Fracture toughness of conventional, milled and 3D printed denture bases.

OBJECTIVES: The aim of this study was to determine and compare fracture toughness (K(IC)) and work of fracture (WOF) of a conventional (C) denture base, using the notchless triangular prism (NTP) specimen K(IC) test, with CAD/CAM (milled, M) and 3D-printed (P) materials at 7 d and 90 d. METHODS: Lucitone 199 (C), Lucitone 199 CAD (M) and Lucitone Digital Print (P) (Dentsply, USA) were used to fabricate NTP specimens. Samples were stored in 37 degrees C water for 7 d (20/group) and 90 d (20/group) and conditioned in 23 degrees C water for 1 h prior to testing. For testing, samples were secured in custom-made jigs and loaded in tension until crack arrest/failure. The maximum-recorded load was used to calculate KIC. The results were analyzed by two-way ANOVA, Scheffe multiple mean comparisons (alpha = 0.05), independent t-tests and Weibull. WOF (in KJ/m(2)) was calculated by dividing the area under the load-displacement graphs by twice the corresponding crack-arrested cross sectional area of the fractured surfaces. RESULTS: The results have shown that: 1) the tested materials had significantly different K(IC) (P > C > M; p < 0.005) and WOF at both 7d and 90d; 2) ageing in 37 masculineC water for 90 d resulted in a significant decrease of K(IC) in the C and M groups (p < 0.001) and of WOF in all groups. SIGNIFICANCE: The tested P denture base exhibited significantly higher K(IC) and WOF, suggesting that it could be more resistant to crack propagation than the C and M materials tested. Water storage for 90 d significantly decreased K(IC) of C and M materials and WOF of all.