Methods for medical applications

In the present work, sheet-forming processes, i.e. super plastic forming and single-point incremental forming, have been adopted for the manufacturing of custom prostheses, instead of subtractive and additive techniques that are time- and cost-consuming for a single-piece production. Regarding concerns of the material, three different titanium alloys were used: pure titanium and two grades of the alloy Ti-6Al-4V (the standard one and the extra low interstitial one). Since no standard protocol exists to assess the mechanical performance of cranial implants, an experimental procedure has been designed and used in this work for producing polymethylmethacrylate supports, on which the cranial prostheses were firmly connected and subjected to impact puncture tests (drop tests). An experimental campaign could thus be conducted to investigate the effect on the mechanical response of (a) the titanium alloy, (b) the initial blank thickness and (c) the manufacturing process. Drop tests, carried out according to the proposed procedure, have shown no failure of the prostheses, neither in the area of the impact nor in the anchoring region and have revealed that, irrespective of the adopted manufacturing process, which does not alter the material, the amount of energy absorbed by the implants is always larger than 70%.

Keywords: Drop test , Pure titanium , SPF , SPIF , Ti-6Al-4V , Ti-6Al-4V-ELI

Versatile, cheap and non-invasive 3D acquisition techniques have received attention and interest in the field of biomedicine in recent years as the accuracy of developed devices permits the acquisition of human body shapes in detail. Interest in these technologies derives from the fact that they have the potential to overcome some limitations of invasive techniques (CT, X-rays, etc.) and those based on 2D photographs for the acquisition of 3D geometry. However, the data acquired from the 3D scanner cannot be directly used but need to be processed as they consist of 3D coordinates of the acquired points. Therefore, many researchers have proposed different algorithms which recognise the shape of human body and/or its features when starting from a 3D point cloud. Among all possible human body features to be evaluated, symmetry results the most relevant one. Accordingly, this survey systematically investigates the methods proposed in the literature to recognise 2D symmetry by the symmetry line and bilateral symmetry by the symmetry plane. The paper also analyses qualitative comparisons among the proposed methods to provide a guide for both practitioners and researchers.

Keywords: 3D scan , Digital human model , Symmetry line , Symmetry plane

Meniscectomy significantly change the kinematics of the knee joint by reducing the contact area between femoral condyles and the tibial plateau, but the shift in the contact area has been poorly described. The aim of our investigation was to measure the shift of the tibiofemoral contact area occurring after meniscectomy. We used laser scans combined to surface texturing for measuring the 3D position and area of the femoral and tibial surfaces involved in the joint. In particular, natural condyles (porcine model) were analysed and the reverse engineering approach was used for the interpretation of the results from compression tests and local force measurements in conjunction with staining techniques. The results suggested that laser scans combined to surface texturing may be considered as a powerful tool to investigate the stained contours of the contact area. Beside the largely documented reduction of contact area and local pressure increase, a shift of the centroid of the contact area toward the intercondylar notch was measured after meniscectomy. As a consequence of the contact area shift and pressure increase, cartilage degeneration close to the intercondylar notch may occur.

Keywords: Biomechanics , Centroid , Image analysis , Laser scanning , Surface texturing , Tibiofemoral contact area

Material structure-property relationship is strongly related to the employed process technology. Over the past years, laser processing of engineering materials has been proposed in many fields and different uses for diode lasers have been found in dentistry. In this contest, the potential of GaN- and InGaN-based laser diodes to cure dental materials was analysed. Two wavelengths of 405 nm and 445 nm were used as heat or light sources for warm condensation of gutta-percha, light transmission in dental posts and brackets or light curing of dental composites. Additive manufacturing approach was considered to fabricate 3D root analogues, suitable supports, positioning systems and moulds for optical measurements. A three-axis CAD/CAM system was implemented for positioning and aligning the laser beam. The ability of diode-pumped solid-state lasers to cure dental materials or to transmit light was compared to that of a traditional instrument. Temperature profile at the apex of an additive manufactured root canal sealed with gutta-percha, light transmission through translucent quartz fiber post or through aesthetic ceramic bracket, bending properties and morphological features of light cured dental composites (Gradia Direct - GC Corporation and Venus Diamond - Heraeus Kulzer) were measured. Results showed a very high potential of diode-pumped solid-state lasers to be used in endodontics, orthodontics and restorative dentistry.

Keywords: CAD/CAM system , Ceramic bracket , Dental materials , Laser diode , Mechanical analysis

The ability to engineer scaffolds that resemble the transition between tissues would be beneficial to improve repair of complex organs, but has yet to be achieved. In order to mimic tissue organization, such constructs should present continuous gradients of geometry, stiffness and biochemical composition. Although the introduction of rapid prototyping or additive manufacturing techniques allows deposition of heterogeneous layers and shape control, the creation of surface chemical gradients has not been explored on three-dimensional (3D) scaffolds obtained through fused deposition modelling technique. Thus, the goal of this study was to introduce a gradient functionalization method in which a poly(ε-caprolactone) surface was first aminolysed and subsequently covered with collagen via carbodiimide reaction. The 2D constructs were characterized for their amine and collagen contents, wettability, surface topography and biofunctionality. Finally, chemical gradients were created in 3D printed scaffolds with controlled geometry and porosity. The combination of additive manufacturing and surface modification is a viable tool for the fabrication of 3D constructs with controlled structural and chemical gradients. These constructs can be employed for mimicking continuous tissue gradients for interface tissue engineering.

Keywords: collagen , functionalization , interface tissue engineering , poly(ε-caprolactone) , scaffold

This study proposes a novel automatic method for facial landmark localization relying on geometrical properties of 3D facial surface working both on complete faces displaying different emotions and in presence of occlusions. In particular, 12 descriptors coming from Differential Geometry including the coefficients of the fundamental forms, Gaussian, mean, principal curvatures, shape index and curvedness are extracted as facial features and their local geometric properties are exploited to localize 13 soft-tissue landmarks from eye and nose areas. The method is deterministic and is backboned by a thresholding technique designed by studying the behaviour of each geometrical descriptor in correspondence to the locus of each landmark. Occlusions are managed by a detection algorithm based on geometrical properties which allows to proceed with the landmark localization avoiding the covered areas. Experimentations were carried out on 3132 faces of the Bosphorus database and of a 230-sized internal database, including expressive and occluded ones (mouth, eye, and eyeglasses occlusions), obtaining 4.75 mm mean localization error.

Keywords: 3D face , Differential geometry , Face analysis , Feature extraction , Landmark localization

Improving soft tissue attachment and reducing bacterial colonization on titanium abutments are key factors for the long-term maintenance of healthy soft and hard peri-implant tissues. This in vitro study was conducted to compare the biocompatibility and antibacterial activity of four different surfaces: uncoated Ti6Al4V, anodized, and coated with titanium nitride or zirconium nitride. Surface topography was investigated with a high-resolution system for measuring surface finishes. Human gingival fibroblast (HGF) adhesion and proliferation were examined using MTT assay, Scanning Electron Microscopy (SEM) imaging, immunofluorescence analysis and real-time PCR for selected target genes. The hemolysis and AMES tests were performed to assess the chemical compounds' blood compatibility and mutagenic potential, respectively. Antibacterial activity was tested against five bacterial strains isolated from the oral cavity (Streptococcus salivarius, S. sanguinis, S. mutans, S. sobrinus, S. oralis), and the percentage of dead bacteria was calculated. Roughness measurements confirmed a substantial similarity between the surfaces and their compatibility with clinical applications. MTT assay, SEM analysis and immunofluorescence staining showed adhesion and proliferation of HGFs cultured on all the examined surfaces. PCR confirmed that HGFs produced extracellular matrix components efficiently on all the surfaces. No hemolytic activity was detected, and the AMES test confirmed the surfaces' clinical safety. For all tested bacterial strains, biofilms grown on the zirconium nitride surface showed a higher percentage of dead bacteria than on the other disks. The titanium nitride surface inactivated bacterial biofilms, too, but to a lesser extent.

Purpose: The aim of this in vitro study was to verify whether or not stock and computer-aided design/ computer-aided manufacturing (CAD/CAM) abutments show similar precision in the connection with the respective implants. Materials and Methods: Ten CAD/CAM titanium abutments were compared with 10 stock titanium abutments. Each abutment fit a regular-platform implant (Institute Straumann). Implants and abutments were measured independently and then connected. During the connection procedure, the torque was measured using a six-axes load cell. Then, outer geometric features of the implant-abutment connection were measured again. Finally, the assembly was sectioned to provide the analysis of inner surfaces in contact. The geometric measurements were performed using a multisensored opto-mechanical coordinate measuring machine. The following parameters were measured and compared for the CAD/CAM and stock titanium abutment groups, respectively: width of interference and interference length between the conical surfaces of the implant and abutment; and volume of material involved in the implant-abutment connection. Results: Interference width mean ± SD values of 18 ± 0.5 and 14 ± 0.5 μm were calculated for the stock and CAD/CAM titanium abutment groups, respectively. The difference was statistically significant (P = .02). Furthermore, the interference length mean ± SD values of 763 ± 10 and 816 ± 43 μm were calculated for stock and CAD/CAM titanium abutment groups, respectively. The difference was also statistically significant (P = .04). Finally, the volume of material involved in the implant-abutment connection was compared between stock and CAD/CAM titanium abutment groups; the mean ± SD values of 0.134 ± 0.014 and 0.108 ± 0.023 mm3 were significantly different (P = .009). Conclusion: Both standard and CAD/CAM abutment groups showed a three-dimensional (3D) seal activation after the screw tightening. Nevertheless, stock titanium abutments showed a significantly higher volume of material involved in the implant-abutment connection compared with that of CAD/CAM titanium abutments.

Keywords: CAD/CAM abutments , Implant-abutment connection , Stock titanium abutments

The Marchetti-Vicenzi's nail is an intramedullary device where six curved nails are kept straight by a closing ring in order to allow their insertion into the medullary canal of a long bone; in a following step, these nails stabilize the fracture due to the ring withdrawal and to the consequent elastic expansion of the nails. Pre-clinical testing of this sort of device is strongly advocated in order to be able to foresee their stability inside the medullary canal and to quantify their stiffening action on a broken bone. In this numerical work, an MB (Multi Body) model of the device has been developed, with the dual purpose of evaluating forces between the bone and the systemcomponents during its progressive opening and verifying the behavior of the stabilized bone when it undergoes external loading. Different solutions, for flexible body modeling (discretization with lumped parameters, "flexible body," "FE Part"), have been analyzed and compared in terms of accuracy of results and required computational resources. Contact parameters have been identified and criteria to simplify geometries and therefore to reduce simulation times have been given. Results have allowed to demonstrate how amoderate lateral force is able to dislocate the fracture and how the final position of the retention nut can be optimized. On the whole, a tool for the pre-clinical testing of elastic intramedullary nails has been given.

Keywords: FE analysis , Flexible bodies , Intramedullary nails , Marchetti-Vicenzi's nail , Multibody analysis , Sliding contacts

This paper presents an approach for monitoring exercises of hand rehabilitation for past stroke patients. The developed solution uses a Leap Motion controller as hand-tracking device and embeds a supervised Machine Learning methodology. Support Vector Machine (SVM) is used in order to assess the correctness of a set of simple rehabilitation exercises performed with a single hand. The basic SVM model was extended with particular interest for defining feature vectors in a continues environment. The proposed method incorporated leap motion data, normalization of angles and gesture recognition. A software system was developed to provide patients with a set of exercise corrections and guidance for rehabilitation.

Keywords: Hand Rehabilitation , Leap Motion Controller , Stroke Patients , Support Vector Machines

During the last years, various approaches on an individualized drug therapy for benign cells have been researched. However, due to the complex topic a universal approach has not been found up until this point. Commonly, the effect of cytotoxic drugs on benign cells is in most cases the same compared to regular cells while the actual effect on patient still can't be predicted. In order to reduce unwanted side effects or unspecific drug reactions a test system for patients which allows to analyse the interaction between cytotoxic agents and the targeted cells is needed. Furthermore, this should also include an adequate measurement system which is capable to work in a natural environment and without any additional preparation. In terms of this work, a first proof of concept with different benign cells and cytotoxic agents is presented while monitoring the obtained displacement using electronic speckle pattern interferometry (ESPI).

Keywords: Chemotherapeutika , ESPI , Interferometrie , zelluläre Verformungen

The institute of medicine (US) Committee on Quality of Health Care in America defined that health care should be safe, effective, patient-centered, timely, efficient and equitable. In order to ensure this, scientists analyses the complex development of cancer and novel strategies for a treatment. One common approach is the chemotherapy which is defined as a treatment of cancer using specific chemical agents or drugs that are selectively destructive to malignant cells and tissues. As already mentioned, every kind of cancer and patient is unique which means that an almost successful treatment could be ineffective for the next patient. In most cases, this effect is caused by a chemical resistance against the applied anticancer drug. The formation or increase of unwanted side effects which weaken the patient unnecessarily can result in additional consequences. As a result, a great variety of anticancer drugs nowadays have been primarily evaluated utilizing in vitro or in vivo model. Usually, the efficacy of such complex pharmaceuticals is verified either by minimal inhibitory concentration or with optical microbiological detection methods. However, such an interaction between cells and drugs should only be regarded as an approximation since it is not directly tested on human cells or still needs to be modified for the according detection method. Thus, the samples are often modified and no more natural. A direct adaption of these obtained results are therefore often not possible and not even safe or effective for the patient. One promising approach which could solve these previous mentioned demands, could be the electronic speckle pattern interferometry (ESPI). Alternations of the cells are detected by ESPI, providing false-phase images which are visually evaluated with a color scale. These results are compared regarding the applied drugs, providing better insight on the drug cell-surface interactions. With the help of a false-phase image and the linked color scale as a result of the ESPI the change of the cell during a given time frame are calculated. Afterwards the results to each applied drug are compared and the different effect on the cell is visible.

Keywords: anticancer drugs , cellular displacement , ESPI , Interferometry

Smartphones are developing into all-purposes devices. In the present work, the employment/application of smartphones as medical devices in home care and point-of-care (POC) diagnostics are investigated in the analysis of Lateral Flow Assays (LFA). A smartphone-based LFA reader was developed for the quantitative analysis of D-Dimer – a biomarker indicating e.g. thrombotic event or danger of embolism. The proof-of-concept has been shown with multiple smartphones in establishing: • Optimal dimensions of the LFA cell of 72.11mm distance of smartphone to D-Dimer test leading to a coefficients of variances (CV) between 0.8% and 4.2% • Inter-device investigations: CVs around 13.5%; a limit of detection (LOD) of 100ng/ml (DDU) D-Dimer • Inter-smartphone investigations: CV about 16%, a limit of detection (LOD) at 66.4ng/ml (DDU) • Calibrations: CV and LOD of three smartphones are comparable to the commercial available LFA reader Further development to put the multiple smartphone-based LFA reader on the market.

Keywords: App , Home-Care , Lateral Flow Assay , LFA Reader , Point-Of-Care (POC) , Quantitative analysis , Smartphones

Modern cell culture as well as sophisticated bio-applications involve complex biochemical processes, which are required to induce growth, product development or material degradation. Tracking the reaction processes inside the application presents a major challenge due to its complexity. The development of new analysis and tracking mechanisms for such application presents a solution to fully understand the process. In addition, the applied sensors are required to monitor the reactions enable a live tracking of the process. Furthermore, this gives the opportunity to influence and manipulate reactions to further enhance the application of the process. Possible analytes for tracking during processes can be chemical origin such as glucose, cytokines, antibiotics and growth factors, which are included in the culture medium. Based on the complexity of the culture or bio-application the sensor tracking mechanism has to be adapted to ensure full process control. A variety of different approaches can be used for the tracking mechanism.

Keywords: Bio application , Polymer materials , Sample tracking

Modern medical science delivers through innovative chemical or mechanical/physical means new strategies to treat patients mildly and fight diseases accurately. In line with this development a screening procedure for tissue samples under usage of the electronic speckle pattern interferometry is developed at the University of Applied Science Wildau. The paper at hand provides the corner stone for such a procedure in form of an incubation system that is adapted to the properties of an electronic speckle pattern interferometer and allows the incubation as well as study of samples over time. As a result the developed system can regulate its own temperature and is constructed for use in an electronic speckle pattern interferometry (ESPI) setup. Its design allows a simple modular approach for further development.

Keywords: Advance Manufacturing , Applications , Fabrication , Processing

Finite element models in conjunction with adequate constitutive relations are pivotal in several physiological and medical applications related to both native and engineered tissues, allowing to predict the tissue response under various loading states. In order to get reliable results, however, the validation of the constitutive models is crucial. Therefore, the main purpose of this work is to provide an experimental-computational approach to the biomechanical investigation of soft tissues such as the dermis. This is accomplished by implementing and validating three widely adopted hyperelastic constitutive models (the Ogden, the Holzapfel, and the Gasser-Ogden-Holzapfel laws) supposed to be adequate to reproduce human reticular dermis mechanical behavior. Biaxial experimental data have represented the basis for the determination of the respective material parameters identified thanks to the definition of a cost function accounting for the discrepancy between experimental and predicted data. Afterwards, the experimental tests have been reproduced through finite element simulations. Hence, the constitutive laws have been validated comparing experimental and numerical outcomes in terms of displacements of four reference points and stress-strain relations. Hence, an experimental-numerical framework is proposed for the investigation of collagenous tissues, which could become more accurate with larger and independent experimental datasets. [Figure not available: see fulltext.].

Keywords: Anisotropy , Biaxial test , Finite element , Human dermis , Hyperelastic models

The surgical treatment of pelvic fractures has been proved to be technically challenging; 3D imaging and navigation can give a substantial benefit; a further step is here introduced with robotized fracture reduction. A specific device to be interfaced with existing surgical tables has been designed; its main specifications are allowing 3D fluoroscopy of wide areas, and housing a hexapod robot for fracture reduction. This robot can be remotely controlled by a joystick; therefore it can accurately reproduce reduction trajectories established in the pre-operative planning and it can maintain the reduced position while synthesis devices are applied. A prototype has been built and tested in order to assess its range of movement, its accuracy, and its learnability. Further efforts will address the implementation of navigated surgery and to the development of a haptic interface in order to let the surgeon sense soft tissue resistance.

Keywords: 3D imaging , Computer assisted surgery , Hexapod , Medical robotics , Pelvic fractures , Surgical Table

Our research explores the potential of wearable Mixed Reality (MR) for people with Neuro-Developmental Disorders (NDD). The paper presents HoloLearn, a MR application designed in cooperation with NDD experts and implemented using HoloLens technology. The goal of HoloLearn is to help people with NDD learn how to perform simple everyday tasks in domestic environments and improve autonomy. An original feature of the system is the presence of a virtual assistant devoted to capture the user's attention and to give her/him hints during task execution in the MR environment. We performed an exploratory study involving 20 subjects with NDD to investigate the acceptability and usability of HoloLearn and its potential as a therapeutic tool. HoloLearn was well-accepted by the participants and the activities in the MR space were perceived as enjoyable, despite some usability problems associated to HoloLens interaction mechanism. More extensive and long term empirical research is needed to validate these early results, but our study suggests that HoloLearn could be adopted as a complement to more traditional interventions. Our work, and the lessons we learned, may help designers and developers of future MR applications devoted to people with NDD and to other people with similar needs.

Keywords: Augmented Reality , Holo Lens , Holograms , Mixed Reality , Neuro-developmental Disorders , Virtual assistant

Objective To assess the effect of a ferrule design with specific post material-shape combinations on the mechanical behavior of post-restored canine teeth. Methods Micro-CT scan images of an intact canine were used to create a 3-D tessellated CAD model, from which the shapes of dentin, pulp and enamel were obtained and geometric models of post-endodontically restored teeth were created. Two types of 15 mm post were evaluated: a quartz fiber post with conical–tapered shape, and a carbon (C) fiber post with conical–cylindrical shape. The abutment was created around the coronal portion of the posts and 0.1 mm cement was added between prepared crown and abutment. Cement was also added between the post and root canal and a 0.25 mm periodontal ligament was modeled around the root. Four models were analysed by Finite Element (FE) Analysis: with/without a ferrule for both types of post material and shape. A load of 50 N was applied at 45° to the longitudinal axis of the tooth, acting on the palatal surface of the crown. The maximum normal stress criterion was adopted as a measure of potential damage. Results Models without a ferrule showed greater stresses (16.3 MPa) than those for models with a ferrule (9.2 MPa). With a ferrule, stress was uniformly distributed along the abutment and the root, with no critical stress concentration. In all models, the highest stresses were in the palatal wall of the root. Models with the C-fiber post had higher stress than models with the quartz fiber posts. The most uniform stress distribution was with the combination of ferrule and quartz fiber post. Significance The FE analysis confirmed a beneficial ferrule effect with the combination of ferrule and quartz fiber post, with tapered shape, affording no critical stress concentrations within the restored system.

Keywords: CAD , Dental materials , Endodontic treatment , Finite element analysis , Image analysis , Materials properties

Purpose: To study the influence of the resin bonding layer thickness and the bulk filling material stiffness in adhesive class II mesio-occlusal-distal (MOD) restorations using numerical finite element analysis (FEA). Methods: Four 3D-FE models of teeth restored with different filling material stiffness and resin bonding layer thickness were built-up and analyzed. The 3D model of a sound lower molar was also analyzed and compared with restored ones. The tooth tissues . (enamel, dentin), dental restoration and bolus on the occlusal surface, was divided into 3D solid CTETRA elements with four grid points. The adhesive bonding around the dental restoration was modeled with shell elements. Polymerization shrinkage was simulated with a thermal expansion approach. Mechanical behavior of restored models in terms of stress and displacement distributions, under the combination effects of polymerization shrinkage and occlusal load (600 N), was analyzed. All the materials were assumed to behave as elastic materials throughout the entire deformation. Results: Numerical results show that the mechanical response of the restored models was very different compared to the sound tooth ones, where the stress was uniformly distributed from enamel to dentin with no critical stress concentration. In the | restored models, the highest stress values were detected in the enamel, near the enamel-dentin interface and in the bulk ' restorative material. Tooth preparations A and B showed lower gradient stresses than corresponding C and D. The value of the vertical displacement components in models A and B were higher than corresponding C and D. The maximum displacement values were mainly located around the groove and were higher by an order of magnitude than the sound models. The results showed better mechanical response with models A and B compared to C and D. It is also evident that resin bonding thickness slightly affected the stress level of the restored teeth.