Objectives: The aim of our study is to evaluate and compare the presence and severity of external root resorption in patients treated with either clear aligners (Invisalign) versus conventional fixed orthodontic appliances. Material and Methods: A retrospective study was performed on 203 patients, which includes 30 treated with Invisalign and 173 with fixed appliances. 60 cases (30 per group) were matched based on extraction status, treatment duration, gender, age, and malocclusion classification after inclusion criteria were applied. Radiographic evaluations were conducted with standardized periapical radiographs and Panoramic radiographs (OPG). Comparing radiographs taken before and after treatment allowed for the measurement of the extent of external root resorption. Results: In the matched cases, external root resorption was present in 92% of patients in the Invisalign group and 77% of patients in the fixed appliance group. Maxillary incisors were the most afflicted teeth, particularly in situations involving tooth extractions. The greatest percentage of root resorption (100%) was recorded in Class II malocclusion, which was followed by Class I (84%) and Class III (77%). Although Invisalign treatments demonstrated an increased incidence of root resorption, fixed appliances were associated with more severe root reduction. There were not significant distinctions between the groups, according to statistical analysis (p > 0.05). Conclusions: A frequent adverse effect of orthodontic treatments involving both fixed appliances and Invisalign is external root resorption. Root resorption was more common in Invisalign patients, but it was greater in fixed appliance cases. These results highlight the need for more expansive prospective studies to confirm these findings and enable clinicians minimize side effects associated with treatment.

The authors have declared no competing interest.

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The author(s) received no specific funding for this work.

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The Faculty of Dentistry's Research Ethics Committee at king Abdulaziz University provided its approval to the research being performed (Approval number: 161-12-20).

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Data cannot be shared publicly because of IRB rules in the instritution. Data are available from the radiographs Institutional Data Access / Ethics Committee (contact via email only) for researchers who meet the criteria for access to confidential data.

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