Abstract

Background: Direct-Printed Aligners (DPAs) represent a recent advancement in the application of additive manufacturing in Dentistry. Among the technical factors affecting their clinical and laboratory performance, print orientation stands out for its influence on parameters such as geometric fidelity, mechanical strength, surface finish, and resin consumption. Despite this, oblique orientations remain widely adopted based on guidelines that are not always supported by scientific evidence, highlighting the need for a critical review of this practice. Materials and methods: A narrative review of the scientific literature was conducted to investigate the impact of three-dimensional print orientation on critical performance variables in DPAs. This review was conducted through searches in the PubMed, ScienceDirect, Springer Link, Scopus, Web of Science, and Cochrane Library databases. The selection included studies published in the last five years, in English idiom, investigating light-curable resins applied to Dentistry, with emphasis on DPAs. Exclusion criteria: studies addressing non-resin materials, applications unrelated to Dentistry, or that did not describe print orientation parameters were excluded. Results: The horizontal (0°) printing of DPAs has been associated with greater dimensional accuracy, reduced surface roughness, superior mechanical performance, and more efficient material usage. Although some studies have not identified statistically significant differences among various printing orientations, the evidence points to the technical and clinical advantages of the horizontal position. In contrast, inclined orientations for aligner printing, despite being recommended by manufacturers, have been linked to lower geometric fidelity, increased roughness, and poorer aesthetic appearance.

Keywords

Direct-printed aligners, additive manufacturing, print orientation, digital orthodontics