Mechanical and surface properties of a 3D-printed dental resin reinforced with graphene

Objectives: Commercial photocurable polymers used in dental additive manufacturing still have mechanical limitations. The incorporation of graphene may provide interesting advan-tages in this field. This study aimed to evaluate in vitro the effect of adding graphene nan-oparticles to a 3D-printed polymethylmethacrylate dental resin in terms of surface rough-ness, flexural properties, and hardness. Methods: A 3D-printed dental resin (Dental Sand, Harz Lab) was loaded with four different graphene nanoplatelet (Graphenest) concentrations: 0.01wt%, 0.1wt%, 0.25wt%, and 0.5wt%. The neat resin was used as the control group. The surface roughness was measured with a contact profilometer using bar-shaped specimens (50x10x4mm). The flexural strength of specimens (80x10x4mm) from each group was calculated using the 3-point bending test in a Universal Test Machine. Hardness shore D was measured using a manual durometer on round-shaped specimens (12x6mm). Data were evaluated using the Kruskall-Wallis test followed by post-hoc Bonferroni corrected pairwise inter-group comparisons. Statistical significance was set at p<0.05. Results: Graphene improved 3D-printed PMMA resin hardness with statistical significance at a concentration of 0.01wt% (p=0.043). Surface roughness increased with graphene con-centrations above 0.01wt%, with statistically significant differences at 0.25wt% (p=0.006) and 0.5wt% (p=0.005) concentrations. Flexural properties worsened with increased graphene concentrations, and these differences were significant in the concentrations of 0.25wt% (p=0.028) and 0.5wt% (p=0.006). Conclusions: The use of graphene as a mechanical reinforcement nanomaterial seems to be viable at low concentrations without prejudice to the surface roughness of a 3D-printed polymethylmethacrylate resin. (Rev Port Estomatol Med Dent Cir Maxilofac. 2023;64(1):12-19) (c) 2023 Sociedade Portuguesa de Estomatologia e Medicina Dentaria. Published by SPEMD. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).