Lip positional changes asssociated with upper incisor AP correction

Noticeable clinical changes occur in upper lip position as incisor malalignment is orthodontically corrected. Is there a significantly predictable relationship between change of upper incisor (U1) anterioposterior (AP) position and the associated AP changes of upper lip(UL) and lower lip (LL)? “Objectives:” Determination of any predictable relationship (ratio) of these changes in Caucasian patients was the Objective of this study. “Methods:” Pre- and post-orthodontic lateral cephalograms from de-identified records of 37 (18 male, 19 female) Caucasian private orthodontic practice “non-extraction” patients (mean age= 14 yrs, 5mos) who originally presented CL I minimal crowding or slight CL II malocclusions were traced, analyzed and compared. UL and LL positions were determined by linear measures from E line. Upper incisor (U1) incisal edge position was measured linearly perpendicularly from NP plane and from E plane. “Results:” Statistical analysis showed that with a mean retraction of UI-E of 3.30mm, the UL-E retracted by a mean of 1.7mm and LL-E 1.65mm (p<0.001). For every one mm retraction of U1-NP, UL-E reduced 0.68mm and LL-E 0.65mm (p<0.05). “Conclusion:” From this study one can conclude that in Caucasian patients of this age group, one mm upper incisor retraction will result in approximately 1/2mm reduction in lip procumbency; a ratio of 2:1.