Tensile strength of type IV dental stones dried in a microwave oven

Statement of problem. It is known that drying dental stones in a microwave oven can save time, but the strength of the material may be affected by different drying methods. Purpose. This study evaluated the diametral tensile strength (DTS) of 5 type IV gypsum products at different time intervals using microwave and air-drying methods. Material and methods. total of 300 cylinder specimens were prepared from S type IV dental stories (Moldano, Amberok,, Herastone, Shera-Sockel, and Fujirock; n = 60 per stone) in accordance with the manufacturers' recommendations. Half of the specimens of each stone (n = 30) were dried in open air within a temperature range of 20 +/- 2degreesC; the other half (n = 30) underwent initial setting in a silicone rubber mold in open air for 10 minutes and then were dried in a microwave oven for 10 minutes. Within these groups, 10 specimens were tested under diametral compression at each of the following time periods: 30, 60, and 120 minutes after drying. Three-way analysis of variance and Scheffe's post hoc test were performed for statistical comparisons at a significance level of P < .05. Results. At all time intervals, the diametral tensile strength values for dental stones dried in a microwave oven (mean 2.99 MPa) were significantly higher (P < .01) than the values for specimens dried in open air (mean 2.53 MPa). Conclusion. Within the limitations of this study, microwave oven drying had a positive effect on the diametral tensile strength of 5 type IV dental stones.