A comparative study of pre- and post-treatment cephalometric measurements: Upper premolar extraction only vs. upper/lower premolar extraction groups

Kim, Young Seok; Kim, Su Jung; Kang, Seung Goo; Lee, Young Jun

Abstract

OBJECTIVE
The objective of this study was to provide guidelines for the diagnosis and successful treatment of orthodontic treatment with upper premolar extraction only.
METHODS
The sample group consisted of 40 patients (20 with upper premolar extraction only, 20 with both upper and lower premolar extractions) who showed an overjet of more than 7 mm and were finished successfully. Lateral cephalographs were taken before and after orthodontic treatment. Landmarks showing the position of the upper and lower incisors and the position of the upper and lower lip were determined and angular measurement of these values were obtained for statistical analysis (Mann-Whitney test).
RESULTS
At pre-treatment, the position of the lower incisor was less labially inclined and the convexity of the lower lip was smaller in the upper premolar extraction only group than in the upper/lower premolar extraction group. At post-treatment, there was no difference in all measurements except for the position of the lower incisor. A comparison of changes between pre- and post-treatment showed that the retraction of upper & lower incisors and the decrease in convexity of the lower lip were greater in the upper/lower premolar extraction group.
CONCLUSIONS
Treatment by upper premolar extraction can be of benefit for patients whose lower incisor proclination and lower lip protrusion are not excessive.