Thermal expansion of dental casting alloys and phosphate-bonded investments.
For a dental investment to render accurate castings, it is essential 1) that the setting expansion is low enough not to cause any distortion of the wax pattern, and 2) that the thermal expansion is high enough to compensate fully for the solid thermal contraction of the casting alloy used1-8). However, all phosphate-bonded investments known today when used according to the manufacturers' instructions, are characterized by a relatively high setting expansion, and by a thermal expansion insufficient to compensate adequately for the solid thermal contraction of conventional casting alloys. Recent studies9) have shown that the setting expansion of representative European brands of phosphate-bonded investments may be reduced to an acceptable low value by modifying the mixing liquid. It was the purpose of the present work to study the thermal expansion of thus modified products, and for comparison also the thermal expansion of several dental casting alloys.
Influencia da reutilização do hidrocoloide reversivel na alteração dimensional linear de modelos de revestimento utilizados no processo de fundição de proteses parciais removiveis
O objetivo deste trabalho foi avaliar a alteracao linear de modelos refratarios obtidos a partir de moldes de hidrocoloide reversivel (HR) de duas marcas comerciais (DUPLlCADOR VIPI® -Dental VIPI Ltda. e DUPLlCADOR K27® - Knebel Produtos Dentarios Ltda.), submetidos a 15 ciclos de reutilizacao. Para isto, foi utilizado um modelo metalico com 4 marcacoes (A, B, C e D) que quando unidas, admitiam a mensuracao linear das distâncias AB, BC, CD, DA, BD e AC. A partir deste modelo, foram confeccionados 10 modelos em gesso tipo IV, divididos aleatoriamente, para cada marca comercial de HR, em dois grupos com 5 modelos cada um (Grupo Controle). O HR foi fluidificado em forno de microondas de acordo com as instrucoes dos fabricantes e vertido no interior da mufla que continha o modelo de gesso. O molde era preenchido com revestimento de silicato de etila (REFRADEN® - Knebel Produtos Dentarios Ltda.), e deste eram obtido os seus modelos refratarios, respectivos a cada marca comercial. Esta metodologia foi repetida nos 15 ciclos de reutilizacao de cada HR. Os modelos refratarios gerados pela 1a fluidificacao, 5a, 10a e 15a reutilizacoes dos HRs, totalizando 40 modelos, foram mensurados em um microscopio mensurador (Mesuring Microscope STM - Olympus®). As medias foram submetidas a analise estatistica pelos testes de Analise de Variância, Tukey e Dunnett, ao nivel de 5% de significância. Os resultados evidenciaram que os modelos refratarios obtidos pelo HR da marca VIPI® apresentaram alteracoes lineares em relacao ao Grupo Controle, nas distâncias AB (1a fuidificacao= -1,25% e 5a reutilizacao= -1,20%); AD (1a fluidificacao=0,76%, 10a =0,65% e 15a =0,52% reutilizacoes); BD (1a fluidificacao=0,58%). De acordo com os resultados obtidos, foi possivel concluir que, mesmo havendo diferenca significativa ate 15 ciclos de reutilizacoes do HR, este fator nao comprometeu a finalidade protetica que se propoe o HR, gerando modelos de revestimento aceitaveis para ambas marcas comerciais investigadas 
Abstract
The Role of Democratic Politics in Transforming Moral Convictions into Law
Professor Michael Perry's new book, Morality, Politics, and Law, is an ambitious attempt to address the extent to which moral and religious beliefs in a pluralistic society, such as ours, can legitimately influence law. He departs from the common opinion in legal circles that moral beliefs are a matter of taste or "values," and defends an older conception that it is possible to attain moral "knowledge." ' He also departs from the "liberal political-philosophical project," 2 which claims that it is possible (and desirable) for governments to steer a neutral course between competing moral understandings of the good. This, he suggests, is an illusion, and a disguise for the imposition of a particular moral structure without opportunity for open deliberation and reflection. Professor Perry brings some refreshing common sense to these riddles of moral philosophy. His "naturalist" approach has obvious roots in Aristotle-not a bad place to begin thinking about ethics. His dismissal of