[Aligners: review of their chemical components, recycling, mechanical properties and therapeutic needs - Part 1].

INTRODUCTION

The aligner is a thermoformed plastic device composed of various chemical components: polyurethane, polyethylene terephthalate glycol, polypropylene… All these plastics must be sufficiently resistant to abrasion and translucent for aesthetic purposes, but their solubility to salivary enzymes, insertion-disinsertion fatigue and recyclability vary according to material. From an orthodontic point of view, they must facilitate tooth movement. However, their behavior differs from that of orthodontic archwires: their Young's modulus, resilience and unloading curve are distinct, resulting in mechanical properties that fall significantly below the orthodontic requirements of multi-bracket systems.

OBJECTIVE

The aim of this article was to review the chemical composition, recycling and mechanical properties of aligners, and to put them into perspective with therapeutic indications.

MATERIALS AND

METHODS

Literature data were approximated to orthodontic needs.

RESULTS

Neither plastic nor direct printing can match the mechanical properties of our archwires or the procedures of a reliable vestibular multi-attachment appliance.

DISCUSSION: Aligners remain an interesting tool in targeted indications.