Impact of repeated firing on biaxial flexural strength of computer-aided design and computer-aided manufacturing ceramics

Abstract Statement of problem After fabrication of ceramic restorations, they may undergo repeated firing cycles whether for glazing, contouring, staining or other purposes, the knowledge about the impact of this procedure on the mechanical characteristics of computer-aided design and computer-aided manufacturing (CAD-CAM) ceramics is minimal. Purpose This in-vitro study assessed the impact of repeated firing cycles on biaxial flexural strength (BFS) of three CAD-CAM ceramics. Patients and methods Three CAD-CAM ceramics were used in this study, Vita suprinity (S), Katana HT zirconia (Z), and CEREC Tessera (T). 40 cylindrical discs from each material were used. Specimens have been allocated into four subgroups according to the number of firing cycles first, second, third, and fourth (10 each). Specimens were then thermocycled for 5000 cycles, and then the BFS for each group has been measured. Results Suprinity and tessera were nonsignificantly affected by repeated firing, while zirconia showed significant decrease in the values of the BFS after the 4 th firing. Regardless of the number of cycles, zirconia recorded the highest BFS, followed by suprinity, and the lowest values were recorded by tessera as indicated by two-factors ANOVA test. Pair-wise Tukey’s post-hoc test revealed nonsignificant variation between suprinty and tessera. Conclusion The type of CAD-CAM ceramic can alter the values of the BFS. Zirconia showed lower values when fired four times than when fired once. Suprinity and tessera showed nonsignificant affection after four firings compared to one firing.