Conceptual designs of 1.5 and 3.0 T full-body magnetic resonance imaging (MRI) magnets using conduction cooled MgB ₂ superconductor are presented. The sizes, locations, and number of turns in the eight coil bundles are determined using optimization methods that minimize the amount of superconducting wire and produce magnetic fields with an inhomogeneity of less than 10 ppm over a 45 cm diameter spherical volume. MgB ₂ superconducting wire is assessed in terms of the transport, thermal, and mechanical properties for these magnet designs. Careful calculations of the normal zone propagation velocity and minimum quench energies provide support for the necessity of active quench protection instead of passive protection for medium temperature superconductors such as MgB ₂ . A new ‘active’ protection scheme for medium T _c based MRI magnets is presented and simulations demonstrate that the magnet can be protected. Recent progress on persistent joints for multifilamentary MgB ₂ wire is presented. Finite difference calculations of the quench propagation and temperature rise during a quench conclude that active intervention is needed to reduce the temperature rise in the coil bundles and prevent damage to the superconductor. Comprehensive multiphysics and multiscale analytical and finite element analysis of the mechanical stress and strain in the MgB ₂ wire and epoxy for these designs are presented for the first time. From mechanical and thermal analysis of our designs we conclude there would be no damage to such a magnet during the manufacturing or operating stages, and that the magnet would survive various quench scenarios. This comprehensive set of magnet design considerations and analyses demonstrate the overall viability of 1.5 and 3.0 T MgB ₂ magnet designs.

An endodontic post is required to retain and support the core restoration in case of insufficient remaining coronal dentin after root canal therapy. This study analyzed the biomechanical and thermal behavior of PEEK prefabricated post after choosing the head design that produces the least amount of stress on the core and remaining tooth structure. These results were compared with the most common commercially available prefabricated post, which is titanium and glass fiber post. Thus a CBCT scanning of a maxillary central incisor with its supporting structure was used to construct a 3D solid model of an endodontically treated teeth for finite element analysis (FEA). The restored tooth with the spherical head design of PEEK prefabricated post yielded a more benign stress distribution and repairable failure mode on the crown, luting cement, core, and dentin under both mechanical and thermal loads, followed by glass fiber post and titanium post respectively.

Background: The ability of modern implant dentistry to achieve goals such as normal contour, function, comfort, esthetics, and health to totally or partially edentulous patients guaranteed it to be more effective and reliable method for the rehabilitation process of many challenging clinical situations. In regard to this, the current study evaluates the effect of changing implant shape design parameters on interface stress distribution within the mandible bone. Materials and Methods: A numerical procedure based on finite element (FE) method was adopted to investigate the influence of using different body design and thread depth of the inserted implant on the final stress situation. For the purpose of evaluation, a three-dimensional realistic FE models of mandible bone and inserted implant were constructed and analyzed using a pack of engineering software (Solidworks, and ANSYS). Six different commercial implant models (cylindrical and tapered) with three different V-shaped thread depths (0.25 mm, 0.35 mm, and 0.45 mm) were designed to be used in this study. The suggested implants used in this study were threaded in two different locations of mandible bone; the anterior region (Type I model) and posterior region (Type II model). A vertical static load of 250 N was directly applied to the center of the suprastructure of the implant for each model. Results: For both models, evaluations were achieved to figure out the stress distribution patterns and maximum equivalent von Mises. The results obtained after implementation of FE dental-implant models show that the highest stresses were located at the crestal cortical bone around the implant neck. In addition, the simulation study revealed that taper body implant had a higher peak value of von Mises stress than that of cylinder body implants in all types of bones. Moreover, a thread depth of 0.25 mm showed highest peak of maximum von Mises stresses for Type I and Type II models. Conclusion: The simulation results indicate that all models have the same von Mises stress distribution pattern and higher peak von Mises stresses of the cortical bone were seen in tapered implant body in contrast to the cylindrical body.