PURPOSE This study aimed to evaluate the effect of incorporating zirconium oxide nanoparticles (nano-ZrO 2 ) in polymethylmethacrylate (PMMA) denture base resin on flexural properties at different material thicknesses. MATERIALS AND METHODS Heat polymerized acrylic resin specimens (N = 120) were fabricated and divided into 4 groups according to denture base thickness (2.5 mm, 2.0 mm, 1.5 mm, 1.0 mm). Each group was subdivided into 3 subgroups (n = 10) according to nano-ZrO 2 concentration (0%, 2.5%, and 5%). Flexural strength and elastic modulus were evaluated using a three-point bending test. One-way ANOVA, Tukey's post hoc, and two-way ANOVA were used for data analysis (α = .05). Scanning electron microscopy (SEM) was used for fracture surface analysis and nanoparticles distributions. RESULTS Groups with 0% nano-ZrO 2 showed no significant difference in the flexural strength as thickness decreased ( P = .153). The addition of nano-zirconia significantly increased the flexural strength ( P < .001). The highest value was with 5% nano-ZrO 2 and 2 mm-thickness (125.4 ± 18.3 MPa), followed by 5% nano-ZrO 2 and 1.5 mm-thickness (110.3 ± 8.5 MPa). Moreover, the effect of various concentration levels on elastic modulus was statistically significant for 2 mm thickness ( P = .001), but the combined effect of thickness and concentration on elastic modulus was insignificant ( P = .10). CONCLUSION Reinforcement of denture base material with nano-ZrO 2 significantly increased flexural strength and modulus of elasticity. Reducing material thickness did not decrease flexural strength when nano-ZrO 2 was incorporated. In clinical practice, when low thickness of denture base material is indicated, PMMA/nano-ZrO 2 could be used with minimum acceptable thickness of 1.5 mm.

Purpose To investigate the influence of reducing material thickness on flexural properties of computer‐aided design and computer‐aided manufacturing (CAD‐CAM) denture base resins. Materials and methods Four CAD‐CAM denture base acrylic resin materials were selected; two were made via the subtractive method (AvaDent and IvoCad) and two were made with the additive method (FormLabs and NextDent). One heat‐polymerized denture base material was used as a control. Specimens were fabricated with varying thicknesses (n = 10/group): 3.3 mm, 2.5 mm, 2 mm, or 1.5 mm. Flexural strength was evaluated via a three‐point bending test. One‐ and two‐way ANOVA were used for data analysis along with Tukey's post hoc comparison (α = 0.05). Results Reducing the thickness of materials made via the subtractive method did not influence flexural strength up to 2 mm (p > 0.05). However, the difference was significant at a 1.5 mm thickness (p ˂ 0.001). For materials made via the additive method, NextDent specimens had no significant decrease in flexural strength when the thickness was reduced to 2 mm (p = 0.58). FormLabs specimens showed a significant decrease (p ˂ 0.001), although the values of flexural strength were clinically acceptable. During testing, specimens manufactured via the additive method at a 1.5 mm thickness bent without fracturing and were therefore excluded. All materials showed a reduction in elastic modulus as the thickness decreased (p ˂ 0.001). Conclusion Heat‐polymerized, AvaDent, and IvoCad materials may be used for denture base fabrication at a minimum thickness of 1.5 mm. FormLabs and NextDent may be fabricated at a 2 mm minimum thickness, with clinically acceptable flexural properties.