J Korean Acad Prosthodont.
2001 Oct;39(5):514-525.
EFFECT OF TIME AND TEMPERATURE ON THE MARGINAL FIT OF PROVISIONAL RESIN CROWN DURING POLYMERIZATION
Abstract
- The purpose of this study was to compare the marginal fit of provisional restorations by differentiating the removal time and setting temperature during resin polymerization. After mixing autopolymerizing methyl metharcrylate resin, the material was placed in a preformed resin shell crown. The crown was seated on a die with 1mm shoulder margin. Crowns were removed after 3,4,5,6 minutes and polymerization was continued under the following conditions : 25degrees C air,30degrees C, 40degrees C, 50degrees C,60degrees C,70degrees C water. After polymerization, the crown was sectioned. The marginal & occlusal discrepancies were measured. The mean marginal discrelpancies at 3 minutes, 4 minutes, 5 minutes and 6 minutes of removing time were 96.6micrometer,84.6micrometer, 86.7micrometer and 105.6micrometer.The mean occlusal discrepancies at 3 minutes, 4 minutes, 5 minutes and 6 minutes of removing time were 106.7micrometer, 89.3micrometer, 98.6micrometer and 127.7micrometer.There was significant difference between 4 minutes group and 6 minutes group in occlusal discrepancies. The mean marginal & occlusal discrepancies for crowns polymerized in 25degrees C air were 98.2micrometer and 124.1micrometer. The crowns polymerized in 50degrees C water demonstrated the smallest marginal & occlusal discrepancies. The mean value of marginal & occlusal discrepancies in 50degrees C water were 73.1micrometer and 77.5micrometer. These values were smaller than that of 25degrees C air.There were significant differences in the occlusal discrepancies between 25degrees C air and water conditions of 50degrees C water (alpha=0.05) but, no significant differences in marginal discrepancies. There was no significant difference in the interaction between time and temperature. 4 minutes waiting time & 50degrees C water polymerizing condition produces the best fit at the margin of the provisional crown.
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