Lower incisor position and profile changes in extraction treatment.  I am often asked about the effect of upper premolar extraction treatment on the facial profile and many believe that this will significantly retract the upper and lower lip positions.  In most orthodontic cases we must treat the occlusion to the labiolingual position of the lower incisors.  This is because the bone surrounding them is thin both on the facial and lingual aspect of their roots.  If the maxillary anterior teeth are more crowded than the lowers and a class II molar relationship is present, there is usually not a significant overjet.  When upper premolars are removed in these cases the maxillary canines are retracted into the missing premolars' positions and the incisors are uncrowded.  The lower incisors are held in their most stable and healthy location while the overbite and overjet is coordinated to them.  Thus, the profile won't change much and proper canine and incisal guidances are obtained.  Next we'll talk about how the anterior-posterior relationship of the maxilla and mandible relate to profile and incisor angulation.