Advancements in Clear Aligner Fabrication: A Comprehensive Review of Direct-3D Printing Technologies

Abstract

Clear aligners have revolutionized orthodontic treatment by offering an esthetically driven treatment modality to patients of all ages. Over the past two decades, aligners have been used to treat malocclusions in millions of patients worldwide. The inception of aligner therapy goes back to the 1940s, yet the protocols to fabricate aligners have been continuously evolved. CAD/CAM driven protocol was the latest approach which drastically changed the scalability of aligner fabrication—i.e., aligner mass production manufacturing. 3D printing technology has been adopted in various sectors including dentistry mostly because of the ability to create complex geometric structures at high accuracy while reducing labor and material costs—for the most part. The integration of 3D printing in dentistry has been across, starting in orthodontics and oral surgery and expanding in periodontics, prosthodontics, and oral implantology. Continuous progress in material development has led to improved mechanical properties, biocompatibility, and overall quality of aligners. Consequently, aligners have become less invasive, more cost-effective, and deliver outcomes comparable to existing treatment options. The promise of 3D printed aligners lies in their ability to treat malocclusions effectively while providing esthetic benefits to patients by remaining virtually invisible throughout the treatment process. Herein, this review aims to provide a comprehensive summary of studies regarding direct-3D printing of clear aligners up to the present, outlining all essential properties required in 3D-printed clear aligners and the challenges that need to be addressed. Additionally, the review proposes implementation methods to further enhance the effectiveness of the treatment outcome.

Digital Model in Orthodontics: Is It Really Necessary for Every Treatment Procedure? A Scoping Review

“…Digital light processing (DLP), stereolithography (SLA), polyjet (PJ), and other specialized vat polymerization (VP) methods are commonly used to print aligners. In these applications, safety and strength are of utmost importance [49].…”

“…It is finally important to mention that 3D-printed aligners provide higher geometric precision and can be tailored to any patient's needs. Continuous contact between the aligner and the teeth is necessary to ensure its ideal performance since any gaps could prevent the aligner from reaching its maximum mechanical capability [49]. A printed aligner should ideally be recyclable [50].…”

“…Several challenges need to be resolved before the product is used in a clinical setting. These issues fall into the following categories: (1) workflows, (2) anisotropic behavior, (3) characteristics, (4) precision, (5) cost, (6) tooth movement effectiveness, and (7) hygiene of 3D-printed clear aligners [49].…”

Color and Chemical Stability of 3D-Printed and Thermoformed Polyurethane-Based Aligners

“…Those are composed of thermoplastic resin polymers such as poly(vinyl chloride) (PVC), poly(ethylene terephthalate) (PET), poly(ethylene terephthalate glycol) (PETG), and thermoplastic polyurethane Polymers 2024, 16, 1067 2 of 18 (TPU). On the other hand, 3D printing, or additive manufacturing, builds the aligner layer by layer directly from a digital model [8][9][10]. These methods employ polyurethanebased materials, chosen for their balance of clarity, strength, and flexibility, which are essential for the continuous force application required to move teeth into their desired positions [9,11].…”

In vitro study examines posterior torque impact on 3D mechanics of anterior teeth in clear aligner treatment

“…Compared with fixed braces, clear aligners have gained increasing popularity among patients and orthodontic professionals due to their aesthetic appeal and comfort advantages [ 3 – 6 ]. With the advancement of digital technology and in-depth research on the biomechanical properties of materials, the scope of treatment with clear aligners has expanded from non-extraction cases to include extraction cases [ 7 – 10 ].…”