Methods for medical applications

Nowadays, it is widely recognized that a large number of phenomenological degrees of freedom basically rule the functionality of bone tissue scaffolds. As a consequence of this, the design of scaffolds for tissue engineering involves multidisciplinary and multi-scale aspects, the latter being the subject of intensive investigation by the research community. In this chapter we present an overview on the computational aspects of bone tissue engineering, with particular emphasis on the recent mechanobiological based finite element models, as well as on novel aspects regarding the numerical characterization of the network of scaffold voids.

Keywords: Bone tissue engineering , Finite element modelling , Mechanobiology , Percolation analysis , Scaffold

The zona pellucida (ZP) is a specialized extracellular matrix surrounding the developing oocyte. This thick matrix consists of various types of glycoprotein that play different roles in the fertilization process. Nowadays, several techniques are available for assessing ZP's mechanical response. The basic assumption behind these methods is that the ZP behaves like an elastic body: hence, dissipative forces are neglected and Young's modulus remains unaffected by probe dynamics. However, dissipative forces are strongly regulated by the slippage of ZP chains past one another while reaction forces related to elastic deformations (driven by the ability of each chain to stretch) depend on the ZP structure (i.e. number of cross-links and distances between knots). Although viscous reaction forces generated by the ZP are one of the main factors regulating sperm transit, their peculiar behaviour along the ZP structure remains poorly understood and rarely investigated. In order to overcome this limitation, a novel visco-hyperelastic model describing the porcine ZP reaction forces generated by nanoindentations at different probe rates is developed and verified in this study. Visco-hyperelastic parameters of porcine ZP membranes are determined by means of a hybrid characterization framework combining atomic force microscopy nanoindentation measurements, nonlinear finite-element analysis and nonlinear optimization. Remarkably, it is possible to separate the contributions of hyperelastic and viscous terms to ZP mechanical response and evaluate the error made in the determination of ZP mechanical properties if viscous effects were not considered. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Keywords: Atomic force microscopy , Finite-element analysis , Nonlinear optimization , Porcine zona pellucida , Prony series , Visco-hyperelasticity

The purpose of this study is to compare the shear bond strength of different resin bases and artificial teeth made of ceramic or acrylic resin materials and whether tooth-base interface may be treated with aluminium oxide sandblasting. Experimental measurements were carried on 80 specimens consisting of a cylinder of acrylic resin into which a single tooth is inserted. An ad hoc metallic frame was realized to measure the shear bond strength at the tooth-base interface. A complete factorial plan was designed and a three-way ANalysis Of VAriance (ANOVA) was carried out to investigate if shear bond strength is affected by the following factors: (i) tooth material (ceramic or resin); (ii) base material (self-curing or thermal-curing resin); (iii) presence or absence of aluminium oxide sandblasting treatment at the tooth-base interface. Tukey post hoc test was also conducted to evaluate any statistically significant difference between shear strength values measured for the differently prepared samples. It was found from ANOVA that the above mentioned factors all affect shear strength. Furthermore, post hoc analysis indicated that there are statistically significant differences (p-value=0.000) between measured shear strength values for: (i) teeth made of ceramic material vs. teeth made of acrylic resin material; (ii) bases made of self-curing resin vs. thermalcuring resin; (iii) specimens treated with aluminium oxide sandblasting vs. untreated specimens. Shear strength values measured for acrylic resin teeth were on average 70% higher than those measured for ceramic teeth. The shear bond strength was maximized by preparing samples with thermal-curing resin bases and resin teeth submitted to aluminium oxide sandblasting.

Keywords: Acrylic Resin Teeth , Ceramic Teeth , Resin Bases , Sandblasting , Shear Bond Strength

Minimally invasive percutaneous fixation techniques play a role of crucial relevance in the clinical practice. In spite of their consolidated use, little is reported in the literature to provide a mechanobiological explanation on how design of fixation devices can affect the healing process within fractured vertebrae. The aim of the study is to develop a multi-scale mechano-regulation model capable of predicting how the patterns of tissue differentiation within a vertebral fracture change in the presence or in the absence of fixation devices and how the dimensions of the device, and the materials it is made from, can affect the outcome of the healing process. To this purpose, a multi-scale mechano-regulation model is developed that combines a macro-scale model representing the spinal segment L3-L4-L5 including the fractured body of the L4 vertebra, and a micro-scale model of a fractured portion of cancellous bone. The macro-scale model includes also a minimally invasive percutaneous fixation device. The above mentioned model allows us to investigate how spatial and temporal patterns of tissue differentiation in the fracture gap change for different dimensions of the fixation device components and for different materials (Ti-6A1-4V alloy and Co-Cr alloy). Furthermore, the model provides information on the stress state in the fixation device and hence allows the risk of failure of the device itself to be estimated. The mechanical properties of the forming tissue change as the healing process progresses. In order to validate the mechano-regulation model, displacement fields will be measured with moiré and holography and compared with numerical computations. The model predicts that fixation devices significantly shorten healing times. Increasing values of the rod diameter D and decreasing values of its radius of curvature R lead to shorter durations of the healing period. Manufacturing the rods in Cobalt-Chrome alloy is predicted to reduce slightly the healing period by providing greater mechanical stability within the fracture callus. © The Society for Experimental Mechanics, Inc. 2014.

Keywords: Mechanobiology , Minimally invasive percutaneous fixation , Moiré , Tissue differentiation , Vertebral fracture

This paper investigates the shape memory capabilities of semicrystalline networks, focusing the attention on poly(ε-caprolactone) (PCL) systems, a class of materials that allows to satisfy important requirements for their applications as biomedical devices, such as the good biocompatibility, the fast recovery of large "temporary" shape configurations, and the easy tailoring of the transformation temperatures. The materials were prepared with various crosslink densities and crosslinking methodologies; in particular, beside a thermal crosslinking based on reactive methacrylic end groups, a novel type of covalently crosslinked semicrystalline systems was prepared by a sol-gel approach from alkoxysilane-terminated PCL precursors, so as to avoid potentially toxic additives typically used for free-radical thermal curing. The materials were subjected to biological tests, to study their ability in sustaining cell adhesion and proliferation, and to thermal characterizations, to evaluate the possibility to tailor their melting and crystallization temperatures. The one-way shape memory (i.e., the possibility to set the material in a given configuration and to recover its pristine shape) and the two-way shape memory response (i.e., the triggered change between two distinguished shapes on the application of an on-off stimulus) were studied by applying optimized thermo-mechanical cyclic histories. The ability to fix the applied shape and to recover the original one on the application of heating (i.e., the one-way effect) was evaluated on tensile bars; further, to investigate a potential application as self-expandable stents, isothermal shape memory experiments were carried out also on tubular specimens, previously folded in a temporary compact configuration. The two-way response was studied through the application of a constant load and of a heating/cooling cycle from above melting to below the crystallization temperature, leading to a reversible elongation/contraction effect, involving maximum strain changes up to about 80%, whose extent may be controlled through the crosslink density. © 2014 ASM International.

Keywords: advanced characterization testing , biomaterial , creep and stress rupture , mechanical

The perception of haptic textures depends on the mechanical interaction between a surface and a biological sensor. A texture is apprehended by sliding one's fingers over the surface of an object. We describe here an apparatus that makes it possible to record the mechanical fluctuations arising from the friction between a human fingertip and easily interchangeable samples. Using this apparatus, human participants tactually scanned material samples. The analysis of the results indicates that the biomechanical characteristics of individual fingertips clearly affected the mechanical fluctuations. Nevertheless, the signals generated for a single material sample under different conditions showed some invariant features. We propose that this apparatus can be a valuable tool for the analysis of natural haptic surfaces.

Keywords: Apparatus , Biomechanics , Biotribology , Humans , Texture

In oral implantology, proper execution of the holes for the installation of dental implants is directly related to the correct functioning and durability of the system itself. For this reason, the procedure discussed here, which was once performed freehand in all its phases, is now being implemented through aids with more precision. Masks currently in use are created in resin ad hoc; surgical stents are inserted into the holes that will then be used as a guide. These aids are fixed into the jaw by means of micro bone screws in order to prevent movement during surgery. Despite this, we still use the guides as they are, centered properly with the help of drilling jigs. The same technique is also used in partially edentulous cases through smaller jig fixed on teeth near to the implant zone. In this article, we propose a guidance system for milling cutters used in partially edentulous cases involving from one to three adjacent installations. The purpose of the study was to realize a modular model adaptable to most dental implants, as well as efficient, quick, and low cost by pouring the resin into a plaster mold of the teeth, and then drilling the masks into position in the plants at the required angle.

Keywords: Dental implants , Drilling aid

Nowadays Virtual Prototyping (VP) of robots dynamics is an effective tool to simulate the system behavior and improve the quality of rehabilitation activities. Using a VP software environment, the patients can be visually guided in their actions and the physiotherapist can control the system parameters easily to investigate the patients' performances in real time. In this paper VP concept is introducted to support the use of an upper-limb orthosis and to improve therapeutic efficacy in rehabilitation. The system adopted is a human-worn rehabilitation exoskeleton enhanced with a VP-based application to make therapeutic exercises more accessible while reducing the effort in using the system and managing the therapy. The VP application in particular merges computational musculoskeletal analysis with simplified controls, 3D viewing and real time simulation of the patients' movements. The application has been designed to specifically address the needs of patients and therapists and improve the satisfaction in use of the global system as well as the therpy results. The system validation is based on an ad-hoc evaluation protocol and is carried out by directly involving final users furing rehabilitation sessions. Experimental results demonstrated how VP prototyping effectively support the system use from both patients and physiotherapists: on one hand patients are nove motivated and they learn extract movements faster; on the other hand physiotherapists are supportedin diagnosis and data elaboration, and finally the rehabilitation therapy efficiency is improved.

This study aimed at investigating the effects of titanium implants and different configurations of full-arch prostheses on the biomechanics of edentulous mandibles. Reverse engineered, composite, anisotropic, edentulous mandibles made of a poly(methylmethacrylate) core and a glass fibre reinforced outer shell were rapid prototyped and instrumented with strain gauges. Brånemark implants RP platforms in conjunction with titanium Procera one-piece or two-piece bridges were used to simulate oral rehabilitations. A lateral load through the gonion regions was used to test the biomechanical effects of the rehabilitations. In addition, strains due to misfit of the one-piece titanium bridge were compared to those produced by one-piece cast gold bridges. Milled titanium bridges had a better fit than cast gold bridges. The stress distribution in mandibular bone rehabilitated with a one-piece bridge was more perturbed than that observed with a two-piece bridge. In particular the former induced a stress concentration and stress shielding in the molar and symphysis regions, while for the latter design these stresses were strongly reduced. In conclusion, prosthetic frameworks changed the biomechanics of the mandible as a result of both their design and manufacturing technology.

Keywords: Composite , Dental implants , Mandible , Stress concentration , Stress shielding

Purpose: The main purpose of this research work is to study the effect of poly lactic acid (PLA) addition into poly (e-caprolactone) (PCL) matrices, as well the influence of the mixing process on the morphological, thermal, chemical, mechanical and biological performance of the 3D constructs produced with a novel biomanufacturing device (BioCell Printing). Design/methodology/ approach: Two mixing processes are used to prepare PCL/PLA blends, namely melt blending and solvent casting. PCL and PCL/PLA scaffolds are produced via BioCell Printing using a 300-mm nozzle, 0/908 lay down pattern and 350-μm pore size. Several techniques such as scanning electron microscopy (SEM), simultaneous thermal analyzer (STA), nuclear magnetic resonance (NMR), static compression analysis and Alamar BlueTM are used to evaluate scaffold's morphological, thermal, chemical, mechanical and biological properties. Findings: Results show that the addition of PLA to PCL scaffolds strongly improves the biomechanical performance of the constructs. Additionally, polymer blends obtained by solvent casting present better mechanical and biological properties, compared to blends prepared by melt blending. Originality/value: This paper undertakes a detailed study on the effect of the mixing process on the biomechanical properties of PCL/PLA scaffolds. Results will enable to prepare customized PCL/PLA scaffolds for tissue engineering applications with improved biological and mechanical properties, compared to PCL scaffolds alone. Additionally, the accuracy and reproducibility of by the BioCell Printing enables to modulate the micro/macro architecture of the scaffolds enhancing tissue regeneration. © Emerald Group Publishing Limited.

Keywords: Biological analysis and testing , Fused deposition modelling , Polymers , Scaffolds

The application of three-dimensional (3D) facial analysis and landmarking algorithms in the field of maxillofacial surgery and other medical applications, such as diagnosis of diseases by facial anomalies and dysmorphism, has gained a lot of attention. In a previous work, we used a geometric approach to automatically extract some 3D facial key points, called landmarks, working in the differential geometry domain, through the coefficients of fundamental forms, principal curvatures, mean and Gaussian curvatures, derivatives, shape and curvedness indexes, and tangent map. In this article we describe the extension of our previous landmarking algorithm, which is now able to extract eyebrows and mouth landmarks using both old and new meshes. The algorithm has been tested on our face database and on the public Bosphorus 3D database. We chose to work on the mouth and eyebrows as a separate study because of the role that these parts play in facial expressions. In fact, since the mouth is the part of the face that moves the most and affects mainly facial expressions, extracting mouth landmarks from various facial poses means that the newly developed algorithm is pose-independent.

Keywords: 3D face , 3D scanner , Differential geometry , Face morphology , Medical diagnosis , Soft-tissue landmarks

The face is perhaps the most important human anatomical part, and its study is very important in many fields, such as the medical one and the identification one. Technical literature presents many works on this topic involving bi-dimensional solutions. Even if these solutions are able to provide interesting results, they are strongly subjected to images distortion. Thanks to the significant improvements obtained in the 3D scanner domain (photogrammetry for instance), today it is possible to replace the 2D images with more precise and complete 3D models (triangulated points clouds). Working on three-dimensional data, in fact, it is possible to obtain a more complete set of information about the face morphology. At present, even if it is possible to find interesting papers on this field, there is the lack of a complete protocol for converting the big amount of data coming from the three-dimensional point clouds in a reliable set of facial data, which could be employed for recognition and medical tasks. Starting from some anatomical human face concepts, it has been possible to understand that some soft-tissue landmarks could be the right data set for supporting many processes working on three-dimensional models. So, working in the Differential Geometry domain, through the Coefficients of the Fundamental Forms, the Principal Curvatures, Mean and Gaussian Curvatures and also with the derivatives and the Shape and Curvedness Indexes, the study has proposed a structured methodology for soft-tissue landmark formalization in order to provide a methodology for their automatic identification. The proposed methodology and its sensitivity have been tested with the involvement of a series of subjects acquired in different scenarios. © 2012 Springer Science+Business Media, LLC.

Keywords: 3D models , 3D scanners , Face morphology , Soft tissue landmarks

In the last decade, three-dimensional landmarking has gained attention for different applications, such as face recognition for both identification of suspects and authentication, facial expression recognition, corrective and aesthetic surgery, syndrome study and diagnosis. This work focuses on the last one by proposing a geometrically-based landmark extraction algorithm aimed at diagnosing syndromes on babies before their birth. Pivotal role in this activity is the support provided by physicians and 3D ultrasound tools for working on real faces. In particular, the landmarking algorithm here proposed only relies on descriptors coming from Differential Geometry (Gaussian, mean, and principal curvatures, derivatives, coefficients of first and second fundamental forms, Shape and Curvedness indexes) and is tested on nine facial point clouds referred to nine babies taken by a three-dimensional ultrasound tool at different weeks' gestation. The results obtained, validated with the support of four practitioners, show that the localization is quite accurate. All errors lie in the range between 0 and 3.5 mm and the mean distance for each shell is in the range between 0.6 and 1.6 mm. The landmarks showing the highest errors are the ones belonging to the mouth region. Instead, the most precise landmark is the pronasal, on the nose tip, with a mean distance of 0.55 mm. Relying on current literature, this study is something missing in the state-of-the-art of the field, as present facial studies on 3D ultrasound do not work on automatic landmarking yet.

Keywords: 3D echography , 3D face , 3D ultrasound , Dysmorphisms , Landmarking , Syndrome diagnosis

In the last decades, several three-dimensional face recognition algorithms have been thought, designed, and assessed. What they have in common can be hardly said, as they differ in theoretical background, tools, and method. Here we propose a new 3D face recognition algorithm, entirely developed in Matlab ® ,whose framework totally comes from differential geometry. First, 17 soft-tissue landmarks are automatically extracted relying on geometrical properties of facial shape. We made use of derivatives, coefficients of the fundamental forms, principal, mean, and Gaussian curvatures, and shape and curvedness indexes. Then, a set of geodesic and Euclidean distances, together with nose volume and ratios between geodesic and Euclidean distances, has been computed and summed in a final score, used to compare faces. The highest contribution of this work, we believe, is that its theoretical substratum is differential geometry with its various descriptors, which is something totally new in the field.

Keywords: 3D face , Face recognition , Geodesic distance , Geometry , Landmark , Shape index

Mini-invasive surgery deserves increasing attention to lower the post-operative stay in hospital and lessen falls-off complications. This leads to the trends in robots, as innovative integrated computer-aided implements. Out of front-end haptic effectors, the background support is turning to inclusive on-duty functions, e.g., surgical planners, operation assistants, etc., making possible the rethinking of protocols to progressively embed the innovations offered by the micro- and nano-technologies. The chapter brings in surgical robotics, with focus on technology and design issues of the remote-mode operation assistants. The investigation leads to define the technical characteristics of a CRHA, Co-Robotic Handling Appliance, to be purposely developed, to support the duty-split approach surgical planner. The expected features are outlined, including analysis of operation potential of special-purpose contrivances (i.e., automatic changing device of the surgical tools) and of scope-driven enhancers (i.e., exploration of the intervention theatre, IT).

The goal of the study is investigating the odd claim of the human civilisation, which modifies the wild natural surrounds by synthetic alterations, defined improvements, bestowing 〈value added〉. Indeed, the history seems sanctioning that the 〈life-quality〉 on the earth has been expanding, with enhanced chances and increased resources, compared to the native prospects of the wilderness. Only at the millennium turnover, the ecology globalisation shows the impeding threats of over-depletion/pollution, exceeding the extant recovery and reclamation capabilities of the environment. The new imperative turns to be the 〈sustainable growth〉, with caginess in defining if the trends can be positive, being conditioned by the empowered recycling, retrieval and renovation measures. In fact, sustainability requires lifecycle supply-chain visibility, resource bookkeeping and revamp planning. The lifecycle starts when the idea of a product is born and lasts until complete disposal after realisation and operation. In the musts' specification/analysis, the crucial policy (global plans, detailed design, assembly plots, etc.) are followed by manufacturing, testing, delivery, diagnostics and operation, advertising, service, maintenance, etc.; then, disassembly and firing are scheduled, requiring reclamation and recovery, via re-cycling (material reprocessing) or re-using (part refurbishing). The present study summarises pilot cues for understanding the product-process agendas, using the TYPUS metrics and the KILT model, prospected by the authors, in previous works. © J.UCS.

Keywords: Eco-project , Ecology globalisation , Economy globalisation , Lifecycle management , Sustainable growth

This paper presents a novel stereo acuity test that is realized by a software program on a PC with 3D capabilities. The 3D technology is used to provide two separate images to the two eyes. The test is a classical random dot test, but differently to other test printed on paper, the images shown to the patient can vary and there is no monocular clue. These features allow to deliver the test also in groups (instead of individuals) like school classes, and to increase the sensitivity. The system can be easily used also by not specialized personnel and this may further increase the cost efficiency of the test. Experiments carried on with a large set of children of age between five and seven years are presented. The obtained results are discussed through some comparisons between traditional approach and our innovative idea.

Keywords: 3D , Amblyiopia , Randomdot test , Stereopsis

Amblyopia (also called lazy eye) is a condition in which the eye and the brain do not work properly together; this condition causes poor vision in the lazy eye. It involves around 4% of the children. We have devised a system for the diagnosis and treatment of amblyopia by using 3D technology. To be successful, the proposed treatment must be enjoyable and suitable for domestic use (for instance by watching TV) and carried out with a constant supervision by the doctors. We present a system in which patients and doctors exchange information about the prescribed activities. © 2014 Springer International Publishing Switzerland.

In this paper, a theoretical framework is presented for the design of hollow fiber membrane bioreactors (HFMBs) operated in closed-shell mode in the presence of high recirculation flows in the cell compartment. Navier-Stokes and Brinkman equations were used to describe fluid transport, and the convection-diffusion-reaction equations to describe transport of dissolved oxygen and glucose to cells. Numerical solutions were sought with the finite element method for the high permeability typical of new medical membranes, and operating conditions typical of therapeutic applications. Generalized charts intended to help the bioreactor designer were obtained giving the non-hypoxic (or well-nourished) fractional shell volume as a function of the main dimensionless groups influencing the magnitude of the recirculation flow. Results indicate that designs and operations promoting moderate-to-high recirculation flows in the bioreactor shell markedly enhance solute transport and permit much better cell oxygenation and nourishment, and control of the pericellular environment, than diffusion-limited bioreactors. With these charts, bioreactor design may be optimized for a given therapeutic treatment, or operation adjusted to the properties of the cell aggregate as tissue forms in tissue engineering applications, so as to provide cells with a physiological supply of oxygen and nutrients and a physiological pericellular environment.

Keywords: Bioreactor , Convection-enhanced , Hollow fiber membrane , Model , Transport