Abstract
After an extensive review of the literature, regarding zinc.oxide/eugenol impression pastes, we selected 20 of the most representatives as our references. Trough personal information of several of the investigators it was discovered that dimensional changes of theese materials is one of the most difficult properties to be measured. A new method was developed to measure dimensional changes ot 4 (four) of the most widely used zinc.oxide/eugenol impression materials in Brazil. The results, presented through several graphs and tables showed that dimensional changes varied from 0,003%, values which may probably be considered negligible from a clinical point of view. We noticed, however, high values for standard deviation and variance which indicate the high variability within the experiments. Those values were not found when we used the same method with mercaptan and silicone impression materials, in which the measurement of dimensional changes was highly reproducible. One hypothesis (which we intend to investigate in a later research) is that, during storage, a sedimentation could occur, of the components of greater density! Consequently ther might result a change in composition, independent of the method used to establishe the proportion of the two pastes, be it by wheight or measurement of lenght, which could be the cause of variability of the composition of each mixture!
Highlights
Trough personal information of several of the investigators it was discovered that dimensional changes of theese materials is one of the most difficult properties to be messured
Phe results, presented through several graphs and tables showed that dimensional changes varied from 0,003%, values which may probably pe considered negligible from a clini
J. A study of lhe zinc oxide — eugenol type impression materials
Summary
Utilizaram.se 4 marcas de pastas zincoenólicas, comumente encontradas em nosso mercado de artigos o. dontológicos, cujos nomes, fabrican. Tes bem como série e no de partida, constam da tabela de No 1. As proporções ZnO/Eugenól, bem como o tempo de espatulação e o tempo de permanência na Estufa a SToC e U.R.100%, dos corpos de prova de cada uma das pastas, constam da Tabela de No 2. Tanto a proporção das pastas, bem como o seu tempo de espatulação, era os indicados pelos respectivos fabricantes, A indicação de proporção dizia comprimentos iguais de ambas as pastas. Camos que necessitavamos, aproximadamente de 8 cm de cada uma das pastas, TABELA No 1. O material correspondente às referidas dimensões, era pesado e face à distinta composição de cada uma das pastas, resultaram pesos diferentes, conforme se pode observar na Tabe. Procurou-se destarte, simular as condições bu. cais por ocasião de uma moldagem
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