The objective of this study was to investigate the effect of cyclic fatigue loading on the fracture load to failure of three commercial machinable all-ceramics, one machinable composite resin and one experimental resin-infused ceramics.
Methods:
Standardized acrylic dies were prepared with a 5-degree convergence angle and a 90-degree, 1-mm shoulder. A master die was scanned and a biogeneric full contour crown was designed and fabricated with the CAD/CAM system (CEREC InLab®). Full contour monolithic crowns were fabricated from machinable feldspathic porcelain (Vita Mark II), leucite-reinforced glass ceramic (IPS Empress CAD), lithium disilicate (IPS e.max CAD), composite resin (Paradigm MZ100) and experimental resin-infused ceramics (RIC). Crowns were cemented with self-adhesive resin cement (RelyX Unicem). After cementation, ten cemented crowns of each material were loaded with a universal testing machine until crowns failed catastrophically. Other 10 cemented crowns of each material were fatigued with for 150,000 cycles with a maximum load of 450 N and minimum load of 0 N at room temperature. After cyclic fatigue, cemented crowns were subjected to the load to failure test.
Results:
The mean load to failure of composite crowns (MZ 100) was relatively high (2972.69 ± 68.53 N) and did not significantly differ from IPS e.max crowns. Vita Mark II crowns showed the least mean fracture load to failure (1199.05 ± 148.69 N). After cyclic fatigue, loads to failure of the experimental resin-infused RIC, IPS Empress CAD and e.max CAD milled crowns significantly decreased 20, 10, and 12 %, respectively. There was no significant effect of the cyclic fatigue on the load to failure of Vita Mark II and MZ 100 milled crowns.
Conclusions:
Feldspathic porcelain (Vita Mark II) and composite resin (Paradigm MZ100) CAD/CAM milled crowns showed no significant change in load to failure after cyclic fatigue.