IADR Abstract Archives
Cyclic Fatigue of CAD/CAM Materials and Clinical Predictability
Objectives: The objectives of the present study were to provide mechanistic fatigue parameters of current dental CAD/CAM materials under cyclic biaxial flexure and assess their suitability in predicting clinical fracture behaviors.
Methods: Eight CAD/CAM materials (Vitablocs Mark II, VITA; IPS e.max CAD, Ivoclar-Vivadent; Suprinity PC, VITA; Celtra Duo, Dentsply-Sirona; IPS Empress CAD, Ivoclar-Vivadent; Enamic, VITA; Lava Ultimate, 3M Oral Care) were evaluated. Thirty rectangular plates (12 x 12 x 1.2 mm3) with highly polished surfaces were prepared and tested in biaxial cyclic fatigue in water until fracture using the Ball-on-Three-Balls (B3B) test. Cyclic fatigue parameters n and A* were obtained from the lifetime data and further use to build SPT diagrams. A threshold stress intensity factor (Kth) was determined by extrapolation of the v-K curves to v = 10-12 m/s. These fatigue parameters were used to compare in-vitro with in-vivo fracture distributions for IPS e.max CAD and IPS Empress CAD.
Results: Susceptibility to slow crack growth (SCG) under cyclic loading was observed for all materials, being more severe (n ≤ 20) in lithium-based glass-ceramics and Vitablocs Mark II. Strength degradations of 40% up to 60% were predicted after only 1 year of service. Threshold stress intensity factors (Kth) representing the onset of SCG, were estimated to lie in the range of 37 – 44% of KIc for the lithium-based glass-ceramics and Vitablocs Mark II and between 51 – 59% of KIc for the other materials. Failure distributions associated with mechanistic estimations of strength degradation in-vitro showed to be useful in interpreting failure behavior in-vivo. The parameter Kth stood out as a better predictor of clinical performance in detriment to the SCG n parameter.
Conclusions: Fatigue parameters obtained from cyclic loading experiments are more reliable predictors of the mechanical performance of contemporary dental CAD/CAM restoratives than quasi-static mechanical properties.
Methods: Eight CAD/CAM materials (Vitablocs Mark II, VITA; IPS e.max CAD, Ivoclar-Vivadent; Suprinity PC, VITA; Celtra Duo, Dentsply-Sirona; IPS Empress CAD, Ivoclar-Vivadent; Enamic, VITA; Lava Ultimate, 3M Oral Care) were evaluated. Thirty rectangular plates (12 x 12 x 1.2 mm3) with highly polished surfaces were prepared and tested in biaxial cyclic fatigue in water until fracture using the Ball-on-Three-Balls (B3B) test. Cyclic fatigue parameters n and A* were obtained from the lifetime data and further use to build SPT diagrams. A threshold stress intensity factor (Kth) was determined by extrapolation of the v-K curves to v = 10-12 m/s. These fatigue parameters were used to compare in-vitro with in-vivo fracture distributions for IPS e.max CAD and IPS Empress CAD.
Results: Susceptibility to slow crack growth (SCG) under cyclic loading was observed for all materials, being more severe (n ≤ 20) in lithium-based glass-ceramics and Vitablocs Mark II. Strength degradations of 40% up to 60% were predicted after only 1 year of service. Threshold stress intensity factors (Kth) representing the onset of SCG, were estimated to lie in the range of 37 – 44% of KIc for the lithium-based glass-ceramics and Vitablocs Mark II and between 51 – 59% of KIc for the other materials. Failure distributions associated with mechanistic estimations of strength degradation in-vitro showed to be useful in interpreting failure behavior in-vivo. The parameter Kth stood out as a better predictor of clinical performance in detriment to the SCG n parameter.
Conclusions: Fatigue parameters obtained from cyclic loading experiments are more reliable predictors of the mechanical performance of contemporary dental CAD/CAM restoratives than quasi-static mechanical properties.