THE EFFECTIVENESS OF FLEXIBLE ALIGNERS IN THE 3D CONTROL OF TEETH: A A SYSTEMATIC REVIEW

Introduction: Orthodontic aligners are removable, invisible devices implemented to move teeth without a rim, floss or bracket. It is, in fact an alternative therapy to conventional orthodontic techniques inorder to move the teeth gradually that involves wearing a series of transparent aligners following the steps. Each aligner takes the shape of a dental splint which is tailor-made, thermoformed medical polycarbonate that can be removable, comfortable, and compatible with the oral cavity. Each splint must be worn for a duration of 300 hours, that is two weeks, day and night, at a rate of 22 hours per day.The aim of this systematic review was to assess and evaluate the effectiveness of aligners in the 3D control of teeth in cases with and without extractions, in particular the control of dental axes during translational motion, the efficiency of the derotation of anterior and lateral teeth, torque control and the ability to intrude and extrude the anterior and posterior teeth. Equipment and Methods: A literature review search strictly related to publications in English and French was carried out on the following databases: Medline, Ebsco Host, Cochrane Library and Science Direct. This research included, in vivo, prospective, or retrospective research studies published up to 2019. Furthermore, this study was based on the PICO format whose target subjects were patients treated with orthodontic aligners with or without the use of devices with the objective to study the efficiency of aligners in the aforementioned 3D control by the predictability of programmed dental movements after orthodontic treatment by splint only or in comparison with fixed multi-bracket treatments. Results:Sixteen relevant articles were selected (four prospective studies and 12 retrospective studies). The control of the dental axes in translation (canine retreat, alignment, version) was predictable by orthodontic aligners with the use of attachments. Nevertheless, rotation, torque (control of the root axes) as well as vertical movements (intrusion, extrusion) were difficult to achieve with orthodontic aligners and required the incorporation of attachment to improve the obtained result. Distalization was not possible with orthodontic aligners. Conclusion: Based on results obtained from various studies carried out on orthodontic aligners, the effectiveness of the latter in the control of dental axes is low. In addition, the variation of the experimental protocols generated a low level of evidence on the predictability of certain dental movements (version, intrusion, extrusion, rotation, torque) with a certain unpredictability of the distalization movement.