[Materials for dies in fixed prosthesis: a comparative in-vitro analysis of their detail-reproducing capacity and of their surface quality].

The authors examine the detail reproduction capacity and surface roughness of 11 commercially available materials [6 plasters (stones?), 2 epoxy resins and 3 polyurethane resins] indicated for the construction of working models with individually extractable dies. The study was performed in vitro according to the method outlined by the ADA in specification no. 19 relating to materials for elastomeric imprints. This specification describes the use of a steel test-block with which it is possible to prepare a master imprint in polyvinylsiloxane. This imprint allows the grooves of the test-block to be reproduced in the form of angular crest which represent the details to be reproduced. Both the master imprint and the samples to be tested were prepared according to the manufactures instructions. The study was performed in three stages: macroscopic analysis, microscopic analysis, profilometric analysis. The macroscopic analysis did not show any differences between the different materials tested. The microscopic analysis showed that when enlarged 40 times the resins revealed a smoother surface than the plasters. The surface quality of plasters was improved by using a hardening solution recommended by the manufacturer as an alternative to water, or by using spacer paint. The plaster materials gave excellent angular definition contrary to the epoxy and polyurethane resins. The use, where advised, of the hardening solution as an alternative to water did not alter this parameter. The electronic profilometer used for the profilometric analysis comprised a diamond sensor which, when run along the surface, recorded all roughness, translating it into chart form.(ABSTRACT TRUNCATED AT 250 WORDS)