[Application of microwave for dental technique. 5. Injection molding system for resin base denture]

An injector and FRP denture flask were developed for injection molding and the fit of the denture base constructed with this injection molding system was evaluated. In addition, the flow and pressure of the dough, that is polymer-monomer mixture, in the mold space were investigated. The monomer of 10 mg/cm2 in the dough vaporized during the 5 minutes it took for the flash to be removed. When pressure of more than 55 kgf/cm2 was exerted to the dough, the dough was completely packed in the mold space. Fastening of the sprue with a bolt within 2 minutes after injection of the dough made the pressure of the dough increase to about 30 kgf/cm2. The dough in the mold space was maintained at a pressure of above 20 kgf/cm2 for microwave heating time. The adaptability of the resin base denture constructed with a combination of injection molding and microwave polymerization was 2 or 3 times greater than that of the denture constructed with microwave heating from the tissue side of the denture base.