Objective The aim of this study was to evaluate the effects of the addition of low-silicon dioxide nanoparticles (nano-SiO₂) on the flexural strength and elastic modulus of polymethyl methacrylate (PMMA) denture base material. Materials and Methods A total of 50 rectangular acrylic specimens (65 × 10 × 2.5 mm³) were fabricated from heat-polymerized acrylic resin. In accordance with the amount of nano-SiO₂, specimens were divided into the following five groups (n = 10 per group): a control group with no added SiO₂, and four test groups modified with 0.05, 0.25, 0.5, and 1.0 wt% nano-SiO₂ of acrylic powder. Flexural strength and elastic modulus were measured by using a 3-point bending test with a universal testing machine. A scanning electron microscope was used for fracture surface analyses. Data analyses were conducted through analysis of variance and Tukey’s post hoc test (α = 0.05). Results Compared with the control group, flexural strength and modulus of elasticity tended to significantly increase (p ˂ 0.001) with the incorporation of nano-SiO₂. In between the reinforced groups, the flexural strength significantly decreased (p ˂ 0.001) as the concentrations increased from 0.25 to 1.0%, with the 1.0% group showing the lowest value. Furthermore, the elastic modulus significantly increased (p ˂ 0.001) at 0.05% followed by 1.0%, 0.25%, 0.5%, and least in control group. Conclusion A low nano-SiO₂ addition increased the flexural strength and elastic modulus of a PMMA denture base resin. Article published online: 24 August 2021 © 2021. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (https://creativecommons.org/licenses/by/4.0/). Thieme Medical and Scientific Publishers Private Ltd A-12, Second Floor, Sector -2, NOIDA -201301, India

Objectives: This in vitro study assessed the accuracy (trueness and precision) of different 3D-printed resin denture bases with 0°, 45°, and 90° printing orientations. Methods: Denture base was designed and fabricated using three 3D-printed denture base resins (DentaBASE, Denture 3D+, and FormLabs). Each resin was printed with its own printer and fabricated with different printing orientations, resulting in a total of 72 specimens (n = 8). Trueness and precision were evaluated before and after thermal aging using the superimposition method with best-fit alignment. The data were collected and analyzed using two-way ANOVA followed by post hoc Tukey’s test (α = 0.05). Results: The printing orientation significantly affected the trueness of 3D-printed resins (p < 0.001). The highest trueness was observed for NextDent at 0° printing orientation, while the lowest value was observed for ASIGA at 0° and 45° printing orientations. The precision of the denture base was significantly affected by different printing orientations for ASIGA (p = 0.006) and NextDent (p < 0.001) before thermal cycling, while the precision of FormLabs was significantly affected (p = 0.017) after thermal cycling. The highest precision was recorded for FormLabs at 45° printing orientation, while the lowest precision was observed for NextDent at 45° and 90° printing orientations. Moreover, the effect of thermal cycling on trueness was only significant for ASIGA at 0° printing orientation; however, the effect of thermal cycling on precision was significant for NextDent at 0° and 90° printing orientations. A 45° printing orientation provided the most accurate clinical fit. Conclusions: ASIGA showed the lowest trueness, while FormLabs exhibited the lowest precision, revealing performance differences between printers.