The Impact of Layer Thickness on Key Parameters Affecting 3D-Printed Dental Materials: A Systematic Review

Background: Three-dimensional (3D) printing has transformed restorative, and prosthetic dentistry, providing new possibilities for the fabrication of dental materials. Nevertheless, the influence of printing layer thickness on the final properties of dental resins remains insufficiently clarified. Study Design (Methods): A systematic review was conducted through a comprehensive electronic search of PubMed, Scopus, and Web of Science up to June 2025. Eligible in-vitro studies investigated the effect of 3D printing layer thickness on the mechanical properties, dimensional accuracy, surface roughness, and bond integrity of dental resins. Thirty-seven studies met the inclusion criteria, and were analyzed narratively due to heterogeneity in study designs, materials, and testing methods. Results: Printing layer thickness demonstrated a significant effect on dental resin performance. Thinner layers (25-50 µm) were generally associated with enhanced flexural strength, hardness, surface smoothness, and color stability. However, in some composite-based materials, thicker layers yielded superior mechanical properties. Dimensional accuracy, and marginal fit varied across studies, with some reporting optimal results at 50 µm, and others at 100 µm. Conclusion: Layer thickness represents a critical parameter influencing the performance of 3D-printed dental resins. Optimal outcomes depend on a balance between layer thickness, build angle, and post-curing protocols. Further standardized investigations, including clinical studies, are essential to establish evidence-based guidelines for layer thickness selection in dental additive manufacturing.