Face Vertical Dimension Change and Incisors Position Following Orthodontic Treatment with Extraction of Four First Premolars

The aim of this study was to evaluate vertical dimension of face and position of incisors following extraction of four first premolars in patients with class I malocclusion and bimaxillary dentoalveolar protrusion and/or crowding.

 This study evaluated 22 patients with class I molar relationship, bimaxillary dentoalveolar protrusion and/or crowding with the treatment plan of extraction of all four first premolars. The change in U1-PP, L1-MP, IMPA, U1-SN, saddle angle, articular angle, gonial angle, and the sum of Bjork was determined by assessing the before and after-treatment cephalograms. The changes in cephalometric parameters were analyzed by ANOVA and paired t-test.

 The U1-SN, IMPA, U1-PP and sum of Bjork significantly changed following extraction of the four first premolars (P<0.05). However, the changes in saddle, articular and gonial angles and L1-MP were not significant (P>0.05).

 We observed retraction and extrusion of incisors and increase of vertical dimension following extraction. Retraction of incisors will relatively retract lips. Also, it is not advisable to extract premolars to improve vertical dimension, although extrusion of incisors will facilitate the bite closure.