[Corrosion of burnished or polished amalgam samples, using loss of mass after immersion in 1% NaCl solution]. / Corrosão de corpos de prova de amálgamas brunidos ou polidos medida por perda de massa, quando submetidos à imersão alternada em solução de NaCl a 1%.

This research evaluates the corrosion as expressed by the mass loss of experimental samples of both (conventional amalgam alloys (New True, Dentalloy and Velvalloy) and copper-rich alloys (Dispersalloy, Rezzizt II, Novaloy and Novaloy Plus) after immersion in a 1% NaCl solution. The sequence of treatments was: a) carved and burnished and b) carved, burnished and polished under uniform and controlled conditions the samples were weighed and alternatively submitted to immersion and finally brushed and weighed again after period of 30, 60 and 90 days. The polished samples exhibited a mass loss significantly lower than the burnished ones. The mass loss was statistically significant for the three experimental periods of time and presented a continuous mode. Differences among the alloys were detected either as to composition or surface treatment adapted.

Fracture strength of dental amalgams restoring exclusively proximal Elderton and Almquist cavity preparations.

The purpose of this investigation was to evaluate under experimental conditions the influence of six different brands of dental amalgam, exclusively in proximal cavity preparations (proposed by Elderton and Almquist and associates) on failure characteristics of these "restored dice" teeth. The volume of amalgam contained in each cavity was also calculated. The static "masticatory force" was applied through a small steel-ball (2.5 mm) in order to cause the failure of the amalgam condensed in a cavity on prepared Ni-Cr dice. No statistical significance at 0.05 level was observed for the variables (two types of cavity and six amalgam alloys), considering that the cavity design proposed by Elderton has a volume of material about 18.35% smaller than the Almquist one.

Mechanical resistance of extensive amalgam "restorations" anchored with the aid of threaded pins and amalgapins.

This study dealt with laboratory tests (oblique force application of 45 degrees to check the fracture strength), in order to compare two types of dentin pins: threaded metallic TMS Whaledent pins and amalgapins. It was used multiple number of these elements, with or without thermal cycling. The statistical analysis has indicated a highly significance difference between these pins, where the amalgapins provide to be more efficient than the steel one. As the resistance with the use of 3 or 4 amalgapins are similar, is up to the professional to choose the number of pins. It was also observed that the use of 2 or 3 steel pins had the same results. In this study it was observed that almost all of the specimens were able to resist to oblique load of more than 70 kgf. This value is higher than any force occurring in the mouth (HELKINO & INGERVALL 10). Hence, the results in vitro indicate that extensive amalgam restorations may well work in the oral cavity. Clinical studies must be conducted in order to check if really these mastication, since it is practically impossible to duplicate these natural condition in a laboratory environment.

Punch shear strength of polycarboxylate cements.

Two general conclusions are drawn which apply to all the four commercial polycarboxylate cements: First, the effect of storage condition upon shear strength was much more pronounced after 24 hours than after 1 hour of storage time; second, the effect of storage condition was most extreme when the specimens were tested free of their matrices. Additionally some specific comparisons between the four products tested can be made based on differences of shear strength within the same experimental condition. The effect of confinement decreased in the following order: Boston greater than Bondal greater than PCA greater than Durelon. Sensitivity to storage conditions decreased in this order: Durelon greater than Bondal greater than PCA greater than Boston. Finally sensitivity to storage times decreased in the order Bondal greater than Durelon greater than Boston greater than PCA.