title: Third-molar mineralization as a function of available retromolar space.
abstract: OBJECTIVE
  To test in the maxilla and mandible for an association between stage of third-molar (M3) mineralization and space in the jaws for M3 eruption. Mineralization is hypothesized to be delayed not only for impacted M3s but also for M3s with eruption space less than their mesiodistal crown diameter.
  
  
  METHODS
  Retrospective cone beam computed tomography (CBCT) scans of 37 females and 32 males aged 17-24 years, for a total sample of 197 upper and lower M3s, were used to assess the status of M3 eruption and measure the M3 crown diameter (CD) relative to the length of the retromolar space (RS). Stage of M3 mineralization was then compared between impacted and erupting M3s as well as between two conditions of relative eruption space (RS/CD ≥ 1 versus RS/CD < 1) using Mann-Whitney U tests.
  
  
  RESULTS
  Impacted M3s were at significantly earlier (delayed) stages of mineralization compared to erupting M3s. Mineralization was also delayed for M3s with eruption space less than their mesiodistal crown diameter (e.g. RS/CD < 1). A moderate positive correlation between stage of M3 mineralization and space was seen in both jaws, and was stronger in the mandible.
  
  
  CONCLUSIONS
  Our study shows for the first time that stage of M3 mineralization is associated not only with impaction but also with amount of retromolar space, and that these associations are consistent in upper and lower jaws. Present findings underscore that M3 mineralization stage may be a clinically useful predictor of M3 impaction that thus merits further investigation.
authors.affiliation: a College of Medicine, Department of Anatomy and Cell Biology , University of Saskatchewan , Saskatoon , Saskatchewan , Canada.|b College of Dentistry , University of Saskatchewan , Saskatoon , Saskatchewan , Canada.
authors.forename: Denver F
authors.initials: DF
authors.lastname: Marchiori
authors.affiliation: b College of Dentistry , University of Saskatchewan , Saskatoon , Saskatchewan , Canada.
authors.forename: Garnet V
authors.initials: GV
authors.lastname: Packota
authors.affiliation: a College of Medicine, Department of Anatomy and Cell Biology , University of Saskatchewan , Saskatoon , Saskatchewan , Canada.
authors.forename: Julia C
authors.initials: JC
authors.lastname: Boughner
mesh_terms: D000293:Adolescent; D002508:Cephalometry / Q000379:methods; D054893:Cone-Beam Computed Tomography / Q000379:methods; D003724:Dental Arch / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008297:Male; D008334:Mandible / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D008437:Maxilla / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D008964:Molar, Third / Q000000981:diagnostic imaging / Q000502:physiology*; D009805:Odontogenesis / Q000502:physiology; D009811:Odontometry / Q000379:methods; D012189:Retrospective Studies; D014074:Tooth Calcification / Q000502:physiology*; D019228:Tooth Crown / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D014078:Tooth Eruption / Q000502:physiology*; D014095:Tooth, Impacted / Q000000981:diagnostic imaging / Q000473:pathology; D055815:Young Adult
keywords: Impacted teeth; cone-beam computed tomography; maxillofacial development; teeth calcification; tooth eruption