Law Of Tooth Movement After Orthodontic Treatment With Four Second Premolar Extractions: Cephalometric Study

This study is designed to examine the law of tooth movement and maxillary structural changes after orthodontic treatment with four 2^nd premolars extracted.Purpose: To examine the distance and pattern of tooth movement, ratio of anterior to posterior tooth movements and maxillary structural changes after treatment with four 2^nd premolars extracted.Method: Pre- and post-treatment cephalometric X-rays of 26 patients treated by one experienced orthodontist, with four 2^nd premolars extracted, are examinated. These patients all have slight crowding, slight bi-maxillary protrusion and Class I molar relation. Distance of tooth movement and change of inclination are measured in relation to different reference lines as follows: occlusal plane, PM line, McNamara line, NA line, NB line, NP line, AP line, and S and N point.