Transverse molar movements during growth.
The purpose of this study was to evaluate changes in molar crown torque and intermolar arch width from the time of permanent first molar eruption to early adulthood. Molar crown torque and intermolar arch width were measured in 36 untreated subjects with Class I occlusion from the Iowa Facial Growth Study at approximate ages 7.5, 10.3, 12.9, 16.5, and 26.4 years. On average, the mandibular first and second molars uprighted buccally by 5.0 degrees and 7.5 degrees, respectively. Mandibular first and second molar intermolar width increased by 2.2 and 0.78 mm, respectively. On average, maxillary first and second molars uprighted lingually by 3.3 degrees and 5.9 degrees, respectively. Maxillary first and second intermolar width increased by 2.8 and 2.0 mm, respectively. Results of statistical analysis by the Wilcoxon signed rank test indicate that (1) maxillary molars erupt with buccal crown torque and upright with age, whereas mandibular molars erupt with lingual crown torque and upright with age (P <.01), and (2) molar crown torque changes are accompanied by concurrent increases in maxillary and mandibular intermolar width (P <.01).
Marshall
Steve
S
Department of Preventive and Community Dentistry, College of Dentistry, University of Iowa, Iowa City, IA 52242, USA.
Dawson
Deborah
D
Southard
Karin A
KA
Lee
Adam N
AN
Casko
John S
JS
Southard
Thomas E
TE
D000293:Adolescent; D000328:Adult; D002648:Child; D003724:Dental Arch / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D008297:Male; D008445:Maxillofacial Development; D008963:Molar / Q000033:anatomy & histology / Q000254:growth & development*; D009811:Odontometry; D012016:Reference Values; D018709:Statistics, Nonparametric; D019228:Tooth Crown / Q000033:anatomy & histology / Q000254:growth & development*; D014078:Tooth Eruption / Q000502:physiology*; D019415:Torque