Flexural Fatigue Limit of Four Different CAD/CAM Material Classes

Objectives: This investigation compares the initial strength under dry and wet conditions with the flexural fatigue limit of a new resin nano ceramic material, an acrylic CAD composite, a feldspathic glass ceramic and a lithium disilicate glass ceramic material.

Methods: Initial strength of Lava Ultimate, VITA CAD-Temp, IPS Empress CAD and IPS e.max CAD was determined according to ISO 6872 in a 3-point-bending geometry under dry and wet conditions (bars 1.2 x 4 x 16 mm, 12 mm span width). For the fatigue test a sinusoidal load at 10 Hz was applied with a hydropulser (858 Mini Bionix®II, MTS, Berlin) under water using the same 3-point-bending geometry. Flexural fatigue limit was determined according to the staircase method for 50% survival at 10000 cycles. Flexural strength data were analyzed pair wise with one-way ANOVA and Tukey's t-test (p<0.05).  n=30 for all groups.

Results: The table shows the mean strength values and FFL in MPa. 

Conclusions: Initial strength of resin nano ceramic was higher than the feldspathic glass ceramic and acrylic composite and lower than lithium disilicate.  Resin nano ceramic was the only material investigated that maintained its initial strength when changing from dry to wet conditions. All materials show a decrease in strength upon cycling fatigue in water. FFL of resin nano ceramic is at 74% of its initial dry strength, lithium disilicate maintained 50% and feldspathic glass ceramic and acrylic composite were at 64%.