Alida Mazzoli

Selective laser sintering in biomedical engineering

Selective laser sintering (SLS) is a solid freeform fabrication technique, developed by Carl Deckard for his master’s thesis at the University of Texas, patented in 1989. SLS manufacturing is a technique that produces physical models through a selective solidification of a variety of fine powders. SLS technology is getting a great amount of attention in the clinical field. In this paper the characteristics features of SLS and the materials that have been developed for are reviewed together with a discussion on the principles of the above-mentioned manufacturing technique. The applications of SLS in tissue engineering, and at-large in the biomedical field, are reviewed and discussed.

Palatal Volume Following Rapid Maxillary Expansion in Mixed Dentition

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.

A method for performance evaluation of RE/RP systems in dentistry

Purpose – The purpose of this paper is to investigate a method for comparing the scanning and reproducing accuracy of highly shaped objects like plaster casts used in dentistry.Design/methodology/approach – Theoretical considerations on errors introduced by the scanning systems and subsequent point clouds data elaboration have led to a method to estimate the accuracy of the whole process. Suitable indices have been chosen and computed at each stage. As a final result, the overall chain, scanning and reproducing systems can be assessed. In order to validate the proposed method casts have been scanned by means of commercial systems and then reproduced by using different rapid prototyping technologies, materials and parameters. Error indices have been computed and reported.Findings – Since it is not possible to define reliable and meaningful reference models for non‐standard shapes, an absolute accuracy value for the scanning process cannot be stated. Anyway the proposed method, thanks to relative performanc...

Selective laser sintering manufacturing of polycaprolactone bone scaffolds for applications in bone tissue engineering

Purpose – The purpose of this study is to show how selective laser sintering (SLS) manufacturing of bioresorbable scaffolds is used for applications in bone tissue engineering. Design/methodology/approach – Polycaprolactone (PCL) scaffolds were computationally designed and then fabricated via SLS for applications in bone and cartilage repair. Findings – Preliminary biocompatibility data were acquired using human mesenchymal stem cells (hMSCs) assuring a satisfactory scaffold colonization by hMSCs. Originality/value – A promising procedure for producing porous scaffolds for the repair of skeletal defects, in tissue engineering applications, was developed.

Particle size, size distribution and morphological evaluation of glass fiber reinforced plastic (GRP) industrial by-product

The waste management of glass fiber reinforced polymer (GRP) materials, in particular those made with thermosetting resins, is a critical issue for the composites industry because these materials cannot be reprocessed. Therefore, most thermosetting GRP waste is presently sent to landfill, in spite of the significant environmental impact caused by their disposal in this way. The limited GRP waste recycling worldwide is mostly due to its intrinsic thermosetting properties, lack of characterization data and unavailability of viable recycling and recovery routes. One of the possibility for re-using GRP industrial by-product is in form of powder as a partial aggregate replacement or filler addition in cement based composites for applications in sustainable construction materials and technologies. However, the feasibility of this kind of reutilization strongly depends on the morphology and particle size distribution of a powder made up of polymer granules and glass fibers. In the present study, the use of image analysis method, based on scanning electron microscopy (SEM) and ImageJ processing program, is proposed in order to evaluate the morphology of the particles and measure the particle size and size distribution of fine GRP waste powder. The obtained results show a great potential of such a method in order to be considered as a standardized method of measurement and analysis in order to characterize the grain size and size distribution of GRP particles before exploiting any compatibility issue for its recycling management.

DSP cement composites for electromagnetic shielding: practice and experimental analysis

In this work, the shielding effectiveness (SE) of a densified-small-particles (DSP) cement composite, with different loading particles embedded in, has been investigated through the nested reverberation chamber facility. Particular effort has been spent in characterizing the SE behavior with the increasing drying and in improving the experimental practice to solve out previously faced measurement troubles. Findings are of interest in architectural shielding, microwave spectroscopy and investigation of physical-chemical properties of DSP materials.

Preliminary results on the use of a noninvasive instrument for the evaluation of the depth of pigmented skin lesions: numerical simulations and experimental measurements

The early detection of cutaneous pigmented lesions is an important aid to the clinician in recognizing malignant melanoma. In an attempt to correlate the depth of a pigmented skin lesion with its malignant potential, phantoms able to simulate the diffuse reflectance of some lesions of different thicknesses were manufactured and tested to validate a diagnostic instrument developed in-house. Such optical skin-tissue phantoms may be useful for accelerating and optimizing the diagnosis of suspicious lesions of the skin. In fact, benign melanocytic lesions are different in terms of their diffuse reflectance from melanoma. The diffuse reflectance of pigmented skin lesions depends on the amount and distribution of the absorbing/diffusing chromophores embedded in the skin layers. The basic phantom material is a PVA hydrogel in which appropriate amounts of optical scatter are added extraneously at the time of formation to achieve tunability of the optical properties. Liquid Indian ink is used to simulate melanin and all the other chromophores. Slabs were prepared to mimic lesions of different depths. The optical properties of the tissue phantoms were determined in the visible and near-infrared spectral ranges using a noninvasive instrument made from a purpose-modified digital camera. The measured reflectance was correlated with the depth of the lesion both in a Monte Carlo simulation environment and in a laboratory experiment.

Binders alternative to Portland cement and waste management for sustainable construction—part 1:

This review presents “a state of the art” report on sustainability in construction materials. The authors propose different solutions to make the concrete industry more environmentally friendly in order to reduce greenhouse gases emissions and consumption of non-renewable resources. Part 1—the present paper—focuses on the use of binders alternative to Portland cement, including sulfoaluminate cements, alkali-activated materials, and geopolymers. Part 2 will be dedicated to traditional Portland-free binders and waste management and recycling in mortar and concrete production.

Mechanical Behaviour and Thermal Conductivity of Mortars with Waste Plastic Particles

In the present paper an investigation of mechanical behaviour and thermal conductivity of a lightweight building material containing either styrene butadiene rubber (SBR) or polyurethane (PU) waste particles is presented. Several mortar mixtures were prepared by replacing quartz sand with 0, 10 and 30% of either SBR or PU post-consumer plastics particles. The influence of rubber particle addition on fresh mortar behaviour, compressive and flexural strength of mortar as well as on mortar thermal conductivity was investigated. An optimization of mortar mixture proportions was carried out by adding a limestone powder as filler. The experimental investigation showed that the addition of rubber particles reduces both the material unit weight and the thermal conductivity. The thermal insulating effect of rubber particles indicates a promising potential for future developments. On the other hand, the addition of limestone powder produced higher thermal conductivity as well as higher compressive and flexural strength.

Preliminary simulation model toward the study of the effects caused by different mandibular advancement devices in OSAS treatment

Abstract The paper aims to evaluate the effects caused by a Mandibular Advancement Device (MAD) for Obstructive Sleep Apnoea Syndrome (OSAS) treatment. This study is based on Finite Element Method (FEM) for evaluating the load distribution on temporomandibular joint, especially on the mandibular condyle and disc, and on periodontal ligaments. The stress values on condyle and periodontal ligaments lead authors to consider MAD a safe procedure even for a long period. The obtained results also show the relationship between MAD material and load distribution at the periodontal ligaments. The paper is a step toward future analyses for studying and comparing the effects of MAD features, such as material, shape and dimensions, in order to allow the clinician prescribing the most fitting device.