Background: With the rising popularity of clear aligners therapy, understanding the incidence and severity of apical root resorption in patients following treatment with both clear aligners and fixed appliances becomes increasingly crucial. The purpose of this systematic review of the literature is to compare the incidence/severity of root resorption in patients treated with clear aligners and fixed appliances and to determine the main factors responsible of the variation in root resorption between these two systems. Materials and Methods: Pubmed, Cochrane, ScienceDirect and Google Scholar were used to search for systematic reviews, randomized or non-randomized controlled trials, cohort studies and case-control studies conducted in humans and published within ten years (since 2014 until 2023). AMSTAR 2, RoB 2 and NHLBI, NIH were used to assess the risk of bias of the included studies. Results: In total, 21 articles (human studies): 10 systematic reviews, 7 cohort studies (6 retrospective and 1 prospective), 3 randomized controlled trials and 1 case-control study were included. Conclusion: The majority of the studies showed that the incidence/severity of apical root resorption is less in clear aligners compared to fixed appliances treated patients. However, these studies are characterized by different baseline malocclusions, treatment durations/modalities, study designs flaws, inconsistency in outcomes measurement/calculation. Future high-quality clinical trials are needed to further support these results.