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Sviluppo e caratterizzazione di materiali nano-rinforzati per applicazioni odontoiatriche
No full textIn questa tesi di dottorato, si sono investigate diverse strategie per migliorare la durata dei restauri dentali. Nonostante tutti i progressi nella odontoiatria conservativa negli ultimi anni, i compositi a base di resina continuano ad avere un alto tasso di fallimento. Una delle principali ragioni è lo sviluppo di micro-infiltrazioni batteriche lungo i margini del restauro e, di conseguenza, la formazione di carie secondarie ricorrenti.
In particolare, questo lavoro può essere diviso in due sezioni principali: (i) lo sviluppo e la caratterizzazione di adesivi contenenti composti antibatterici; (ii) lo sviluppo e la caratterizzazione di compositi dentali a base di resina contenenti diversi riempitivi al fine di migliorarne le prestazioni.
Nella prima parte di questa tesi, sono stati selezionati quattro monomeri bis-quaternari di-metacrilati antibatterici polimerizzabili (bis-QAMs; ovvero DDE, DDPyMMA, DDMAPMA e DDM), sviluppati da Fanfoni et al. [1], al fine di attribuire proprietà antimicrobiche a due diversi agenti adesivi commerciali, ScotchBond Multipurpose e Scotchbond Universal, un adesiv0 3-steps etch-and-rinse e un adesivo universale self-etch, rispettivamente. Per un eventuale utilizzo clinico, è necessario che l'aggiunta di queste molecole non riduca la resistenza di adesione dell'adesivo, anche a lungo termine, e soprattutto che l'attività antibatterica sia preservata dopo la polimerizzazione. I risultati della forza di adesione (μTBS), sia a tempo 0 che dopo un invecchiamento termomeccanico in vitro (simulando 5 anni di servizio clinico), e la valutazione antibatterica in vitro (contro Streptococcus mutans) hanno dimostrato che il sistema adesivo Scotchbond Multipurpose è più adatto per l'incorporazione di queste molecole, in particolare DDMAPMA può quindi essere identificato come il miglior monomero antibatterico, che non influisce sulle proprietà meccaniche e superficiali.
La seconda parte di questo progetto si è concentrata sullo sviluppo e la caratterizzazione di materiali compositi dentali nano-rinforzati mediante l'incorporazione di idrossiapatite (nHAp) di dimensioni nanometriche come riempitivo, che presenta proprietà antibatteriche e di remineralizzazione grazie alla presenza di un vetro bioattivo (BGMS10), sintetizzato da Bellucci et al. [2]. L'analisi mediante microscopia elettronica a scansione (SEM) e microscopia elettronica a trasmissione (TEM) delle polveri di filler, HAp e BGMS10, ha confermato la presenza di particelle nanoscopiche per entrambi i riempitivi. La caratterizzazione meccanica ha mostrato che i compositi sperimentali realizzati con diverse proporzioni resina/riempitivo (R2/HAp-BGMS10) non presentavano valori adeguati di resistenza alla flessione e micro-durezza Vickers per il loro utilizzo. Tuttavia, è interessante notare che i valori di durezza dei compositi sperimentali nelle condizioni che simulano l'ambiente orale (immersione in acqua distillata a 37°C per un totale di 40 giorni) non diminuiscono. Inoltre, sia la valutazione delle proprietà antibatteriche (contro Staphylococcus aureus) che la bioattività hanno dimostrato un comportamento comparabile al ben noto vetro bioattivo 45S5, utilizzato come riferimento in questa tesi. Inoltre, è stato riscontrato che questo composito sperimentale presenta una bassa citotossicità nei confronti delle cellule staminali umane della polpa dentale (HDPSCs).
Bibliografia
[1] Lidia Fanfoni, Eleonora Marsich, Gianluca Turco, Lorenzo Breschi, and Milena Cadenaro. Development of di-methacrylate quaternary ammonium monomers with antibacterial activity. Acta Biomaterialia, 129:138–147, 2021.
[2] Devis Bellucci and Valeria Cannillo. A novel bioactive glass containing strontium and magnesium with ultra-high crystallization temperature. Materials Letters, 213:67–70, 2018.In this PhD thesis, we investigated different strategies to improve the durability of dental restorations. Indeed, despite all the advances in conservative dentistry in recent years, resin-based composites continue to have a high failure rate. One of the main reasons is the development of bacterial microleakage along the margins of restorations and, as a result, the formation of recurrent secondary caries.
In particular, this work can be divided into two main sections: (i) the development and the characterization of adhesives containing antibacterial compounds; (ii) the development and the characterization of resin-based dental composites containing different fillers in order to improve their performances.
In the first part of this thesis, four polymerizable antibacterial di-methacrylate bis-quaternary ammonium monomers (bis-QAMs; namely DDE, DDPyMMA, DDMAPMA and DDM), developed by Fanfoni et al. [1], were selected to attribute antimicrobial features to two different commercial bonding agent, ScotchBond Multipurpose and Scotchbond Universal, 3 steps etch-and-rinse and universal self-etch adhesive, respectively. For eventual clinical use, it is necessary that the addition of these molecules does not reduce the bond strength of the adhesive, also in the long term, and especially that the antibacterial activity is preserved after polymerization. The results of the microtensile bond strength (μTBS), both at time 0 and after in vitro thermo-mechanical aging (simulating 5 years of clinical service), and in vitro antibacterial assessment (towards Streptococcus mutans) have shown that Scotchbond Multipurpose adhesive system is more suitable for the incorporation of these molecules, in particular DDMAPMA can therefore be identified as the best antibacterial monomer, that does not affect mechanical and surface properties.
The second part of this project focused on the development and characterization of nano-reinforced dental composite materials through the incorporation of nanometer-sized hydroxyapatite (nHAp) as a filler, which exhibits antibacterial and remineralization features due to the presence of a lab-made bioactive glass (BGMS10), synthetized by Bellucci et al [2]. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis of the filler powders, HAp and BGMS10, confirmed the presence of nanoscopic particles for both fillers. Mechanical characterization showed that the experimental composites made with different resin/filler ratios (R2/HAp-BGMS10) did not have adequate flexural strength and Vickers microhardness values for their use. However, it is interesting to note that the hardness values of the experimental composites under the conditions simulating the oral environment (immersion
in distilled water, at 37°C for a total of 40 days) do not decrease. Moreover, both the assessment of antibacterial properties (against Staphylococcus aureus) and bioactivity demonstrated comparable behaviour to the well-known bioactive glass 45S5, used as a reference in this thesis. In addition, this experimental composite has been found to have low cytotoxicity towards Human Dental Pulp Stem Cells (HDPSCs).
Bibliography
[1] Lidia Fanfoni, Eleonora Marsich, Gianluca Turco, Lorenzo Breschi, and Milena Cadenaro. Development of di-methacrylate quaternary ammonium monomers with antibacterial activity. Acta Biomaterialia, 129:138–147, 2021.
[2] Devis Bellucci and Valeria Cannillo. A novel bioactive glass containing strontium and magnesium with ultra-high crystallization temperature. Materials Letters, 213:67–70, 2018
Erratum to: Current Trends in the Oncologic and Surgical Managements of Breast Cancer in Women with Implants: Incidence, Diagnosis, and Treatment
Full text linkThe Given Names and Family Names were inadvertently inverted. The correct order is Paolo Veronesi, Francesca De Lorenzi, Pietro Loschi, Mario Rietjens and Umberto Veronesi
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
New and emerging strategies in platelet-rich plasma application in musculoskeletal regenerative procedures: General overview on still open questions and outlook
Full text linkDespite its pervasive use, the clinical efficacy of platelet-rich plasma (PRP) therapy and the different mechanisms of action have yet to be established. This overview of the literature is focused on the role of PRP in bone, tendon, cartilage, and ligament tissue regeneration considering basic science literature deriving from in vitro and in vivo studies. Although this work provides evidence that numerous preclinical studies published within the last 10 years showed promising results concerning the application of PRP, many key questions remain unanswered and controversial results have arisen. Additional preclinical studies are needed to define the dosing, timing, and frequency of PRP injections, different techniques for delivery and location of delivery, optimal physiologic conditions for injections, and the concomitant use of recombinant proteins, cytokines, additional growth factors, biological scaffolds, and stems cells to develop optimal treatment protocols that can effectively treat various musculoskeletal conditions
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