The influence of repeated firings on the remained porcelain rate / 实用口腔医学杂志

Objective: To study the influence of repeated firings on the PFM bond strength. Methods: 25 specimens of PFM in the diameter of 13.0 mm and thickness of (1.0?0.02) mm were prepared and fired at 920 ℃ for 1, 3, 5, 7 or 9 times(5 samples for each time). The remained porcelain rate(RPR) was measured by Mackert method and used to evaluate the bond strength.Results: After 3 firings, the RPR of PFM decreased obviously, and additional firings had no obvious effect on the RPR. Conclusion: 3 times firing or more may decrease the bond strength of PFM.