Zdeněk Florian

Finite element analysis of dental implant loading on atrophic and non-atrophic cancellous and cortical mandibular bone – a feasibility study

The first aim of this study was to assess displacements and micro-strain induced on different grades of atrophic cortical and trabecular mandibular bone by axially loaded dental implants using finite element analysis (FEA). The second aim was to assess the micro-strain induced by different implant geometries and the levels of bone-to-implant contact (BIC) on the surrounding bone. Six mandibular bone segments demonstrating different grades of mandibular bone atrophy and various bone volume fractions (from 0.149 to 0.471) were imaged using a micro-CT device. The acquired bone STL models and implant (Brånemark, Straumann, Ankylos) were merged into a three-dimensional finite elements structure. The mean displacement value for all implants was 3.1 ±1.2 µm. Displacements were lower in the group with a strong BIC. The results indicated that the maximum strain values of cortical and cancellous bone increased with lower bone density. Strain distribution is the first and foremost dependent on the shape of bone and architecture of cancellous bone. The geometry of the implant, thread patterns, grade of bone atrophy and BIC all affect the displacement and micro-strain on the mandible bone. Preoperative finite element analysis could offer improved predictability in the long-term outlook of dental implant restorations.

Comparison of the Resistance to Bending Forces of the 4.5 LCP Plate-rod Construct and of 4.5 LCP Alone Applied to Segmental Femoral Defects in Miniature Pigs

The study deals with the determination of mechanical properties, namely resistance to bending forces, of flexible buttress osteosynthesis using two different bone-implant constructs stabilizing experimental segmental femoral bone defects (segmental ostectomy) in a miniature pig ex vivo model using 4.5 mm titanium LCP and a 3 mm intramedullary pin (“plate and rod” construct) (PR-LCP), versus the 4.5 mm titanium LCP alone (A-LCP). The “plate and rod” fixation (PR-LCP) of the segmental femoral defect is significantly more resistant ( p < 0.05) to bending forces (200 N, 300 N, and 500 N) than LCP alone (A-LCP). Stabilisation of experimental segmental lesions of the femoral diaphysis in miniature pigs by flexible bridging osteosynthesis 4.5 mm LCP in combination with the “plate and rod” construct appears to be a suitable fixation of non-reducible fractures where considerable strain of the implants by bending forces can be assumed. These findings will be used in upcoming in vivo experiments in the miniature pig to investigate bone defect healing after transplantation of mesenchymal stem cells in combination with biocompatible scaffolds. Fracture fixation, comminuted fracture, ostectomy, buttress osteosynthesis, implant failure

Stress-Deformation Analysis of an Elbow Articulation with Radial Head Replacement

this contribution speaks about the progress of forming a geometric elbow model, generating the FEM network in the created volumes; stress-deformation analysis of the Final Element Model (contact task) and suggests possible geometric models of partial alloplasty of the radius’s proximal part.

STRESS ANALYSIS OF THE RADIAL HEAD REPLACEMENT IN AN ELBOW ARTICULATION

The paper is focused on computational modeling of elbow articulation with radial head replacement. The main part of the project is aimed towards the creation of computational model of suitable partial endoprothesis of proximal part of the radial bone tissue which would keep the function of the elbow articulation while replacing the distance created by resection. The geometrical and computational models of radial head replacements and elbow joint were created. Computational models with these implants were compared with given physiological state of elbow articulation. The influence of friction and material characteristics of bone tissue and cartilage on changes in contact pressure (and therefore to the abrasion) were analyzed using those models.

Comparative Study of Two Different Types of Human Mandible Boundary Conditions Used in Finite Element Calculations

The aim of the presented work is compare a two different way of prescribing muscles and chewing force boundary condition. First variant of boundary condition consider muscle forces and their direction taken from literatures. Second variant of boundary condition consider muscles modeled as finite elements connecting lower jaw and skull together. At second variant a muscles material characteristic of Young ́s modulus was changed in range from 1e4 MPa to 2,1e5 MPa. Models of living tissues were created on base of CT images and modeled in 3D CAD software SolidWorks. Calculations were computed in the finite element software ANSYS. Material models were considered as homogenous, isotropic and linearly elastic for all parts. First, both variants of boundary condition were analyzed separately and after that, selected variables (as muscle forces and muscle direction scale factors) from both variant were compared together.

Stress Strain Analysis of High Porous Ceramics

The presented paper describes the creation of a computational model of highly porous materials, and a stress-strain analysis is performed. The computational model is created using micro-CT by the finite element method in the ANSYS 12.0 software. The micro-CT slices are converted into a 3D model using image processing. The local equivalent stress (HMH criterion) and struts deformation are analyzed. Commercially available ceramic foam, 85%Al2O3-14%SiO2- 1%MgO, was used in the experiment part of the paper.

Microstructural Finite-Element Analysis of Influence of Bone Density and Histomorphometric Parameters on Mechanical Behavior of Mandibular Cancellous Bone Structure

Using porous bioceramics became recently an alternative approach to increase bone density which is a key factor for successful dental implant application. These novel biomaterials should substitute missing natural trabecular structures in terms of material strength as well as deformation characteristics. However, mechanical behavior of these materials used as bone fillers are still in question. This problem is made more difficult by the fact that bone structure itself exhibits a complex mechanical behavior which is still in question as well and, therefore, appropriate analytical criteria should to be established. The purpose of this paper is to determine typical mechanical behavior of trabecular structure of mandibular cancellous bone using computational simulations which can serve as a basis for establishing such criteria. For this purpose, four bone specimens of various bone density were μCT-scanned and high-level finite element models including detailed trabecular structure were created on their basis to analyze relevant mechanical quantities for various loadings in terms of bone density and various histomorphometric parameters.

Computational Modelling of the Shape Deviations of the Sphere Surfaces of Ceramic Heads of Hip Joint Replacement

The problem of the damage of the bioimplants is very important today. In the endoprosthesis surgery there is a large percentage of implant defects, which cause the failure of the whole prosthesis. One kind of the total hip replacement functionality loss is acetabular cup pull-off from pelvis bone. This paper is aimed at manufacture perturbations (shape deviations) analysis as one of the possible reasons to this kind of failure. Dimension and of geometry manufacturing perturbations (roundness) were analyzed in detail. It was found, that these perturbations affect considered values of contact pressure and frictional moment. Contact pressure and frictional moment are quantities affecting replacement success and durability.

Computational Modeling of Porous Ceramics with Bioactive Layer

The paper deals with a creation of computational model of a high porous ceramic material. This type of material has a large-scale industrial utilization. The computational model was created based on micro-CT data in the ANSYS 14.0 software using Finite Element Method. A creation of a porous ceramic struts model which respect a micro architecture is quite difficult (computer demanding and micro-CT data). The micro-CT slices are converted into a 3D model using image processing (used software STL Model Creator). The local first principle stress was analyzed because, ceramic is the brittle material. Furthermore, the influence of the thick layer around the individual struts was analyzed.

Computational Modeling of Interaction of Dental Implant with Mandible

This paper is focused on computational modeling of an interaction of dental implant with mandible bone. It describes creation of computational model including model of geometry, materials, loads and constraints. There is a comparative stress-strain analysis of the levels of cancellous bone model. Computations are performed with the use of finite element method. Results show differences between the model which includes trabecular architecture of cancellous bone tissue and the model with non-trabecular cancellous bone tissue. For better description of the processes in bone tissue and at the interface between bone tissue and implant, it is necessary to create the computational model on the highest possible level, i.e. with the trabecular bone tissue.