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Objective: To analyze the influence of congested and noncongested fixture periods during 2 seasons in a professional male football team on soft-tissue injury incidence and external load. Methods: Thirty-three professional football players from a Portuguese Liga I team participated in this study. Weekly external load and soft-tissue injury rate and burden of 2 consecutive seasons (2021–22 and 2022–23) were analyzed. Results: Total soft-tissue injury rate and burden for the 2 seasons were 3.9 and 3.2 injuries per 1000 hours and 71.8 and 60.5 days per 1000 hours for congested and noncongested periods, respectively. No significant differences were observed between congested and noncongested periods. Total high-speed running, sprint distance, distance above 80% and 90% of maximal velocity, and meters accelerating and decelerating above 2 m/s2 were significantly higher for noncongested weeks. Match accelerations and decelerations above 3 m/s2 were higher during congested periods and training during noncongested periods. No differences between the 2 periods were observed for the total number of accelerations and decelerations above 3 m/s2. Overall, physical outputs per week were higher for training during noncongested weeks, whereas matches during congested periods registered higher external load. Conclusions: No effect of a congested schedule was observed on soft-tissue injury rates and injury burden. Higher match exposure during congested periods increased external load performed per week, and during noncongested periods, training load was superior to congested weeks. [ABSTRACT FROM AUTHOR]

Objective: This study investigated the protective effects of low fluid shear stress (FSS ≤ 2 dyn/cm²) against interleukin-1β (IL-1β)-induced chondrocyte apoptosis and explored the underlying molecular mechanisms. Methods: Chondrocytes were cultured under four conditions: control, IL-1β stimulation, low FSS, and combined low FSS + IL-1β stimulation. Apoptosis was assessed using Hoechst staining and flow cytometry. Western blotting determined the expression of caspase-3 (CASP3), caspase-8 (CASP8), and NF-κB p65. Quantitative real-time PCR measured miR-143-3p expression. The roles of miR-143-3p and the extracellular signal-regulated kinase 5 (ERK5)/Krüppel-like factor 4 (KLF4) signaling pathway were further investigated using miR-143-3p mimics and inhibitors, an ERK5 inhibitor, and a KLF4 overexpression vector. Results: IL-1β induced significant chondrocyte apoptosis, which was markedly inhibited by low FSS. Mechanistically, low FSS suppressed miR-143-3p expression, thereby enhancing ERK5 signaling. This activated ERK5 subsequently upregulated KLF4 expression, further mitigating IL-1β-induced damage. Importantly, miR-143-3p overexpression under low FSS conditions exacerbated IL-1β-induced apoptosis, while miR-143-3p inhibition attenuated it. Consistent with this, ERK5 inhibition augmented IL-1β-induced apoptosis, whereas KLF4 overexpression suppressed it. Conclusion: Low FSS protects chondrocytes from IL-1β-induced apoptosis by suppressing miR-143-3p and activating the ERK5/KLF4 signaling pathway. This study reveals a novel mechanism by which mechanical stimulation protects cartilage. [ABSTRACT FROM AUTHOR]

Background: This study aims to compare the biomechanics of six zygomatic implants (ZIs) and dental implants (DIs) combined with four ZIs with different maxilla defects. Methods: Three-dimensional constructs of the ZIs, DIs human skulls, and maxillary prostheses were created using SolidWorks Software (Version 2015, Dassault Systems SolidWorks Corporation, Waltham, MA, USA). Eight finite element models of the skull with four different alveolar defect types (0–4) were constructed. Type 0: No defect; Type 1: Bilateral posterior defects; Type 2: Right posterior defect; Type 3: Anterior and left posterior defects; Type 4: Bilateral posterior and anterior defects. In two models with the same defect type (for defect types 0–2), six ZIs or two DIs combined with four ZIs were inserted into the maxilla. Six ZIs were inserted in the maxilla models with defect types 3 and 4. Vertical (150 N) and masseteric (300 N) loads were simulated on the prosthesis. The maximum Von Mises stress in the implants/surrounding bone and bone deformation were evaluated. Results: The maximum Von Mises stresses in bone/implant were found highest in the defect type 2 model with four ZIs combined with two DIs. The lowest maximum Von Mises stress for bone was detected in the model with defect type 0 and with six ZIs. Conclusion: Among the four types of defects, the posterior unilateral defect caused the highest stress value. [ABSTRACT FROM AUTHOR]

Various mechanical loadings, including mechanical stress, orthodontics forces, and masticatory force, affect the functions of periodontal ligament cells. Regulation of periodontal tissue destruction, formation, and differentiation functions are crucial processes for periodontal regeneration therapy. Numerous studies have reported that different types of mechanical loading play a role in maintaining periodontal tissue matrix homeostasis, and osteogenic differentiation of the periodontal ligament cells. This scoping review aims to evaluate the studies regarding the effects of various mechanical loadings on the secretion of extracellular matrix (ECM) components, regulation of the balance between formation and destruction of periodontal tissue matrix, osteogenic differentiation, and multiple differentiation functions of the periodontal ligament. An electronic search for this review has been conducted on two databases; MEDLINE via PubMed and SCOPUS. Study selection criteria included original research written in English that reported the effects of different mechanical loadings on matrix homeostasis and differentiation potential of periodontal ligament cells. The final 204 articles were mainly included in the present scoping review. Mechanical forces of the appropriate magnitude, duration, and pattern have a positive influence on the secretion of ECM components such as collagen, as well as regulate the secretion of matrix metalloproteinases and tissue inhibitors of matrix metalloproteinases. Additionally, these forces regulate a balance between osteoblastic and osteoclast differentiation. Conversely, incorrect mechanical loadings can lead to abnormal formation and destruction of both soft and hard tissue. This review provides additional insight into how mechanical loadings impact ECM homeostasis and multiple differentiation functions of periodontal ligament cells (PDLCs), thus making it valuable for regenerative periodontal treatment. In combination with advancing technologies, the utilization of ECM components, application of different aspects of mechanical force, and differentiation potential of PDLCs could bring potential benefits to future periodontal regeneration therapy. [ABSTRACT FROM AUTHOR]

Background: Occlusal veneer had been evaluated for mechanical properties using lithium disillicate. However, studies evaluating the mechanical properties of occlusal veneer with different preparation designs and ceramic materials are lacking. So, this in vitro study aimed to evaluate the fracture resistance of occlusal veneers with two designs fabricated from two different ceramic materials. Material and methods: Fourty mandibular third molars were distributed to 2 groups (n = 20) according to preparation design: group (O) anatomical occlusal reduction and group (OA) anatomical occlusal and 1 mm axial reduction. Each group was additionally subdivided into two subgroups (n = 10) according to ceramic materials; in subgroup X, lithium disilicate (e.max CAD, Ivoclar AG, Schaan, Liechtenstein) was used, and in subgroup S, zirconia-reinforced lithium silicate (ZLS) (Vita Suprinity, VitaZahnfabrik, Bad Säckingen, Germany) was used. All specimens were cemented with a light-cure resin cement (Choice 2, Bisco, Schaumburg, USA). 5000 thermocycles were applied to all specimens with both temperatures of 5 °C and 55 °C in two water baths; the dwell time was 30s at each bath, and the transfer time was 10s. Then all specimens were subjected to a fatigue simulation under dynamic loading of 200 N for 250,000 cycles. A universal testing machine (5500R/1123, Instron, Norwood, USA) was used to evaluate the fracture strength with a crosshead speed of 1 mm/min. All data were analyzed statistically by using a two-way ANOVA, and for some violations of assumptions, these results were compared with those obtained by the nonparametric test (Scheirer Ray Hare) (α = 0.05). Results: A statistically significantly higher fracture resistance in the 'OA' (3389 N) compared to the 'O' (2787 N) group regardless of the ceramic material (P <.001) and a statistically significantly higher fracture resistance in the 'X' (3295 N) compared to the 'S' (2881 N) regardless of the preparation design (P =.015). Conclusions: For occlusal veneers, all preparation designs and materials (such as Vita Suprinity and e.max CAD) had clinically acceptable fracture resistance values that were greater than the maximal biting forces. On the other hand, the e.max CAD with occlusal veneer, including axial reduction design, demonstrated the maximum fracture resistance value. Finally, no relationship between fracture strength and mode of failure was found. Clinical implications: Proper preparation design and the use of dental materials with high fracture resistance are key factors in extending the life of occlusal veneer restorations. The highest fracture resistance was demonstrated by lithium disilicate glass-ceramic occlusal veneers with axial preparation, which may increase the clinical longevity of teeth restored with occlusal veneers. [ABSTRACT FROM AUTHOR]

Acute cartilage injuries, such as intra-articular fractures and blunt impacts, frequently result in chondrocyte death and extracellular matrix (ECM) degradation, significantly elevating the risk of post-traumatic osteoarthritis (PTOA). Despite advances in treatment, no effective therapies currently exist to fully cure PTOA or halt its progression. This study explores the protective effects of the dietary fatty acid eicosapentaenoic acid (EPA) on human primary chondrocytes (HPCs) and cartilage explants exposed to mechanical overload and blunt trauma. HPCs were isolated and subjected to mechanical stretching using BioFlex six-well culture plates, while cartilage explants were subjected to impact loading via a customized drop tower. EPA was incorporated into the culture medium, followed by assays to evaluate cell viability, calcium (Ca²⁺) influx, apoptosis, reactive oxygen species (ROS) levels, and collagen type II alpha (Col-2a) expression. EPA treatment markedly decreased chondrocyte mechanical sensitivity, as demonstrated by enhanced cell viability and reduced lactate dehydrogenase (LDH) release. Furthermore, EPA inhibited Piezo1 activation, leading to lower intracellular Ca²⁺ concentrations, decreased apoptosis, and diminished ROS levels. In cartilage explants, EPA improved chondrocyte viability, minimized structural damage, and sustained higher Col-2a expression compared to the blunt trauma group. These results indicate that EPA effectively shields chondrocytes and cartilage explants from mechanical overload-induced damage by inhibiting Piezo1 activation and mitigating Ca²⁺ influx, apoptosis, and oxidative stress. The findings suggest that EPA supplementation could offer a promising strategy for preventing PTOA progression following acute cartilage injuries. Further research is warranted to assess the clinical applications of EPA and confirm its efficacy in larger animal models and human trials. [ABSTRACT FROM AUTHOR]

Objective: This study aimed to examine the shear bond strength (SBS) of repair material to conventionally, subtractive‐, and additive‐manufactured denture bases after different surface treatments. Materials and Methods: Disk‐shaped test specimens (N = 300) were prepared from denture base materials produced by one conventional (Procryla), one subtractive (Yamahachi), and one additive (Curo Denture) method. The test specimens were randomly divided into five groups (n = 10) and exposed to a variety of surface treatments—Group A: no surface treatment; Group B: grinding with silicon carbide paper; Group C: sandblasting; Group D: erbium: yttrium‐aluminum‐garnet laser; and Group E: plasma. Repair was performed with autopolymerizing acrylic resin (Meliodent). Surface roughness analyses were performed with a profilometer. Scanning electron microscopy was used to examine one specimen from each subgroup. SBS was evaluated on a universal testing machine. Failure types were observed under a stereomicroscope. Results: Surface roughness values were significantly higher in all test materials in Group D than in the other groups (p < 0.001). For conventional resin, the SBS values were higher in Group C than in Groups A, D, and E (p < 0.001). For CAD/CAM material, Groups B and C had significantly greater SBS increases compared with Group E (p < 0.001). For 3D material, Group D showed higher SBS than all groups except Group C (p < 0.001). Conclusions: For SBS, sandblasting was most effective in the conventional group, whereas laser treatment was the most effective in the additive‐manufactured group. For the subtractive group, surface treatments other than plasma exhibited similar SBS. Clinical Significance: In repairing fractured prostheses, any degree of roughening suitable for the material content may provide an SBS benefit. [ABSTRACT FROM AUTHOR]

Objective: The most recent edition of the International Clinical Practice Guideline for the Prevention and Treatment of Pressure Ulcers/Injuries was released in 2019. Shortly after, in 2020, the first edition of the SECURE Prevention expert panel report, focusing on device-related pressure ulcers/injuries, was published as a special issue in the Journal of Wound Care. A second edition followed in 2022. This article presents a comprehensive summary of the current understanding of the causes of pressure ulcers/injuries (PU/Is) as detailed in these globally recognised consensus documents. Method: The literature reviewed in this summary specifically addresses the impact of prolonged soft tissue deformations on the viability of cells and tissues in the context of PU/Is related to bodyweight or medical devices. Results: Prolonged soft tissue deformations initially result in cell death and tissue damage on a microscopic scale, potentially leading to development of clinical PU/Is over time. That is, localised high tissue deformations or mechanical stress concentrations can cause microscopic damage within minutes, but it may take several hours of continued mechanical loading for this initial cell and tissue damage to become visible and clinically noticeable. Superficial tissue damage primarily stems from excessive shear loading on fragile or vulnerable skin. In contrast, deeper PU/Is, known as deep tissue injuries, typically arise from stress concentrations in soft tissues at body regions over sharp or curved bony prominences, or under stiff medical devices in prolonged contact with the skin. Conclusion: This review promotes deeper understanding of the pathophysiology of PU/Is, indicating that their primary prevention should focus on alleviating the exposure of cells and tissues to stress concentrations. This goal can be achieved either by reducing the intensity of stress concentrations in soft tissues, or by decreasing the exposure time of soft tissues to such stress concentrations. [ABSTRACT FROM AUTHOR]

The distribution of forces within the ankle joint plays a crucial role in joint health and longevity. Loading disorders affecting the ankle joint can have significant detrimental effects on daily life and activity levels. This study aimed to enhance our understanding of the mechanical behavior of tibiotalar joint articular cartilages in the presence of varus deformity using finite element analysis (FEA) applied to patient-specific models. Two personalized ankle models, one healthy and another with varus deformity, were created based on CT scan images. Four static loading scenarios were simulated at the center of pressure (COP), coupled to the hindfoot complex. The contact area, contact pressure, and von Mises stress were computed for each cartilage. It was found that the peak contact pressure increased by 54% in the ankle with varus deformity compared to the healthy ankle model. Furthermore, stress concentrations moving medially were observed, particularly beneath the medial malleolus, with an average peak contact pressure of 3.5 MPa and 4.7 MPa at the tibial and talar articular cartilages, respectively. Varus deformities in the ankle region have been consistently linked to elevated contact pressure, increasing the risk of thinning, degeneration, and eventual onset of osteoarthritis (OA), emphasizing the need for prompt interventions aimed at mitigating complications. [Display omitted] [ABSTRACT FROM AUTHOR]

Background: Unicompartmental knee arthroplasty (UKA) has been proved to be a successful treatment for osteoarthritis patients. However, the stress shielding caused by mismatch in mechanical properties between human bones and artificial implants remains as a challenging issue. This study aimed to properly design a bionic porous tibial implant and evaluate its biomechanical effect in reconstructing stress transfer pathway after UKA surgery. Methods: Voronoi structures with different strut sizes and porosities were designed and manufactured with Ti6Al4V through additive manufacturing and subjected to quasi-static compression tests. The Gibson-Ashby model was used to relate mechanical properties with design parameters. Subsequently, finite element models were developed for porous UKA, conventional UKA, and native knee to evaluate the biomechanical effect of tibial implant with designed structures during the stance phase. Results: The internal stress distribution on the tibia plateau in the medial compartment of the porous UKA knee was found to closely resemble that of the native knee. Furthermore, the mean stress values in the medial regions of the tibial plateau of the porous UKA knee were at least 44.7% higher than that of the conventional UKA knee for all subjects during the most loading conditions. The strain shielding reduction effect of the porous UKA knee model was significant under the implant and near the load contact sites. For subject 1 to 3, the average percentages of nodes in bone preserving and building region (strain values range from 400 to 3000 μm/m) of the porous UKA knee model, ranging from 68.7 to 80.5%, were higher than that of the conventional UKA knee model, ranging from 61.6 to 68.6%. Conclusions: The comparison results indicated that the tibial implant with designed Voronoi structure offered better biomechanical functionality on the tibial plateau after UKA. Additionally, the model and associated analysis provide a well-defined design process and dependable selection criteria for design parameters of UKA implants with Voronoi structures. [ABSTRACT FROM AUTHOR]

Osteoarthritis (OA) is one of the most common causes of disability around the globe, especially in aging populations. The main symptoms of OA are pain and loss of motion and function of the affected joint. Hyaline cartilage has limited ability for regeneration due to its avascularity, lack of nerve endings, and very slow metabolism. Total joint replacement (TJR) has to date been used as the treatment of end-stage disease. Various joint-sparing alternatives, including conservative and surgical treatment, have been proposed in the literature; however, no treatment to date has been fully successful in restoring hyaline cartilage. The mechanical and frictional properties of the cartilage are of paramount importance in terms of cartilage resistance to continuous loading. OA causes numerous changes in the macro- and microstructure of cartilage, affecting its mechanical properties. Increased friction and reduced load-bearing capability of the cartilage accelerate further degradation of tissue by exerting increased loads on the healthy surrounding tissues. Cartilage repair techniques aim to restore function and reduce pain in the affected joint. Numerous studies have investigated the biological aspects of OA progression and cartilage repair techniques. However, the mechanical properties of cartilage repair techniques are of vital importance and must be addressed too. This review, therefore, addresses the mechanical and frictional properties of articular cartilage and its changes during OA, and it summarizes the mechanical outcomes of cartilage repair techniques. [ABSTRACT FROM AUTHOR]

Background: Mechanical complications affect the stability of implant restorations and are a key concern for clinicians, especially with the frequent introduction of new implant designs featuring various structures and materials. This study evaluated the effect of different prosthetic index structure types and implant materials on the stress distribution of implant restorations using both in silico and in vitro methods. Methods: Four finite element analysis (FEA) models of implant restorations were created, incorporating two prosthetic index structures (cross-fit (CF) and torc-fit (TF)) and two implant materials (titanium and titanium-zirconium). A static load was applied to each group. An in vitro study using digital image correlation (DIC) with a research scenario identical to that of the FEA was conducted for validation. The primary strain, sensitivity index, and equivalent von Mises stress were used to evaluate the outcomes. Results: Changing the implant material from titanium to titanium-zirconium did not significantly affect the stress distribution or maximum stress value of other components, except for the implant itself. In the CF group, implants with a lower elastic modulus increased the stress on the screw. The TF group showed better stress distribution on the abutment and a lower stress value on the screw. The TF group demonstrated similar sensitivity for all components. DIC analysis revealed significant differences between TF-TiZr and CF-Ti in terms of the maximum (P < 0.001) and minimum principal strains (P < 0.05) on the implants and the minimum principal strains on the investment materials in both groups (P < 0.001). Conclusions: Changes in the implant material significantly affected the maximum stress of the implant. The TF group exhibited better structural integrity and reliability. [ABSTRACT FROM AUTHOR]

Background: Mesenchymal stem cells (MSCs) derived from the synovium, known as synovium mesenchymal stem cells (SMSCs), exhibit significant potential for articular cartilage regeneration owing to their capacity for chondrogenic differentiation. However, the microRNAs (miRNAs) governing this process and the associated mechanisms remain unclear. While mechanical stress positively influences chondrogenesis in MSCs, the miRNA‐mediated response of SMSCs to mechanical stimuli is not well understood. Objective: This study explores the miRNA‐driven mechano‐transduction in SMSCs chondrogenesis under mechanical stress. Methods: The surface phenotype of SMSCs was analysed by flow cytometry. Chondrogenesis capacities of SMSCs were examined by Alcian blue staining. High throughput sequencing was used to screen mechano‐sensitive miRNAs of SMSCs. The RNA expression level of COL2A1, ACAN, SOX9, BMPR2 and miR‐143‐3p of SMSCs were tested by quantitative real‐time polymerase chain reaction (qRT‐PCR). The interaction between miR‐143‐3p and TLR4 was confirmed by luciferase reporter assays. The protein expression levels of related genes were assessed by western blot. Results: High‐throughput sequencing revealed a notable reduction in miR‐143‐3p levels in mechanically stressed SMSCs. Gain‐ or loss‐of‐function strategies introduced by lentivirus demonstrated that miR‐143‐3p overexpression hindered chondrogenic differentiation, whereas its knockdown promoted this process. Bioinformatics scrutiny and luciferase reporter assays pinpointed a potential binding site for miR‐143‐3p within the 3′‐UTR of bone morphogenetic protein receptor type 2 (BMPR2). MiR‐143‐3p overexpression decreased BMPR2 expression and phosphorylated Smad1, 5 and 8 levels, while its inhibition activated BMPR2‐Smad pathway. Conclusion: This study elucidated that miR‐143‐3p negatively regulates SMSCs chondrogenic differentiation through the BMPR2‐Smad pathway under mechanical tensile stress. The direct targeting of BMPR2 by miR‐143‐3p established a novel dimension to our understanding of mechano‐transduction mechanism during SMSC chondrogenesis. This understanding is crucial for advancing strategies in articular cartilage regeneration. [ABSTRACT FROM AUTHOR]

We used finite element analysis to study the mechanical stress distribution of a new intramedullary implant used for proximal interphalangeal joint (PIPJ) arthrodesis (PIPJA) to surgically correct the claw‐hammer toe deformity that affects 20% of the population. After geometric reconstruction of the foot skeleton from claw toe images of a 36–year‐old male patient, two implants were positioned, in the virtual model, one neutral implant (NI) and another one 10° angled (10°AI) within the PIPJ of the second through fourth HT during the toe‐off phase of gait and results were compared to those derived for the non‐surgical foot (NSF). A PIPJA was performed on the second toe using a NI reduced tensile stress at the proximal phalanx (PP) (45.83 MPa) compared to the NSF (59.44 MPa; p < 0.001). When using the 10°AI, the tensile stress was much higher at PP and middle phalanges (MP) of the same toe, measuring 147.58 and 160.58 MPa, respectively, versus 59.44 and 74.95 MPa at corresponding joints in the NSF (all p < 0.001). Similar results were found for compressive stresses. The NI reduced compressive stress at the second PP (−65.12 MPa) compared to the NSF (−113.23 MPa) and the 10°AI (−142 MPa) (all p < 0.001). The von Mises stresses within the implant were also significantly lower when using NI versus 10°AI (p < 0.001). Therefore, we do not recommend performing a PIPJA using the 10°AI due to the increase in stress concentration primarily at the second PP and MP, which could promote implant breakage. [ABSTRACT FROM AUTHOR]

Aims: Excessive occlusal force with periodontitis leads to rapid alveolar bone resorption. However, the molecular mechanism by which inflammation and mechanical stress cause bone resorption remains unclear. We examined the role of Piezo1, a mechanosensitive ion channel expressed on osteoblasts, in the changes in the receptor activator of nuclear factor‐kappa B ligand (RANKL)/osteoprotegerin (OPG) ratio in mouse MC3T3‐E1 osteoblast‐like cells under Porphyromonas gingivalis lipopolysaccharide (P.g.‐LPS) and mechanical stress. Methods: To investigate the effect of P.g.‐LPS and mechanical stress on the RANKL/OPG ratio and Piezo1 expression, we stimulated MC3T3‐E1 cells with P.g.‐LPS. After 3 days in culture, shear stress, a form of mechanical stress, was applied to the cells using an orbital shaker. Subsequently, to investigate the role of Piezo1 in the change of RANKL/OPG ratio, we inhibited Piezo1 function by knockdown via Piezo1 siRNA transfection or by adding GsMTx4, a Piezo1 antagonist. Results: The RANKL/OPG ratio significantly increased in MC3T3‐E1 cells cultured in a medium containing P.g.‐LPS and undergoing mechanical stress compared to cells treated with P.g.‐LPS or mechanical stress alone. However, the expression of Piezo1 was not increased by P.g.‐LPS and mechanical stress. In addition, phosphorylation of MEK/ERK was induced in the cells under P.g.‐LPS and mechanical stress. MC3T3‐E1 cells treated with P.g.‐LPS and mechanical stress when cocultured with RAW264.7 cells induced their differentiation into osteoclast‐like cells. The increased RANKL/OPG ratio was suppressed by either Piezo1 knockdown or the addition of GsMTx4. Furthermore, GsMTx4 inhibited the phosphorylation of MEK/ERK. Conclusion: These findings suggest that P.g.‐LPS and Piezo1‐mediated mechanical stress induce MEK/ERK phosphorylation and increase RANKL expression in osteoblasts. Consequently, this leads to the differentiation of osteoclast precursor cells into osteoclasts. [ABSTRACT FROM AUTHOR]

This study compares the fracture strength of teeth restored with conventional round fiber post (CP) and bundle post (BP) in two different lengths. A total of 48 mandibular premolars were selected. Endodontic treatment was performed, and the premolars were divided into four groups (n = 12 per group): Group C9 = 9-mm CP; Group C5 = 5-mm CP; Group B9 = 9-mm BP; Group B5 = 5-mm BP. Post spaces were prepared, and posts were disinfected with alcohol. Silane was applied, and posts were placed with self-etch dual-cure adhesive. The core structures were created using dual-cure adhesive and standardized core-matrix. Specimens were embedded in acrylic, and the periodontal ligament was simulated with polyvinyl-siloxane impression material. Thermocycling was performed, and specimens were then loaded at a 45-degree angle to the long axis. The failure mode was analyzed with x5 magnification, and statistical analyses were performed. No statistical difference was found between post systems and post lengths (P > .05). Chi-square test revealed no statistical difference in the failure mode (P > .05). BP did not affect fracture resistance compared to CP. For the restoration of extremely irregular canals with a fiber post, BP can be used as an alternative system because it does not reduce the fracture strength. If necessary, longer posts can be used without decreasing the fracture resistance. [ABSTRACT FROM AUTHOR]

Purpose: To examine and compare stress values of implants, highest tensile and compressive values, and their distribution in cortical and trabecular bone near and around the implant region using different materials (aramid fiber, glass fiber, polyethylene fiber, carbon fiber, and cobalt-chromium [Co-Cr] alloy). Four dental implants were placed in the maxillary crest with two different location scenarios, and the 3D finite element analysis method was used to evaluate stress characteristics. Materials and Methods: Two maxillary models were created in which the implants were placed in different locations (lateral and first premolar, canine and second premolar). Four implant-supported overdenture prostheses were reinforced, applying Co-Cr alloy, glass fiber, aramid fiber, and carbon fiber. Static loads of 200 N were applied on the first molar region using the food stuff method. Stresses around the implants and denture-bearing areas and compression and tensile stresses on the cortical and trabecular bone were evaluated. Results: In all tested models, the highest von Mises stresses on implants and prostheses were observed in aramid fiber--reinforced overdentures. This was followed by glass fiber, Co-Cr alloy, and carbon fiber groups, respectively. It was observed that the lowest tensile and highest compression stress values in cortical and trabecular bone occurred in prostheses supported with carbon fiber. In all infrastructure materials, the design in which the implants were placed bilaterally in the lateral teeth and the first premolar region was found to be advantageous in terms of stress levels and distribution. Conclusion: High elastic modulus fiber--reinforced overdenture prostheses transmitted less stress to implants and surrounding tissues than Co-Cr alloy. Anteriorly placed implant design illustrated lower stress values in the prosthesis, implant, and cortical and trabecular bone, and this placement design may increase the survival rates of both dental implants and overdentures. In light of this study, fibers can be recommended for clinical use and securely applied as an alternative material to metal support. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the fracture behavior of human molars with extensive MOD restorations using short‐fiber‐reinforced resin composite of varying viscosities. Materials and Methods: Human molars were randomly divided into seven groups (n = 12): intact teeth (control); restoration using conventional high‐viscosity resin composite without (Filtek Z350XT, 3M) or with fibers (everX Posterior, GC); conventional low‐viscosity resin composite without (Filtek Supreme Flowable, 3M) or with fibers (everX Flow Dentin Shade, GC); bulk‐fill low‐viscosity resin composite (Filtek Bulk Fill Flow, 3M) or with fibers (everX Flow Bulk Shade, GC). Restorations were performed on extensive MOD preparations, following the manufacturers' recommendations for each material. Specimens underwent fracture strength testing (N) and fracture pattern (%) categorized as repairable, possibly repairable, or non‐repairable. Results were analyzed using a generalized linear model (N) and Fisher's exact test (%), with α = 0.05. Results: Restorations performed with high‐viscosity materials showed fracture strength values similar to the control and higher than those of restorations using low‐viscosity resin composites (p < 0.0001), except for the bulk‐fill low‐viscosity resin composite with fibers (p > 0.05). Teeth restored using low‐viscosity resin composite with fibers showed a higher % of repairable and possibly repairable fractures than the control (p = 0.0091). Conclusions: The viscosity of materials mediated the fracture strength, with restorations using high‐viscosity resin composites promoting values similar to the intact tooth; however, the presence of fibers influenced the fracture pattern. Clinical Significance: Teeth with MOD cavities restored with high‐viscosity resin composites showed similar fracture strength to intact teeth. Fiber‐reinforced low‐viscosity resin composite for the base of restoration resulted in a more repairable/possibly repairable fracture pattern. [ABSTRACT FROM AUTHOR]

The article explains the importance of assessing cardiac output for optimal vessel opacification in computed tomography for proper diagnoses. Topics discussed include different classifications of heart failure based on the sidedness and pumping abilities of the heart, determinants of cardiac output such as heartbeat, heart rate, preload, contractility and afterload, as well as Laplace's law of physiological wall stress and its effects on cardiac output.

Purpose: To compare the biomechanical behaviors of different surgical options that are preferred for implant-supported fixed prosthetic rehabilitation of the atrophic edentulous maxilla. Materials and Methods: A 3D finite element analysis (FEA) model was generated from the computed tomography data of a patient with an atrophic edentulous maxilla. Four scenarios were created in the atrophic maxilla. In model 1, the maxilla was reconstructed with an onlay bone graft harvested from the anterior iliac crest, and sinus augmentation procedures were performed. Standard dental implants were placed in the lateral incisor, first premolar, and first molar regions on each side. In model 2, the anterior part of the atrophic maxilla was reconstructed with an onlay bone graft harvested from the mandibular ramus, and zygomatic implants were placed in the posterior part of the maxilla. In models 3 and 4, two-piece subperiosteal implants made of titanium and polyether ether ketone (PEEK) materials, respectively, were placed in the atrophic maxilla. All implants were loaded with 150-N and 50-N forces in vertical and lateral directions, respectively. Stress accumulation on bones, implants, abutments, and prosthetic frameworks was investigated. Results: The tensile stress in both cortical and trabecular bone was highest in the iliac bone grafting group under vertical loading. The compressive stress in both cortical and trabecular bone was the highest in the PEEK subperiosteal implant model, and the compressive stress value on the trabecular bone exceeded the strength of the trabecular bone. The highest von Mises stress in the implants was obtained in the iliac bone grafting group under vertical loading. The highest stress value in the abutments was detected for the titanium subperiosteal implant. The highest von Mises stress in the prosthetic framework was detected in the titanium subperiosteal implant group, under both vertical and lateral loading. Conclusion: Based on the stress accumulation results of the four different scenarios, it can be seen that there is no ideal treatment modality for the fixed implant-supported prosthetic rehabilitation of the atrophic edentulous maxilla. Various intraoperative and prosthetic modifications are suggested to decrease the risk of biomechanical complications during long-term follow-up. [ABSTRACT FROM AUTHOR]

Simple Summary: Image-guided solid tumor ablation therapy is an expanding practice designed to effectively target and eradicate malignant tissue through noninvasive or minimally invasive techniques. There exist several ablation systems that can utilize localized heating or mechanical stress to induce cell death of malignant cells. The provider selects a technique based on patient comorbidities, the type of malignancy, the size and location of the tumor, and the desired goal of therapy. Over the past two decades, several studies have validated the safety and efficacy of these techniques in humans to be used as an alternative to medical and surgical therapy or as an adjunct in a hybrid treatment plan. Compared to conventional surgical therapies, these procedures are better tolerated, with reduced morbidity and mortality, providing options to patients that are not surgical candidates. This article reviews the new and common techniques in solid tumor ablation and the research supporting their use in oncological treatment. Image-guided solid tumor ablation methods have significantly advanced in their capability to target primary and metastatic tumors. These techniques involve noninvasive or percutaneous insertion of applicators to induce thermal, electrochemical, or mechanical stress on malignant tissue to cause tissue destruction and apoptosis of the tumor margins. Ablation offers substantially lower risks compared to traditional methods. Benefits include shorter recovery periods, reduced bleeding, and greater preservation of organ parenchyma compared to surgical intervention. Due to the reduced morbidity and mortality, image-guided tumor ablation offers new opportunities for treatment in cancer patients who are not candidates for resection. Currently, image-guided ablation techniques are utilized for treating primary and metastatic tumors in various organs with both curative and palliative intent, including the liver, pancreas, kidneys, thyroid, parathyroid, prostate, lung, breast, bone, and soft tissue. The invention of new equipment and techniques is expanding the criteria of eligible patients for therapy, as now larger and more high-risk tumors near critical structures can be ablated. This article provides an overview of the different imaging modalities, noninvasive, and percutaneous ablation techniques available and discusses their applications and associated complications across various organs. [ABSTRACT FROM AUTHOR]

Background: High tibial osteotomy (HTO) aims to realign the varus knee to alleviate stress in the medial compartment. However, detailed information on the impact of HTO on stress distribution across the tibiofemoral joint surface still needs to be completely elucidated. Purpose/Hypothesis: The present study aimed to analyze the subchondral bone density distribution to validate the alignment threshold causing paradoxical changes. We hypothesized that there would be a paradoxical stress change in the medial compartment beyond a specific threshold for lower limb realignment after HTO. Study Design: Case series; Level of evidence, 4. Methods: A retrospective clinical study of 32 knees from 30 patients who underwent medial opening-wedge HTO between 2015 and 2019 was conducted at Hokkaido University Hospital. The subchondral bone density across the tibiofemoral joint was analyzed using computed tomography–osteoabsorptiometry before and after HTO. The high-density area (HDA) within the medial and lateral compartments and their subregions, which were quartered in the coronal plane, was specifically examined. Results: The hip-knee-ankle angle, medial proximal tibial angle (MPTA), joint line obliquity (JLO), and joint line convergence angle significantly changed after HTO (P <.01). The HDA of the medial compartment to the total HDA ratio decreased from 83% to 77%. Paradoxically, the HDA in the most central subregion of the medial compartment increased from 24% to 30%. There were significant differences between MPTA and JLO in patients with and without paradoxical changes in the HDA. MPTA and JLO cutoff values causing paradoxical changes in the HDA were 94° and 4°, respectively. Conclusion: There was a paradoxical stress increase in the M4 region at the medial compartment associated with the MPTA and JLO beyond specific thresholds. Therefore, surgical planning should be cautiously performed to prevent overcorrection, which can lead to adverse stress distribution changes. [ABSTRACT FROM AUTHOR]

Background: The minimally invasive approach for the treatment of displaced scapular neck or body fractures has the advantages of less trauma and minimal muscle dissection. In clinical practice, the minimally invasive approach combined with an anatomical locking plate has been used to treat scapular body fractures. In addition, we have made minor modifications to the minimally invasive approach. However, the biomechanical study about the approach combined with an anatomical locking plate in treating scapular body fractures was limited. Methods: Finite element analysis (FEA) was used to conduct the biomechanical comparison between the anatomical locking plate (AP model) and reconstructive plate (RP model) in the treatment of scapular body fractures through the modified minimally invasive approach. A healthy male volunteer with no history of scapula or systemic diseases was recruited. High-resolution computed tomography images of his right scapula were obtained. Two scapula models were constructed and analyzed by the software of Mimics 21.0, Geomagic Wrap 2021, SolidWorks 2021, and ANSYS Workbench 2022, respectively. Results: Through static structural analysis, in terms of equivalent von Mises stress, equivalent elastic strain, and total deformation, the AP model exhibited superior safety characteristics, enhanced flexibility, and anticipated stability compared with the RP model. This was evidenced by lower maximum stress, lower maximum strain and displacement. Conclusion: The minimally invasive approach combined with an anatomical locking plate for scapular body fractures had better biomechanical stability. The study provided a biomechanical basis to guide the clinical treatment of scapular body fractures. [ABSTRACT FROM AUTHOR]

Background: The effects of traction forces at different angles on impacted central incisors(ICI)with varying inverted angles (IA) may be different. The objective of this study was to analyze the biomechanical effects of different force directions (FD) on developmentally inverted ICI with multi-angle variations and to offer insights and guidance for the treatment of inverted ICI. Methods: Three-dimensional finite element method was employed to simulate clinical scenarios of inverted ICI traction. As such, 0.2 N of force (direction: antero-superior angles of 90°, 100°, 110°, 120°, and 130° relative to the long axis of the inverted ICI crown) was applied to the inverted ICI with inverse angles (IA) of 40°, 30°, 20°, 10° and 0°. Inverted ICI apical displacement and Von Mises stress on periodontal ligament (PDL) and alveolar bone were compared. Results: IA and FD showed minimal influence on the stress distribution in the PDL, as higher stresses were concentrated in the apical region. The higher stresses in the alveolar bone are focused on the cervical and apical regions of the tooth. In particular, IA exerts a more significant impact on stress distribution in the alveolar bone than FD. The influence of IA on the apical displacement of inverted ICI is larger than that of FD. Conclusions: To promote the health of the root and periodontal tissues, it is recommended to use an angle of 100°-110° relative to the long axis of the ICI crown when dealing with a large IA (> 20°) developmentally inverted ICI. Conversely, an angle of 110°-120° can be used. [ABSTRACT FROM AUTHOR]

Objectives: Abnormal mechanical stress is the pivotal risk factor of temporomandibular joint osteoarthritis (TMJOA). This study investigated the pathogenic mechanism by which abnormal mechanical stress induced chondrocyte senescence. Materials and Methods: Cellular senescence was investigated in the rodent model of unilateral anterior crossbite and in the chondrocytes subjected to mechanical overloading in vitro. The effects of Yes‐associated protein (YAP) in chondrocyte senescence and its correlation with methyltransferase‐like 3 (METTL3) and N6‐methyladenosine (m6A) modification were evaluated. The role of m6A modification in chondrocyte senescence was determined. The therapeutic effects of m6A inhibition in TMJOA were investigated. Results: Senescent chondrocytes were accumulated in the mechanically induced TMJOA lesions in rats and mechanical overloading could trigger chondrocyte senescence in vitro. This mechanical stress‐induced cellular senescence was revealed to be mediated by YAP deficiency that promoted METTL3‐dependent m6A modification. Moreover, inhibition of m6A modification rescued chondrocyte senescence in vitro and in vivo, and suppressed TMJOA progression in rats. Conclusions: This study uncovered the underlying mechanism of mechanically induced senescence in TMJOA from the perspective of epitranscriptomics and revealed the therapeutic potential of m6A inhibition in TMJOA. [ABSTRACT FROM AUTHOR]

Background: Knee osteoarthritis (KOA) represents a widespread degenerative condition among adults that significantly affects quality of life. This study aims to elucidate the biomechanical implications of proximal fibular osteotomy (PFO), a proposed cost-effective and straightforward intervention for KOA, comparing its effects against traditional high tibial osteotomy (HTO) through in-silico analysis. Methods: Using medical imaging and finite element analysis (FEA), this research quantitatively evaluates the biomechanical outcomes of a simulated PFO procedure in patients with severe medial compartment genu-varum, who have undergone surgical correction with HTO. The study focused on evaluating changes in knee joint contact pressures, stress distribution, and anatomical positioning of the center of pressure (CoP). Three models are generated for each of the five patients investigated in this study, a preoperative original condition model, an in-silico PFO based on the same original condition data, and a reversed-engineered HTO in-silico model. Results: The novel contribution of this investigation is the quantitative analysis of the impact of PFO on the biomechanics of the knee joint. The results provide mechanical evidence that PFO can effectively redistribute and homogenize joint stresses, while also repositioning the CoP towards the center of the knee, similar to what is observed post HTO. The findings propose PFO as a potentially viable and simpler alternative to conventional surgical methods for managing severe KOA, specifically in patients with medial compartment genu-varum. Conclusion: This research also marks the first application of FEA that may support one of the underlying biomechanical theories of PFO, providing a foundation for future clinical and in-silico studies. [ABSTRACT FROM AUTHOR]

Background: Cervical pedicle screw-rod fixation presents a complex approach in spinal surgery, offering enhanced spine stabilization in variable conditions considering traumatic injuries, degenerative changes, as well as orthopaedic and oncological ailments. This technique employs small diameter screw implants strategically placed to bolster the mechanical integrity of the spine. Notably, it involves minimally invasive procedures, resulting in smaller incisions and reduced patient discomfort. This study aims to assess the effects of trapezoidal thread screws in pedicle sections of the cervical spine during flexion-extension loadings, focusing on factors such as range of motion (ROM), implant stress, and stress on adjacent bone. Methods: Utilizing CT scan data, a finite element model of the cervical spine (C2-C7 vertebrae) was prepared. Trapezoidal thread screws were integrated into a single-level pedicle screw-rod fixation at the C5-C6 vertebrae. The C2 vertebra were given a compressive load of 50 N along with a moment of 1 Nm, resulting in the immobilization of the C7. Results and Discussion: The results indicate a reduction in ROM at the C5-C6 level by 69% to 77% compared to the intact spine during flexion-extension loading, with a slight increase in ROM observed at adjacent cervical spine levels. Stress analysis revealed that the trapezoidal thread screws induced stresses ranging from 24 MPa to 29 MPa in PEEK trapezoidal screw-rod implants, which fall below the material's yield stress. Conclusions: This suggests that the trapezoidal thread profile may be advantageous in minimizing stress concentration, attributed to its larger contact area with the vertebrae bone between the threads. [ABSTRACT FROM AUTHOR]

Objectives: The acetabular cup design plays a critical role in reducing contact stress between femur head acetabular cup. Many studies used ellipsoidal and spheroidal geometry in acetabular cup design to effectively reduce contact stress. The present study focuses on elevated acetabular cup rim with round corner design to reduce contact stress with round corner geometry. Methods: The cobalt chromium femur head and cup are considered for finite element (FE) model of hip resurfacing. The gait loads of routine activities of humans like normal walking, stair ascending and descending and sitting down and getting up gait activities are applied to the developed 3D FE model. Five microseparations of 0.5, 1, 1.5, 2 and 2.5 mm are considered in the present study. The acetabular cup inclination angle considered for this study are 35°, 45°, 55°, 65° and 75°. The contact stress and von Mises stress plot for each gait activities under these microseparations are analyzed for betterment of longevity of implants. Results: Overall elevated cup rim design helped in reducing contact stress to a greater extent than conventional cup with different geometries. Also, the predicted von Mises stress for all the parameters considered in the current study are well within the yield strength of CoCr material. Therefore, elevated cup rim could be used as a better alternative to spline and, ellipsoidal and circular geometries of cup. [ABSTRACT FROM AUTHOR]

To validate the correlation between the signal intensity gradient (SIG) from time-of-flight magnetic resonance angiography (TOF-MRA) and wall shear stress (WSS) determined by phase contrast magnetic resonance (PC-MR), we conducted both experimental and human studies. In the experimental study, we measured WSS in four tubes of different sizes with variable flow rates using PC-MR and TOF-MRA. The flow rates of water in the experimental study ranged from 0.06 to 12.75 mL/s, resulting in PC-WSS values between 0.1 and 1.6 dyne/cm2. The correlation between PC-WSS and SIG was statistically significant, showing a coefficient of 0.86 (P < 0.001, R2 = 0.75). The line fit provided the conversion equation as Y = 1.6287X − 1.1563 (Y = PC-WSS, X = SIG). For the human study, 28 subjects underwent TOF-MRA and PC-MR examinations of carotid and vertebral arteries. Arterial PC-WSS and SIG were determined in the same segment for each subject. The arterial PC-WSS ranged from 1.9 to 21.0 dyne/cm2. Both carotid and vertebral arteries showed significant correlations between PC-WSS and SIG, with coefficients of 0.85, 0.86, 0.91, and 0.81 in the right and left carotid and vertebral arteries, respectively. Our results show that SIG from TOF-MRA and SIG-WSS derived from the conversion equation provide concurrent in vivo hemodynamic information on arterial shear stress. This study was registered on ClinicalTrials.gov with the identifier NCT04585971 on October 14, 2020. [ABSTRACT FROM AUTHOR]

This study delves into an in-depth examination of the biomechanical characteristics of various materials commonly utilized in the fabrication of artificial ankle joints. Specifically, this research focuses on the design of an ankle joint resembling the salto-talaris type, aiming to comprehensively understand its performance under different loading conditions. Employing advanced finite element analysis techniques, this investigation rigorously evaluates the stresses and displacements experienced by the designed ankle joint when subjected to varying loads. Furthermore, this study endeavors to identify the vibrating frequencies associated with these displacements, offering valuable insights into the dynamic behavior of the ankle joint. Notably, the analysis extends to studying random frequencies across three axes of motion, enabling a comprehensive assessment of directional deformities that may arise during joint function. To validate the effectiveness of the proposed design, a comparative analysis is conducted against the star ankle design, a widely recognized benchmark in ankle joint prosthetics. This comparative approach serves dual purposes: confirming the accuracy of the findings derived from the salto-talaris design and elucidating the relative efficacy of the proposed design in practical application scenarios. [ABSTRACT FROM AUTHOR]

Implant-supported-screw-retained prostheses are highly popular. Some of the most frequent complications are connected with the mechanical properties of the fixing elements. These include abutment screw loosening or even screw fracture. Using an intermediate abutment can offer several advantages. However, few studies detail how this affects the mechanical behavior of dental restorations. This study focuses on understanding the mechanical behavior of implant-supported restorations with a transepithelial component compared to direct implant-supported restoration. It was carried out using the finite element method (FEM) and was experimentally validated. The results showed that in the case of transepithelial-supported restoration, the prosthetic screw mounted over the transepithelial component suffered higher stress than the one screwed directly into the implant. After applying a cyclic fatigue load, it was experimentally proven that, in the transepithelial-supported restorations, the fuse changed from being the screw that went into the implant to being the upper one. In conclusion, we can state that the use of an intermediate abutment in dental restoration not only provides better protection for the rest of the dental restoration but also allows for easier repair in the event of a fracture. This can potentially lead to more efficient procedures and improved patient outcomes. [ABSTRACT FROM AUTHOR]

The flow of fluid through the porous matrix of a reservoir rock applies a seepage force to the solid rock matrix. Although the seepage force exerted by fluid flow through the porous matrix of a reservoir rock has a notable influence on rock deformation and failure, its effect on hydraulic fracture (HF) propagation remains ambiguous. Therefore, in this study, we improved a traditional fluid–solid coupling method by incorporating the role of seepage force during the fracturing fluid seepage, using the discrete element method. First, we validated the simulation results of the improved method by comparing them with an analytical solution of the seepage force and published experimental results. Next, we conducted numerical simulations in both homogeneous and heterogeneous sandstone formations to investigate the influence of seepage force on HF propagation. Our results indicate that fluid viscosity has a greater impact on the magnitude and extent of seepage force compared to injection rate, and that lower viscosity and injection rate correspond to shorter hydraulic fracture lengths. Furthermore, seepage force influences the direction of HF propagation, causing HFs to deflect towards the side of the reservoir with weaker cementation and higher permeability. [ABSTRACT FROM AUTHOR]

Aim: Preoperative identification of acetabular corrections that optimally improve joint stability and reduce elevated contact stresses could further reduce osteoarthritis progression in patients with hip dysplasia who are treated with periacetabular osteotomy (PAO). The purpose of this study was to investigate how providing patient-specific, mechanically optimal acetabular reorientations to the surgeon during preoperative planning affected the surgically achieved correction. Methods: Preoperative CT scans were used to create patient-specific hip models for 6 patients scheduled for PAO. A simulated acetabular fragment was extracted from the preoperative pelvis model and computationally rotated to simulate candidate acetabular reorientations. For each candidate, discrete element analysis was used to compute contact stresses during walking, which were summed over the gait cycle and scaled by patient age to obtain chronic contact stress-time exposure. The ideal patient-specific reorientation was identified using a cost function that balances minimising chronic stress exposures and achieving surgically acceptable acetabular coverage angles. The optimal reorientation angles and associated contact mechanics were provided to the surgeon preoperatively. After PAO was performed, a model of the surgically achieved correction was created from a postoperative CT scan. Radiographic coverage and contact mechanics were compared between preoperative, optimal, and surgically achieved orientations. Results: While surgically achieved reorientations were not significantly different from optimal reorientations in radiographically measured lateral (p = 0.094) or anterior (p = 0.063) coverage, surgically achieved reorientations had significantly (p = 0.031) reduced total contact area compared to optimal reorientations. The difference in lateral coverage and peak chronic exposure between surgically achieved and optimal reorientations decreased with increasing surgeon experience using the models (R² = 0.758, R2 = 0.630, respectively). Conclusions: Providing hip surgeons with a patient-specific, computationally optimal reorientation during preoperative planning may improve contact mechanics after PAO, which may help reduce osteoarthritis progression in patients with hip dysplasia. [ABSTRACT FROM AUTHOR]

The subclavian vein is typically used in cardiovascular implantable electronic device (CIED) implantations. External stress on the subclavian vein can lead to lead‐related complications. There are several causes of this stress, such as frequent upper extremity movements or external injury. Venous thoracic outlet syndrome (TOS) can also become the cause of external lead stress. However, the diagnosis of venous TOS can be challenging because subclavian venography can appear normal at first glance. We present a unique case of a device infection in a patient with venous TOS. A careful observation of the imaging studies is vital for diagnosing venous TOS and a leadless pacemaker implantation could be an alternative therapeutic option. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate root-analog implants (RAIs) fabricated by selective laser melting (SLM). Materials and Methods: Two types of implants (a maxillary right first molar RAI and a screw-cylinder--type molar implant) were designed using CAD software. Both implant types were fabricated with the SLM technique using Ti-6Al-4V powder. The stress distribution and micromotion of the implants were evaluated using finite element analysis, and the mechanical properties of the printed implants (relative density and compression test), surface properties of an SLM-fabricated specimen (morphology, roughness, and contact angle test), and biocompatibility of an SLM-fabricated specimen (osteoblast attachment, metal ion precipitation analysis, cell viability, and osteogenic gene expression) were evaluated. Results: The RAI model exhibited better stress distribution and less micromotion than the screw-cylinder implant model. The screw-cylinder implant was better than the RAI at withstanding pressure, but both implant types could withstand masticatory forces. The densities of both implant types were similar to those of the bulk materials. Block samples made using the same SLM technique as the RAI exhibited good surface properties and excellent biocompatibility. Conclusion: The properties of the molar RAI fabricated with the SLM technique suggest that it may have potential for future clinical use, but this will need to be verified by in vivo studies. [ABSTRACT FROM AUTHOR]

Purpose: This research aimed to evaluate the stress and fatigue generated in short implants compared to regular implants in rehabilitation with fixed full-arch implant-supported prostheses in atrophic mandibles using the finite element method (FEM). Materials and Methods: Four models were constructed with different implants lengths: 4, 6, 8, and 10 mm. A 100-N oblique load was applied to evaluate the stress on the bone, implant, and prosthetic components. Results: Similar behavior was observed for all groups, except for 4 mm, which showed more discrepant values. During the fatigue test, all the groups exhibited infinite lives except G4. Conclusion: Based on the similarity of all the models, it is suggested that all short implants investigated are seemingly viable alternatives for the rehabilitation of atrophic mandibles. However, the 6-mm-long and 8-mm-long implants evinced more favorable mechanical behavior than the 4-mm-long type. [ABSTRACT FROM AUTHOR]

Objective: The temporomandibular joint (TMJ) disc cushions intraarticular stress during mandibular movements. While mechanical overloading is related to cartilage degeneration, the pathogenesis of TMJ disc degeneration is unclear. Here, we determined the regulatory role of mechanoinductive transient receptor potential vanilloid 4 (TRPV4) in mechanical overload‐induced TMJ disc degeneration. Methods: We explored the effect of mechanical overload on the TMJ discs in a rat occlusal interference model in vivo, and by applying sustained compressive force in vitro. TRPV4 inhibition was delivered by small interfering RNA or GSK2193874; TRPV4 activation was delivered by GSK1016790A. The protective effect of TRPV4 inhibition was validated in the rat occlusal interference model. Results: Occlusal interference induced TMJ disc degeneration with enhanced extracellular matrix degradation in vivo and mechanical overload promoted inflammatory responses in the TMJ disc cells via Ca2+ influx with significantly upregulated TRPV4. TRPV4 inhibition reversed mechanical overload‐induced inflammatory responses; TRPV4 activation simulated mechanical overload‐induced inflammatory responses. Moreover, TRPV4 inhibition alleviated TMJ disc degeneration in the rat occlusal interference model. Conclusion: Our findings suggest TRPV4 plays a pivotal role in the pathogenesis of mechanical overload‐induced TMJ disc degeneration and may be a promising target for the treatment of degenerative changes of the TMJ disc. [ABSTRACT FROM AUTHOR]

Myocardial bridging (MB) is a segment of coronary arteries with an intramural course, typically spared from atherosclerosis, while the adjacent proximal segment is reported to be atherosclerosis-prone, a phenomenon contributed to local endothelial shear stress (ESS). We aimed to describe the ESS milieu in coronaries with MBs combining coronary computed tomography angiography with computational fluid dynamics and to investigate the association of atherosclerosis presence proximal to MBs with hemorheological characteristics. Patients (n = 36) were identified and 36 arteries with MBs (11 deep and 25 superficial) were analyzed. ESS did not fluctuate 5 mm proximally to MBs vs 5 mm within MBs (0.94 vs 1.06 Pa, p =.56). There was no difference when comparing ESS in the proximal versus mid versus distal MB segments (1.48 vs 1.37 vs 1.9 Pa, p = ns). In arteries with plaques (n = 12), no significant ESS variances were observed around the MB entrance, when analyzing all arteries (p =.81) and irrespective of morphological features of the bridged segment (deep MBs; p =.65, superficial MBs; p =.84). MBs are characterized by homogeneous, atheroprotective ESS, possibly explaining the absence of atherosclerosis within bridged segments. The interplay between ESS and atherosclerosis is potentially not different in arteries with MB compared with arteries without bridges. [ABSTRACT FROM AUTHOR]

Restorative dentistry is the repairing of damaged teeth and restoring oral health and function. Dental implants are typically placed within the cortical bone of the jaw to provide stability and support for prosthetic restorations. The successful restoration of complex anatomical features of the maxillary anterior is difficult for prosthodontists. Using a 3D slicer, CT scan images were used to create a detailed three-dimensional model of the maxilla bone. This study utilizes ANSYS Workbench, a finite element software program, to analyze the abutment angles, ranging from 0° to 25°, and the impact stress distribution within peri-implant bone. The outcomes of our studies align with and substantiate certain evidence in the literature documenting bone resorption, specifically at the level of the implant neck and near the cortical bone. The study aims to provide a comprehensive understanding of angled abutment stress patterns in the bone surrounding dental implants, offering valuable insights for clinical applications in critical areas of the mouth. [ABSTRACT FROM AUTHOR]

The literature shows evidence of the mechanical investigation of numerous polymeric dental biomaterials using a static approach. A more representative mechanical analysis of such materials must take into account the dynamic masticatory load of the oral cavity. The aim of this work is to study the dynamic mechanical proprieties and provide an in vitro characterization of 11 3D-printed new dental biomaterials to understand their clinical applications under physiological conditions. The analysis included Dynamical Mechanical Analysis (DMA) and an MTT cytotoxicity assay. The mechanical results at low frequencies (1–11 Hz) show high uncertainty, less fragility, and less strength. The biological results show a significant reduction in cell viability (p < 0.01) at both the 3 and 24 h timepoints, with a degree of recovery observed at 24 h. To assess the clinical potential of dental biomaterials, it is necessary to determine whether there are good dynamic mechanical properties and reduced adverse biological effects on oral cells. This may allow for the facile fabrication via 3D printing of prosthetic devices that can support masticatory loads over long periods of time. Further investigations of the presented polymeric materials are needed, exploring biological assessments for longer than 24 h. [ABSTRACT FROM AUTHOR]

Background: Osteochondritis dissecans (OCD) is a joint disorder predominantly affecting the knee, elbow, and ankle of children and adolescents. This comprehensive review delves into the epidemiology, etiology, clinical manifestations, diagnostic approaches, and treatment of OCD. Results: The most common cause of OCD is repetitive microtrauma, typically associated with sports activities, alongside other significant factors such as genetic predisposition, ischemia, and obesity. In early stages or when lesions are small, OCD often presents as non-specific, vaguely localized pain during physical activity. As the condition progresses, patients may experience an escalation in symptoms, including increased stiffness and occasional swelling, either during or following activity. These symptom patterns are crucial for early recognition and timely intervention. Diagnosis in most cases is based on radiographic imaging and magnetic resonance imaging. Nonsurgical treatment of OCD in young patients with open growth plates and mild symptoms involves activity restriction, immobilization methods, and muscle strengthening exercises, with a return to sports only after symptoms are fully resolved and at least six months have passed. Surgical treatment of OCD includes subchondral drilling in mild cases. Unstable lesions involve methods like restoring the joint surface, stabilizing fractures, and enhancing blood flow, using techniques such as screws, anchors, and pins, along with the removal of fibrous tissue and creation of vascular channels. The specifics of OCD treatment largely depend on the affected site. Conclusions: This synthesis of current research and clinical practices provides a nuanced understanding of OCD, guiding future research directions and enhancing therapeutic strategies. [ABSTRACT FROM AUTHOR]

Introduction: For individuals with limb loss, bone-anchored implants create a direct structural and functional connection to a terminal prosthesis. Here, we characterized the mechanical loads distal to the abutment during several functional performance tests in Service members with transfemoral (TF) limb loss, to expand on prior work evaluating more steady-state ambulation on level ground or slopes/stairs. Methods: Two males with unilateral TF limb loss and two males with bilateral TF limb loss participated after two-stage osseointegration (24 and 12 months, respectively). Tri-directional forces and moments were wirelessly recorded through a sensor, fit distal to the abutment, during six functional tests: Timed Up and Go (TUG), Four Square Step Test (FSST), Six Minute Walk Test (6MWT), Edgren Side-Step Test (SST), T-Test (TTEST), and Illinois Agility Test (IAT). Additionally, participants performed a straight-line gait evaluation on a 15 m level walkway at a self-selected speed (0.93-1.24 m/s). Peak values for each component of force and moment were extracted from all six functional tests; percent differences compared each peak with respect to the corresponding mean peak in straight-line walking. Results: Peak mechanical loads were largest during non-steady state components of the functional tests (e.g., side-stepping during SST or TTEST, standing up from the ground during IAT). Relative to walking, peak forces during functional tests were larger by up to 143% (anterior-posterior), 181% (medial-lateral), and 110% (axial); peak moments were larger by up to 108% (flexion-extension), 50% (ab/adduction), and 211% (internal/external rotation). Conclusions: A more comprehensive understanding of the mechanical loads applied to bone-anchored implants during a variety of activities is critical to maximize implant survivability and long-term outcomes, particularly for Service members who are generally young at time of injury and return to active lifestyles. [ABSTRACT FROM AUTHOR]

Background: The selection of post-core material holds significant importance in endodontically treated teeth, influencing stress distribution in the dental structure after restoration. The use of computer-aided design/computer-aided manufacturing (CAD/CAM) glass fiber post-core possesses a better adaptation for different root canal morphologies, but whether this results in a more favorable stress distribution has not been clearly established. Materials and methods: This study employed finite element analysis to establish three models of post-core crown restoration with normal, oversized, and dumbbell-shaped root canals. The three models were restored using three different materials: CAD/CAM glass fiber post-core (CGF), prefabricated glass fiber post and resin core (PGF), and cobalt-chromium integrated metal post-core (Co-Cr), followed by zirconia crown restoration. A static load was applied and the maximum equivalent von Mises stress, maximum principal stress, stress distribution plots, and the peak of maximum displacement were calculated for dentin, post-core, crown, and the cement acting as the interface between the post-core and the dentin. Results: In dentin of three different root canal morphology, it was observed that PGF exhibited the lowest von Mises stresses, while Co-Cr exhibited the highest ones under a static load. CGF showed similar stress distribution to that of Co-Cr, but the stresses were more homogeneous and concentrated apically. In oversized and dumbbell-shaped root canal remnants, the equivalent von Mises stress in the cement layer using CGF was significantly lower than that of PGF. Conclusions: In oversized root canals and dumbbell-shaped root canals, CGF has shown good performance for restoration of endodontically treated teeth. Clinical relevance: This study provides a theoretical basis for clinicians to select post-core materials for residual roots with different root canal morphologies and should help to reduce the occurrence of complications such as root fracture and post-core debonding. [ABSTRACT FROM AUTHOR]

Background: The aim of this study is to investigate, through finite element analysis (FEA), the biomechanical behavior of the built-in angle corrected dental implant versus implant with angled multiunit abutment used in All-On-Four treatment protocol. Methods: Two (3D) finite element models of a simplified edentulous mandible were constructed with two different posterior implant designs based on the All-On-Four protocol. Four implants were placed in each model, the two anterior implants were positioned vertically at the lateral incisor/canine sites. Depending on the implant fixture design in posterior area, there are two models created; Model I; the mandible was rehabilitated with four co-axis (4 mm in diameter × 15 mm in length) implants with distally built-in angle corrected implants (24-degree angle correction).While Model II, the mandible was rehabilitated with four conventional (4 mm in diameter × 14 mm in length) implants with a distally inclined posterior implants (25 degree) and angled multiunit abutments. CAD software (Solidworks© 2017; Dassault Systems Solidworks Corp) was used to model the desired geometry. Axial and inclined Loads were applied on the two models. A Finite element analysis study was done using an efficient software ANSYS© with specified materials. The resultant equivalent Von-Misses stresses (VMS), maximum principal stresses and deformation analysis were calculated for each part (implants and prosthetic components). Results: When applying axial and non-axial forces, model II (angled multiunit model) showed higher deformation on the level of Ti mesh about 13.286 μm and higher VMS 246.68 MPa than model I (angle corrected implant). Model I exhibited higher maximum stresses 107.83 MPa than Model II 94.988 MPa but the difference was not statistically significant. Conclusion: Within the limitation of the FEA study, although angle correcting implant design is showing higher values in maximum principle stresses compared with angled multiunit abutments, model deformation and resultant VMS increased with angled multiunit abutments. The angle correcting designs at implant level have more promising results in terms of deformation and VMS distribution than angle correction at abutment level. [ABSTRACT FROM AUTHOR]

Statement of problem: CAD/CAM occlusal veneers have been developed for minimally invasive prosthetic restoration of eroded teeth. Marginal adaptation and fracture resistance are crucial for the long-term survivability and clinical success of such restorations. Virgilite-based lithium disilicate glass-ceramic is a newly introduced material with claims of high strength. However, constructing occlusal veneers from this material of varying thickness has not been investigated. Purpose: The current study aimed to assess the impact of CAD/CAM occlusal veneer thickness and materials on marginal adaptation and fracture resistance. Materials and methods: Thirty-two occlusal veneers were constructed and divided into two groups (n = 16) based on the CAD/CAM material into Brilliant Crios and CEREC Tessera. Each group was further subdivided into two subgroups (n = 8) according to the thickness: 0.6 and 0.9 mm. Occlusal veneers were bonded to epoxy resin dies. The marginal gap was evaluated before and after thermodynamic aging. Fracture resistance and failure mode were evaluated for the same samples after aging. Marginal adaptation was analyzed using the Mann-Whitney U test. Fracture resistance was analyzed using Weibull analysis (α = 0.05). Results: The marginal gap was significantly increased following thermodynamic aging for tested groups (P < 0.001). CEREC Tessera showed a significantly higher marginal gap than Brilliant Crios before and after aging for both thicknesses (P < 0.05). CEREC Tessera recorded lower significant fracture load values compared to Brilliant Crios (P < 0.05). Conclusions: Both CEREC Tessera and Brilliant Crios demonstrated clinically accepted marginal gap values. All groups showed fracture resistance values higher than the average masticatory forces in the premolar region except for 0.6 mm CEREC Tessera. Clinical implications: Reinforced composite occlusal veneers demonstrated more favorable outcomes in terms of marginal gap and fracture resistance at both tested thicknesses compared to virgilite-based lithium disilicate glass-ceramic. Additionally, caution should be exercised during the construction of occlusal veneers from virgilite-based lithium disilicate glass-ceramic with reduced thickness. [ABSTRACT FROM AUTHOR]

Hypoxic exercise, which can induce arterial and tissue deoxygenation, promotes physiological adaptations. However, reduced oxygen availability can lower the absolute training intensity (i.e., mechanical stress). Adding normoxic recovery to sprint interval exercise (SIE) is one potential approach to strike a balance between providing a hypoxic stimulus and maintaining the absolute training intensity. However, the effects of adding normoxic recovery to SIE on performance and physiological responses are uncertain. We tested the hypothesis that hypoxic SIE with normoxic recovery enhances arterial deoxygenation and muscle deoxygenation levels without impeding performance compared to an entirely normoxic condition. On separate days, seven male sprinters performed 4 × 30‐s 'all‐out' cycle sprints with 4.5‐min recovery with hypoxic exposure (FiO2: 12.7%O2) applied continuously (hypoxia, HYP), intermittently during sprint periods only (intermittent, INT), or not at all (normoxia, NOR). Power output, oxygen saturation, muscle oxygenation, surface electromyography (EMG) activity, heart rate, blood lactate concentration, and ratings of perceived exertion were measured. The total work significantly decreased in HYP than NOR (p < 0.05) and INT (p < 0.01). The aTrterial oxygen saturation was lower during HYP than NOR (∼86% vs. ∼97%; p < 0.001), while lower values were also obtained for INT than NOR during sprint periods (∼85% vs. ∼97%; p < 0.001) but not during recovery periods (∼96% vs. ∼97%). The heart rate differed (p < 0.05) between conditions (NOR: ∼164 bpm; INT: ∼160 bpm; HYP: ∼156 bpm). No other variables demonstrated significant differences between conditions. Adding hypoxia during exercise while recovering in normoxia did not compromise exercise capacity during SIE, despite inducing larger arterial deoxygenation levels compared to normoxia. Highlights: Utilizing severe hypoxia during exercise and normoxia during recovery induces a substantial hypoxic stimulus while safeguarding mechanical performance in sprinters.This approach maintains neuromuscular, metabolic, and perceptual parameters without any detrimental effects, ensuring athletes can perform at their best.Alternating hypoxia and normoxia during active and passive phases shows potential for optimizing hypoxic training, striking an ideal balance between the hypoxic stimulus and training intensity and load. [ABSTRACT FROM AUTHOR]

Background: The aim of this study is to evaluate the stress distributions of a primary molar tooth restored with a stainless steel crown (SSC) using resin and glass ionomer luting cements by Finite Element Analysis (FEA). Methods: Original DICOM data of a primary molar was used to create a 3D model. One model was prepared as a tooth model with SSC. A 30 μm cement layer was used in model. Two different luting cements were tested in the study: self-cure adhesive resin cement, and glass ionomer cement. Vertical and oblique loads of 330 N were applied to simulate maximum bite force and lateral forces in the occlusal contact areas of the models. Maximum von Mises stress values in the models were evaluated as MPa. Results: The maximum von Mises stress value was observed in the force application and general occlusal contact areas for all models. The maximum von Mises stress values were higher in the tooth model with SSC using self-cure adhesive resin cement (478.09 MPa and 214.62 MPa) than in the tooth model with SSC using glass ionomer cement (220.06 MPa and 198.72 MPa) in both vertical and oblique loading, respectively. Conclusions: Depending on the magnitude of the bite force on the SSC, fracture of the luting cement materials could occur if the stress exceeds the endurance limit of the luting cement. Cementation with glass ionomer cement may help to reduce stress levels in SSC restorations of primary molars in children. [ABSTRACT FROM AUTHOR]

Purpose: Rapidly destructive coxarthrosis (RDC) is a rare syndrome of unknown etiology. This study evaluated sagittal spinopelvic alignment (SSPA) in patients with RDC and compared it with that in patients with hip osteoarthritis (HOA). In addition, finite element analysis (FEA) was performed to investigate the distribution of stress on the femoral head in RDC versus HOA. Methods: This retrospective study included patients who had undergone primary total hip arthroplasty for RDC (n = 33) and HOA (n = 99; age- and sex-matched to patients with RDC) at three hospitals from June 2014 to September 2020. Preoperative SSPA parameters and inflammatory blood markers were compared between the two groups. FEA on the computed tomography data was performed for four patients from each group with similar pelvic tilt (PT) and lateral center–edge angle (LCEA). The distribution of Drucker–Prager equivalent stress was assessed at the loaded area of the femoral head. Results: Patients with RDC had significantly higher PT, lower sacral slope, decreased lumbar lordosis (LL), higher sagittal vertical axis, and higher pelvic incidence minus LL than patients with HOA, indicating sagittal spinal imbalance. Blood test revealed patients with RDC had higher levels of inflammation markers than patients with HOA. FEA revealed no statistically significant difference in the degree of stress concentration or the maximum equivalent stress between the two groups when PT and LCEA were comparable. Conclusion: Patients with RDC tend to have sagittally imbalanced spine. Decreased acetabular coverage of the femoral head may heighten mechanical load of the hip joint in patients with RDC. [ABSTRACT FROM AUTHOR]

Background: Evans and Hintermann lateral column lengthening (LCL) procedures are both widely used to correct adult acquired flatfoot deformity (AAFD), and have both shown good clinical results. The aim of this study was to compare these two procedures in terms of corrective ability and biomechanics influence on the Chopart and subtalar joints through finite element (FE) analysis. Methods: Twelve patient-specific FE models were established and validated. The Hintermann osteotomy was performed between the medial and posterior facets of the subtalar joint; while, the Evans osteotomy was performed on the anterior neck of the calcaneus around 10 mm from the calcaneocuboid joint surface. In each procedure, a triangular wedge of varying size was inserted at the lateral edge. The two procedures were then compared based on the measured strains of superomedial calcaneonavicular ligaments and planter facia, the talus-first metatarsal angle, and the contact characteristics of talonavicular, calcaneocuboid and subtalar joints. Results: The Hintermann procedure achieved a greater correction of the talus-first metatarsal angle than Evans when using grafts of the same size, indicating that Hintermann had stronger corrective ability. However, its distributions of von-Mises stress in the subtalar, talonavicular and calcaneocuboid joints were less homogeneous than those of Evans. In addition, the strains of superomedial calcaneonavicular ligaments and planter facia of Hintermann were also greater than those of Evans, but both generally within the safe range (less than 6%). Conclusion: This FE analysis study indicates that both Evans and Hintermann procedures have good corrective ability for AAFD. Compared to Evans, Hintermann procedure can provide a stronger corrective effect while causing greater disturbance to the biomechanics of Chopart joints, which may be an important mechanism of arthritis. Nevertheless, it yields a better protection to the subtalar joint than Evans osteotomy. Clinical relevance: Both Evans and Hintermann LCL surgeries have a considerable impact on adjacent joints and ligament tissues. Such effects alongside the overcorrection problem should be cautiously considered when choosing the specific surgical method. Level of evidence: Level III, case–control study. [ABSTRACT FROM AUTHOR]

Background: In recent years, zygomatic implants and the all-on-four treatment concept have been increasingly preferred for rehabilitation of atrophic maxillae. However, debate continues regarding the optimal configuration and angulation of the implants. The aim of this study was to analyze the biomechanical stress in implants and peri-implant bone in an edentulous maxilla with zygomatic implants and the all-on-four concept, using multiple implant configurations. Methods: A total of 7 models consisting different combinations of 4-tilted dental implants and zygomatic implants were included in the study. In each model, a total of 200 N perpendicular to the posterior teeth and 50 N with 45° to the lateral tooth were applied. A finite element analysis was performed for determination of stress distribution on implants and peri-implant bone for each model. Results: Higher stress values were observed in both cortical and trabecular bone around the 45°-tilted posterior implants in all-on-four models when compared to zygomatic implants. In cortical bone, the highest stress was established in an all-on-four model including 45°-tilted posterior implant with 4,346 megapascal (MPa), while the lowest stress was determined in the model including anterior dental implant combined with zygomatic implants with 0.817 MPa. In trabecular bone, the highest stress was determined in an all-on-four model including 30°-tilted posterior implant with 0.872 MPa while the lowest stress was observed in quad-zygoma model with 0.119 MPa. Regarding von Mises values, the highest stress among anterior implants was observed in an all-on-four model including 17° buccally tilted anterior implant with 38.141 MPa, while the lowest was in the including anterior dental implant combined with zygomatic implants with 20,446 MPa. Among posterior implants, the highest von Mises value was observed in the all-on-four model including 30°-tilted posterior implant with 97.002 MPa and the lowest stress was in quad zygoma model with 35.802 MPa. Conclusions: Within the limits of the present study, the use of zygoma implants may provide benefit in decreasing biomechanical stress around both dental and zygoma implants. Regarding the all-on-four concept, a 17° buccal angulation of anterior implants may not cause a significant stress increase while tilting the posterior implant from 30° to 45° may cause an increase in the stress around these implants. [ABSTRACT FROM AUTHOR]