Evaluation and comparison of the effect of repeated microwave irradiations on some mechanical and physical properties of heat cure acrylic resin and valplast (nylon)‎ denture base materials

Abstract EN

Background : Microwave irradiation has been considered for denture sterilization / disinfection instead of chemical solutions since it has no expiration date and does not induce resistance to the microorganisms.

The aim of this study was to evaluate the effects of repeated microwave disinfection on heat cure and valplast (nylon) denture base materials in some mechanical and physical properties.

Material and method : A total No.

of 320 specimens (80 maxillary denture bases and 240 specimens) were prepared in this study, then divided into two main groups according to the type of material used (heat cure resin and valplast resin).Each main group was subdivided into four subdivisions according to the type of test used (Transverse strength test, Surface hardness test, Surface roughness test, and fitness test), for each test 40 samples were divided into four groups according to the number of cycles of microwave disinfection that were applied (control, 1 microwave cycle, 3 microwave cycles, and 7 microwave cycles).

The term cycle refer to 3min of microwave disinfection at 680 watt.

Each specimen was disinfected (subjected to one cycle) one time per a day then transferred to container contain distilled water until another cycle applied in the next day.

Result : The repeated microwave irradiation of heat cure and valplast specimens showed slight but no significant decrease in transverse strength, shore D hardness, and surface roughness.

The results of the fitness of denture base materials to stone cast showed an improvement in the fitness of heat cure and valplast denture base materials after the first microwave cycle, and no further improvements in the fitness were taken place after repeated microwave disinfection.