Pedro Yoshito Noritomi

Short fibre-reinforced composite for extensive direct restorations: a laboratory and computational assessment

ObjectivesThe objective of the study was to evaluate the effectiveness of a short fibre-reinforced composite (FRC) applied in combination with a conventional filler composite (CFC) on the fatigue resistance, fracture strength, failure mode and stress distribution, for restorations of premolars under two loading angles.Material and methodsThirty-two inferior premolars received extensive cavities with removal of the lingual cusp. Teeth were restored directly using ‘FRC (EverX Posterior, GC) + CFC (G-aenial, GC)’ or ‘CFC only’ and received two fatigue/fracture loadings at two different angles (0°/45°) (nxa0=xa08). Data were submitted to two-way ANOVA (αxa0=xa05xa0%) and Tukey test. Failure mode was analysed using SEM. Four 3D finite element (FE) models were constructed and static, linear and elastic analyses were performed. Maximum principal and von Mises stresses were evaluated.ResultsAll specimens survived the mechanical fatigue simulation. No statistical difference in fracture resistance was recorded between FRC + CFC and CFC only, considering both loading angles (pxa0=xa00.115). However, the 0° loading showed a statistical significant higher strength than the 45° loading (pxa0=xa00.000). Failure mode analysis revealed more repairable fractures upon 0° loading, versus more root fractures (unrepairable) upon 45° loading. FE revealed a higher amount of stress upon 45° loading, with tensile stress being imposed to the lingual cervical area.ConclusionThe fracture strength was not increased using the FRC. Loading at a 45° decreased significantly the fracture resistance.Clinical relevanceThe restoration of extensive cavities in posterior tooth is a challenge for the clinicians and the choice of the material that increases the fracture strength of tooth-restoration complex is required.

Computer Fluid Dynamics Analysis for Efficient Cooling and Lubrication Conditions in Micromilling of Ti6Al4V Alloy

Titanium alloy Ti6Al4V is a material that has been used extensively in industries, such as the medical field for prostheses and surgical instruments, because of its biocompatibility. However, it is considered a difficult-to-machine material owing to its inherent mechanical and thermal properties (which cause severe tool wear and shorten tool life), diminished surface quality, and it conducts low productivity. The aim of this work is to evaluate the efficiency of minimum quantity lubrication (MQL) in micromilling in terms of dry machining and jet application. The effect of cutting fluid flow was analyzed through Computational Fluid Dynamics (CFD) analysis and jet application, in the context of the microscale, was found to cause a disordered flow that did not reach the desired target, in this case the two flutes of the tool. These results were accordant with those obtained in the micromilling experiments. In addition, recent machining concerns are related to sustainability and aim to reduce or even eliminate the use of cutting fluids altogether; in this sense, applying MQL in micromilling would represent a substantial reduction in cutting fluid consumption.

Stress Distribution in Human Zygomatic Pillar Using Three-Dimensional Finite Element Analysis

El objetivo de este articulo fue analizar la distribucion de la tension en el pilar cigomatico humano durante la contraccion del musculo masetero utilizando analisis de elementos finitos tridimensionales. Un modelo de tres dimensiones de dientes del hemicraneo facial fueron producidos sobre la base de datos de CT-scan. Se utilizo como modelo un craneo adulto de sexo masculino con la integridad de la anatomia estructural. Fuerzas musculares se aplicaron en el origen de los ascensores de los musculos de la mandibula y soportes se aplicaron a la superficie oclusal del primer y segundo molar para simular una carga masticatoria y estimular el pilar cigomatico. Condiciones de simetria se colocaron en el plano mediano. Se utilizaron restricciones en los planos superior y posterior. El analisis de las tensiones equivalentes von-Mises y maximo director se realizo a traves del campo de esfuerzos a lo largo del pilar cigomatico. Fue representada la concentracion de esfuerzos en el proceso alveolar, hueso cigomatico, proceso frontal y temporal del hueso cigomatico y el arco superciliar. La linea de tension indica la distribucion de la tension del maxilar hacia el hueso frontal y temporal. Las tensiones se produjeron debido a las fuerzas oclusales resultantes, que se apoyan principalmente por el hueso cigomatico, distribuidas de manera no uniforme y sobre todo a traves del pilar cigomatico. Este estudio ha contribuido a una mejor comprension de la distribucion de la tension en el pilar cigomatico para entender la influencia de la masticacion sobre la morfologia de este pilar y ser de utilidad en la practica clinica.

Inter-institutional protocol describing the use of three-dimensional printing for surgical planning in a patient with childhood epilepsy: From 3D modeling to neuronavigation

This study is the first step in an effort to develop three-dimensional (3D) printing for use in pediatric surgical planning. In order to accomplish this, we established an effective collaboration between Ribeirao Preto Clinics Hospital (HCRP) and Renato Archer Center for Information Technology (CTI). Printed biomodels can be used to support discussions, decision-making, and neuronavigation before surgery. The main purpose of 3D printing for specific case handling is to reduce damage by enhancing knowledge of orientation during surgical planning and personnel training before surgery. Here, we produced an object that represented the brain and face segment of a patient via additive manufacturing technology based on magnetic resonance imaging (MRI) data. Specific landmarks were measured by three distinct methods: manual caliper, an InVesalius software measurement tool, and neuronavigation coordinate detection. The mean coefficient of variation was 7.17% between all methods and landmarks measured. Our results validate the combined use of biomodels with InVesalius software tools for the assessment of individual brain anatomy facilitating manual handling and visualization of 3D models. The establishment of communication protocols between the teams involved, as well as navigation protocols for quality control, presents the possibility of developing long term training programs, and promotes the congregation of individuals from research areas in Medical Physics, Medical Sciences, and Neuroscience.

Biomechanics of the Human Canine Pillar Based on its Geometry Using Finite Element Analysis

Este estudio evaluo la distribucion de la tension sobre la geometria del pilar canino en el craneo humano, utilizando analisis de elementos finitos. Se uso la tomografia computarizada de craneo humano para construir un modelo de elementos finitos compuesto por todas las estructuras oseas del pilar canino: eminencia canina, fosa canina, proceso frontal del maxilar, glabela y arco superciliar. Se aplico en la simulacion un soporte ubicado sobre el contacto de mordida del diente canino maxilar y una fuerza resultante de los musculos de la masticacion. Tensiones Equivalentes de Von-Mises y tensiones principales maximas fueron analizadas a lo largo de las estructuras que componen la geometria de pilar canino. La tension de Von-Mises fue alta y concentrada en la fosa canina y proceso frontal del maxilar. La tension principal maxima mostro areas de compresion en la fosa canina y parte del proceso frontal y la tension de traccion en la eminencia canina y parte del proceso frontal. Las diferentes areas de tension significan diferentes concentraciones de tensiones transmitida a lo largo de la geometria del pilar canino durante una mordedura canina maxima.

Modeling and Simulation of Diffusion Process in Tissue Spheroids Encaged into Microscaffolds (Lockyballs)

Abstract Nutrition, organization, growth and signal transduction in cells are largely determined by diffusion mechanisms. The complex three-dimensional shapes of cellular environment complicate the experimental analysis and computational simulation of diffusion in live cells. Three-dimensional cell aggregates are called tissue spheroids and they are widely used in the field of tissue engineering because emulate in vivo microenvironments more accurately than conventional monolayer cultures. The greater contact of the cells with the culture medium is directly related to oxygen diffusion and thereafter with the cell viability and the increase of proliferation rate. Due to the characteristics of a 3D environment, at some zones within the tissue spheroids the cells are not equally exposed to the culture medium, and the result of an insufficient supply of oxygen to the cell impact in the formation of microenvironments with decreased oxygen, nutrients and soluble factors produced by cellular metabolism leading to the formation of low proliferation areas and consequently hypoxia and necrosis (cell death). The fusion of cells also changes the catabolites flow, generating a very heterogeneous diffusion. The idea of this work is to develop and improve microscaffolds based on the concept of lockyballs that have cell support function for tissue engineering. These microscaffolds are composed by hooks (which attach to other hooks or loops of neighbor lockyballs), loops (elevated pentagons, which allows hooks attaching) and tubes (that preventing entry of cells). It is presented one original type of lockyball (control) which has no internal structure (it is a hollow structure) further other three types of lockyballs. The first model has a spherical outer structure and inner hollow microsphere constituted by pores with diameters smaller than the cell ones, whose function would be to prevent cell entry. The second model has tubes constituted by pores and the third model has a spiral tube constituted by pores too. These inner structures provide an environment suitable to the diffusion gradient necessary for the cell viability of the spheroid avoiding necrosis. The first stage of the work consisted on the generation of different three-dimensional models by Computer Aided Design (CAD) software Rhinoceros 5.0. At the second stage, the CAD model was imported into volume element method (VEM) software (Star-CCMxa0+/CD-Adapco) to perform computational fluid simulation (CFD). The CFD simulations were essential to predict the diffusion phenomenon inside the whole 3D structure. The development of new microscaffolds models can enhance the regenerative capacity and 3D tissues construction.

Use of 3D Printing in Surgical Planning: Strategies for Risk Analysis and User Involvement

This report aimed at promoting communication among project participants (hospital personnel and medical residents), increasing autonomy in decision-making during surgical planning. The steps taken for neuro navigation on a head model produced by additive manufacturing were analyzed for quality and risk assessment. Danger related to each navigation step, expected event sequence, dangerous situation and damage were pinpointed. User involvement was required from each project participant. After technical description of model preparation (filling and target deployment), the following steps were described: 1. Biomodel fixation, 2. T1-weighted image acquisition, 3. Target planning, 4. Stereotactic procedure, 5. Tomography acquisition, 6. Accuracy verification, 7. Disassembly. Error sources were identified and standardized procedures were established. A series of proposals were listed to assure quality and reproducibility. We concluded that accuracy can be improved as materials and procedures used for stereotaxy are optimized.