Cephalometric Study of Upper Premolar Extraction Orthodontic Treatment

Methods: The sample group consisted of 40 patients(20 for upper premolar only, 20 for upper/lower) who showed overjet more than 7mm at first examination and were finished successfully. Lateral cephalographs were taken before and after orthodontic treatment. Landmarks showing the position of the upper and lower incisors and changes of soft tissue were determined and angular measurement of the values and statistical processes were performed. The statistical methods to be used for analysis are: the independent t tests and the mann-whitney U tests for difference in change of upper and lower incisor position and soft tissues.

Results: 1. At pre-treatment, the position of lower incisor was less labially inclined and convexity of lower lip was less in upper premolar extraction only than in upper/lower premolar extraction. 2. At post-treatment, there was no difference in all measurements except the position of lower incisor. 3. A comparison of changes between pre- and post-treatment showed that the retraction of upper incisors and the decrease of convexity of lower lip were more in upper/lower premolar extraction. There was no difference in the position of upper lip between two groups.

Conclusion:

The position of lower incisor was considerable measurement to provide sufficient information in selection of extraction pattern. At first visit, the convexity of upper and lower lips should be measured(especially, the lower lip is important). The patients who have acceptable profile esthetics with inexcessive convexity of lower lip can be treated successfully with upper premolar extraction only.