The Effect of Clear Aligners on Root Length in Endodontically Treated Teeth: A Systematic Review of Split-Mouth Studies.

: Clear aligners are increasingly prescribed for orthodontic treatment, primarily in adult patients; however, concerns have been raised that this treatment approach may negatively impact root length, especially in endodontically treated teeth. The present investigation aims to systematically synthesize available research addressing the potential effects of clear aligner orthodontic treatment on root length changes in endodontically treated teeth. : Four electronic databases were searched until May 2025, and lists of references from relevant publications were screened to identify studies (randomized clinical trials, controlled clinical trials, and observational studies) written in the English language with no date restriction. Clinical studies comparing clear aligner orthodontic treatment in endodontically treated teeth versus vital pulp teeth in humans, using cone beam computed tomography or panoramic radiographs to evaluate root resorption, were assessed. Following study selection and data extraction, the risk-of-bias assessment was evaluated with the Newcastle-Ottawa tool for the observational studies. : A total of 173 studies were retrieved, and ultimately 2 observational cohort studies were included in the systematic review, encompassing 135 patients (69.6% female; with an average age of 22.5 years). The present review found an association between endodontic status and root resorption, with vital pulp teeth (VPT) exhibiting a greater degree of resorption compared to root canal treated teeth (RCT). Clear aligner (CA) orthodontic treatment resulted in less root resorption than fixed orthodontic appliances (FAs). : Limited evidence indicates that clear aligner orthodontic treatment leads to a lower occurrence of root resorption and fewer cases of severe root resorption in endodontically treated teeth. Based on findings from studies comparing CAs to FAs, there is overall significantly greater resistance to root resorption in RCT than VPT, irrespective of the orthodontic treatment modality (CAs or FAs).