Labiopalatal bodily movement and torque control of incisors with aligners: A systematic review

Objectives: To assess aligners’ potential to induce labiopalatal bodily movement or achieve torque control of incisors and evaluate the scientific evidence related to the impact of aligner modifications and their recommended geometries.
Materials and methods: The electronic databases PubMed, Science Direct, Cochrane Central Register of Controlled Clinical Trials, IEEE Xplore, National Library of Medicine Catalog and Google Scholar were screened from January 1991 to February 2020. Quality assessment was performed using an individual scoring system and a 4-point grading system based on the Grading of Recommendations Assessment, Development and Evaluation tool. The studies were classified according to the aligner system, material and aligner modifications used.
Results: Six studies were included for qualitative analysis: two experimental in vitro studies, one prospective study and three retrospective clinical trials. In total, the quality score for all the included studies was 26.2 points, corresponding to a grade C (low quality of evidence). The labiopalatal bodily movement and torque control of incisors using aligners were transmitted inconsistently. When comparing aligner modifications, the accuracy for torque movement was higher using Power Ridges (Align Technology, San Jose, CA, USA) (51.5%) than attachments (49.1%), with torque values of 7.9 and 6.7 Nmm, respectively. As yet, there is no specific recommendation for the modification geometry.
Conclusion: The potential of aligners to induce labiopalatal bodily movement or achieve torque control of incisors without modifications is limited. The implementation of aligner modifications and adequate aligner system–dependent staging might increase the efficacy of these forms of movement. More studies, especially randomised controlled trials, are required to clarify the predictability of these tooth movements.