Abstract:

Objective: To evaluate the effect of the upper first molar extraction on maxillary and mandibular posterior spaces. Materials and Method: The material of the study consisted of lateral cephalometric radiographs of 20 individuals with dental Class II malocclusion who were treated with fixed appliances by extraction of the upper two premolars, before treatment (T1), after treatment (T2), and after retention (T3). On the lateral cephalometric radiographs, 7 dimensional and 4 angular measurements were performed by the same investigator. The Shapiro-Wilk test was used to determine whether the distribution of continuous numerical variables was close to normal. The statistical evaluations of the measurements were performed with Wilks' Lambda test for parametric variables and Friedman test for nonparametric variables. Multiple comparisons with Bonferroni correction or Dunn-Bonferroni post-hoc tests were done. A p value of <0.05 was considered statistically significant. Results: The SNB angle increased significantly in T3 compared to T1 (p<0.05). The ANB angle decreased in T3 compared to T1 (p<0.05). The U1-NA distance decreased in both T2 and T3 compared to T1 (p<0.001). The U6-PTV distance increased significantly in both T2 and T3 compared to T1 and in T3 compared to T2 (p<0.001). The CLMD distance increased significantly in both T2 (p<0.01) and T3 (p<0.001) compared to T1 and in T3 compared to T2 (p<0.05). The DC distance increased in both T2 and T3 compared to T1 and in T3 compared to T2 (p<0.001). The CL1 distance significantly increased in T3 compared to T1 (p<0.05). Conclusion: An increase was observed in the maxillary posterior space due to premolar extraction. The increase in the mandibular posterior space was less than that in the maxillary posterior space. Retraction of maxillary incisors and mesial movement of maxillary molars were observed.

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