Mechanical, Physical And Optical Properties Comparison Between Direct Printed And Thermoformed Aligners - A Systematic Review

Abstract

Background: Clear aligners are a popular choice for orthodontic treatment due to their aesthetic appeal, comfort, and the ability to be easily taken on and off, unlike fixed appliances, which cannot be removed once treatment begins. Two common fabrication methods for aligners are direct 3D printing and thermoforming. This systematic review aims to compare the mechanical, physical, and optical properties of 3D-printed aligners (DPAs) and thermoformed aligners (TFAs) to provide evidence-based insights for clinicians and researchers.
Material and Methods: A comprehensive literature search was conducted in electronic data-bases, including PubMed, Scopus, Web of Science and Google Scholar, to identify studies evaluating and comparing DPAs and TFAs. Studies were selected based on predefined inclusion and exclusion criteria, focusing on outcomes such as load-deflection behavior, dimensional accuracy, tensile strength, force decay, thickness, and transparency. The quality of the included studies was assessed using the RoBDEMAT tool for in vitro studies and the ROBINS-I tool for in vivo studies. Data synthesis involved narrative and qualitative approaches to summarize the findings.
Results: A total of ten studies were included, comprising eight in vitro studies and two in vivo studies. The included studies exhibited moderate risk of bias due to insufficient reporting of randomization and operator blinding. DPAs demonstrated superior dimensional accuracy, thickness uniformity, and optical properties compared toTFAs. However, TFAs exhibited better force retention and consistent load. While the mechanical strength of DPAs was higher, TFAs showed greater stability in long-term force delivery.
Conclusions: DPAs provide superior precision and aesthetics, while TFAs offer better durability and sustained force retention, highlighting the need for case-specific aligner selection.