Processing dentures using a microwave technique

Abstract

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.

Effect of microwave disinfection on physical and mechanical properties of acrylic resins

“…In the present study, when Knoop hardness was analyzed under no-disinfection and microwave-disinfection conditions (Table 1), the KHN values obtained for Clássico, QC-20 and OndaCryl acrylic resins differed significantly from each other. Although some authors have stated that hardness is not influenced by the acrylic resin type (12,13), in the present study Onda-Cryl presented the highest hardness, followed by Clássico and QC-20.…”

The Use of Microwave Energy to Polymerize Acrylic Resins

“…İlbay ve ark. 26 da araştırmalarında su emilimi açısından iki yöntem arasında anlamlı fark bulamamışlar ve elde edilen su emilimi değerlerinin ADA standartlarına uygunluğundan bahsetmişlerdir.…”

The Use of Microwave Energy in Dental Prosthesis

“…Considering the processing methods for acrylic resins, some authors (Austin et al, 1982;May et al,1992) have stated that polymerization for short period of time promotes higher color instability. Porosity and its consequences have been studied to resin processed by microwave energy (Reitz et al, 1985;Wolfaardt et al, 1986;De Clerck, 1987;Al Doori et al, 1988;Truong & Thomasz, 1988;Levin et al, 1989;Shlosberg et al, 1989;Alkhatib et al, 1990;Bafile et al,1991;Sadamori et al, 1994;Ilbay et al,1994;) and some authors verified that it depends on the base thickness (Sanders et al, 1987) or the selection of the material, despite of the microwave processing. (Yannikakis et al, 2002).…”

“…From this point of view, the degree of conversion is one of the most important characteristic of resin, on account of the high residual monomer levels that could be unreacted. Its presence has an adverse effect on physical and mechanical properties (Yunus et al, 1994) as well as on the biocompatibility (Ilbay et al, 1994). Acrylic resin also presents water sorption that is directly related to the polar properties of resin molecules, the physical process of water diffusion through intermolecular space (Takahashi et al, 1998), and the amount of residual monomer in the polymerized mass (Wong et al, 1999).…”

“…Because of the quick and instantaneous heating, the polymerization of monomers could be damaged by the microwave energy. However, classical studies have been shown that microwavepolymerized acrylic resin presents lower or the same residual monomer levels relative to conventionally polymerized resins (McCabe & Basker, 1976;Austin & Basker, 1980;Austin & Basker, 1982;Huggett et al, 1984;DeClerck, 1987;Truong & Thomasz, 1988;Al Doori et al, 1988;Sadamori et al, 1994;lbay et al, 1994;Yunus et al, 1994;Shlosberg et al, 1989;Jacob et al, 1997). Other researches showed resin polymerized by microwave energy presented similar solubily, residual monomer or water sorption levels than conventional or fast polymerization process.…”