[Testing of various methods for the determination of processing time for amalgam]

Four different test methods for the determination of the processing time of freshly mixed amalgam pastes were examined with the view to their utility, using 9 commercial powder alloys of different setting speeds. The tests used were a schematised stuffing test, close to the procedure used in practise, the cutting test and the compressive strength test after 10 minutes, both of which are still quoted as alternatives in the provisional standard DIN 13904, as well as a Hg addition test described by Jørgensen. The compressive strength test proved to be the quickest and most accurate. It is therefore best suited for routine examinations and general control and is recommended for inclusion in the DIN. It is necessary to set up calibration curves with the help of the stuffing test in order to estimate the processing time. These have to be separately estimated for filing amalgam and globular amalgam. The cutting test proved to be relatively inaccurate. The Hg addition test, though giving usable values, consumed too much time and material.