Influence of printing orientation on the accuracy, fit and mechanical properties of 3D-printed full-coverage prostheses: a systematic review.

AIM: This systematic review evaluated the influence of 3D printing orientation on the mechanical properties, accuracy, and marginal fit of full-coverage dental prostheses. MATERIALS AND METHODS: A comprehensive search was conducted through PubMed, Embase, Scopus, and Web of Science databases for in vitro studies published between January 2014 and June 2024. Following PRISMA 2020 guidelines based on a predefined PICO framework, in vitro studies assessed the printing orientation of 3D-printed full-coverage dental prostheses over the past ten years and published in English were included. Data extraction focused on printing orientation, technology, evaluation methods, and outcomes. RESULTS: About 20 studies were included. Printing orientation significantly affected mechanical properties, including flexural and compressive strength, particularly in vertically or obliquely oriented specimens, whereas microhardness, density, and porosity were less influenced. Trueness and precision were significantly improved by printing orientation angles such as 0°, 30°, and 45°, while the greatest deviations were reported at 45°, depending on prosthesis type, tooth morphology, and printer system. Marginal fit was highly dependent on experimental conditions, with no universally optimal printing angle identified. CONCLUSION: Overall, printing orientation plays a critical role in the functional and dimensional performance of 3D-printed dental prostheses. Oblique orientations generally provide a favorable balance between mechanical strength and accuracy.