title: Congenitally missing mandibular incisors and mandibular symphysis morphology.
abstract: OBJECTIVE
  To explore the association between congenital absence of permanent mandibular incisors and craniofacial and mandibular symphysis morphology in Japanese orthodontic patients.
  
  
  METHODS
  A total of 27 girls with one or two congenitally absent mandibular incisors (group M) were selected and divided into group 1M (16 girls with the absence of one incisor) and group 2M (11 girls with the absence of two incisors). In addition, 20 other Japanese girls without hypodontia and with little or no mandibular incisor crowding were enrolled as a control (group C). Using the lateral cephalogram of each subject, 17 angular, 8 linear, and 3 area measurements were made for evaluation of craniofacial and mandibular symphysis morphology. The cephalometric data thus obtained were statistically analyzed and compared between the groups.
  
  
  RESULTS
  A significantly greater retroclination of the retained mandibular incisors was found in group 1M than in group C. Groups 1M and M showed a significantly greater retroclination of mandibular alveolar bone than group C. Groups 2M and M exhibited a significantly smaller mandibular symphysis area than group C.
  
  
  CONCLUSIONS
  The retroclination of the mandibular incisors and alveolar bone and the reduced mandibular alveolar bone area should be taken into consideration in planning orthodontic treatment on patients with congenitally missing permanent mandibular incisors.
authors.affiliation: Department of Orthodontics, The Nippon Dental University Niigata Hospital, Niigata, Japan. endoto@ngt.ndu.ac.jp
authors.forename: Toshiya
authors.initials: T
authors.lastname: Endo
authors.forename: Rieko
authors.initials: R
authors.lastname: Ozoe
authors.forename: Koji
authors.initials: K
authors.lastname: Kojima
authors.forename: Shohachi
authors.initials: S
authors.lastname: Shimooka
mesh_terms: D000539:Alveolar Process / Q000033:anatomy & histology; D000704:Analysis of Variance; D000848:Anodontia / Q000000981:diagnostic imaging / Q000209:etiology*; D044466:Asian People; D016022:Case-Control Studies; D002508:Cephalometry; D002648:Child; D005260:Female; D006801:Humans; D007180:Incisor / Q000002:abnormalities*; D008334:Mandible / Q000002:abnormalities* / Q000000981:diagnostic imaging; D011859:Radiography