Viscosity of dental waxes by use of Stokes' law.

The rheological properties of dental waxes control their fabrication procedures and are dominated by their temperature dependence. Indeed, it is their rapid change in deformability with temperature which enables them to be used. Some measure of flow rate is therefore needed for characterization and quality control. A modified Stokes' method is proposed which allows measurement of an analogue of Newtonian viscosity and is suited to routine use in the range 10(4)-10(10) Pa.s, and which leads naturally to a determination of the activation energy for the process. This activation energy is of the order of 700 kJ/mole at low stress.