Each of the resin pastes used in the present study showed temperature dependence of its characteristics in the temperature range examined (20-30 degrees C) and thixotropic fluidity. However, the flow characteristics of these resin pastes differed significantly, suggesting that the flow characteristics may affect the manipulation of resin formativeness.
Two types of hard resin for crowns and bridges were investigated. The results of each investigation changed according to the products used, and the proper use for each case and application was suggested. AbstractPurpose: Hard resins for crowns and bridges are wide ly used for esthetic restorations. The objective of this study was to evaluate the mechanical properties of new commercial hard resins and to compare the results with those of the other hard resins previously investigated. Methods:Dentin and enamel made with two new hard resins (Epricord ® : EP, Kuraray, Co., Ltd., Osaka, Japan and Prossimo ® : PR, GC, Co., Ltd., Tokyo, Japan) were used in this study. Regarding the fundamental charac teristics, the thermal expansion/shrinkage coefficient, the filler content, the polymerization shrinkage, and the wear were examined. Regarding the strength of resin, the bending strength, hardness, compression strength, elastic modulus, and fracture strength of a jacket crown were measured.Results: These resins showed comparatively lower lev els than the other hard resins regarding the bending strength, hardness, compression strength, and fracture strength of the jacket crown. The total filler content rate and wear amount of these resins exhibited similar values to those of the other resins. The thermal expan sion/shrinkage coefficients of these resins exhibited higher values than those of the other resins. EP showed a different tendency from PR about the compression strength, elastic modulus, and polymerization shrink age.Conclusions: PR and EP did not show dramatically better physical properties. However, the results of each examination in this study may be acceptable clinically.The results of each investigation changed according to the products used, and proper use for each case and ap plication was suggested.Key words: hard resin for crown and bridge, mechani cal property, resin facing cast crown, resin jacket crown
: In this study, the relationship between the composition and the flow properties of three commercial tissue conditioners was investigated.Analysis of the composition was chiefly done by infrared spectroscopy (IR). As for the liquid, plasticizer was qualitatively determined and the content of alcohol was measured by distillation. The characteristics of polymer powders were obtained by means of gel permeation chromatography (GPC) , particle size analyzer and SEM. As for the flow property, the apparent viscosity of a mixture of liquid and powder was measured by a cone and plate rotational viscometer.As a result, the liquid was a mixture of a phthalic ester plasticizer (dibutyl phthalate) with up to 13% ethyl alcohol. The polymer powders generally consisted of polyethyl methacrylate (PEMA) , but one was a blend of PEMA and polyisobutyl methacrylate (iso-PBMA).The viscosities of mixtures were found to increase rapidly with an increase in the ethyl alcohol content, and an increase in temperature. Further, the viscosity curve of the tissue conditioner, of which the powder was a blend of PEMA and iso-PBMA, showed characteristic behavior.Thus it was suggested that the flow property of the tissue conditioner was affected by the molecular structure of the polymer powder.
The purpose of this study was to give polyaddition-type silicone impression materials (Regular Type) the characteristics that the pastes are easy to mix, and they are difficult to hang down from the tray.In a previous study, the inorganic filler significantly affected the flow characteristics of impression materials.
Abstract:The purpose of this study was to investigate flow characteristics of four commercial polyaddition-type silicone impression materials (Regular Type) before mixing.Base and catalyst pastes were filler and polymer separated by a centrifugal separator with benzene for component analysis. As a result, weight fraction of filler was 39-55% and the chief ingredient was silica.The main polymer of base and catalyst pastes was polydimethylsiloxane. Especially, base polymer included hydrogen polydimethylsiloxane which was a crosslinking agent. The molecular weight (Mw) of these polymer was mostly about 40,000-70,000.
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