title: Transverse growth of the maxilla and mandible in untreated girls with low, average, and high MP-SN angles: a longitudinal study.
abstract: BACKGROUND
  The purpose of this study was to investigate maxillary and mandibular transverse growth in untreated female subjects with low, average, and high mandibular plane angles longitudinally from ages 6 to 18.
  
  
  METHODS
  Eighty-one untreated white girls with low (< or = 27 degrees , n = 16), average (> 27 degrees to < 37 degrees , n = 41), and high (> or = 37 degrees , n = 24) mandibular plane angles at age 6 were selected from the Bolton-Brush and Burlington Growth Studies. For each subject, longitudinal posteroanterior cephalograms at different ages (from ages 6 to 18) were traced, and the widths of maxilla and mandible were measured. All the measurements were converted by using a magnification factor of 8.5% (the subject-to-film distance was set at 13 cm).
  
  
  RESULTS
  At age 6, the high-angle group had narrower maxillary and mandibular widths than the low-angle group, and this trend continued until age 18. From ages 6 to 14, maxillary width showed a steady and similar rate of increase for all 3 groups (0.90-0.95 mm per year), yet a plateau was reached at age 14 for all groups. Mandibular width increased at a steady rate (about 1.6 mm/year) for all 3 groups until age 14, and a plateau was reached for the high-angle group. For the low- and average-angle groups, mandibular growth continued from ages 14 to 18 but at a slower rate (0.85 mm and 0.39 mm per year, respectively).
  
  
  CONCLUSIONS
  Vertical facial patterns (with low or high mandibular plane angles) might play a strong role in the transverse growth of the maxilla and the mandible.
authors.affiliation: Department of Orthodontics, University of Pennsylvania School of Dental Medicine, Robert Schattner Center, 240 S. 40th Street, Philadelphia, PA 19104, USA.
authors.forename: Dawn M
authors.initials: DM
authors.lastname: Wagner
authors.forename: Chun-Hsi
authors.initials: CH
authors.lastname: Chung
mesh_terms: D000293:Adolescent; D000367:Age Factors; D002508:Cephalometry; D002648:Child; D005145:Face / Q000033:anatomy & histology; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008334:Mandible / Q000254:growth & development*; D008437:Maxilla / Q000254:growth & development*; D012044:Regression Analysis; D014716:Vertical Dimension