The Effect of Microwave Oven Drying on the Compressive Strength of Type III and IV Dental Stones at Different Time Intervals

Suha Fadhil Dulaimi,Sabiha Mehdi Kanaan

doi:10.2174/1874210601812010494

Suha Fadhil Dulaimi, Sabiha Mehdi Kanaan

Open Access

https://doi.org/10.2174/1874210601812010494

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Abstract

Background:Dental stone cast needs 24 to 48 hours to evaporate excess water and acquire enough strength for manipulation. The microwave oven is used to save time by drying and disinfecting stone casts.Objectives:The aim of the present study is to evaluate the effect of microwave oven drying on the compressive strength of Type III and Type IV dental stone in three time intervals-3 hours, 5 hours and 24 hours after pouring.Methods:The study involved 120 samples: 60 samples for each type of dental stone. Thirty samples were subjected to air drying at 3, 5 and 24 hours) and 30 samples were dried in the microwave oven at 2450 MHZ -900 W for 150 seconds (at 3, 5 and 24 hours). The samples were tested by unconfined compression machine, with a 2000 kg proving ring at cross-head speed of 1 mm/min.Results:For the Type III dental stone drying at 3 hours, microwave radiation causes a significant increase in compressive strength and shows the highest score (mean 125 kg/cm); however, at 5 hours no significant difference was observed. However, at the 24 hour time interval, microwave drying causes significant reduction in the mean (100 kg/cm) p<0.01 .For the Type IV dental stone testing at all-time intervals (3,5, 24 hours), a significant reduction (p<0.05) in mean values was shown(80,85,87 respectively).Conclusion:Microwave oven drying increased the compressive strength of Type III dental stone at the 3 hour time interval from pouring, while microwave drying at the 5 hour interval had no significant effect; and at 24 hour the compressive strength of the dental stone was reduced. For the Type IV dental stone microwave drying had a detrimental effect on compressive strength at all-time intervals.

Highlights

Cross-contamination in prosthodontics practice can be prevented by microwave irradiation of stone cast [1]
The aim of the present study is to investigate the effect of microwave drying on compressive strength of Type III and IV dental stone at 3, 5 and 24 hour time intervals
At the 24 hour time interval, microwave drying (100 kg/cm2) caused a significant reduction in compressive strength in comparison to air drying with a P-value < 0.01 (Table 2 and Fig. 3)

Summary

Introduction

Cross-contamination in prosthodontics practice can be prevented by microwave irradiation of stone cast [1]. The stone cast should exhibit enough compressive strength and abrasion resistance to withstand the carving process, at the margin [2]. Poured stone cast needs 24-48 hours to lose excess water and gains. In clinical and laboratory practice, it is sometimes necessary to save drying time and handle the stone cast sooner after its fabrication. There is a need to disinfect the stone cast. Dental stone cast needs 24 to 48 hours to evaporate excess water and acquire enough strength for manipulation. The microwave oven is used to save time by drying and disinfecting stone casts

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