Effect of microwave disinfection on some properties of gypsum products

الملخص EN

Background : Dental casts can be contaminated by saliva and blood from patient’s mouth through impression materials, record bases, trial dentures...etc.

Different methods were used to disinfect the dental cast ; e.g.

immersing in, spraying with, or incorporating the disinfectant directly into the dental stone powder.

These methods produced an adverse affect on the properties of dental stone.

This study was intended to evaluate the effect of different methods of microwave disinfection ; immersing in water, NaCl solution, or in dry air on the reproduction of details and surface hardness of type III and type IV gypsum products at different time intervals.

Materials and methods : A microwave oven was used to disinfect type III and IV dental stone at 850 watt for 10 minutes while immersed in water, 40 % Sodium chloride solution, and in dry air during the disinfection procedure.

Surface hardness of the dental stone samples was evaluated by using the Brinell hardness test at different time Intervals ; after 1hour, 2 hours, 24 hours, and after one week of start of mixing.

Reproduction of details of the dental stone samples was also evaluated.

Results : The surface hardness was significantly different for all the test groups at different time intervals except for the water group after 1 and 2 hour for type III dental stone.

The dry air group and water group were insignificantly different after1hr for type IV dental stone.

The test for reproduction of details showed no significant difference for all the test groups except for NaCl group which was significantly different, the score was 2 which was clinical insignificant.

Conclusion : Microwave disinfection can be used for dental stone casts while in dry air for type III and immersed in water for type IV, with no effect on reproduction of details and with least adverse effects on the surface hardness of the gypsum products.