Method: A CEREC MCXL (Sirona) milling machine was used to fabricate twenty 1.2 mm thick IPS e.maxCAD (Ivoclar Vivadent) specimens for each firing group. The tensile side of each specimen was polished sequentially to 600 grit while the opposing side was glazed.
The specimens were sintered using the Programat CS furnace (Ivoclar Vivadent) according to one of three firing cycles: CR firing cycle, Standard firing cycle, and Ultra-Fast firing cycle. Following the recommendations for each program, the CR specimens were sintered one at a time on a large tray, the Standard specimens were sintered two at a time on a large tray and the Ultra-Fast group was sintered two at a time on a smaller tray.
Afterward, the piston on three-ball test (ISO 6872) was utilized to evaluate the biaxial flexural strength of each specimen by way of an Instron Universal testing machine at a crosshead speed of 1.0mm/min. The color and translucency of each specimen were evaluated using the UltraScan Vis color measurement spectrophotometer (Hunter Lab). Analysis was performed using one-way analysis of variance (ANOVA, p<.05) and Tukey post hoc.
Result: The biaxial flexural strength (Mean±STD) of each group is listed below. Statistically similar groups are shown by the same letter.
Firing Groups (N=20) |
Total Firing Time |
Mean±STD (MPa) |
CR Firing Cycle |
12 min 40 sec |
269.4±56.3a |
Standard Firing Cycle |
19 min 30 sec |
363.2±47.7b |
Ultra-Fast Firing Cycle |
14 min 50 sec |
378.5±53.2b |
Conclusion: Within the parameters of this study, the flexural strength achieved by the Standard and Ultra-Fast firing times were significantly higher than those obtained by the CR firing schedule. A faster firing cycle can be utilized without compromising biaxial flexural strength.