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

OBJECTIVES

The aim of this study was to determine and compare fracture toughness (K) and work of fracture (WOF) of a conventional (C) denture base, using the notchless triangular prism (NTP) specimen K 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 °C water for 7 d (20/group) and 90 d (20/group) and conditioned in 23 °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, Scheffé multiple mean comparisons (α = 0.05), independent t-tests and Weibull. WOF (in KJ/m) 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 (P > C > M; p < 0.005) and WOF at both 7d and 90d; 2) ageing in 37 ºC water for 90 d resulted in a significant decrease of K 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 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 of C and M materials and WOF of all.