Upper lip changes correlated to maxillary incisor retraction--a metallic implant study

The soft tissue changes after the extraction of maxillary first premolars and subsequent anterior tooth retraction were evaluated for 16 Class II, division 1 patients. Pre- and posttreatment lateral head cephalograms were evaluated using superimpositions on Björk-type metallic implants in the maxilla. The patient sample was divided into group I patients, those who did exhibit lip seal at rest in the pretreatment cephalogram and group II patients, those who did not exhibit lip seal at rest in the pretreatment cephalogram. Upper incisor retraction was followed by a similar ratio of upper lip retraction in both the lip seal and nonsealed groups (1:0.75 and 1:0.70 mean ratios, respectively). However, those without lip seal did demonstrate more retraction at stomion (USt). The final upper lip position (Ls) was reasonably correlated with retraction of the cervical maxillary incisor point (cU1) with determination coefficients of 63.6% in the lip sealed and 68.5% in the lip incompetent groups. Although labial and nasolabial angles tended to open after incisor retraction, there was little predictability for this response.