Optical and mechanical properties of conventional, milled and 3D-printed denture teeth

Objectives: Investigate the effect of various liquids on the optical properties and Vickers hardness of conventional, milled and 3D-printed denture teeth. Methods: Six different types of denture teeth (Maxillary anteriors of three different conventional teeth, Vivodent DCL, SR Phonares II, Vita Physiodens; milled teeth, IvotionDent; and two different 3D-printed teeth, Asiga DentaTooth and NextDent C&B MFH) were investigated (total n = 336). The labial surface of each specimen was prepared to a dimension of 10 x 5 x 3mm. Specimens were immersed in artificial saliva, coffee, red wine and denture cleaner with artificial aging to simulate denture use of 12 and 24 months in vivo. Measurements of translucency parameter (TP), shade change (Delta E), surface roughness (Ra) and Vickers hardness (VHN) were conducted at baseline and after artificial aging while immersed in the liquids at each timeframe. Data were statistically analysed by ANOVA and post-hoc test (SPSS Ver 27). Surfaces of specimens were analysed under scanning electron microscopy (SEM). Results: Milled teeth had the highest overall translucency parameter (5.33 +/- 0.76-7.3 +/- 0.99). All materials had statistically significant change in translucency parameter and shade after 24 months simulated aging (p < 0.05), especially the milled and 3D-printed teeth (p < 0.01). Surface roughness of all materials were under plaque accumulation threshold Ra = 0.2 mu m. At baseline, Vita Physiodens teeth (PMMA with microfillers) demonstrated the highest hardness (33.99 kgf/mm(2)+/- 3.7), whereas both 3D-printed materials exhibited the lowest hardness (13.27 kgf/mm(2)+/- 0.36-18.13 kgf/mm(2)+/- 0.93). Artificial saliva, red wine and denture cleaner had a statistically significant impact (p < 0.05) on hardness of all materials (12.1 kgf/mm(2)+/- 1.17-30.77 kgf/mm(2)+/- 2.98). Conclusions: Milled teeth exhibited the best optical properties (highest overall translucency parameter and lowest shade change). Milled teeth were also the only material that showed colour change (Delta E values) within clinically acceptable limits. Denture cleaner had the most impact on optical and mechanical properties of all materials. Surface roughness and hardness of 3D-printed teeth had the most change after artificial aging.