فهرست نشریات علمی دسترسی آزاد ایران

Aim: This study aimed to determine the changes in mandibular incisor proclination and mandibular arch widths after leveling the curve of Spee (COS).Methods: Patients included in this quasi-experimental study were scheduled for fixed orthodontic treatment with a non-extraction therapy in the mandibular arch, no posterior crowding, eruption of all mandibular teeth except third molars, no spacing, and Little’s irregularity index greater than 2. The COS depth and mandibular arch widths (inter-canine and inter-molar widths) were measured on plaster casts and recorded in millimeters. Mandibular incisor inclinations were measured on a cephalogram according to the incisor mandibular plane angle (IMPA) and lower incisor to NB (L1) angle. The pre- and post-treatment values were compared using paired-samples t-test. Pearson’s correlation was used to analyze the association between COS changes and other variables. P-value<0.05 was considered statistically significant.Results: Fifty-eight subjects with an average age of 25.10±6.81 years participated in this study. COS depth values significantly reduced after treatment (2.34±0.78 mm vs. 1.75±0.56 mm) (P<0.001). Average IMPA and L1-NB values significantly increased following COS flattening (P<0.001). Mandibular inter-canine and inter-molar widths also significantly increased after treatment (P<0.001). Pearson’s correlation revealed a significant inverse correlation between COS changes and mandibular arch width and mandibular incisor proclination values (P<0.001 for both). The patients’ age and gender did not significantly affect the COS depth.Conclusion: Flattening of COS leads to an increase in lower incisor proclination and mandibular arch width.