Nanoindentation is a useful technique for probing the mechanical properties of bone, and finite element (FE) modeling of the indentation allows inverse determination of elastoplastic constitutive properties. However, all but one FE study to date have assumed frictionless contact between indenter and bone. The aim of this study was to explore the effect of friction in simulations of bone nanoindentation. Two-dimensional axisymmetric FE simulations were performed using a spheroconical indenter of tip radius 0.6 μm and angle 90°. The coefficient of friction between indenter and bone was varied between 0.0 (frictionless) and 0.3. Isotropic linear elasticity was used in all simulations, with bone elastic modulus E = 13.56 GPa and Poisson's ratio of 0.3. Plasticity was incorporated using both Drucker-Prager and von Mises yield surfaces. Friction had a modest effect on the predicted force-indentation curve for both von Mises and Drucker-Prager plasticity, reducing maximum indenter displacement by 10% and 20% respectively as friction coefficient was increased from zero to 0.3 (at a maximum indenter force of 5 mN). However, friction has a much greater effect on predicted pile-up after indentation, reducing predicted pile-up from 0.27 to 0.11 μm with a von Mises model, and from 0.09 to 0.02 μm with Drucker-Prager plasticity. We conclude that it is potentially important to include friction in nanoindentation simulations of bone if pile-up is used to compare simulation results with experiment.
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http://dx.doi.org/10.1016/j.jmbbm.2011.03.026 | DOI Listing |
Orthop Surg
January 2025
Orthopedics Department, Gongli Hospital of Shanghai Pudong New Area, Shanghai, China.
Objective: Soft tissue defects and postoperative wound healing complications related to calcaneus fractures may result in significant morbidity. The aim of this study was to investigate whether percutaneous minimally invasive screw internal fixation (PMISIF) can change this situation in the treatment of calcaneal fractures, and aimed to explore the mechanical effects of different internal fixation methods on Sanders type III calcaneal fractures through finite element analysis.
Methods: This retrospective analysis focused on 83 patients with Sanders II and III calcaneal fractures from March 2017 to March 2022.
BMC Oral Health
January 2025
Department of Endodontics, Faculty of Dentistry, Erciyes University, Kayseri, Turkey.
Background: This study assessed stress distributions in simulated mandibular molars filled with various materials after the removal of fractured instruments from the apical thirds of the root canals.
Methods: Finite element models of the mesial and distal root canals were created, where fractured instruments were assumed to be removed using a staging platform established with a modified Gates-Glidden bur (Woodpecker, Guangxi, P.R.
BMC Oral Health
January 2025
Removable Prosthodontics Department, Faculty of Dentistry, October 6 University, Giza, Egypt.
Background: The continuous development in digital prosthodontics allowed the customization of attachments and retentive inserts which offers an easy and cheap solution for regular maintenance of locator overdentures during daily practice. The present study compared the change in retention values of the fully digitally manufactured custom-made locator attachment retentive insert with the ready-made ones after insertion, removal, and masticatory cycles.
Methods: A complete denture was constructed over a mandibular edentulous epoxy model.
J Biomech
January 2025
Department of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong Special Administrative Region.
This study explored how systematic changes in running shoe degradation and foot inversion alter the distribution and peak value of heel pressure and calcaneus stress, as well as the total stress-concentration exposure (TSCE) within the calcaneal bone. A foot-shoe finite element model was employed and three shoe wear conditions (new shoe (CON), moderate worn shoe (MWSC), excessive worn shoe (EWSC)) coupled with three foot inversion angles (0°, 10°, 20°) were further modulated. Simulations were conducted at the impact peak instant during running.
View Article and Find Full Text PDFJMIR Med Educ
January 2025
Department of Orthopedics, First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
Background: Teaching severe pelvic trauma poses a significant challenge in orthopedic surgery education due to the necessity of both clinical reasoning and procedural operational skills for mastery. Traditional methods of instruction, including theoretical teaching and mannequin practice, face limitations due to the complexity, the unpredictability of treatment scenarios, the scarcity of typical cases, and the abstract nature of traditional teaching, all of which impede students' knowledge acquisition.
Objective: This study aims to introduce a novel experimental teaching methodology for severe pelvic trauma, integrating virtual reality (VR) technology as a potent adjunct to existing teaching practices.
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