Search PubMed⌕ Search

Biomedical subjects

M M Vrijhoef

Publications and source records attributed to M M Vrijhoef.

At least 73 records · Page 4Linked to original sources
PubMed1979

Diametral tensile strength of twenty-three hardened commercial amalgams.

In view of the ever increasing number of high copper alloys, it was the aim of this study to investigate the tensile strength property of some of the new alloy systems. The factors alloy system and heat treatment were investigated in relation to the tensile strength. The factors alloy system as well as the heat treatment turned out to be significant. The study suggests that the introduction of "dispersion" alloys did not change the dental picture as to the property of the tensile strength. The selection of strength values in the range of 35-55 MN/m2 for the diametral tensile strength probably have no clinical relevancy as to the prevention of bulk fractures of amalgam restorations under oral conditions.

Copper↗
PubMed1977

Influence of the heat treatment of commercial amalgam alloys on the phase composition of the alloys and the creep of the resulting amalgams.

The influence of heat treatment of dental alloys at several temperatures on the phases present in the alloy and the creep of the resulting amalgam as well as the correlation between phase changes and the creep was investigated. A dependence of the creep on the temperature of the heat treatment of the alloy was established. Substantial phase changes were observed after the different heat treatments. No correlation was detected between the creep rate and the changes in phases present in the dental alloys. A thermodynamically oriented explanation of the relation between the creep of the amalgam and the state of (non-) equilibrium of the corresponding amalgam alloy was proposed and discussed.

Dental Alloys↗
PubMed1977

The influence of some manipulative factors on creep.

The effects of a number of factors on creep in dental amalgam was investigated. The factors studied were the delayed time between mixing and packing, the packing technique, the alloy system and the annealing or ageing of specimens at 37 degrees C for one and 190 days. The delayed time and the alloy system factors as well as an interaction between them had a significant influence on the one day annealed specimens. The alloy system in the 190 days annealed specimen was the only factor to affect creep.

Dental Amalgam↗
PubMed1976

[The tensile strength of amalgam after 15 minutes].

The authors are mainly interested in the investigation of the tensile strength of a setting amalgam acquired after 15 minutes after the end of the trituration. Knowledge about this property is of interest because generally this moment corresponds with the time that a patient is asked to put the amalgam restoration into contact with the antagonist tooth. In two series of experiments eight commercial amalgam alloys, two different trituration techniques (hand and Silamat mixing machine) as well as two condensation techniques (hand and Bergendal vibrator) were tested. The reslts reveal that the tensile strengths of the different treatment combinations of amalgams prepared from Dispersalloy are significantly much higher than the minimum value of 2 MN/m2 which is required by the new stipulations of the A.D.A. specification n degrees 1. Some amalgams do not satisfy this requirement. Although the influence of the trituration technique as well as that of the condensation technique turns out to be significant, apparently the influence of the amalgam alloy is of much greater importance.

Dental Amalgam↗
PubMed1976

[Resistance to traction forces in different brands of amalgam].

In a previous study the initial tensile strength of several dental amalgams after 15 minutes has been investigated. The present study scrutinized a large number of dental amalgams for the tensile strength after 15 minutes up to 60 minutes. All the dental amalgam specimens used in this study were prepared according to A.D.A. specification no. 1. The results obtained from this study show that out of the twenty three dental amalgams only approximately the half conformed to the minimum value of 2.0 MN/m2 as required for the tensile strength after 15 minutes by A.D.A. specification no. 1. Contrary to the results obtained by other investigators, the dental amalgam obtained from the spherical type of alloys does not acquire a superior initial strength in comparison with those from the conventional types of amalgam alloys. In this study the new dental amalgam alloy Indiloy (n.z.) (Shofu Corporation, Japan) demonstrated a superior tensile strength for all the testing times. If the tensile strength after 15 minutes is taken as a selection criterion, the five best alloys in this investigation are Indiloy (n.z.), Optalloy II, Micro II, Revalloy and Cavex SF. If the previous study is considered likewise. Dispersalloy (fast setting form) should be taken into account as well.

Dental Amalgam↗