[Electrolytic etching of different alloys. 1. Weight loss of samples]. / Ataque electrolítico de ligas de composições diversas. Parte 1: perda de peso dos corpos de prova.

The adhesive fixed partial denture is a relatively new alternative in Dental Prostheses area, then it needs many studies in order to reach technique improvement. This work has the objective of studying the behavior of a copper-aluminium and two nickel-chrom dental alloys that were subjected to electrolytical etching with two experimental solutions and an electrolytic solution commented by TANAKA et alii, 1979. After weight-loss studies we can conclude that the alloy composition is a fundamental factor and to each alloy should be developed specifics electrolytical solutions.

[Medical rugosity (Ra) of the surface of stone models from alginate impressions using two processes: manual spatulation and vacuum mechanical spatulation]. / Avaliação da rugosidade média (Ra) da superfície de modelos de gessopedra, obtidos de moldes de alginatos manipulados por dois processos: espatulação manual e espatulação mecânica a vácuo.

The differences in superficial smoothness of 108 stone models, obtained from three marks of alginates, manipulated by two different techniques of spatulation (a. manual; and b. mechanic with vibration under vacuum), were studied. The 108 stone models (resultant from the factorial product: 3 alginates x 2 techniques x 6 stones x 3 replica = 108) were analysed by means rugosimeter (Talisurf 10). The results showed that the superficial smoothness of the models was not affected significantly by any of the two techniques tested. The alginate Jeltrate offered the best results, and the group represented by the stones Moldaroc/Gaúcha III/Durastone T/Castone was better than the Vel-Mix, and the Vel-Mix statistically better than the Glastone.

[Comparative study of the capacity of elastomers in reproduction and transmission of details to gypsum models]. / Estudo comparativo da capacidade dos elastômeros na reprodução e transferência de detalhes para os modelos de gesso.

The authors studied the ability of three elastomeric impression materials in reproducing and transmitting three grooves, engraved in the polished surface of a stainless steel model, to gypsum models. The grooves were 17, 21 and 25 micrometers wide, and the fails in reproducing, as well as in transmitting the minor details to gypsum, were also investigated as to the effects of gypsum particle size, proportional relation water/powder and plasticity of the mixture. The three elastomeric impression materials used were a polysulfide, a silicone and a polyether, and the six gypsum products were two improved stones type IV, two dental stones type III and two dental plasters type II. Scores 3, 2 and 1 were attributed respectively to the 17, 21 and 25 micrometers grooves reproduced in the molds, as well to the same grooves transmitted to the gypsum models. The results showed that all the impression materials tested were able to reproduce in the molds all the three grooves present in the steel model. Nevertheless, when gypsum models were examined, it was verified that the grooves so well reproduced in the molds were neither equally nor uniformely registered in the respective models, the best results being achieved by the polysulfide and the silicone, an the worst by polyether, As to the gypsum products, the type II gypsum presented the most unfavorable results.

[Evaluation of cervical discrepancy of gold crowns in stone dies from various impression materials]. / Avaliação do desajuste cervical de coroas de liga de ouro em troquéis de gesso-pedra, obtidos a partir de materiais de moldagens diversos.

A stainless steel master die simulating a dental preparation for crown was used to make 3 gold castings from wax patterns obtained in 3 different ways: a) directly from the naked master die; b) from the same master die with a copper coping 30 microns thick; and c) with a similar copper coping, but 40 microns thick. The discrepancies of fit of the 3 master gold crowns were evaluated in 99 stones dies (33 for each casting) obtained from 11 different elastomeric impression materials (3 replicae of each). The results showed that: 1) stone dies with no coping presented a medium discrepancy of 284 microns, inadequate for clinical use; 2) the 30 microns and 40 microns copings presented medium discrepancies of 18 and 9 microns respectively, both suitable for clinical use. Thus, the use of copings tend to equalize the cervical discrepancy of fit of gold crowns, whatever be the elastomeric impression material used.

[Influence of mercaptan impression storage conditions on linear dimensional changes in improved plaster-stone casts]. / Influência da condição de armazenamento de moldes de mercaptana nas alterações dimensionais lineares ocorridas nos modelos de gesso-pedra melhorado.

A study was conducted on the influence of storage conditions of mercaptan molds on the linear dimensional alterations occurring in improved plaster-stone casts. Two types of storage were used: A) in which the molds were left on the bench for 5 minutes at 25 degrees C and 55% relative humidity; and B) in which the molds were placed in an incubator at 37 degrees C and 100% relative humidity for 40 minutes. Casts were built using 5 different brands of improved plaster-stone, 5 casts per brand. Thus, considering the 2 types of storage, the 5 brands of plaster-stone and the 5 replications, a total of 50 improved plaster-stone casts were constructed. The linear dimensional alterations were measured with the aid of a linear measurement microscope, which measured the space between two hemisections of the standard fixed bridge, both when the fixed bridge was adapted to the master cast and to the plaster cast.

[Cervical adaptation of complete cast crowns of various metal alloys, with and without die spacers]. / Adaptação cervical de coroas totais fundidas com diversas ligas metálicas, usando troquéis com e sem espaçador.

A metallic replica from a dental preparation for crown was used to make 8 class-IV stone dies. The wax patterns for the casting of the crowns were obtained in two conditions: a) from the stone die with no spacer; and b) from the stone die with an acrylic spacer. Thus, 64 metallic crowns were casted, using 4 different alloys: DURACAST (Cu-Al), NICROCAST (Ni-Cr) and DURABOND (Ni-Cr), and gold. The casted crowns were fitted in the metallic replica and measured as to the cervical discrepance of fitting. The results showed that the use of die spacers decreases the clinical discrepancies of fitting of the casted crowns (in a statistically significant level), no matter the metallic alloy employed.

[Surface roughness of investment samples and their metal castings]. / Avaliaçao da rugosidade superficial de corpos de prova de revestimento e respectivos blocos metálicos obtidos.

Three phosphate bonded investments and three calcium type were studied observing the influence of investment on the final cast surface roughness. Increased dilution also incremented roughness for the phosphate investments. Between the two types of investments there was only significant difference concerning two specific commercial brands, but there were differences in the same type of investment among these different brands.

[High temperature investments. 1. Evaluation of some physical properties]. / Revestimentos para altas temperaturas. Parte I. Avaliação de algumas propriedades físicas.

An evaluation of linear dimensional alterations of normal and hygroscopic setting of 3 phosphate-bonded investments and gypsum-bonded investments was made. The phosphate-bonded investments were processed with 100, 75, 50 and 25% special liquid. We investigated the maximum temperatures tolerated by the investments, in relation to the normal setting reactions. To evaluate expansion of normal and hygroscopic setting an electronic palpater was used, with the investments confined. The temperatures of the thermal reactions were detected by a digital thermometer. We confirmed that the CERAMIGOLD and HI-TEMP investments, processed with 75% special liquid, presented a greater linear expansion than the normal settings. The HI-HEAT presented less expansion than the normal setting and greater linear expansion than the hygroscopic setting. The MULTI-VEST tolerated the highest temperature during the evaluation.