72 resultados para brocas
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Apical surgeries are part of a segment of root canal treatment by which we can correct or eliminate iatrogenic deficiencies arising from conventional endodontic treatment. Currently no consensus among authors regarding to the factors linked to the surgery success as the execution of an apex resection followed by retropreparation and retrofilling. The apex resection performed 3mm from apical vertex allows the elimination of most apical ramifications, and it is a consensus part of the treatment. The preparation of cavities using ultrasonic tips has advantages over those made with drills such as better cleaning of the cavity, the possibility of lower cutting angle of the apical resection and deeper retropreparation. Another detail to consider is the type of tip, since the diamond tips in a more angulated inclination have higher cutting efficiency but causing increased formation of debris on the dentin walls. Finally, filling the cavity with an apical filling material allows proper sealing of the intracanal contents favoring apical healing.
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Objetivo: o objetivo desse estudo in vitro foi avaliar a infiltração marginal coronária após o preparo para retentor em dentes obturados com três diferentes cimentos, de acordo com o período entre a obturação do canal radicular e o preparo para retentor. Métodos: Noventa dentes humanos recentemente extraídos foram limpos e instrumentados e, então, obturados com Sealapex, Endométhasone ou TopSeal. Brocas Gates-Glidden foram utilizadas para o preparo imediato de 10 dentes de cada cimento até manter 5mm de obturação remanescente. Sessenta raízes obturadas foram incubadas a 37°C em meio úmido por 30 e 60 dias para serem, depois, preparadas para os retentores como descrito anteriormente. A superfície externa de cada raiz foi coberta com Araldite. Os espécimes foram imersos em corante azul de metileno a 2% sob vácuo por 24h, para então poderem ser analisados. A infiltração foi mensurada pelo software Sigma Scan da parte superior da obturação à porção apical alcançada pelo corante. Resultado: o Sealapex e o TopSeal apresentaram menor infiltração após o preparo para retentor do que o Endométhasone. O preparo imediato para o retentor apresentou menor infiltração do que o preparo para o retentor após 30 e 60 dias da obturação do canal radicular.
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OBJETIVO: Avaliamos a influência do diâmetro e do modo de preparação do orifício piloto na resistência ao arrancamento e no torque de inserção dos parafusos pediculares com diâmetro interno cônico. MÉTODOS: Ensaios mecânicos foram realizados com parafusos pediculares com alma cônica e diâmetro de 4,2mm e 5,2mm inseridos nos pedículos vertebrais lombares de suínos. O orifício piloto foi confeccionado com de broca e sondas (pontiaguda e cortante) com diferentes diâmetros. RESULTADOS: Testando o parafuso de 4,2mm a perfuração com orifício igual ou inferior ao menor diâmetro interno do parafuso, aumentou o torque e a resistência ao arrancamento. Perfurações com diferentes instrumentos apresentaram comportamento semelhante. Perfurações com sondas permitiram que orifícios confeccionados com dimensões superiores ao menor diâmetro interno do parafuso apresentassem resistência semelhante a das perfurações com dimensões iguais ao menor diâmetro interno do implante, realizadas com sondas e brocas. CONCLUSÕES: Nos de 4,2 mm o diâmetro e o modo de preparação do orifício influenciam o torque e a resistência, nos de 5,2 mm apenas o torque de inserção. Não há correlação entre força de arrancamento e torque de inserção. Nível de evidência II, Estudos terapêuticos - Investigação dos Resultados do Tratamento.
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The characteristics of aphasics’ speech in various languages have been the core of numerous studies, but Arabic in general, and Palestinian Arabic in particular, is still a virgin field in this respect. However, it is of vital importance to have a clear picture of the specific aspects of Palestinian Arabic that might be affected in the speech of aphasics in order to establish screening, diagnosis and therapy programs based on a clinical linguistic database. Hence the central questions of this study are what are the main neurolinguistic features of the Palestinian aphasics’ speech at the phonetic-acoustic level and to what extent are the results similar or not to those obtained from other languages. In general, this study is a survey of the most prominent features of Palestinian Broca’s aphasics’ speech. The main acoustic parameters of vowels and consonants are analysed such as vowel duration, formant frequency, Voice Onset Time (VOT), intensity and frication duration. The deviant patterns among the Broca’s aphasics are displayed and compared with those of normal speakers. The nature of deficit, whether phonetic or phonological, is also discussed. Moreover, the coarticulatory characteristics and some prosodic patterns of Broca’s aphasics are addressed. Samples were collected from six Broca’s aphasics from the same local region. The acoustic analysis conducted on a range of consonant and vowel parameters displayed differences between the speech patterns of Broca’s aphasics and normal speakers. For example, impairments in voicing contrast between the voiced and voiceless stops were found in Broca’s aphasics. This feature does not exist for the fricatives produced by the Palestinian Broca’s aphasics and hence deviates from data obtained for aphasics’ speech from other languages. The Palestinian Broca’s aphasics displayed particular problems with the emphatic sounds. They exhibited deviant coarticulation patterns, another feature that is inconsistent with data obtained from studies from other languages. However, several other findings are in accordance with those reported from various other languages such as impairments in the VOT. The results are in accordance with the suggestions that speech production deficits in Broca’s aphasics are not related to phoneme selection but rather to articulatory implementation and some speech output impairments are related to timing and planning deficits.
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We compared the suitability of two skeletal materials of the Atlantic brain coral Diploria strigosa for 230Th/U-dating: the commonly used bulk material comprising all skeletal elements and the denser theca wall material. Eight fossil corals of presumably Last Interglacial age from Bonaire, southern Caribbean Sea, were investigated, and several sub-samples were dated from each coral. For four corals, both the ages and the activity ratios of the bulk material and theca wall agree within uncertainty. Three corals show significantly older ages for their bulk material than for their theca wall material as well as substantially elevated 232Th content and (230Th/238U) ratios. The bulk material samples of another coral show younger ages and lower (230Th/238U) ratios than the corresponding theca wall samples. This coral also contains a considerable amount of 232Th. The application of the available open-system models developed to account for post-depositional diagenetic effects in corals shows that none of the models can successfully be applied to the Bonaire corals. The most likely explanation for this observation is that the assumptions of the models are not fulfilled by our data set. Comparison of the theca wall and bulk material data enables us to obtain information about the open-system processes that affected the corals. The corals showing apparently older ages for their bulk material were probably affected by contamination with a secondary (detrital) phase. The most likely source of the detrital material is carbonate sand. The higher (230Th/232Th) ratio of this material implies that detrital contamination would have a much stronger impact on the ages than a contaminant with a bulk Earth (230Th/232Th) ratio and that the threshold for the commonly applied 232Th reliability criterion would be much lower than the generally used value of 1 ng g^-1. The coral showing apparently younger ages for its bulk material was probably influenced by more than one diagenetic process. A potential scenario is a combination of detrital contamination and U addition by secondary pore infillings. Our results show that the dense theca wall material of D. strigosa is generally less affected by post-depositional open-system behaviour and better suited for 230Th/U-dating than the bulk material. This is also obvious from the fact that all ages of theca wall material reflect a Last Interglacial origin (~125 ka), whereas the bulk material samples are either substantially older or younger. However, for some corals, the 230Th/U-ages and activity ratios of the bulk material and the theca wall samples are similar. This shows that strictly reliable 230Th/U-ages can also be obtained from bulk material samples of exceptionally well-preserved corals. However, the bulk material samples more frequently show elevated activity ratios and ages than the corresponding theca wall samples. Our findings should be generally applicable to brain corals (Mussidae) that are found in tropical oceans worldwide and may enable reliable 230Th/U-dating of fossil corals with similar skeletal architecture, even if their bulk skeleton is altered by diagenesis. The 230Th/U-ages we consider reliable (120-130 ka), along with a recently published age of 118 ka, provide the first comprehensive dating of the elevated lower reef terrace at Bonaire (118-130 ka), which is in agreement in timing and duration with other Last Interglacial records.
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We review research on the neural bases of verbal working memory, focusing on human neuroimaging studies. We first consider experiments that indicate that verbal working memory is composed of multiple components. One component involves the subvocal rehearsal of phonological information and is neurally implemented by left-hemisphere speech areas, including Broca’s area, the premotor area, and the supplementary motor area. Other components of verbal working memory may be devoted to pure storage and to executive processing of the contents of memory. These studies rest on a subtraction logic, in which two tasks are imaged, differing only in that one task presumably has an extra process, and the difference image is taken to reflect that process. We then review studies that show that the previous results can be obtained with experimental methods other than subtraction. We focus on the method of parametric variation, in which a parameter that presumably reflects a single process is varied. In the last section, we consider the distinction between working memory tasks that require only storage of information vs. those that require that the stored items be processed in some way. These experiments provide some support for the hypothesis that, when a task requires processing the contents of working memory, the dorsolateral prefrontal cortex is disproportionately activated.
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Mode of access: Internet.
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Mode of access: Internet.