Accuracy of three-dimensionally printed retainers and aligners : A systematic review

With the constant improvement of photopolymerizable resin, direct three-dimensional (3D) printing of retainers and aligners (R&A) has gained popularity in recent years. The primary objective of this research was to systematically evaluate the evidence regarding the accuracy of 3D-printed R&A in terms of trueness and precision (T&P).

Electronic database searches were performed on PubMed, Science Direct, Web of Science, Scopus, Ovid, and Clinicaltrial.gov through 17 November 2023. The Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool was used to assess the risk of bias and applicability concerns of the methodologic quality of the articles.

A total of 12 in vitro studies were selected. Five studies reported the accuracy of 3D-printed retainers and another seven reported on aligners. For the 3D-printed retainer group, only Naeem et al. [1] reported both T&P and found that stereolithography (SLA) and PolyJet photopolymer (PPP) printers demonstrated higher accuracy than digital light processing (DLP) and continuous digital light processing (cDLP) printers. For the 3D-printed aligners group, only Koenig et al. [2] reported both T&P and found that 3D-printed aligners fabricated with photopolymerizable polyurethane resin demonstrated higher trueness (0.14 ± 0.020 mm) compared to conventional thermoformed aligners (0.188 ± 0.074 and 0.209 ± 0.094).

The existing digital workflow involving various printing materials, angulations, printing thickness, and printing technologies is feasible for the fabrication of direct 3D printing of R&A with variable degrees of accuracy. Most techniques worked within the clinically acceptable level of accuracy of 0.25 mm.

PROSPERO CRD 42022312907.