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UBC Theses and Dissertations

Fracture toughness of conventional, milled and printed denture bases Mann, Ravdeep Singh


Purpose: The aim of this study was to determine KIC of a conventional denture base material, using the notchless triangular prism (NTP) specimen KIC test, and compare it with that of CAD/CAM and 3D-printed denture base materials after 7 d and 90 d storage in 37 °C water. Materials and methods: Lucitone 199 (C), Lucitone 199 CAD (M) and Lucitone Digital Print (P) (Dentsply International Inc., York, PA) were used to fabricate NTP specimens (40/group). Samples were stored in 37 °C water for 7 d (20/group) and 90 d (20/group) and were conditioned, according to ISO 20795-1. For testing, samples were secured in custom-made jigs, replicating the chevron-notch short rod specimen configuration. The test assembly was loaded in tension (0.1 mm/min) until crack arrest or failure. The maximum-recorded load was used to calculate KIC. Two-way ANOVA, followed by Scheffé multiple mean comparisons (α = 0.05), independent t-tests and Weibull statistics were used to analyze the results. Light and scanning electron microscopy were used to characterize fractured surfaces. Results: Crack arrest was observed in all test specimens. The analyses of the results have shown that the three tested materials had significantly different KIC at 7 d and 90 d, with the same ranking, i.e., P > C > M (p < 0.005). The analyses of the results have also shown that ageing in 37 ºC water for 90 d resulted in a significant decrease in KIC in the C and M groups (p < 0.001). Significant crazing was observed in the 3D-printed specimens, which resulted in them having significantly larger work of fracture values (~8 KJ/m2 vs ~3 KJ/m2). Conclusion: The tested 3D-printed denture base material had significantly higher KIC, exhibited crazing, had a higher absorbed energy before fracture and was stable under ageing conditions, suggesting that it could be more resistant to crack propagation than the tested conventional and milled materials. The tested milled denture base showed the least resistance to crack propagation, with the lowest KIC values both at 7 d and 90 d. Water storage for 90 d significantly decreased KIC of the tested conventional and milled materials.

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