Effect of layer thickness on the integrity of additively manufactured interim crowns: a systematic review and meta-analysis

Printing parameters such as layer thickness can influence the integrity of printed interim crowns and their clinical performance. Adjustments to the thickness of each printed layer can influence the mechanical strength and attributes such as aesthetics, marginal adaptation, and surface quality, ultimately impacting the durability of interim crowns. This systematic review aimed to compare the 50 μm layer thickness with other protocols and evaluate the effect of layer thickness on the physical and mechanical properties for additively manufactured interim crowns. Two researchers independently searched for relevant studies published from August 2019 to September 2025 using electronic databases (PubMed/MEDLINE, Scopus, Web of Science and LILACS). The PICO question was, "Does a layer thickness of 50 μm promote better physical properties for 3D printed interim crowns when compared to other thicknesses?" Studies that compared the properties of different printing layer thickness were included. Sixteen in-vitro studies were selected for qualitative analysis. Regarding flexural strength, marginal and internal fit and hardness, the meta-analysis indicated difference, with better results for the 50 μm layer thickness (flexural strength, p = 0,001; marginal fit, p < 0,00001; hardness, p = 0,05). When evaluating surface roughness and trueness the 25 μm, 20 μm and 50 μm thicknesses had similar performances. Compared to other thicknesses, the 50 μm layer presented better results for flexural strength, hardness and marginal and internal fit. When analyzing surface roughness and trueness, layers thinner than 50 μm yielded similarly satisfactory results.