Riabilitazione del mascellare posteriore atrofico mediante impianti corti (6-8 mm) o rialzo di seno con contestuale inserimento di impianti di lunghezza standard: studio retrospettivo con follow up a 3 anni

Background: sebbene la letteratura recente abbia suggerito che l’utilizzo degli impianti corti possa rappresentare una alternative preferibile alle procedure di rigenerazione ossea nelle aree posteriori atrofiche, perché è un trattamento più semplice e con meno complicazioni, esistono solo pochi studi a medio e lungo termine che abbiano comparato queste tecniche. Scopo: lo scopo di questo studio retrospettivo è quello di valutare se gli impianti corti (6-8 mm) (gruppo impianti corti) possano presentare percentuali di sopravvivenza e valori di riassorbimento osseo marginali simili a impianti di dimensioni standard (≥11 mm) inseriti contemporaneamente ad una grande rialzo di seno mascellare. Materiali e Metodi: in totale, 101 pazienti sono stati inclusi: 48 nel gruppo impianti corti e 53 nel gruppo seno. In ciascun paziente da 1 a 3 impianti sono stati inseriti e tenuti sommersi per 4-6 mesi. I parametri clinici e radiografici valutati sono: i fallimenti implantari, le complicazioni, lo stato dei tessuti molli, e il riassorbimento osseo marginale. Tutti i pazienti sono stati seguiti per almeno 3 anni dal posizionamento implantare. Risultati: il periodo di osservazione medio è stato di 43.47 ± 6.1 mesi per il gruppo impianti corti e 47.03 ± 7.46 mesi per il gruppo seno. Due su 101 impianti corti e 6 su 108 impianti standard sono falliti. Al follow-up finale, si è riscontrato un riassorbimento osseo medio di 0.47 ± 0.48 mm nel gruppo impianti corti versus 0.64 ± 0.58 mm nel gruppo seno. Non sono presenti differenze statisticamente significative fra i gruppi in termini di fallimenti implantari, complicazioni protesiche, tessuti molli, e riassorbimento osseo. Il gruppo seno ha presentato, invece, un maggior numero di complicazioni chirurgiche. Conclusioni: entrambe le tecniche hanno dimostrato un simile tasso di successo clinico e radiografico, ma gli impianti corti hanno ridotto il numero di complicazioni chirurgiche.

Nanofibrous-structured polymers and their engineering applications

Monolithic materials cannot always satisfy the demands of today’s advanced requirements. Only by combining several materials at different length-scales, as nature does, the requested performances can be met. Polymer nanocomposites are intended to overcome the common drawbacks of pristine polymers, with a multidisciplinary collaboration of material science with chemistry, engineering, and nanotechnology. These materials are an active combination of polymers and nanomaterials, where at least one phase lies in the nanometer range. By mimicking nature’s materials is possible to develop new nanocomposites for structural applications demanding combinations of strength and toughness. In this perspective, nanofibers obtained by electrospinning have been increasingly adopted in the last decade to improve the fracture toughness of Fiber Reinforced Plastic (FRP) laminates. Although nanofibers have already found applications in various fields, their widespread introduction in the industrial context is still a long way to go. This thesis aims to develop methodologies and models able to predict the behaviour of nanofibrous-reinforced polymers, paving the way for their practical engineering applications. It consists of two main parts. The first one investigates the mechanisms that act at the nanoscale, systematically evaluating the mechanical properties of both the nanofibrous reinforcement phase (Chapter 1) and hosting polymeric matrix (Chapter 2). The second part deals with the implementation of different types of nanofibers for novel pioneering applications, trying to combine the well-known fracture toughness enhancement in composite laminates with improving other mechanical properties or including novel functionalities. Chapter 3 reports the development of novel adhesive carriers made of nylon 6,6 nanofibrous mats to increase the fracture toughness of epoxy-bonded joints. In Chapter 4, recently developed rubbery nanofibers are used to enhance the damping properties of unidirectional carbon fiber laminates. Lastly, in Chapter 5, a novel self-sensing composite laminate capable of detecting impacts on its surface using PVDF-TrFE piezoelectric nanofibers is presented.

Electrospun nanofibrous interleaves in composite laminate materials

The present work aims for investigate the influence of electrospun Nylon 6,6 nanofibrous mat on the behavior of composite laminates. The main idea is that nanofibrous interleaved into particular ply-to-ply interfaces of a laminate can lead to significant improvements of mechanical properties and delamination/damage resistance. Experimental campaigns were performed to investigate how nanofibers affect both the static and dynamic behavior of the laminate in which they are interleaved. Fracture mechanics tests were initially performed on virgin and 8 different configuration of nanomodified specimens. The purposes of this first step of the work are to understand which geometrical parameters of the nanointerleave influence the behavior of the laminate and, to find the optimal architecture of the nanofibrous mat in order to obtain the best reinforcement. In particular, 3 morphological parameters are investigated: nanofibers diameter, nanofibers orientation and thickness of the reinforce. Two different values for each parameter have been used, and it leads to 8 different configurations of nanoreinforce. Acoustic Emission technique is also used to monitor the tests. Once the optimum configuration has been found, attention is focused on the mechanism of reinforce played by the nanofibers during static and dynamic tests. Low velocity impacts and free decay tests are performed to attest the effect of nanointerlayers and the reinforce mechanism during the dynamic loads. Bump tests are performed before and after the impact on virgin and two different nanomodified laminates configurations. The authors focused their attention on: vibrational behavior, low velocity impact response and post-impact vibration behavior of the nano-interleaved laminates with respect to the response of non-nanomodified ones. Experiments attest that nanofibers significantly strength the delamination resistance of the laminates and increase some mechanical properties. It is demonstrated that the nanofibers are capable to continue to carry on the loads even when the matrix around them is broken.

A study of new and more sustainable catalytic routes for the synthesis of adipic acid

The aim of my PhD research project was to investigate new and more sustainable routes, compared to those currently used, for the production of adipic acid (AA). AA is a very important chemical intermediate. The main use of AA is the production of Nylon-6,6 fibers, resins, polyesters, plasticizers. My project was divided into two parts: 1. The two-step oxidation of cyclohexene, where the latter is first oxidized into trans-1,2-cyclohexanediol (CHD) with aqueous hydrogen peroxide, and then the glycol is transformed into AA by reaction with molecular oxygen. Various catalysts were investigated in this process, both heterogeneous (alumina-supported Ru(OH)x and Au nanoparticles supported on TiO2, MgO and Mg(OH)2) and homogeneous (polyoxometalates). We also studied the mechanism of CHD oxidation with oxygen in the presence of these catalysts. 2. Baeyer-Villiger oxidation of cyclohexanone with aqueous hydrogen peroxide into ɛ-caprolactone, as a first step on the way to produce AA. Study on the mechanism of the uncatalyzed (thermal) oxidation of cyclohexanone were also carried out. Investigation on how the different heterogeneous catalysts affect the formation of the reaction products and their distribution was done.

Mechanical behavior of flat and curved laminates interleaved by electrospun nanofibers

A major weakness of composite materials is that low-velocity impact, introduced accidentally during manufacture, operation or maintenance of the aircraft, may result in delaminations between the plies. Therefore, the first part of this study is focused on mechanics of curved laminates under impact. For this aim, the effect of preloading on impact response of curved composite laminates is considered. By applying the preload, the stress through the thickness and curvature of the laminates increased. The results showed that all impact parameters are varied significantly. For understanding the contribution rate of preloading and pre-stress on the obtained results another test is designed. The interesting phenomenon is that the preloading can decrease the damaged area when the curvature of the both specimens is the same. Finally the effect of curvature type, concave and convex, is investigated under impact loading. In the second part, a new composition of nanofibrous mats are developed to improve the efficiency of curved laminates under impact loading. Therefore, at first some fracture tests are conducted to consider the effect of Nylon 6,6, PCL, and their mixture on mode I and mode II fracture toughness. For this goal, nanofibers are electrospun and interleaved between mid-plane of laminate composite to conduct mode I and mode II tests. The results shows that efficiency of Nylon 6,6 is better than PCL in mode II, while the effect of PCL on fracture toughness of mode I is more. By mixing these nanofibers the shortage of the individual nanofibers is compensated and so the Nylon 6,6/PCL nanofibers could increased mode I and II fracture toughness. Then all these nanofibers are used between all layers of composite layers to investigate their effect on damaged area. The results showed that PCL could decrease the damaged area about 25% and Nylon 6,6 and mixed nanofibers about 50%.

Fiber-Optic Technologies for Wireline and Wireless In-building Networks

This doctoral dissertation aims to establish fiber-optic technologies overcoming the limiting issues of data communications in indoor environments. Specific applications are broadband mobile distribution in different in-building scenarios and high-speed digital transmission over short-range wired optical systems. Two key enabling technologies are considered: Radio over Fiber (RoF) techniques over standard silica fibers for distributed antenna systems (DAS) and plastic optical fibers (POFs) for short-range communications. Hence, the objectives and achievements of this thesis are related to the application of RoF and POF technologies in different in-building scenarios. On one hand, a theoretical and experimental analysis combined with demonstration activities has been performed on cost-effective RoF systems. An extensive modeling on modal noise impact both on linear and non-linear characteristics of RoF link over silica multimode fiber has been performed to achieve link design rules for an optimum choice of the transmitter, receiver and launching technique. A successful transmission of Long Term Evolution (LTE) mobile signals on the resulting optimized RoF system over silica multimode fiber employing a Fabry-Perot LD, central launch technique and a photodiode with a built-in ball lens was demonstrated up to 525m with performances well compliant with standard requirements. On the other hand, digital signal processing techniques to overcome the bandwidth limitation of POF have been investigated. An uncoded net bit-rate of 5.15Gbit/s was obtained on a 50m long POF link employing an eye-safe transmitter, a silicon photodiode, and DMT modulation with bit and power loading algorithm. With the insertion of 3x2N quadrature amplitude modulation constellation formats, an uncoded net-bit-rate of 5.4Gbit/s was obtained on a 50 m long POF link employing an eye-safe transmitter and a silicon avalanche photodiode. Moreover, simultaneous transmission of baseband 2Gbit/s with DMT and 200Mbit/s with an ultra-wideband radio signal has been validated over a 50m long POF link.