title: The timing of mandibular tooth formation in two African groups.
abstract: BACKGROUND
  Ethnic differences in the timing of human tooth development are unclear.
  
  
  OBJECTIVE
  To describe similarities and differences in the timing of tooth formation in two groups of Sudanese children and young adults.
  
  
  METHODS
  The sample consisted of healthy individuals from Khartoum, Sudan, aged 2-23 years. The Northern group was of Arab origin (848 males, 802 females) and the Western group was of African origin (846 males, 402 females). Each mandibular left permanent tooth from first incisor to third molar was assessed from dental radiographs into one of 15 development stages. Mean ages at entry for 306 tooth stages were calculated using probit regression in males/females in each group and compared using a t-test.
  
  
  RESULTS
  Mean ages were not significantly different in most tooth stage comparisons between ethnic groups for both males (61/75) and females (56/76), despite a tendency of earlier mean ages in the Western group. Mean ages for most tooth stage comparisons between males and females (137/155) were not significantly different within ethnic groups suggesting low sexual dimorphism.
  
  
  CONCLUSIONS
  The mean ages of most mandibular tooth formation stages were generally not significantly different between ethnic groups or between males and females in this study.
authors.affiliation: a Queen Mary University of London, Institute of Dentistry , Bart's and The London School of Medicine and Dentistry , London , UK.|b Khartoum Centre for Research and Medical Training , Khartoum , Sudan.|c El Razi Dental School , Khartoum , Sudan.
authors.forename: Fadil
authors.initials: F
authors.lastname: Elamin
authors.affiliation: d Dental School, University of Dundee , Dundee , UK.
authors.forename: Mark P
authors.initials: MP
authors.lastname: Hector
authors.affiliation: a Queen Mary University of London, Institute of Dentistry , Bart's and The London School of Medicine and Dentistry , London , UK.
authors.forename: Helen M
authors.initials: HM
authors.lastname: Liversidge
mesh_terms: D000293:Adolescent; D000367:Age Factors; D018912:Arabs; D044383:Black People; D002648:Child; D002675:Child, Preschool; D019229:Dentition, Permanent; D005260:Female; D006801:Humans; D008297:Male; D011861:Radiography, Dental; D011862:Radiography, Panoramic; D012737:Sex Factors; D013397:Sudan; D014070:Tooth / Q000000981:diagnostic imaging; D014078:Tooth Eruption; D055815:Young Adult
keywords: Ethnic origin; group differences; individual variation; sexual dimorphism; tooth formation