Mechanical properties, wear resistance and bacterial adhesion of heat-cured and additively manufactured dental polymers in simulated saliva

Additive manufacturing (AM) has emerged as a promising technique for fabricating dental prosthetic materials, driven by its ability to create solid three-dimensional objects with complex geometries. However, concerns persist regarding the printed material properties and their resistance against the aggressive environment within the oral cavity. In this study, the effect of simulated saliva on the mechanical and tribological properties of dental polymers fabricated using digital light processing (DLP) based AM was determined, and the results were compared with those produced by the conventional heat-curing (HC) method. The absorption of simulated saliva, compressive and flexural strength, as well as the impact toughness and wear resistance of both the HC and AM polymers, were determined. The resistance of both specimen groups to bacterial adhesion was assessed with Streptococcus mutans. The results showed the AM specimen absorbed more simulated saliva and exhibited superior mechanical properties compared to the HC specimen. However, the mechanical properties of both specimens decreased under wet conditions in simulated saliva. The AM specimens also demonstrated greater wear resistance, with tribological performance significantly influenced by printing orientation. Both the HC and AM specimens in this research also maintained their stability at the maximum intra-oral temperatures. Meanwhile, the AM specimen was more susceptible to bacterial adhesion, as evidenced by a higher biofilm density consisting of S. mutans compared to the HC specimen.