, whereas natural HA demonstrates greater chemical stability. The remineralization process leads to the formation of new surface layers on both materials. Synthetic CHA develops a fine-grained, homogeneous layer enriched in carbonate and hydrated species, while natural HA shows localized crystal growth within structural defects. The results demonstrate that natural HA exhibits greater chemical stability during demineralization and a more enamel-like response during remineralization, whereas synthetic CHA undergoes more pronounced surface restructuring and forms a highly hydrated, carbonate-rich surface layer. Full article

Background/Objectives: Delivering consistent preclinical instruction for implant attachment procedures can be challenging in large dental cohorts. This report describes the development and implementation of institutionally produced training tools designed to support Locator housing pick-up exercises for second-year predoctoral dental students. Methods: Modified typodont-based simulation tools were integrated into the preclinical curriculum. Clear dentures and gypsum models were fabricated to allow visualization of seating relationships and identification of common interferences. Complete seating of the denture was verified using inspection windows, flange evaluation, and polyvinylsiloxane disclosing materials before housings were incorporated with autopolymerizing acrylic resin. After each session, components were collected, inspected, and prepared for reuse in subsequent cycles. Learner perceptions were obtained through an anonymous voluntary survey. Results: The configuration enabled visualization of seating conditions and identification of misalignment during the exercise. Removal of anterior teeth reduced material use and emphasized posterior stabilization during the pick-up procedure. Of 83 learners, 28 completed the survey (34% response rate), with responses tending toward agreement across items (mean range: 4.5–4.9/5), indicating favorable learner perceptions of the exercise and its organization within the scheduled laboratory period. Across three academic cycles, six dentures required replacement, whereas all gypsum models remained serviceable and no additional fabrication was necessary. Conclusions: This structured simulation approach provided an alternative method for delivering Locator housing pick-up training in a high-volume preclinical environment. The model allowed repeated implementation of the exercise across academic cycles. Full article

Background: This in vitro study evaluated the effect of hydroxyapatite nanoparticle (nano-HAp) incorporation on surface roughness and Vickers hardness of a 3D-printed crown resin after thermocycling. Methods: Disk-shaped specimens (N = 84) were modified and fabricated with 0%, 1%, 2%, and 3% nano-HAp. Surface roughness (Ra) and Vickers hardness (VHN) were measured before and after thermocycling (5000 cycles). Surface morphology was qualitatively assessed using FE-SEM. Data were analyzed using two-way mixed-design ANOVA (α = 0.05). Results: Thermocycling increased surface roughness and reduced hardness in all groups. Ra values were highest in the 3% nano-HAp group after thermocycling (1.16 ± 0.47 µm). Baseline Vickers hardness differed significantly among nano-HAp concentrations, and hardness decreased after thermocycling in all groups; however, the 3% nano-HAp group exhibited the highest post-thermocycling hardness values (24.66 ± 1.51 VHN), which should be interpreted in the context of its higher baseline hardness. FE-SEM observations suggested increased surface irregularities with higher nano-HAp concentrations after thermocycling. Conclusions: Nano-HAp incorporation influenced both surface and mechanical properties, with 3% concentration showing higher hardness after aging but increased roughness. Full article

Background and Objectives: This study aimed to identify osseous and dental mandibular landmarks that consistently indicate the location of the mental foramen, the primary reference for the mental–incisive trunk block. Materials and Methods: Computed Tomography (CT) scans of the mandibles of 100 patients from a Romanian population (N = 100) were retrospectively analyzed to measure the following: distances from the mental foramen to the basal border of the mandible, alveolar process/crest, and midline, as well as the position of the foramen relative to the lower premolars. These measurements were correlated with patients’ age (divided into three groups: 18–30 years, 30–60 years, >60 years) and gender. Results: The mental foramen was found to be closer to the alveolar crest (13.3 mm with SD = 3.3 in males and 10.7 mm with SD = 4.4 in females, overall mean = 12.3 mm, SD = 4.0) (p = 0.001) than to the inferior border of the mandible (14.3 mm with SD = 1.8 in males and 12.9 mm with SD = 1.6 in females, overall mean = 13.7 mm, SD = 1.9) (p < 0.001). In addition, the foramen was most frequently located adjacent to the second premolar (27.0%) rather than between the premolars (20.0%) and at a distance of ≃2.5 cm lateral to the midline (overall mean = 25.2 mm, SD = 3.5) (p = 0.034). Conclusions: Following the measurements performed, the mental foramen was identified as being closer to the alveolar crest in the vertical direction, at a distance of approximately 2.5 cm lateral to the midline, and most frequently located at the level of the second lower premolar. Full article

This research presents an artificial intelligence (AI)-driven 3D scanning and printing system for the fabrication of personalized dental prosthetics, implants, and orthodontic appliances. The proposed system integrates high-resolution intraoral scanning, AI-based data analysis, and additive manufacturing to enhance precision, customization, and treatment efficiency. Patient-specific anatomical data and medical history are incorporated to optimize implant design, material selection, and functional performance. Nano-enhanced biocompatible materials are utilized to improve mechanical strength, durability, and antibacterial properties. Specifically, these materials demonstrate a 30% increase in overall precision and a 50% improvement in durability compared to traditional dental materials. In addition, the system adopts a zero-waste manufacturing strategy by recycling excess materials, supporting sustainable dental practices. The results demonstrate significant improvements in accuracy, patient comfort, and environmental responsibility in modern digital dentistry. Full article

Objective: This narrative review synthesizes current evidence on materials and manufacturing technologies for customized dental implants, highlighting their comparative advantages and limitations. Methods: A structured literature search (December 2024–January 2025) was conducted using PubMed, Web of Science, Scopus, and Google Scholar. Peer-reviewed English-language articles (mainly 2015–2025) addressing implant materials, manufacturing methods, and surface modifications were included. Data were critically analyzed and thematically organized without meta-analysis. Results: Digital workflows are advancing implantology toward patient-specific solutions. Subtractive manufacturing (SM) ensures high precision and surface quality but is limited by material waste and geometric constraints. In contrast, additive manufacturing (AM) enables complex, porous, and customized designs, though often requires post-processing. Titanium and its alloys remain the gold standard due to strength and biocompatibility, while TiZr and β-type alloys may reduce stress shielding. Zirconia offers aesthetic benefits but is brittle, whereas PEEK shows favorable elasticity but limited bioactivity. Surface modifications enhance osseointegration and long-term performance. Conclusions: Combining digital workflows with SM and AM supports development of optimized, patient-specific implants. While titanium dominates clinical use, emerging materials offer specific advantages. Further clinical validation and standardization are required. Full article

Additive manufacturing enables the fabrication of patient-specific zirconia devices with integrated surface features; however, the biological effects of meso-scale topographies remain insufficiently understood. This in vitro study evaluated the influence of defined meso-scale surface modifications on osteoblast behavior using Digital Light Processing (DLP)-fabricated 3Y tetragonal zirconia polycrystal (3Y-TZP) and 5Y partially stabilized zirconia (5Y-PSZ). Planar control specimens and surfaces incorporating regularly distributed columnar structures (height: 100 µm; width: 40 µm; center-to-center spacing: 80, 120, and 160 µm; Mod-80, Mod-120, Mod-160) were fabricated and characterized after sintering. Cytotoxicity was assessed by elution testing and showed cell viability >98% for all groups. Osteoblast adhesion and proliferation (hFOB 1.19) were quantified using metabolic assays. Meso-scale modifications significantly increased early cell adhesion compared to planar controls (p < 0.05), with the strongest effect observed for Mod-160. No significant differences in proliferation rates were detected between groups (p > 0.05). Osteogenic differentiation was evaluated by RT-qPCR (RUNX2, ALPL, COL1A1, BGLAP), revealing material- and geometry-dependent responses. On 3Y-TZP, meso-scale structures, particularly Mod-160, were associated with sustained upregulation of BGLAP, whereas 5Y-PSZ exhibited less pronounced effects. Within the limitations of this in vitro study, meso-scale surface structuring of additively manufactured zirconia enhances early osteoblast adhesion without affecting proliferation and may influence osteogenic differentiation in a material-dependent manner. Full article