3D Printed Materials for Permanent Restorations in Indirect Restorative and Prosthetic Dentistry: A Critical Review of the Literature

The objective of this study was to review the scientific evidence currently available on 3D printable materials and 3D printing technologies used for the fabrication of permanent restorations, focusing on material properties that are clinically relevant. A literature search was performed on four databases (MEDLINE/PubMed, Scopus, Cochrane Library, Web of Science) for articles published from January 2013 until November 2023, using a combination of free words: (restorative dentistry OR prosthetic dentistry) AND (3D printing OR additive manufacturing OR rapid prototyping) AND materials. Two reviewers screened titles and/or abstracts of 2.468 unique studies. In total, 83 studies were selected for full-text reading, from which 36 were included in the review. The assessed variables were mechanical properties, reporting in most of the cases positive results, dimensional accuracy and fit, reporting conflicting results with a predominance of positive, aesthetic properties, with positive reports but scarcely addressed, and biological properties, almost unexplored in independent studies. Despite numerous studies with positive results in favor, papers with negative outcomes were also retrieved. Aesthetic and biological properties are conversely still mostly unexplored. There remains a lack of conclusive evidence for viable 3D printable restorative and prosthodontic materials for permanent restorations. Research should be strengthened by defining international standards for laboratory testing and, where pre-clinical data are promising, conducting clinical trials.