Effect of Extraction of Upper First Premolars on Facial Vertical Dimension (FVD) in Class II Div I Patients

Extraction of the upper first premolars and mesial movement of molars result in mandibular counterclockwise rotation and reduced facial vertical dimension. On the other hand, molar extrusion during the orthodontic treatment changes facial vertical dimension. Therefore, it is possible to avoid vertical changes of the face by maintaining the vertical position of posterior teeth. This study was designed to evaluate changes in the vertical dimension of the face in class II div I patients treated by extraction of the upper first premolars. This cross-sectional study was conducted on 20 patients, with a mean age of 17.8 years, who were selected from a private office. The subjects had class II malocclusion and normal vertical growth. To decreasing the effect of growth on the results, we selected subjects >15 years of age. As a part of their orthodontic treatment their upper first premolars had been extracted. The lateral cephalometric radiographs of the patients were digitized. Image analyses were conducted using View box 3.1.1 software program and data was analyzed with SPSS 20. Paired t-test was used to compare each variable before and after treatment (α = 0.05). In this study, there was no statically significant differences in skeletal variables. However, dental variables of U1-NA (mm), U1-NA, U1-FH, and overjet exhibited significant decreases (p value < 0.05). There was no significant differences in lower incisor variables. U6-palatal P, interincisal angle, U 1-palatal P exhibited significant increases. The results of this trial showed that treatment of class II div I through extraction of upper first premolars results in molar extrusion and in a decrease in upper incisor protrusion with no changes in the facial vertical dimension.