Influence of surgical repositioning of mature permanent dog teeth following experimental intrusion: a histologic assessment

The aim of this study was to evaluate, through histologic examination, the effect of surgical repositioning of intruded dog teeth upon the pulpal and surrounding tissues. Thirty teeth in 10 adult dogs, aged 2-3 years, were used. Fifteen teeth were intruded, surgically repositioned and fixed using orthodontics wire, composite resin, and enamel acid conditioning. All these teeth served as the experimental group. The remaining intruded teeth were not treated ( control group). The animals were sacrificed to allow observations at 7,15, and 30 post-operative days. The maxillary and mandibular archs were removed and processed for histologic exam. Based on the methodology and observed results, we concluded that: pulpal necrosis, external root resorption and ankylosis were common sequelae to severe traumatic intrusion; a careful immediate surgical repositioning of severed intruded permanent tooth with complete root formation has many advantages with few disadvantages.

Oral and maxillofacial reconstruction in a cat using wire and acrylic

A 15-month-old DSH cat was presented with facial deformity secondary to multiple oral and maxillofacial fractures after being struck by an automobile. Multiple wires and dental acrylics were used for fracture repair.

Load compensation in four-wire electrical power systems

This work describes a methodology for power factor control and correction of the unbalanced currents in four-wire electric circuits. The methodology is based on the insertion of two compensation networks, one wye-grounded neutral and another in delta, in parallel to the load. The mathematical development has been proposed in previous work [3]. In this paper, however, the methodology was adapted to accept different power factors for the system to be compensated. on the other hand, the determination of the compensation susceptances is based on the instantaneous values of the load currents. The results are obtained using the MatLab - Simulink environment.

Análise radiográfica computadorizada da reabsorção radicular apical após a utilização de duas mecânicas ortodônticas

OBJETIVO: a reabsorção radicular apical é uma condição comumente observada durante e após o tratamento ortodôntico e fatores como tipo de aparelhagem ortodôntica utilizada, magnitude das forças aplicadas e duração do tratamento podem estar relacionados ao processo de arredondamento do ápice radicular. Buscou-se avaliar, por meio de imagens radiográficas computadorizadas, a quantidade de reabsorção no ápice radicular, quando da utilização de duas diferentes técnicas de mecânica ortodôntica fixa: Edgewise com acessórios padrão e Edgewise com acessórios totalmente programados. METODOLOGIA: a amostra constituiu-se de 20 pacientes tratados pelo mesmo profissional na Clínica de Ortodontia da Faculdade de Odontologia de Araçatuba - UNESP. Os pacientes foram divididos em dois grupos: grupo 1 (Tratados com Edgewise com acessórios padrão e fios de aço) e grupo 2 (Tratados com Edgewise com acessórios totalmente programados e fios de níquel-titânio). A avaliação radiográfica digital foi realizada por um único operador por meio de exposições radiográficas digitais feitas no início do tratamento ortodôntico, após retração de caninos e final de tratamento, utilizando o sistema de escores proposto por Levander e Malmgren (1988). RESULTADOS E CONCLUSÕES: a análise dos escores permitiu concluir que o tratamento ortodôntico empregando a técnica Edgewise com acessórios totalmente programados e fios de níquel-titânio apresentou menores graus de reabsorção radicular apical, em comparação à técnica Edgewise com acessórios padrão e fios de aço. Observou-se que, independentemente da técnica empregada, o tratamento ortodôntico como um todo apresentou um grau moderado de reabsorção radicular apical.

Avaliação qualitativa em modelo experimental fotoelástico do sistema de força gerado pela mola T centralizada com pré-ativações preconizadas por Burstone

OBJETIVO: avaliar o sistema de forças gerado pela mola T centralizada no espaço interbraquete, com pré-ativação preconizada por Burstone. MÉTODOS: utilizando-se modelos fotoelásticos, a mola T com pré-ativações preconizadas por Burstone, confeccionada com fio retangular de titânio-molibdênio (TMA) de secção 0,017x 0,025, centralizada e com ativação de 6mm, 3mm e em posição neutra. Para melhor confiabilidade dos resultados, os testes foram repetidos em três modelos igualmente duplicados e confeccionados pelo mesmo operador. Utilizou-se uma distância interbraquetes de 27mm. Para compreensão dos resultados, as franjas foram visualizadas através do polariscópio, fotografadas e analisadas qualitativamente. RESULTADOS: por meio da análise qualitativa da ordem de franjas no modelo fotoelástico, notou-se que, nas extremidades de retração e ancoragem, ambas apresentaram simetria no sistema de força, em toda extensão radicular.

Orthodontic movement of teeth with intraosseous defects: histologic and histometric study in dogs

The purpose of this study was to evaluate histologically, in dogs, the periodontal healing of 1-walled intraosseous defects in teeth that were subjected to orthodontic movement toward the defects. The defects were surgically created bilaterally at the mesial aspects of the maxillary second premolars and distal aspects of the mandibular second premolars of 4 mongrel dogs. One week after creating the defects, an orthodontic appliance was installed, and the teeth were randomly assigned to 1 of 2 treatment groups: those in the test group received a titanium-molybdenum alloy rectangular wire spring that performed a controlled tipping root movement, and those in the control group received a passive stainless steel wire. Active orthodontic movement of the test teeth lasted 2 months and was followed by a stabilization period of another 2 months, after which the animals were killed. Throughout the study, routine daily plaque control was performed on the dogs with a topical application of a 2% chlorhexicline gel. The results showed no difference between the groups, with some regularization of the defects and periodontal regeneration limited to the apical portion of the defects. Histometric analysis showed a significant difference in bone height; on average, it was 0.53 mm smaller in the test group. It was concluded that orthodontic movement does not interfere with the healing of 1-walled intraosseous defects, with the exception of the linear extent of new bone apposition.

Comment on Effect of spin-orbit interaction on the plasma excitations in a quantum wire

We comment on the recent results [Phys. Rev. B 70, 235314 (2004)] showing the dispersion relations of single-particle and collective excitations in quantum wires in the presence of the Rashba spin-orbit interaction (SOI). We claim that those calculations performed in the absence of SOI, and used as a strong reference to the interacting case, are unlikely to be correct. We show the correct omega-q plane of the system in the absence of Rashba SOI.

Universal zero-bias conductance through a quantum wire side-coupled to a quantum dot

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Comparação de parâmetros periodontais após utilização de contenção ortodôntica com fio trançado e contenção modificada

OBJETIVO: o presente estudo teve como objetivo comparar dois tipos de contenções ortodônticas fixas, em relação a parâmetros periodontais estabelecidos. A contenção com fio trançado é a mais comumente utilizada e a contenção modificada apresenta dobras que têm a finalidade de permitir o livre acesso do fio dental às áreas interproximais. MÉTODOS: para esse estudo cruzado, foram selecionados 12 voluntários que utilizaram, por 6 meses, A) Contenção com fio trançado e B) Contenção modificada - sendo essas fixadas em todos os dentes do segmento anterior. Após esse período experimental, foram feitas as seguintes avaliações: Índice de Placa Dentária, Índice Gengival, Índice de Cálculo Dentário e Índice de Cálculo ao longo do fio de contenção. Os voluntários também responderam a um questionário com relação à utilização, conforto e higienização das contenções. RESULTADOS: foi observado que o índice de placa e o índice gengival foram maiores nas faces linguais (p<0,05) para a contenção modificada. Além disso, o índice de cálculo foi estatisticamente maior (p<0,05) considerando-se as faces linguais e proximais na utilização da contenção modificada. O índice de cálculo ao longo do fio também apresentou valores significativamente maiores (p<0,05) na contenção modificada. em relação ao questionário, 58% dos voluntários consideraram que a contenção modificada é mais desconfortável; e 54% deles preferiram a contenção com fio trançado. CONCLUSÃO: a partir dos resultados obtidos, pode-se concluir que a contenção com fio trançado apresentou melhores resultados do que a contenção modificada, de acordo com os parâmetros periodontais avaliados, além de apresentar maior conforto e preferência na sua utilização.

Vortex lattice of a long superconducting wire with a columnar defect

In the present work we study a long superconducting wire with a columnar defect in the presence of an applied magnetic field. The cross section of the cylinder is assumed to be circular. The field is taken uniform and parallel to the cylinder axis. We use the London theory to investigate the vortex lattice inside the wire. Although this theory is valid in the limit of low vortex density, that is, when the nearest neighbor vortex distance is much larger than the coherence length, we can obtain a reasonable qualitative description of lattice properties. We calculate: (1) the vortex lattice structure using the simulated annealing technique; (2) the magnetization curve as a function of the applied field.

Fault analysis in four-wire distribution networks

The neutral wire in most existing power flow and fault analysis software is usually merged into phase wires using Kron's reduction method. In some applications, such as fault analysis, fault location, power quality studies, safety analysis, loss analysis etc., knowledge of the neutral wire and ground currents and voltages could be of particular interest. A general short-circuit analysis algorithm for three-phase four-wire distribution networks, based on the hybrid compensation method, is presented. In this novel use of the technique, the neutral wire and assumed ground conductor are explicitly represented. A generalised fault analysis method is applied to the distribution network for conditions with and without embedded generation. Results obtained from several case studies on medium- and low-voltage test networks with unbalanced loads, for isolated and multi-grounded neutral scenarios, are presented and discussed. Simulation results show the effects of neutrals and system grounding on the operation of the distribution feeders.

Methodology for load compensation in four-wire electrical power systems based on instantaneous sampling

This work describes a methodology for power factor control and correction of the unbalanced currents in four-wire electric circuits. The methodology is based on the insertion of two compensation networks, one wye-grounded neutral and other in delta, in parallel to the load. The mathematical development has been proposed in previous work [3]. In this paper, however, the determination of the compensation susceptances is based on the instantaneous values of load currents. The results are obtained using the MatLab-Simulink enviroment

Power flow in four-wire distribution networks - General approach

The neutral wire in most power flow software is usually merged into phase wires using Kron's reduction. Since the neutral wire and the ground are not explicitly represented, neutral wire and ground currents and voltages remain unknown. In some applications, like power quality and safety analyses, loss analysis, etc., knowing the neutral wire and ground currents and voltages could be of special interest. In this paper, a general power flow algorithm for three-phase four-wire radial distribution networks, considering neutral grounding, based on backward-forward technique, is proposed. In this novel use of the technique, both the neutral wire and ground are explicitly represented. A problem of three-phase distribution system with earth return, as a special case of a four-wire network, is also elucidated. Results obtained from several case studies using medium- and low-voltage test feeders with unbalanced load, are presented and discussed.

Three- phase four-wire circuits interpretation by means of different power theories

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)