Influence of different print orientations on properties and behavior of additively manufactured resin dental devices: A systematic review and meta-analysis

Statement of problem: Different factors affect 3-dimensionally (3D) printed resin products. However, evidence on the effect of the print orientation on resin dental devices is lacking. Purpose: The purpose of this systematic review and meta-analysis was to assess the impact of print orientation on the properties and accuracy of 3D printed implant surgical guides, occlusal devices, clear orthodontic retainers, and aligners. Material and methods: The electronic databases PubMed (MEDLINE), Cochrane, and Scopus were comprehensively searched in July 2024. A modified Consolidated Standards of Reporting Trials (CONSORT) statement was used to judge the included studies, and the data were analyzed by the RevMan 5.4 software program of the Cochrane collaboration by applying an inverse variance analysis (α=.05). Results: Twenty-six records were included. Complete arch, solid surgical guides with horizontal printing orientation exhibited the highest accuracy (P≤.01). Short-span surgical guides printed vertically showed relatively high accuracy (P≤.05). Hollow or mesh devices might not be affected by orientations. Occlusal device accuracy favored horizontal orientation, but correlated with the technology and materials, while the accuracy of orthodontic aligners revealed controversial findings, assuming the limited impact of orientation on orthodontic aligners. The cytotoxicity of occlusal devices was a material-related biological characteristic and unaffected by orientation. Although flexural strength favors horizontal orientation, conflicting results were observed for physical and other mechanical properties due to several variables. Conclusions: Horizontal orientation is recommended for printing complete arch surgical guides, while the accuracy of short surgical guides might favor vertical orientation. The physical mechanical properties depend on the printing orientation, technology, material, and printed parts, but horizontal orientation might produce parts with the best mechanical performance.