Evaluation of mechanical properties of new zirconia formulations

Objective:

To evaluate the flexural strength and elastic modulus of various new formulations and processing methods for dental zirconia.

Methods:

Four new formulations of zirconia (all processed without a binder) and one conventional zirconia were included: Group 1. Prismatik CZ XT – (iso-pressed TZY powder/ Glidewell); Group 2. Prismatik CZ XT˛  (iso-pressed TZY powder w higher particle size/ Glidewell); Group 3. Prismatik CZ XT³ (made with non iso-pressed TZY powder/ Glidewell); Group 4. experimental zirconia made with iso-pressed generic YTZP powder; Group 5. Lava Y-TZP (3M ESPE) as control. Test bars (n=7-11/ group) measuring 3x4x45 mm were prepared from larger blocks and sintered according to the manufacturer's instructions. All bars were polished with 800 grit diamond disk for surface uniformity by T.Q. Abrasive Machining Santa Ana, CA. The bars were tested for flexural strength (FS) using a 3-point bending test on an Instron universal testing machine with a 10/KN capacity load cell at a crosshead speed of 0.5 mm/min.  Elastic moduli (EM) were calculated using the cross-head extension for strain. One-way ANOVA followed by Tukey's unequal sample size procedure were used for statistical analysis.

Results: Mean FS (MPa), EM (GPa) and SDs are shown below:

Material	group 1	group 2	group 3	group 4	group 5
FS(MPa)	1264.7(145)	1132.4(200)	1023.7(175)	839.8(294)	846.5(177)
EM(GPa)	162.6 (3.9)	157.7 (8.2)	150.2 (9.0)	148.5 (8.0)	143.8 (3.5)

Conclusion: ANOVA revealed a significant difference among the groups (p=0.05). Group 1 had significantly higher FS than groups 4 and 5 and significantly higher EM than groups 3, 4 and 5.

The results demonstrate the potential for processing high strength dental zirconia without a binder and with non-iso pressing methods.

This study was supported by Glidewell laboratories (Newport Beach, CA)