Premolar Extraction Cases Treated with Aligners: Are Contemporary Results Comparable to Fixed Appliances?

Abstract

Introduction: Historically, it has been challenging to treat premolar extraction cases with aligners to the same occlusal standards as fixed appliances. The purpose of this study was to assess whether premolar extraction cases treated with Invisalign in the past 5 years have more comparable results to cases treated with fixed appliances. Methods: Matched pairs of premolar extraction cases were analyzed from 3 private practice orthodontists considered to be experts in both the fixed appliances and aligner techniques. Pre- and post-treatment records were assessed for (1) occlusal outcomes, (2) treatment efficiency, (3) cephalometric parameters, and (4) root parallelism in extraction cases treated with Invisalign versus full fixed appliances whose treatment was completed in the past 5 years. Results: ABO-OGS and PAR scores were comparable for both groups, showing no statistically significant differences. Aligner cases completed treatment 2 months faster, on average, than fixed appliance cases, but this difference was not significantly different. Cephalometric analyses indicated that at the end of treatment, lower incisors had a greater change in retroclination and overbite was deeper in the aligner group. Teeth adjacent to extraction sites in the aligner group had more divergent roots compared to the fixed group. Conclusion: Occlusal outcomes and treatment efficiency were similar in the aligner and fixed appliances patients treated in the past 5 years. However, incisor angulation, overbite, and root parallelism were not managed as well with aligners.