Influence of porcelain re-firing on the formation of surface bubble and on the change in shade of metal-ceramic crown exposed to artificial saliva / 대한치과보철학회지

ABSTRACT

PURPOSE: The purpose of this study was to evaluate the influence of porcelain re-firing on the formation of surface bubble and on the change in shade of metal-ceramic crown exposed to artificial saliva. MATERIALS AND METHODS: Thirty disk-shaped specimens were made in 10 mm diameter with 0.5 mm metal core thickness and 1 mm ceramic thickness. A spectroradiometer was used to determine the CIE Lab coordinates. The number and size of surface bubble were observed with a stereomicroscope. After the exposure to artificial saliva for 7 days, re-firing was performed at glazing temperature. After re-firing, the CIE Lab were calculated, and the number and size of surface bubble were observed again. The change in shade was expressed with DeltaE. Statistical analysis was done with paired t-test for the change in the number of surface bubble and student t-test for the change in the size of surface bubble (alpha= 0.05). RESULTS: Shade difference was calculated 2.14 DeltaE units. The mean number of surface bubble was 1.33 +/- 1.49 before re-firing, 3.27 +/- 2.90 after re-firing. After re-firing, the number of surface bubble was significantly increased (P<.05). The mean size of surface bubble was 81.97 +/- 32.03 microm before re-firing, 142.94 +/- 47.40 microm after re-firing. After re-firing, the size of surface bubble was significantly increased (P<.05). CONCLUSION: Shade change after re-firing was perceptible (DeltaE < 2.0) and clinically acceptable (DeltaE < 3.7). The number and size of surface bubble was significantly increased after re-firing. Further investigation to decrease the surface bubble on the extra oral repair of metal-ceramic crown, will be needed in future study.