Simulation of brittle damage for fracture process of endodontically treated tooth

The mechanics of brittle damage in porcelain of an endodontically treated maxilla incisor tooth was simulated using finite element method (FEM). For this purpose a very complex composite structure of endodontically treated tooth is simulated under transverse loading. Three dimensional (3D) model of human maxilla incisor tooth root was developed based on Computed Tomography (CT) scan images. Crown, core cement, resin core, dental post, post cement and dentin were created using SolidWorks software, and then the model was imported into ABAQUS-6.9EF software for nonlinear behavior analysis. This study utilizes finite element method to simulate onset and propagation of crack in ceramic layer (porcelain) by the cause of both tension and compression loading related to complexity of the geometry of tooth implant. The simulation has been done using brittle damaged model available in ABAQUS/Explicit in quasi-static load condition. The load-displacement response of whole structure is measured from the top of porcelain by controlling displacement on a rigid rod. Crack initiated at the top of porcelain bellow the location of the rod caused by tension damage at equivalent load of 590 N. Damage in porcelain accounts for up to 63% reduction of whole structure stiffness from the undamaged state. The failure process in porcelain layer can be described by an exponential rate of fracture energy dissipation. This study demonstrated that the proposed finite element model and analysis procedure can be use to predict the nonlinear behavior of tooth implant

Finite Element Analysis of Different Pin Diameter of External Fixator in Treating Tibia Fracture

Biomechanical perspective of external fixator is one of the biggest elements that should be considered in treating fracture bone. This is due to the mechanical behavior of the structure could be analyzed and optimized in order to avoid failure, increase bone fracture healing rate and prevents preterm screw loosening. There are three significant factors that affect the stability of external fixator and those are the placement of pin at the bone, configuration and components of external fixator. All these factors contribute to a question, what is the optimum pin diameter which exerts good stress distribution? To date, the research on the above-mentioned factors are limited in the literature. Therefore, this study was conducted to evaluate the unilateral external fixator with different pin sizes in treating tibia shaft fracture via the finite element method. First and foremost, the development of the tibia shaft fracture was conducted using Mimics software. The computed tomography (CT) data image was utilized to develop three-dimensional tibia bone followed by crafting fracture on the bone. Meanwhile, the unilateral external fixator was developed using SolidWorks software. In this study, five pin diameters (4.5, 5.0, 5.5, 6.0 and 6.5 mm) were developed and analyzed. Both tibia bone and external fixator were meshed in 3-matic software. Simulation of this configuration took place in a finite element software, Marc.Mentat. From the findings, it is shown that the larger diameter of pin demonstrated the lowest stress distribution. The size of the 5.5mm pin shows optimum diameter in terms of stress distribution with the value of 21.50 MPa in bone and 143.33 MPa in fixator. Meanwhile the displacement value of 1.42mm in bone and 1.20mm in fixator. In conclusion, it is suggested that the pin diameter of 5.5 mm is the most favorable option in treating tibia shaft fracture in terms of mechanical perspective

Mixed Velocity-Pressure (v-p) Finite Element Method in Assessing the Hemodynamic Wall Shear Stresses in a Fusiform Abdominal Aortic Aneurysm

In this paper, a mixed velocity (v-p) finite element method was used to analyze pulsating blood flow-induced wall shear stress (WSS) in an idealized fusiform abdominal aortic aneurysm (AAA). A three-dimensional mathematical model of the axially symmetric AAA was introduced. The Navier-Stokes and the continuity equations were solved numerically by exploiting the Galerkin method and the fully im-plicit incremental-iterative procedure. A physiologically realistic pulsatile blood flow waveform was im-posed onto the AAA model. This pulsatile condition simulates an in vivo aorta at rest. The developed finite element technique may proof to be useful for biomedical engineers who aim to develop specialized software simulation packages. Computational modeling is becoming a powerful tool in today’s medical treatment planning and predictive methods. Today, clinical application of numerical modeling and computer-aided surgical planning is considered the key for the future of medicine. (Abstract by authors

Finite element analysis of TMJ implant under clenching loads

The temporomandibular joint is one of the most complex anatomical structures and is exposed to high stress conditions during daily movements. Replacing the joint is normally done only in severe cases as success rate of the replaced joint is not as encouraging as other joint replacements. The design of TMJ implant which includes material selection plays a significant role in its success. Two different biomaterials—Ti–6Al–4V and CoCrMo— under static loads simulating five clenching tasks were analysed in this study. A three dimensional model of an adult mandible was developed from Computed Tomography image dataset, as well as a generic TMJ implant with fixation. All the applied clenching tasks consisted of nine principle muscles. The results showed that both materials were totally safe under these loading conditions. However Ti–6Al–4V showed a comparatively lower stress level

Mechanical and corrosion properties of partially degradable bone screws made of pure iron and stainless steel 316L by friction welding

This paper reports a series of in vitro, ex vivo and in vivo mechanical and corrosion studies of pin and screw prototype made of friction welded pure iron and 316L type stainless steel aiming to evaluate the applicability of the partially removable bone screws. Results showed that the pin possesses bending, tensile and torsional strengths of 1706±147, 666±7 and 0.34±0.03 MPa, respectively. The pin degraded at an average weight loss rate of 17.15×10−5 g cm−2 day−1 and released Fe ions at an average concentration of 2.38 ppm. Plastic deformation induced by torsion increased the corrosion rate of the pin from 0.0014 to 0.0137 mm year−1. The maximum pull-out load of the screw prototypes was 3800 N with a calculated failure strength by shear load equal to 22.2 kN which is higher than the strength of the cortical bone. Detailed analysis of the rat’s blood cells during 60 days of the pin implantation indicated a normal response with low neutrophils/ lymphocytes ratio of 0.3‒0.5. Iron ion concentration in the rat’s blood slightly increased from 55 to 61 ppm without affecting the tissue recovering and healing phase. Histological evaluation confirmed the presence of macrophage cells as a normal response to the released iron particles around the iron section of the pin

Elemental Diffusion Behaviour of Biomedical Grade Titanium Alloy through Thermal Oxidation

Major issues related to implant failure are wear debris and metal ions release where Titanium-Aluminium-Niobium alloys still face those problems despite of better biocompatibility. Surface modification is one of the alternatives in order to reduce those wear as well as ion release problems to the host tissue. In this study, experiments were carried out to investigate the element diffusion behaviour of Ti-6Al-7Nb alloy through thermal oxidation in order to obtain coating on the surfaces for diminishing those effects. Thermal oxidation was carried out at 650°C for three different durations 6, 12 and 24 hours. It is found that at prolong time, Niobium diffusion occurs where short duration Aluminium dominates. This suggests that longer heating time promotes heavy metal diffusion by restricting diffusion of light metal and hence, dominates the heavy metal oxide layer formation. The oxide layer formed on the substrate may lead to increase the lifespan of the implant and reduces the harmful effects caused by wear debris or toxic ion from metal alloys

Mechanical, Rheological, and Bioactivity Properties of Ultra High-Molecular-Weight Polyethylene Bioactive Composites Containing Polyethylene Glycol and Hydroxyapatite

Ultrahigh-molecular-weight polyethylene/high-density polyethylene (UHMWPE/HDPE) blends prepared using polyethylene glycol PEG as the processing aid and hydroxyapatite (HA) as the reinforcing filler were found to be highly processable using conventional melt blending technique. It was demonstrated that PEG reduced the melt viscosity of UHMWPE/HDPE blend significantly, thus improving the extrudability. The mechanical and bioactive properties were improved with incorporation of HA. Inclusion of HA from 10 to 50 phr resulted in a progressive increase in flexural strength and modulus of the composites. The strength increment is due to the improvement on surface contact between the irregular shape of HA and polymer matrix by formation of mechanical interlock. The HA particles were homogenously distributed even at higher percentage showed improvement in wetting ability between the polymer matrix and HA. The inclusion of HA enhanced the bioactivity properties of the composite by the formation of calcium phosphate (Ca-P) precipitates on the composite surface as proven from SEM and XRD analysis

A review on medicinal properties of saffron toward major diseases

The stigma of Crocus sativus, known as saffron, is one of the most expensive spices in the world. The bioactive components in saffron, picrocrocin, crocin, and safranal, have demonstrated a wide range of uses and capabilities in the medical field. This review is focused on the potential therapeutic applications of saffron on diabetes mellitus (DM), antitumor, anticancer, anti-depressant, Alzheimer’s disease (AD), cardiovascular disease (CVD), erectile dysfunction and antibacterial effects