title: Mandibular first molar relation to variable lower face skeletal components.
abstract: OBJECTIVE
  To evaluate the position of the mandibular first permanent molar in the mandible relative to several factors.
  
  
  METHODS
  A total of 185 untreated Class I and Class II patients were randomly selected from a sample of 350 patients from a single office. The palatal and mandibular planes were related to Frankfort horizontal to create the interjaw or "B" angle. Age and the mesial contact of the mandibular first molars were used. The landmarks were projected at right angles to the Frankfort horizontal for effective mandibular dimension lengths. Actual-length dimensions were projected at right angles to the mandibular plane. Pearson product moment correlation coefficients were computed to evaluate the effect of age, cranial length, and mandibular contribution to the molar's sagittal position in the mandible. Significance was reported only when P < .05 to determine a 95% confidence level.
  
  
  RESULTS
  Statistically significant positive correlations indicated that the mandibular molar is located more forward with increasing age, longer mandibular body length, and increasing posterior facial height. In contrast, significant negative correlations to the interjaw, mandibular plane, ramal inclination angles, and the linear ramal contribution corresponded to a more posterior position of the molar with increasing angles.
  
  
  CONCLUSIONS
  The mandibular first permanent molar is located more anteriorly with an older patient, a longer mandibular body, greater posterior facial height, and an acute interjaw angle. In contrast, an increase in the forward tip of the ramus places the molar in a more posterior location.
authors.affiliation: Medical University of South Carolina, Pediatric Dentistry and Orthodontics, Charleston, SC 29425, USA. louandria@nuvox.net
authors.forename: Louis Matthew
authors.initials: LM
authors.lastname: Andria
authors.forename: Luis Paulo
authors.initials: LP
authors.lastname: Leite
authors.forename: April M
authors.initials: AM
authors.lastname: Dunlap
authors.forename: Emily C
authors.initials: EC
authors.lastname: Cooper
authors.forename: Lydia Buxbaum
authors.initials: LB
authors.lastname: King
mesh_terms: D000367:Age Factors; D002508:Cephalometry / Q000706:statistics & numerical data*; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D008311:Malocclusion, Angle Class I / Q000473:pathology; D008312:Malocclusion, Angle Class II / Q000473:pathology; D008334:Mandible / Q000033:anatomy & histology*; D008445:Maxillofacial Development; D008963:Molar / Q000033:anatomy & histology*; D009811:Odontometry; D019291:Skull Base / Q000033:anatomy & histology*; D014716:Vertical Dimension