[Lip angle and the position of the maxillary lateral incisor--post orthodontics retention considerations]

The relations between the soft tissues draping, the dentoskeletal structure and teeth position have been thoroughly investigated. Nevertheless, it is still unclear to point on the primary underlying cause for pathology if exists, is it the frame or the content, the chicken or the egg. Those relations are of an utmost importance in the process of determining the retention procedure and length in post orthodontic treatment patients. This paper discusses the issue which, as far as we know, has never been examined - the upper lip angle, (the angle created by 3 points - the two intersections between the lip cupid arch and the lip philtrum columns and the lip commissural point in either side), as it related to the maxillary lateral incisors position. Long term clinical observations were behind our hypothesis that lips with acute angles go along with palatally positioned maxillary lateral incisors, one or two. The lips angel of both the study group (37 orthodontic patients ages 15.7+/-6.8, with at least one maxillary lateral incisor in palatal position), and the control group (37 orthodontic patients ages 16.5+/-8.7 with no mal-aligned maxillary teeth) were measured and compared. It was found that the lip angle of the control group was 152.256+/-5.52 degrees while for the study group it was 149.23+6.68. This result is with statistical difference (p=0.001). It was further found that the more acute the lip angle; the more the lateral maxillary tooth or teeth are palatally positioned. The results of this study and the clinical observations suggest long term fixed retention of the maxillary incisors, following orthodontic treatment especially in patients with acute lip angle.