Processing dentures using a microwave technique.

In this research the technique of curing denture base acrylic resins by microwave energy was investigated with respect to polymerization method, hardness, mechanical and physical properties. Twenty-one different polymerization methods were used by varying radiation power and curing time. The Vickers hardness test was applied to the samples which were polymerized. The average value was found to be 22.46 VHN (Vicker hardness number), that is, almost the same as conventionally cured acrylic. The recommended polymerization method of curing acrylic was 3 min at 550 W in a microwave oven. Mechanical and physical tests were applied to the samples which were cured by the recommended polymerization method. The average transverse load to fracture value was found to be 7.6 kg, and the transverse deflection value was 1.5 mm at 3500 g, and 2.9 mm at 5000 g. Water sorption of acrylic resin cured by microwave energy was 0.72 mg cm-2 and the solubility rate in water was 0.038 mg cm-2. Results conformed with the ADA specification. The findings showed that acrylic resin cured by microwave energy is more resistant to mechanical failure than conventionally cured acrylic and this technique can safely be applied to the production of denture bases.

A comparison of bond strengths of soft denture liners to polymethyl methacrylate polymerized by conventional water bath and microwave curing techniques.

This study compared the tensile bond strengths of soft lining materials polymerized by using conventional water bath methods and microwave energy. The soft lining materials used in this investigation were heat temperature vulcanizing (H.T.V.) silicon material Molloplast-B, and room temperature vulcanizing (R.T.V) acrylic material Getz Soft Oryl. The H.T.V. specimens were prepared with retention, additional retention and without retention, and the R.T.V. specimens were prepared by using bonding agent and bonding agent plus retention. All were cured by both conventional water bath and microwave energy. Results showed that the mean bond strength of H.T.V. specimens ranged from 9.6 to 13.12 kg/cm2, while the mean bond strength of R.T.V. specimens ranged from 0.36 to 1.75 kg/cm2. In both conventional and microwave groups, the specimens prepared with retention, additional retention and without retention or using bonding agent and bonding agent plus retention did not show any significant difference when they were compared separately. But the difference between conventional and microwave groups was found significant in both H.T.V. and R.T.V. specimens. It showed that conventional water bath technique is better than microwave technique.