Abstract
Polymethylmethacrylate (PMMA) is a component of resin teeth, which are generally depolymerized at a temperature of 220-240°C. If resin teeth are used in Polysulfone (PSF) dentures, thermal anamnesis may occur, causing artificial teeth to become worse, when producing dentures.
Therefore, what thermodynamics cause thermal anamnesis of PSF dentures were analyzed in the compressive molding method to determine the influence on resin teeth.
The results were as follows:
PSF dentures use resin teeth and high wear resistant plastic teeth. These teeth are not influenced by thermal depolymerization. The retention strength of artificial teeth weakens during laboratorial operation, and even if dry volatile components are included, their weight decreases slightly. Therefore, artificial teeth should be dried at 130°C after investment and wax removal in a dry oven. Each value will be more than 18.1 kgf, so it will be sufficiently durable for clinical use, taking the results of Okuno et al. and Kimura et al. into consideration.
As a result of the analysis of temperature change between the retention surface of artificial teeth and denture base resin in the finite element method in both cases 1 and 2, the temperature of the projecting part of an artificial tooth shows a temperature of 240°C or more just after completion, however, shortly afterwards, it shows a temperature of 220°C, proving that thermal depolymerization hardly occurs in an artifical tooth, if real thermal capacity, thermal energy, etc. are taken into consideration.
