Aim: The development of new caries lesions in patients undergoing orthodontic treatment is an undesirable side effect of treatment that arises because the fixed appliance tends to accumulate plaque. The aim of this study was to examine the white spot lesions (WSL), caries incidence, and decayed, missing, and filled teeth (DMFT) indices in patients with fixed orthodontic treatments. Methodology: The records of 150 patients treated at Necmettin Erbakan University Department of Orthodontics between 2018 and 2022 who met the study selection criteria were examined. Traditional methods and 2D color photographs were used to detect cavities. Pretreatment (T0) and post-treatment (T1) recordings were made. Results: Overall, 118 patients (78.6%) developed at least 1 new WSL during treatment and 49 patients (32.6%) developed active caries lesions. Increases in WSL, caries incidence, and the DMFT index were important during the treatment process. The length of treatment and the number of oral hygiene warnings were significantly associated with the development of new lesions. Conclusion: Individuals undergoing fixed orthodontic treatment have a significant incidence of WSLs and caries lesions. Patients and physicians should pay strict attention to this problem to effectively prevent caries occurrence during treatment. How to cite this article: Gönder HY, Yıldırım M, Metli ŞN. Incidence of white spot lesions and DMFT among patients treated with comprehensive orthodontics. Int Dent Res 2022;12(Suppl.1):85-9. https://doi.org/10.5577/intdentres.432 Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.