Evaluation of the role of unilateral and bilateral tooth extraction treatment on maxillary arch symmetry in Class II subdivision cases

Background and Aim: Unilateral extractions have been proposed as potential treatment options to correct Class II subdivision malocclusion, suggesting that most side effects associated with asymmetrical mechanics can be avoided, however the post-treatment arch form may not be symmetrical. Therefore, the aim of this study was to determine the post-treatment effects of unilateral premolar extraction on the maxillary dental arch in Class II subdivision malocclusions. Material and Methods: In this case-control study, 34 patients  were chosen with class II subdivison and having  indication of extraction alone with fix orthodenthic treatment. After matching of age and sex, divided into 2 groups of unilateral and bilateral  maxillary extraction and symmetry was evaluated with digital impressions. Anti-post , vertical and horizental  changes , displacement of canine and molar and inclination charges of incisors in lateral cephalometry radiographies were evaluated. For normal distribuaiton of datal,  T-Test and for abnormal one, Man-U-Withneh test were approached     Results: The amount of molars asymmetry in the unilateral extraction group in the transverse dimension was 0.15 mm and in anterior-posterior dimension 4.55 mm more than bilateral extraction group which was statistically significant (p≤0.001).  However, in the vertical plane, the molars showed statistically insignificant differences.   The amount of canines’ asymmetry in the unilateral extraction group in the transverse, vertical and anterior-posterior dimension was 0.18 mm, 0.58 mm and in 0.60 mm respectively, when compared with bilateral extraction group which was statistically significant (p≤0.0001). The difference in the inclination of the upper anterior teeth at the end of treatment was also statistically significant. Conclusion: The effect of unilateral premolars extraction on the symmetry of the dental arch form is significantly different from bilateral premolars extraction.  Unilateral extration leading to more narrow arch and  posterior displacement of molars.