title: Can commonly used profile planes be used to evaluate changes in lower lip position?
abstract: OBJECTIVE
  To determine the validity of five profile planes commonly used to describe the horizontal changes of the lower lip during orthodontic treatment.
  
  
  METHODS
  Pretreatment and posttreatment cephalograms of 79 patients (12.4 ± 2.8 years of age) were evaluated. Lower lip (labrale inferiorus) changes over time were measured relative to the Rickett's E-line, Steiner's S1-line, Burstone's B-line, Sushner's S2-line, and Holdaway's H-line. As an independent measure of actual horizontal lip changes, the labrale inferiorus was measured relative to a stable reference plane registered on the sella and oriented on the SN-7°.
  
  
  RESULTS
  The lower lip actually moved anteriorly 2.35 ± 3.35 mm during orthodontic treatment; the five profile planes indicated that the lower lip moved to a more retrusive, posterior position. The five profile planes also showed no statistically significant sex differences in terms of the treatment changes that occurred, while the actual lip changes showed that males exhibited significantly greater changes than females. Actual treatment changes showed that the lower lip moved to a more protrusive position with nonextraction than with extraction treatments, changes that were not evident based on the five profile lines. While lip changes based on the five profile planes demonstrated moderately high to high intercorrelations ranging from 0.81 to 0.97, they showed only weak correlations (r < .35) with the actual horizontal changes of the labrale inferiorus.
  
  
  CONCLUSIONS
  While all five planes measured similar aspects of positional change, none of them closely reflected the actual lower lip changes that occurred. These planes should not be used to measure changes in lip position that occur during treatment.
authors.affiliation: Department of Orthodontics, Baylor College of Dentistry, Dallas, Tex 75246, USA. PHBuschang@bcd.tamhsc.edu
authors.forename: Peter H
authors.initials: PH
authors.lastname: Buschang
authors.forename: Kimberly
authors.initials: K
authors.lastname: Fretty
authors.forename: Phillip M
authors.initials: PM
authors.lastname: Campbell
mesh_terms: D000293:Adolescent; D002508:Cephalometry / Q000592:standards*; D002648:Child; D005145:Face / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D008046:Lip / Q000254:growth & development / Q000502:physiology*; D008297:Male; D016910:Orthodontic Brackets; D009971:Orthodontics, Corrective / Q000295:instrumentation / Q000379:methods; D012015:Reference Standards; D012189:Retrospective Studies; D018709:Statistics, Nonparametric; D014081:Tooth Extraction