Investigou-se o efeito da radiopacidade de diferentes materiais obturadores sobre a sensibilidade, especificidade e confiabilidade da análise radiográfica de obturações endodônticas. Após determinação da radiopacidade dos materiais, um total de 80 dentes caninos tiveram seus canais radiculares preparados com a técnica clássica antes de serem divididos em 5 grupos cada qual a ser obturado com um dos cimentos obturadores estudados (AH Plus, Endomèthasone®, Sealer 26, Acroseal e cimento não-radiopaco). Antes do preenchimento com a técnica de condensação lateral da guta-percha, em metade dos dentes de cada grupo, inseriu-se um fio de nylon radiolúcido (Ø 0.25 mm), ao longo do canal radicular para simular um defeito de obturação (n=8). Um total de 36 dentes molares superiores, depois de instrumentados, foram divididos em 3 grupos cada qual a ser obturado com um dos cimentos testados (AH Plus, Acroseal e cimento não-radiopaco) (n=12). Antes da obturação com a mesma técnica utilizada nos caninos, um fio de 0.08 mm de espessura foi estendido no canal disto-vestibular de cada dente. Após a utilização de artifícios para simular a sobreposição dos tecidos humanos, os dentes obturados foram radiografados e as imagens periapicais analisadas por endodontistas e radiologistas quanto à presença de defeitos de preenchimento nas obturações. Após análise estatística empregandose os testes exato de Fisher, Kappa e teste t (p<0.05). Observou-se menor sensibilidade no exame dos dentes anteriores obturados com os cimentos radiopacos, principalmente na avaliação dos radiologistas, e identificou-se maior especificidade para as obturações efetuadas com os cimentos endomethasone® e Acroseal. No julgamento dos dentes posteriores, o cimento Acroseal proporcionou menor sensibilidade do que o AH Plus e houve menores valores de especificidade na avaliação dos endodontistas, embora sem diferenças entre os grupos de cimentos estudados. A confiabilidade mostrou-se maior para as obturações dos caninos realizadas com Endomethasone® e Sealer 26 e não se detectaram diferenças entre os grupos na avaliação das obturações dos molares. Concluiu-se que a radiopacidade dos cimentos influenciou na sensibilidade, especificidade e confiabilidade da análise radiográfica de obturações endodônticas, assim como a especialidade dos examinadores. / The aim of this study was to investigate the effect of different radiopaque sealers in the sensitivity, specificity and realiability of radiographic root canal filling exam. After radiopacity distinction of root canal sealing materials, a total of 80 extracted single-rooted upper canines had their canals prepared with classic technique before being divided into 5 groups, each to be filled with one of the tested sealers (AH Plus, Endomèthasone®, Sealer 26, Acroseal and non-radiopaque sealer). In half specimens a radiolucent nylon monofilament string (Ø 0.25 mm) positioned inside the root canal to simulate a radiolucent void before being filled with gutta percha lateral condensation (n=8). A total of 36 maxillary molars were divide into 3 groups, each to be filled with one of the tested sealers (AH Plus, Acroseal and non-radiopaque sealer). Before being filled with lateral condensation technique, a Ø 0.08mm string was positioned alongside distobuccal root canal. After root canal filling, each tooth was strictly positioned in a device to simulate bone and soft tissue before being exposed to X rays. The resulting images were interpreted for presence of voids by radiologists and endodontists. The differences between groups were assessed using Fisher Exact, Cohens Kappa and t test (>0.05). There were less sensitivity for all radiopaque sealers, specially for radiologists, and higher specificity when Endomethasone® and Acroseal were used to fill the upper canines. Root canal fillings performed in maxillary molars with Acrosel showed lower sensibility values than AH Plus mainly to endodontists, but no difference in specificity between groups. There were lower reliability than control group for canines filled with Endomethasone® and Sealer 26. The differences of reliability between groups were not statistically significant. It was concluded that radiopacity of sealers influenced on sensitivity, specificity and reliability of radiographic root canal filling exam, as well as the speciality of examiners.

Over 200 million dental restorations are performed each year in America. A dental restoration require a strong bonding of restoration to tooth structure and relies on the dental adhesive to create this mechanical and chemical bonding. Dental adhesion or bonding is the process of forming an adhesive joint between the composite and tooth substrate: dentin or enamel. Clinical problems such as microleakage at the restoration tooth interface, influx of fluids, or bacteria growth at the cavity wall can be prevented with adhesives that obtain a more intimate bonding. Longevity of the restoration can be enhanced by the adhesive that creates the tight bonding to reduce problems such as postoperative sensitivity, marginal staining, and recurrent caries. The goal of this research project is to investigate the influence of active scrubbing application as compared to passive non-scrubbing application of the etchant component in 4th generation etch-and-rinse adhesive systems. Shear bond stresses have been measured and compared between application techniques. Verification of resin infiltration depth with each etchant application has been examined with scanning electron microscopy by mounting the etched and bonded enamel surface of the tooth in epoxy and slicing the tooth longitudinally producing a transverse, depth-wise view. Results from this study have clarified the role of resin tag formation as well as tooth morphology during an active acid etchant application for dental restoration.

published_or_final_version / Dentistry / Doctoral / Doctor of Philosophy

The dental field shows proliferation in the market of new adhesives. The purpose of this study is to evaluate the mechanical properties on total restoration, based on the manufacturer's technical specifications, experimental and mechanical test results. The optimal dentist's selection will be when the most appropriate adhesive can be chosen for one specific restoration, avoiding wasted time, material and exposure to marginal infections with a failure restoration. This research was developed in stages. The first step is the study of the tooth morphological information. Following, there is the structure identification type and the chemical composition of six different pure adhesives. Next, perform the X-R Diffraction, Energy Disperse Spectroscopy (EDS), and Scanning Electron Microscopy (SEM). The final step is to perform the mechanical test, computer simulation, and discuss the results to obtain the best dental adhesive with and the new finding. Result: The samples show an amorphous structure and a chemical composition in the X-R Diffraction, SEM and EDS experiments. The mechanical test shows real mechanical properties under tension and sheer rupture stress. Poisson ratio, strain, and another relationship will be used in the computer simulation test. Results will be reflected in the Discussion and Conclusion. Significance: The first conclusion is that the amorphous structure is present in all six adhesives experiments. In addition, it shows strong possibilities of bonding with another neighbor's molecules. The discussion will be extended to the bonding advantages for this type of structure in the total dental restoration. / Findings: First, we found that the time delay of photo polymerization was controlled with the variable water evaporation of the etching treatment. In addition, it was found that the variable size of the wavelength of the curing light obtained better molecular organization and avoided internal stress and bonding defect. Lastly, the chemical composition was a variable that provided the opportunity to predict the type of bond and strength. / by Raul Vargas. / Thesis (Ph.D.)--Florida Atlantic University, 2008. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2008. Mode of access: World Wide Web.

We study the distribution of combinatorial statistics that exhibit a structure of crossings and nesting in various discrete structures, in particular, in set partitions, matchings, and fillings of moon polyominoes with entries 0 and 1. Let pi and y be two set partitions with the same number of blocks. Assume pi is a partition of [n]. For any integers l, m >̲ 0, let T (pi, l) be the set of partitions of [n + l] whose restrictions to the last n elements are isomorphic to pi, and T (pi, l, m) the subset of T (pi, l) consisting of those partitions with exactly m blocks. Similarly define T (pi, l) and T (y, l, m). We prove that if the statistic cr (ne), the number of crossings (nestings) of two edges, coincides on the sets T (pi, l) and T (pi, l) for l = 0; 1, then it coincides on T (pi, l, m) and T (y, l, m) for all l, m >̲ 0. These results extend the ones obtained by Klazar on the distribution of crossings and nestings for matchings. Moreover, we give a bijection between partially directed paths in the symmetric wedge y = +̲ x and matchings, which sends north steps to nestings. This gives a bijective proof of a result of E. J. Janse van Rensburg, T. Prellberg, and A. Rechnitzer that was first discovered through the corresponding generating functions: the number of partially directed paths starting at the origin confined to the symmetric wedge y = +̲ x with k north steps is equal to the number of matchings on [2n] with k nestings. Furthermore, we propose a major index statistic on 01-fillings of moon polyominoes which, when specialized to certain shapes, reduces to the major index for permutations and set partitions. We consider the set F(M, s, A) of all 01-fillings of a moon polyomino M with given column sum s whose empty rows are A, and prove that this major index has the same distribution as the number of north-east chains, which are the natural extension of inversions (resp. crossings) for permutations (resp. set partitions). Hence our result generalizes the classical equidistribution results for the permutation statistics inv and maj. Two proofs are presented. The first is an algebraic one using generating functions, and the second is a bijection on 01-fillings of moon polyominoes in the spirit of Foata's second fundamental transformation on words and permutations.

Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 202-236).

Thesis (DR. P.H.)--University of Michigan.

Thesis (M.S.)--University of Michigan, 1983.

Thesis (M.S.)--University of Michigan, 1985.

Thesis (M.S.)--University of Michigan, 1960.