Methods for medical applications

Objective: To evaluate volumetric variations in the palate following rapid expansion, both immediately after treatment and over time. Materials and Methods: The sample was composed of 30 patients in early mixed dentition treated with a Haas-type device cemented onto the primary second molars. The mean age of the patients upon commencement of expansion was 7 years and 6 months (standard deviation [SD], 12 months). Measurement of palatal volume was conducted via 3D acquisition of plaster models using laser scanning before treatment (T1), upon device removal (T2), and 2.6 years afterward (T3). Results: The volume of the palate increased in a statistically significant fashion from T1 to T2 and from T1 to T3, and it decreased in a nonsignificant fashion from T2 to T3. Conclusions: Palatal volume significantly increases with rapid maxillary expansion (RME) treatment with insignificant relapse. The use of virtual 3D models with the aid of Apposite software permits evaluation of the morphologic and volumetric changes induced by orthodontic treatment. © 2010 by The EH Angle Education and Research Foundation, Inc.

Keywords: Laser , Palate , RME , Volume

A hip prosthesis implant produces a significant deviation in the stress pattern compared with the physiologic condition. In this work, the stress patterns are evaluated experimentally on synthetic femora, by means of thermoelastic stress analysis. Two factors have been considered: stem implantation and head offset. Stress maps were obtained using differential thermography and correlated to these factors. Thermoelastic stress maps have demonstrated to be sensitive to the implant and the head offset. In detail, the standard deviation of stresses can reduce from 5% to 50% (with reference to the physiologic one), depending on stem design; peak stresses change their position or disappear for different implant position or press-fitting, the sensitivity of average stresses to the offset is at least equal to 0.07 MPa/mm. On the whole, a methodology was developed, allowing the experimental evaluation and comparison of the stress distributions produced by different implants. © 2010 World Scientific Publishing Company.

Keywords: hip implant , synthetic femora , Thermoelastic stress analysis

This paper presents a new approach to design lower limb prosthesis focusing the attention on geometrical model issues. The new design approach has been developed within national and international research projects and, at present, "ad hoc" tools to carry out specific tasks are under development. Within this context, an important role is played by product and process knowledge and by specific CAD tools to design the most critical component, the socket. The paper discusses acquisition and formalisation of the knowledge related to the prosthesis design, with particular attention to the socket, and presents main features of a CAD tool specifically intended for this highly customised component. © 2009 by ASME.

The aims of this study were to analyse the stress distribution developing around an orthodontic miniscrew (OM) inserted into the maxilla and to determine the stress field changes for different screw lengths and for different levels of osseointegration occurring at the bone/screw interface.An integrated experimental/numerical approach was adopted. Using the photoelastic technique, the stress field arising in the bone after screw insertion and the application of the initial orthodontic load was assessed. The finite element (FE) method was used to determine the stress acting in the bony tissue after a given time following screw application, when, for the viscoelastic relaxation effects, the only stress field remaining was that due to the application of the orthodontic load. Different levels of osseointegration were hypothesized.Photoelastic analyses showed that stress distribution does not change significantly for moderate initial orthodontic loads. From the FE simulations, it was found that critical conditions occur for screws 14 mm long with an orthodontic load of 2 N. The optimal screw length seems to be 9 mm. For such a dimension, small stress values were found as well as low risk of lesion to the anatomical structures.

This is a case of unilateral masseter muscle hypertrophy (MMH) treated with botulinum toxin (NHAI - normalised hemi-facial asymmetry index improvement from 5.48 to 3.04). After 19 months, the treatment was repeated because of hypertrophy relapse (NHAI increase up to 6.82). The volume variations in the masseter area were monitored during 25 months using a laser scanner to compute facial volume. In order to relate the cause of hypertrophy and relapse to the presence of parafunctional activities, a nocturnal electromyography (EMG) study was conducted with positive results (nocturnal parafunctions of patients 4074.99 μV to be compared with a control group value of 1644.63 μV). The lack of the left inferior molars and the consequent right occlusal support seemed to justify the hypertrophy of right masseter (MMRight-POC [percent overlapping coefficient] 91.9%). However, the prosthetic rehabilitation did not prevent relapse in the same muscle. The EMG analysis of both the muscular activation (MMRight-POC 66.0% after relapse) and inhibition activity in Maximum Voluntary Clench (MVC) resulted in contradictory conclusions. At present, the available knowledge regarding MMH physiopathology is very limited and does not support a therapeutic rationale for relapse prevention. © 2009 by CHROMA, Inc.

We developed a model to test new bone constructs to replace spare skeletal segments originating from new generation scaffolds for bone marrow-derived mesenchymal stem cells. Using computed tomography (CT) data, scaffolds were defined using computer-aided design/computer-aided manufacturing (CAD/CAM) for rapid prototyping by three-dimensional (3D) printing. A bone defect was created in pig mandible ramus by condyle resection for CT and CAD/CAM elaboration of bone volume for cutting and scaffold restoration. The protocol produced a perfect-fitting bone substitute model for rapid prototyped hydroxyapatite (HA) scaffolds. A surgical guide system was developed to accurately reproduce virtually planned bone sectioning procedures in animal models to obtain a perfect fit during surgery. © 2008 Elsevier Ltd. All rights reserved.

Keywords: Bone regeneration , CAD-CAM , Maxillofacial prosthesis , Rapid prototyping , Scaffold

At present, computer assisted surgery systems help orthopaedic surgeons both plan and perform surgical procedures. To enable these systems to function, it is crucial to have at one's disposal 3D models of anatomical structures, surgical tools and prostheses (if required). This paper analyses and compares three methods for generating 3D digital models of anatomical structures starting from X-ray images: parametric solid modelling/reconfiguration, global shape modelling and free-form deformation. Seven experiences involving the generation of a femur model were conducted by software developers and different skilled users. These experiences are described in detail and compared at different stages and from different points of view. © 2009 Taylor & Francis.

Keywords: 3D modelling of anatomical structures , CAS systems , Orthopaedic surgery , Surgical planning

Repairing critical human skull injuries requires the production and use of customized cranial implants and involves the integration of computer aided design and manufacturing (CAD and CAM). The main causes for large cranial defects are trauma, cranial tumors, infected craniotomy bone flaps and external neurosurgical decompression. The success of reconstructive cranial surgery depends upon: the preoperative evaluation of the defect, the design and manufacturing of the implant, and the skill of the operating surgeon. Cranial implant design is usually carried out manually using CAD although this process is very time-consuming and the quality of the end product depends wholly upon the skill of the operator. This paper presents an alternative automated method for the design of custom-made cranial plates in a PHANToM®-based haptic environment, and their direct fabrication in biocompatible metal using electron beam melting (EBM) technology. © 2008 Elsevier Ltd. All rights reserved.

Keywords: Custom cranial implant , Electron beam melting (EBM) , Haptic environment , PHANToM-based tools

Tissue engineering represents an interesting approach which aims to create tissues and organs de novo. In designing scaffolds for tissue engineering applications, the principal goal is to mimic the function of the natural extracellular matrix, providing a temporary template for the growth of target tissues. For this reason, scaffolds should possess suitable mechanical properties and architecture to play their specific role. In this paper, limitations of conventional scaffold fabrication methods will be briefly introduced, and rapid prototyping techniques will be described as advanced processing methods to realize customized scaffolds with controlled internal microarchitecture. Among the rapid prototyping techniques, the potential and challenges of 3D fiber deposition to create multifunctional and tailor-made scaffolds will be reviewed. © Società Italiana Biomateriali.

Keywords: 3D fiber deposition , Bioplotter , Rapid prototyping , Scaffolds , Tissue engineering

In this chapter, the role of composite biomaterials as a unique type of material able to reproduce the complexity of the hierarchical structure and the peculiar mechanical properties of ligaments and tendons is discussed. The fundamentals of fibre-reinforced composite materials are reviewed, highlighting critical aspects in designing devices for ligaments and tendons replacement. The various approaches for replacement and regeneration are explored, with the aim of benefiting from composite materials science. Prospective and future challenges for composite materials for ligaments and tendons replacement and regeneration are outlined. © 2010 Woodhead Publishing Limited All rights reserved.

In this chapter, the state of the art of spinal implants such as interbody spacers and intervertebral disc (IVD) prostheses made of conventional materials, is described and the role of composite biomaterials for spine applications highlighted. In particular, the possibility of designing multifunctional devices with tailored mechanical properties is emphasized. A biomimetic approach to developing an IVD prosthesis with appropriate biological, transport and mechanical properties, is also presented. Finally, in the field of composite biomaterials for spine applications, future challenges and strategies are discussed. © 2010 Woodhead Publishing Limited All rights reserved.

Composite hip prostheses have gained an increasingly important role in the development of prosthetic devices. These materials can be engineered more accurately than monolithic structures. Biomechanical properties of tissues composing the hip joint and the concept of composite material and anisotropy are introduced. The state of the art is reviewed for prosthetic components comprising monolithic and composite materials for hip arthroplasty. The final section shows the composite approach to develop the hip stem, including technology, modelling and testing. © 2010 Woodhead Publishing Limited All rights reserved.

An overview is presented of the theoretical approach to the design of polymer composite materials. Composite materials with polymeric matrices are strong candidates for structural applications where high strength and stiffness to weight ratios are required. The fundamental analysis of the mechanical response of composite materials involves investigation on two levels, micro- and macro-scale. This approach encompasses micromechanics and macromechanics, extends to lamination theory and makes clear the physical significance of the basic concepts of composite material design. First, the mechanical behaviour is described of a unidirectional fibre-reinforced lamina as the basic building block of a laminate, showing stress-strain relationships in various coordinate systems. The design of laminates having suitable properties for a particular application is explained and short fibre-reinforced composites and particulate composites are examined. Finally, polymer nanocomposites are discussed as an interesting strategy to improve the mechanical properties of polymers. © 2010 Woodhead Publishing Limited All rights reserved.

This review presents two intriguing multidisciplinary strategies that might make the difference in the treatment of neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. The first proposed strategy is based on the controlled delivery of recombinant proteins known to play a key role in these neurodegenerative disorders that are released in situ by optimized polymer-based systems. The second strategy is the use of engineered cells, encapsulated and delivered in situ by suitable polymer-based systems, that act as drug reservoirs and allow the delivery of selected molecules to be used in the treatment of Alzheimer's and Parkinson's diseases. In both these scenarios, the design and development of optimized polymer-based drug delivery and cell housing systems for central nervous system applications represent a key requirement. Materials science provides suitable hydrogel-based tools to be optimized together with suitably designed recombinant proteins or drug delivering-cells that, once in situ, can provide an effective treatment for these neurodegenerative disorders. In this scenario, only interdisciplinary research that fully integrates biology, biochemistry, medicine and materials science can provide a springboard for the development of suitable therapeutic tools, not only for the treatment of Alzheimer's and Parkinson's diseases but also, prospectively, for a wide range of severe neurodegenerative disorders. © Wichtig Editore, 2009.

Keywords: Alzheimer's disease , Cell housing , Drug delivery , Engineered cells , Hydrogels , Parkinson's disease , Recombinant proteins

The paper approaches an educational application of 3D dynamic interactive images of medical devices. Manuals containing 3D images are considered more efficient than classic manuals. Combination of 3D interactive images with World Wide Web technologies makes the educational activities and especially the e-learning more attractive. Some web technologies used in creation of 3D interactivity were compared in order to choose a suitable environment for learning in the field of medical devices. Results of the study were used in the elaboration of an international e-learning platform in the frame of the Leonardo da Vinci educational program. The originality of the project consists in the interactivity of 3D images used in lessons. © 2009 IEEE.

Keywords: Images , Interactivity , Medical devices

This chapter deals with the structural analysis of bone elements, performed both numerically and experimentally. Among numerical techniques, the finite element method is discussed at length, focusing on its applications to bone biomechanics. The main steps involved in the method are analyzed from the practical perspective, and guidelines about dealing with commonly recurring problems are provided. As for experimental methods, considerable space is devoted to full-field techniques, with special attention to the lesser-known method of thermoelastic stress analysis. The main aim of this chapter is to illustrate how numerical and experimental methodologies can complement each other, explaining why it is beneficial to pursue both approaches.

Chronic wounds represent one of the most frequent pathologies affecting elderly people. In the last few years, several methods have been proposed with the aim at developing systems able to produce automatic and objective assessment of skin ulcers. Despite that, none of the existing technologies seems to be robust enough to work for all the ulcer typologies. In the majority of the clinical contexts, the evaluation of chronic wounds still depends on the experience of physicians rather than on the use of numerically objective attributes. This paper presents a non-invasive methodology to allow automatic measurements of chronic wounds. The proposed system involves the development of a 3D optical scanner, based on a structured light approach, combined with an infrared detector. This arrangement permits the acquisition of geometrical data including both chromatic texture and temperature information. A tool for the automatic detection of damaged skin areas has been developed by segmenting both color and thermal images, making possible to reliably quantify parameters characterizing wounds, such as area, depth and volume, even in absence of a perceptible color characterization. The described technology has been finally experienced in medical environment, proving its effectiveness for an objective assessment of wound healing.

Keywords: 3D segmentation , 3D thermography , Imaging , Wound modelling

This study aimed to (1) devise a standardized method of polishing and finishing acrylic resins, (2) eliminate the variable linked to the single operator, and (3) guarantee the reproducibility of the conditions in which smoothness surface values are obtained for comparative purposes. Twenty acrylic resin samples were fabricated (Lucitone, Dentsply). Samples in group 1 were manually polished by a single experienced operator, while samples in group 2 were polished using an isoparallelometer. Surface roughness was measured for both groups with a ± 0.01-μm resolution profilometer (Mahr, GD25). Data analysis showed that mechanical polishing results in a more uniform surface quality. This preliminary investigation underscores the merits of a standardized method for polishing dental acrylic resins. This approach can eliminate the effect of human factors, thereby making it possible to assess and compare the inherent features of each polished dental material.

Introduction: In this study, we aimed to analyze the displacement field and the level of stability for a human mandible that had symphyseal distraction osteogenesis. The mandible was fitted with various orthodontic devices: tooth borne, bone borne, and hybrid. Three-dimensional nonlinear finite element analyses were performed to study differences between the nominal aperture of the device and the actual mandibular distraction. Furthermore, displacement fields of the mandibular arch evaluated with and without mastication forces were compared to determine the level of stability of each appliance. Methods: Computed tomography scan images of the mandible were processed to create the finite element model, which was completed by modeling the distraction device. Three cases were considered: the distraction device attached to the first molar and the first premolar (tooth borne), to the canine and basal bones (hybrid), or only to the basal bone (bone borne). The nominal aperture of each device was 2 mm. Mandibular displacements in the mastication phase were analyzed in the case of unilateral occlusion on the second premolar. Results and Conclusions: Tooth-borne and hybrid devices allow orthodontists to better control the effective displacement transferred to the mandible by the distractor. Displacements of the mandibular arch were closer to the nominal aperture of the distractor than in the case of the bone-borne device. Hybrid devices were more stable under functional loads. However, parasitic rotations of the mandibular arms caused by mastication might counteract the benefits of distraction. © 2008 American Association of Orthodontists.

Mandibular symphyseal distraction osteogenesis is a common clinical procedure to modify the geometrical shape of the mandible for correcting problems of dental overcrowding and arch shrinkage. In spite of consolidated clinical use, questions remain concerning the optimal latency period and the influence of mastication loading on osteogenesis within the callus prior to the first distraction of the mandible. This work utilized a mechano-regulation model to assess bone regeneration within the callus of an osteotomized mandible. A 3D model of the mandible was reconstructed from CT scan data and meshed using poroelastic finite elements (FE). The stimulus regulating tissue differentiation within the callus was hypothesized to be a function of the strain and fluid flow computed by the FE model. This model was then used to analyse tissue differentiation during a 15-day latency period, defined as the time between the day of the osteotomy and the day when the first distraction is given to the device. The following predictions are made: (1) the mastication forces generated during the latency period support osteogenesis in certain regions of the callus, and that during the latency period the percentage of progenitor cells differentiating into osteoblasts increases; (2) reducing the mastication load by 70% during the latency period increases the number of progenitor cells differentiating into osteoblasts; (3) the stiffness of new tissue increases at a slower rate on the side of bone callus next to the occlusion of the mandibular ramus which could cause asymmetries in the bone tissue formation with respect to the middle sagittal plane. Although the model predicts that the mastication loading generates such asymmetries, their effects on the spatial distribution of callus mechanical properties are insignificant for typical latency periods used clinically. It is also predicted that a latency period of longer than a week will increase the risk of premature bone union across the callus. © International Federation for Medical and Biological Engineering 2007.

Keywords: Finite element modelling , Mandibular distraction osteogenesis , Mechanobiology , Orthodontic devices , Tissue differentiation