Influence of 3D printing orientations on physico-mechanical properties and accuracy of additively manufactured dental ceramics.

Purpose: This systematic review aims to assess the impact of different 3D printing orientations on the physico-mechanical properties, volumetric change, and accuracy of additively manufactured ceramic specimens, as well as their restorations.

Study Selection: The web database containing records for building orientation of 3D-printed ceramics until January 2024 was searched, with no language limitations. PRISMA 2020 guidelines were followed, and the risk of bias was evaluated using the modified CONSORT checklist for laboratory studies on dental materials. The RevMan 5.4 of Cochrane collaboration was used for the meta-analysis with α<0.05.

Results: In this systematic review, 35 out of 2967 records were considered. The printing orientations had a significant influence on the mechanical properties of the additively manufactured specimens (P < 0.05), specifically, the horizontally printed specimens exhibited the best mechanical behavior, while the physical properties exhibited controversial results. Additionally, the printing orientations had a significant impact on the volumetric shrinkage and accuracy of molar teeth (P < 0.05).

Conclusions: The ideal mechanical outcome was observed when ceramic specimens were 3D-printed in a horizontal direction relative to the platform, while vertically printed specimens showed the worst properties. The printing orientations affect the volumetric change of the specimens; however, volumetric change highly depends on the sintering parameters. It is recommended to 3D print ceramic molar crowns at 180° with the occlusal surface facing the printing platform.

Clinical Significance: Several factors affect the additively manufactured restorations throughout the printing procedure. Therefore, printing orientation should be carefully considered before the additive production process of ceramic restorations.