1,721,100 research outputs found
Spostamento ortodontico del primo molare superiore di ratto: studio istomorfologico dell’osso alveolare
No full textÈ stata esaminata la struttura dell'osso alveolare adiacente sia al primo molare superiore sottoposto a spostamento ortodontico che ai denti contigui in 55 ratti Wistar maschi dell'età di 3 e 10 mesi, il movimento è stato ottenuto applicando una molla chiusa di Sentalloy da 50 cN tra il primo molare superiore sinistro e gli incisivi superiori. Ai ratti veniva somministrata tetraciclina per via sottocutanea (50 mg/kg) 48 ore prima del sacrificio dopo i tempi sperimentali di 4, 7, 11 e 14 giorni. I segmenti ossei mascellari venivano fissati in parafolmaldeide tamponata (0,1 M, pH 7,2) per 4 ore e inclusi in metilmetacrilato. Sono state eseguite sezioni trasversali a livello coronale, medio e apicale delle radici dentarie mediante un microtomo a lama circolare diamantata . Le sezioni spesse (100-120 μm), lucidate con carta abrasiva e allumina, sono state microradiografate e analizzate al microscopio a luce ordinaria e fluorescente. Le sezioni sottili (5 μm) sono state colorate con Blu di Toluidina e trattate istochimicamente per TRAP. È stato osservato un cospicuo riassorbimento osteoclastico dell'osso alveolare attorno al dente spostato ortodonticamente e a quelli adiacenti, sia dal lato di tensione che dal lato di compressione. In quest'ultimo è stata osservata anche neodeposizione ossea, ma solo dopo lunghi periodi di trattamento. Una cospicua deposizione ossea, più marcata con l'aumentare dei tempi di trattamento, è stata osservata frequentemente nel versante vestibolare dell'osso alveolare. Non è stata osservata alcuna relazione tra il comportamento dell'osso e l'età dei ratti. In conclusione, questi risultati preliminari indicano che al movimento ortodontico consegue un diffuso riassorbimento osseo, senza relazione con forze di tensione o di compressione. Sembra dunque che il movimento ortodontico abbia luogo in un contesto di globale adattamento scheletrico: assieme ad aree di notevole erosione ossea è possibile osservare nuove aree di deposizione tendenti a ripristinare la stabilità meccanica
Histomorphometric study of bone reactions during orthodontic tooth movement in rats
No full textThe biological response to orthodontic tooth movement has generally focused on reactions within the periodontal ligament (PDL), whereas less attention has been paid to the behavior of neighboring bone. The purpose of the study was to describe the influence of orthodontic force on bone surrounding the displaced tooth and the adjacent, untreated teeth, Bone changes in relation to treatment time and different sites were investigated. A mesial tipping of the left maxillary first molar was obtained from 54 adult male Wistar rats. Oxytetracycline was injected subcutaneously 48 h before killing, which took place after 4, 7, or 14 days. The maxilla was fixed in paraformaldehyde and embedded undecalcified in methylmethacrylate, A set of thick horizontal sections was taken from the cervical, intermediate, and apical levels of the roots. The sections were microadiographed and analyzed microscopically under bright-field and fluorescent illumination. Bone fraction and PDL width was measured using a Zeiss Videoplan device equipped with an overlay system. New bone formation was detected by oxytetracycline labels. The analysis showed a consistent, significant decrease of the alveolar bone fraction around both displaced and adjacent teeth at ail treatment times, Apposition, indicated by the tetracycline uptake, was found on the periosteal side of the treated hemimaxilla and, after 14 days, also on the surface toward which the tooth was moving and around the adjacent teeth. These results suggest that a time rather than a space relationship exists between bone resorption and formation and that the whole hemimaxilla reacts to the mechanical challenge, resembling the regional acceleratory phenomenon (RAP) observed in other circumstances. (C) 1999 by Elsevier Science Inc. All rights reserved
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
Prevalenza di carie e malocclusione in bambini in eta' scolare della provincia di Ferrara
No full textThe Authors examined 459 children for caries and malocclusion in Argenta. 77% of the whole sample had caries and 65% of children had malocclusion. Dental health education and public preventive programs should be organized to prevent caries and malocclusion. An extension and improvement of local epidemiological studies are needed to achieve this purpose
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
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