The effect of four different cooling procedures on the dimensional stability of microwave-activated acrylic resin at different time intervals

Abstract EN

Background : Acrylic denture bases are commonly made of poly methyl methacrylate with different processing methods such procedure deliver denture with acceptable mechanical properties and certain unavoidable dimensional changes.

Several factors may affect final adaptation of the dentures as the type of the acrylic resin, the cooling procedures of the flasks and the water uptake.

This study was design to investigate the effect of four different flask cooling procedure (running water at room temperature for 15 minutes, bench cooling for one hour, bench cooling for four hours and bench cooling for 24 hours) on the dimensional stability of microwave acrylic resin at four different time intervals (immediately, two days, seven days, 30 days) after deflecting.

Materials and methods : Microwave-activated acrylic resin (Acron TM MCGC 2AB) was used to prepare (20) acrylic specimens.

Then after curing procedure different ways of flask cooling was applied for cooling the flasks (rapid cooling for 15 minutes, bench cooling for one hour, bench cooling for four hours and bench cooling for 24 hours) then measurement of the distances where achieved between the centers of selected marks in (mm) after computerized scanning of the acrylic specimens at different time intervals (immediately, two days, seven days, 30 days) after deflecting for the 4 different methods of flask cooling.

Results : The statistical analysis of the results using t test showed that the samples of one hour and four hours bench cooling groups were insignificant difference from the metal pattern at different time intervals.

The quenching group was significant difference from the metal pattern at all time intervals.

And the result of 24 hour bench cooling group show a significant difference from the metal pattern at immediate and 2days after deflecting.

when compared with the metal pattern while it show insignificant difference from the metal pattern at 7 and 30 days after deflecting.

Conclusion : In this study we suggest kept of the microwave acrylic resin in the flask for 1hour and 4hour after processing to obtain accurate and more dimensionally stable dentures.