The influence of extraction versus non-extraction orthodontic treatment on the soft tissue profile.

The aim of the present study was to study profile changes following orthodontic harmonization of enlarged overjet and to attempt to trace predictive aspects regarding prognosis of the soft tissue changes. Lateral cephalograms and study models of 40 female patients, at least 12 years old at the start of treatment, with an overjet of > or = 6 mm were analyzed before (T1) and after treatment (T2). Twenty patients were treated without extractions, while in the remaining 20 patients extractions of premolars were carried out bilaterally in both jaws. The 2 groups were found to be highly homogeneous as regards overjet, cephalometric characteristics, space condition in the upper arch at T1 and both at T1 and T2 as regards age. The most striking aspect of the findings was the considerable amount of variability of the soft tissue changes. These changes were found to be rather unpredictable for the individual patient, since the regression models employed could give only a very wide individual prediction range. The relatively small changes registered, using superimposition methods, in both groups as regards the sagittal position of the lips in comparison to the very strong changes observed in relation to the esthetic line shows that the influence of the growth of the chin and/or the nose on the facial profile might be more important than the influence of the orthodontic treatment. The interpretation of the findings in the present study suggests that, apart from marked cases of skeletal convexity or concavity, the extraction versus non-extraction decision should be based primarily upon current knowledge of long-term stability of orthodontic treatment results.