Prediction of osteoporotic degradation of tibia human bone at trabecular scale.

A theoretical numerical model is proposed to predict patient dependent osteoporotic bone degradation. The model parameters are identified through a particle swarm optimization algorithm and based on individual patient high resolution peripherical quantitative computer tomography (HRpQCT) scan data. The degradation model is based on cellular activity initiated by the elastic strain energy developed in the bone microstructure through patient's body weight.

Decisive structural elements in water and ion permeation through mechanosensitive channels of large conductance: insights from molecular dynamics simulation.

In this paper, a series of equilibrium molecular dynamics simulations (EMD), steered molecular dynamics (SMD), and computational electrophysiology methods are carried out to explore water and ion permeation through mechanosensitive channels of large conductance (MscL). This research aims to identify the pore-lining side chains of the channel in different conformations of MscL homologs by analyzing the pore size. The distribution of permeating water dipole angles through the pore domains enclosed by VAL21 and GLU104 demonstrated that water molecules are oriented toward the charged oxygen headgroups of GLU104 from their hydrogen atoms to retain this interaction in a stabilized fashion.

Prediction of Cortical Bone Thickness Variations in the Tibial Diaphysis of Running Rats.

A cell-mechanobiological model is used for the prediction of bone density variation in rat tibiae under medium and high mechanical loads. The proposed theoretical-numerical model has only four parameters that need to be identified experimentally. It was used on three groups of male Wistar rats under sedentary, moderate intermittent and continuous running scenarios over an eight week period.

A Microfabrication Method of PCL Scaffolds for Tissue Engineering by Simultaneous Two PDMS Molds Replication.

Not very far away, "tissue engineering" will become one of the most important branches of medical science for curing many types of diseases. This branch needs the cooperation of a wide range of sciences like medicine, chemistry, cellular biology, and genetic and mechanical engineering. Different parameters affect the final produced tissue, but the most important one is the quality and biocompatibility of the scaffold with the desired tissue which can provide the functionality of "native ECM" as well.

Cleft Alveolar Bone Graft Materials: Literature Review.

Introduction: Since the early stages of alveolar bone grafting development, multiple types of materials have been used. Iliac cancellous bone graft (ICBG) remains the gold standard.

Design/methods: A review of literature is conducted in order to describe the different bone filling possibilities, autologous or not, and to assess their effectiveness compared to ICBG.

A novel machine learning based computational framework for homogenization of heterogeneous soft materials: application to liver tissue.

Real-time simulation of organs increases comfort and safety for patients during the surgery. Proper generalized decomposition (PGD) is an efficient numerical method with coordinate errors below 1 mm and response time below 0.1 s that can be used for simulated surgery.

Constitutive Modeling of the Tensile Behavior of Recycled Polypropylene-Based Composites.

The effect of reprocessing on the quasi-static uniaxial tensile behavior of two commercial polypropylene (PP)-based composites is experimentally investigated and modeled. In particular, the studied materials consist of an unfilled high-impact PP and a talc-filled high-impact PP. These PP composites are subjected to repeated processing cycles, including a grinding step and an extrusion step to simulate recycling at the laboratory level, the selected reprocessing numbers for this study being 0, 3, 6, 9, and 12.

Homogenization of heterogeneous brain tissue under quasi-static loading: a visco-hyperelastic model of a 3D RVE.

Researches, in the recent years, reveal the utmost importance of brain tissue assessment regarding its mechanical properties, especially for automatic robotic tools, surgical robots and helmet producing. For this reason, experimental and computational investigation of the brain behavior under different conditions seems crucial. However, experiments do not normally show the distribution of stress and injury in microscopic scale, and due to various factors are costly.

A model order reduction approach to create patient-specific mechanical models of human liver in computational medicine applications.

Background And Objective: This paper focuses on computer simulation aspects of Digital Twin models in the medical framework. In particular, it addresses the need of fast and accurate simulators for the mechanical response at tissue and organ scale and the capability of integrating patient-specific anatomy from medical images to pinpoint the individual variations from standard anatomical models.

Methods: We propose an automated procedure to create mechanical models of the human liver with patient-specific geometry and real time capabilities.

A New Software Suite in Orthognathic Surgery : Patient Specific Modeling, Simulation and Navigation.

Orthognathic surgery belongs to the scope of maxillofacial surgery. It treats dentofacial deformities consisting in discrepancy between the facial bones (upper and lower jaws). Such impairment affects chewing, talking, and breathing and can ultimately result in the loss of teeth.

Determinative factors in inhibition of aquaporin by different pharmaceuticals: Atomic scale overview by molecular dynamics simulation.

The inhibition of water permeation through aquaporins by ligands of pharmaceutical compounds is considered as a method to control the cell lifetime. The inhibition of aquaporin 1 (AQP1) by bacopaside-I and torsemide, was explored and its atomistic nature was elucidated by molecular docking and molecular dynamics (MD) simulation collectively along with Poisson-Boltzmann surface area (PBSA) method. Docking results revealed that torsemide has a lower level of docking energy in comparison with bacopaside-I at the cytoplasmic side.

Optimization of Taylor spatial frame half-pins diameter for bone deformity correction: Application to femur.

Using external fixtures for bone deformity correction takes advantages of less soft tissue injury, better bone alignment and enhances strain development for bone formation on cutting section, which cause shorter healing time. Among these fixtures, Taylor spatial frame is widely used and includes two rings and six adjustable struts developing 6 degrees of freedom, making them very flexible for this type of application. The current study describes a method to optimize Taylor spatial frame pin-sizes currently chosen from the surgeon's experiences.

Experimental quantification of the mechanical forces and moments applied on three adjacent orthodontic brackets.

Orthodontic appliances deliver forces and moments that will determine movement of teeth. To analyze this latter, we developed an experimental setup to measure the mechanical forces applied on the teeth and to calculate, through a simplified theoretical analysis, the reactive forces and corresponding moments onto the brackets of three adjacent teeth. To validate the theoretical and experimental results, we use a simplified clinical situation of a maxillary canine in infraclusion and surrounded by its corresponding upper lateral incisor and first premolar.

Mechanical equilibrium of forces and moments applied on orthodontic brackets of a dental arch: Correlation with literature data on two and three adjacent teeth.

Although orthodontics have greatly improved over the years, understanding of its associated biomechanics remains incomplete and is mainly based on two dimensional (2D) mechanical equilibrium and long-time clinical experience. Little experimental information exists in three dimensions (3D) about the forces and moments developed on orthodontic brackets over more than two or three adjacent teeth. We define here a simplified methodology to quantify 3D forces and moments applied on orthodontic brackets fixed on a dental arch and validate our methodology using existing results from the literature by means of simplified hypotheses.

Multiphysics of bone remodeling: A 2D mesoscale activation simulation.

In this work, we present an evolutive trabecular model for bone remodeling based on a boundary detection algorithm accounting for both biology and applied mechanical forces, known to be an important factor in bone evolution. A finite element (FE) numerical model using the Abaqus/Standard® software was used with a UMAT subroutine to solve the governing coupled mechanical-biological non-linear differential equations of the bone evolution model. The simulations present cell activation on a simplified trabeculae configuration organization with trabecular thickness of 200µm.

Numerical simulation and identification of macroscopic vascularised liver behaviour: Case of indentation tests.

Mini-invasive surgery restricts the surgeon information to two-dimensional digital representation without the corresponding physical information obtained in previous open surgery. To overcome these drawbacks, real time augmented reality interfaces including the true mechanical behaviour of organs depending on their internal microstructure need to be developed. For the case of tumour resection, we present here a finite element numerical study of the liver mechanical behaviour including the effects of its own vascularisation through numerical indentation tests in order extract the corresponding macroscopic behaviour.

Examples of multiscale and multiphysics numerical modeling of biological tissues.

Predictive theoretical-numerical modeling of the behavior and evolution of biological tissue is a difficult task since many of the required knowledge tools (experimental, theoretical and numerical) are still not well understood. We present here some methodologies and results specific to multiscale and multiphysics numerical modeling of biological tissues applied to the predictive behavior of cortical veins depending on their local constituents' microstructure and for bone remodeling and reconstruction as a function of the local mechanobiology. Although further work is required to improve the accuracy of the developed models, the proposed approaches highlight their potential usefulness for understanding the mechanical-biological couplings, short and long term predictions of biological evolutions as well as possible further transfer to medical applications.

A novel navigation system for maxillary positioning in orthognathic surgery: Preclinical evaluation.

Appropriate positioning of the maxilla is critical in orthognathic surgery. As opposed to splint-based positioning, navigation systems are versatile and appropriate in assessing the vertical dimension. Bulk and disruption to the line of sight are drawbacks of optical navigation systems.

Assessing the three-dimensional collagen network in soft tissues using contrast agents and high resolution micro-CT: Application to porcine iliac veins.

The assessment of the three-dimensional architecture of collagen fibers inside vessel walls constitutes one of the bases for building structural models for the description of the mechanical behavior of these tissues. Multiphoton microscopy allows for such observations, but is limited to volumes of around a thousand of microns. In the present work, we propose to observe the collagenous network of vascular tissues using micro-CT.

Evolution of the three-dimensional collagen structure in vascular walls during deformation: an in situ mechanical testing under multiphoton microscopy observation.

The collagen fibers' three-dimensional architecture has a strong influence on the mechanical behavior of biological tissues. To accurately model this behavior, it is necessary to get some knowledge about the structure of the collagen network. In the present paper, we focus on the in situ characterization of the collagenous structure, which is present in porcine jugular vein walls.

An optimum approximation of n-point correlation functions of random heterogeneous material systems.

An approximate solution for n-point correlation functions is developed in this study. In the approximate solution, weight functions are used to connect subsets of (n-1)-point correlation functions to estimate the full set of n-point correlation functions. In previous related studies, simple weight functions were introduced for the approximation of three and four-point correlation functions.