Studies on Microleakage with Restorative Materials I. Introductory Experiments on Amalgam

¹ Institute of Pedodontics, University of Lund, Malmö, Sweden

Microleakage with two silver amalgams and one copper amalgam was studied by a radioactive nuclide technic; the results obtained were compared with those from conventional tests of dimensional changes during setting. The leakage was measured as the permeation of ²²Na in the form of isotonic sodium chloride solution according to the method of Söremark and Bergman.³² The standardization of the specimens for the registration of dimensional changes was made according to the technic of Granath.³¹

Four test cups for each type of amalgam were used in the leakage test. Half of the cups were exposed to temperature changes before the experiment, a measure that had no systematic influence on the leakage. The double tests showed great mutual variation, and the leakage increased irregularly for some test cups. According to the mean value of each group, the temperature changes during the experiment increased the leakage with the three amalgams but resulted in decreased relative differences among them. These differences do not correspond to the 24-hour values of the dimensional changes recorded during setting. There was a definite difference between silver and copper amalgam throughout the experiment to the advantage of silver amalgam. However, the measured activity as a result of the leaked ²²Na was considered low in relation to the activity of the surrounding solution also for the copper amalgam. There is a need for more detailed investigations on this subject.