Parastoo Namdar - Assistant Professor, Department of Orthodontics, Dental Research Center, Faculty of Dentistry, Mazandaran University of Medical Sciences, Sari, Iran.
Hamed Karkhi - Dentist, Mazandaran University of Medical Sciences, Sari, Iran.
Nika Rezaeikalantari - Dentist, Mazandaran University of Medical Sciences, Sari, Iran.
Aboalfazl Hosseinnataj - PhD in Biostatics, Department of Biostatics, Faculty of Dentistry, Mazandaran University of Medical Sciences, Sari, Iran.
Mojtaba Namdar - Dentist, Mazandaran University of Medical Sciences, Sari, Iran.
Shahin Arab - PhD in Clinical Biochemistry, Faculty of Medicine, Mazandaran University of Medical Sciences, Sari, Iran.
Maziar Khatami - Department of Periodontics, Dental Research Center, Faculty of Dentistry, Mazandaran University of Medical Sciences, Sari.
Atena Shiva - Associate Professor, Department of Oral and Maxillofacial Pathology, Dental Research Center, Faculty of Dentistry, Mazandaran University of Medical Sciences, Sari, Iran.

Aim: This study aimed to compare the incidence of mucosal lesions and pain during orthodontic treatment with fixed versus removable orthodontic appliances. Methods: This cross-sectional study involved ۵۸ patients with fixed orthodontic appliances and ۵۸ patients with removable orthodontic appliances, all aged between ۱۵ and ۳۰ years. The presence and location of lesions were recorded at two time points: two weeks and four weeks after the start of the study. Additionally, the level of pain experienced by the patients was quantified at these same time points using a Visual Analog Scale (VAS). The Chi-square test was used to compare the frequency of oral lesions between the two groups at the onset of treatment. The Kruskal-Wallis test was used to compare the pain score at the onset of treatment between the two groups. The level of significance was set at ۰.۰۵. Results: The frequency of traumatic lesions at two and four weeks was significantly higher in the fixed group (P<۰.۰۵۰). The frequency of traumatic and allergic lesions increased with time in both groups (P<۰.۰۵۰). Lichenoid reactions, candidiasis, and exophytic lesions were only detected in the removable treatment group. At two and four weeks, the frequency of lesions in the buccal mucosa was significantly higher than in other areas in the fixed group (P<۰.۰۵۰). At four weeks, the pain score of patients was higher in the fixed treatment group (P<۰.۰۵۰). Conclusion: At four weeks, the frequency of lesions was higher in the fixed group. Buccal mucosa was the most common location of lesions in both groups. Pain in the fixed group was higher than the removable group at four weeks.

Orthodontic Appliances, removable, Orthodontics, Corrective, mouth mucosa, Pain