ABSTRACT
The purpose of this study was to evaluate the dentofacial characteristics and the post-treatment dentofacial changes of those treated by four premolar extractions and to investigate the factors affecting extraction decision. The sample consisted of 35 patients ( 27 females, and 8 males ) with no more than 7.0mm crowding, diagnosed as Class I protrusion. Pre-treatment and post-treatment lateral cephalograms were evaluated. Computerized statistical analysis was carried out using SPSS/PC+ program. The results were as follows. 1. There was no significant change in skeletal pattern after treatment while there was significant change in dentoalveolar and soft tissue pattern. 2. In pre-treatment skeletal pattern, a tendency toward vertical discrepancy was found. 3. In pre-treatment dental pattern, interincisal angle was 113.11degrees, Ul to FH was 117.78degrees and Ll to A-Pog was 7.94mm. Pre-treatment upper and lower lip position was 2.88mm and 5.43mm to E line. 4. After treatment, interincisal angle increased 14.46degrees and upper and lower lip moved back 2.45mm and 12mm to Eline. (p<0.001) 5. The EI was 138.71 before treatment and 148.2 after treatment.