Raffaella Aversa

The Importance of Cortical Bone Orthotropicity, Maximum Stiffness Direction and Thickness on the Reliability of Mandible Numerical Models

AIMnTo identify mechanical and geometrical variables affecting the biofidelity of numerical models of human mandible. Computed results sensibility to cortical bone orthotropy and thicknesses is investigated.nnnMETHODSnTwo mandible numerical models of different bone complexities are setup. In the low-complexity model, cortical bone is coupled with isotropic materials properties; constant thickness for cortical bone is adopted along the mandible structure. In the higher complexity model, the cortical bone is considered as an orthotropic material according to an independent mechanical characterization performed on fresh human dentate mandibles. Cortical thickness distribution, the values of the principal elastic moduli and principal directions of orthotropy are considered as piecewise heterogeneous. Forces for masseter (10 N), medial pterigoid (6 N), anterior (4 N) and posterior (4 N) temporalis muscles are applied to the models. Computed strains fields are compared with those experimentally measured in an independent test performed on a real human mandible in the same loading conditions.nnnRESULTSnUnder closure muscles forces both models shows similar strain distribution. On the contrary, strain fields values are significantly different between the presented models.nnnCONCLUSIONSnThe mandible structure is sensible to compact bone orthotropy and thickness at the facial side of condylar neck, retro molar area and at the lingual side of middle portion of the corpus in molars area, anterior margin of the ramus. In these areas, it is advisable to use orthotropic properties for cortical bone to accurately describe the strain state.

Combined microcomputed tomography, biomechanical and histomorphometric analysis of the peri-implant bone: A pilot study in minipig model

OBJECTIVESnTo present a practical approach that combines biomechanical tests, microcomputed tomography (μCT) and histomorphometry, providing quantitative results on bone structure and mechanical properties in a minipig model, in order to investigate the specific response to an innovative dental biomaterial.nnnMETHODSnTitanium implants with innovative three-dimensional scaffolds were inserted in the tibias of 4 minipigs. Primary stability and osseointegration were investigated by means of insertion torque (IT) values, resonance frequency analysis (RFA), bone-to-implant contact (BIC), bone mineral density (BMD) and stereological measures of trabecular bone.nnnRESULTSnA significant positive correlation was found between IT and RFA (r=0.980, p=0.0001). BMD at the implant sites was 18% less than the reference values (p=0.0156). Peri-implant Tb.Th was 50% higher, while Tb.N was 50% lower than the reference zone (p<0.003) and they were negatively correlated (r=-0.897, p=0.006).nnnSIGNIFICANCEnμCT increases evaluation throughput and offers the possibility for qualitative three-dimensional recording of the bone-implant system as well as for non-destructive evaluation of bone architecture and mineral density, in combination with conventional analysis methods. The proposed multimodal approach allows to improve accuracy and reproducibility for peri-implant bone measurements and could support future investigations.

Innovative Biomaterials in Bone Tissue Engineering and Regenerative Medicine

In the last few years the Authors have been coordinating researches in multi key enabling technologies that conveys together activities involving advanced materials and biotechnology. These advancements are allowing innovative biomimetic systems, which are facing societal challenges with high potential for innovation and growth. The use of biocompatible and biomechanically active materials that can be designed to reproduce bone compatible and biomimetic scaffolds that can adapt themselves in mutating physiological conditions is presented in the present chapter.

Geometry and Determining the Positions of a Plan Transporter Manipulator

The conveyor mechanism (working in a plan) to be presented in this study is a classic case of manipulating conveyor, simply with a single degree of mobility. It is a very common mechanism used in classical mechanics, being encountered at lifting platforms, at handicapped chairs, at cranes, forklifts, automatic machines and machines, or at older steam locomotives where it having the role of reversing the rotation-translation movement. Being a simple, common manipulator, he is also a good teaching example, much used in the student courses of mechanics, mechanisms, robotics-mechatronics. That is why we want to present in this study in a concise way the geometry and the kinematics of this mechanism. There will be a constructive and one kinematic scheme. The mechanism consists of a crank (a motor element 1), an RRR dyad composed of elements 2 and 3 and an RRT dyad formed by kinematic elements 4 and 5. The motor element 1 has a complete rotation (360 degrees) being the single driving feature of the entire mechanism. The element 3 is a bar that links the engine element 1 to the rocker element 2. From the rocker element 2, the movement is forwarded through the rod 4 to the final execution member 5, which is a slider (patina), having the role of oscillating linearly (it can also be a piston in a cylinder). The mechanism can also be used by changing the driving element to the driven one so as to become a motor mechanism with the leading element 5 and when the rotation element 1 to become a final driven element. Thus it can be used as a mechanism for producing the movement and transmitting it with the conversion from the rotation to translation movement. We intend to present this mechanism, in the present paper, when it functions as a manipulator, having the motor element 1 and the final element, the execution element, the patina 5. Special emphasis will be placed on the kinematics of the mechanism, studied on elements, but also on structural groups. Obviously there will be presented and some applications of the mechanism.

Proposed Solutions to Achieve Nuclear Fusion

Despite research carried out around the world since the 1950s, no industrial application of fusion to energy production has yet succeeded, apart from nuclear weapons with the H-bomb, since this application does not aims at containing and controlling the reaction produced. There are, however, some other less mediated uses, such as neutron generators. The fusion of light nuclei releases enormous amounts of energy from the attraction between the nucleons due to the strong interaction (nuclear binding energy). Fusion it is with nuclear fission one of the two main types of nuclear reactions applied. The mass of the new atom obtained by the fusion is less than the sum of the masses of the two light atoms. In the process of fusion, part of the mass is transformed into energy in its simplest form: heat. This loss is explained by the Einstein known formula E=mc2. Unlike nuclear fission, the fusion products themselves (mainly helium 4) are not radioactive, but when the reaction is used to emit fast neutrons, they can transform the nuclei that capture them into isotopes that some of them can be radioactive. In order to be able to start and to be maintained with the success the nuclear fusion reactions, it is first necessary to know all this reactions very well. This means that it is necessary to know both the main reactions that may take place in a nuclear reactor and their sense and effects. The main aim is to choose and coupling the most convenient reactions, forcing by technical means for their production in the reactor. Taking into account that there are a multitude of possible variants, it is necessary to consider in advance the solutions that we consider them optimal. The paper takes into account both variants of nuclear fusion, and cold and hot. For each variant will be mentioned the minimum necessary specifications.