title: Bilateral hypodontia is more common than unilateral hypodontia in children with Down syndrome: a prospective population-based study.
abstract: BACKGROUND
  In individuals with simple hypodontia, congenital absence of teeth commonly affects just one tooth of a pair, not both. However, patterns of hypodontia have not been fully explored in children with Down syndrome (DS).
  
  
  OBJECTIVE
  We describe the frequency and left-right symmetry of hypodontia in the permanent dentition of 8- to 9-year-old Norwegian children with DS.
  
  
  METHODS
  This population-based cross-sectional study was part of a national prospective study evaluating upper airway function, hearing, dental, and craniofacial characteristics in a cohort of children with DS born in 2002. The cohort consisted of 29 children with DS and represented 57 per cent of all children born with DS in Norway in 2002. Hypodontia was assessed using panoramic and/or dental radiographs. Data were collected prospectively at TAKO-Centre, National Resource Centre for Oral Health in Rare Medical Conditions, Lovisenberg Diakonale Hospital, Oslo, Norway.
  
  
  RESULTS
  Hypodontia of permanent teeth, excluding third molars, was found in 61.5 per cent of the 26 children included in the final sample. Among the 16 children with hypodontia, 75.0 per cent were missing two or more permanent teeth. Two children (7.7 per cent) had severe hypodontia (oligodontia). The teeth most often missing were the maxillary lateral incisors, followed by the mandibular second premolars and maxillary second premolars. Most (68.9 per cent) cases of hypodontia occurred bilaterally.
  
  
  CONCLUSIONS
  The majority of the children with DS were missing one or more permanent teeth. Unlike in the general population, bilateral hypodontia was more common than unilateral hypodontia in this sample of children with DS.
authors.affiliation: *TAKO-Centre, National Resource Centre for Oral Health in Rare Medical Conditions, Lovisenberg Diakonale Hospital, and**Department of Orthodontics, Dental Faculty, University of Oslo, elsmaria@odont.uio.no.
authors.forename: Els-Marie M
authors.initials: EM
authors.lastname: Andersson
authors.affiliation: *TAKO-Centre, National Resource Centre for Oral Health in Rare Medical Conditions, Lovisenberg Diakonale Hospital, and.
authors.forename: Stefan
authors.initials: S
authors.lastname: Axelsson
authors.affiliation: ***Østfold Hospital Trust, Department of Otorhinolaryngology, Head and Neck Surgery.
authors.forename: Marit E
authors.initials: ME
authors.lastname: Austeng
authors.affiliation: ****Sleep Unit, Department of Otorhinolaryngology/Head and Neck Surgery, Lovisenberg Diakonale Hospital.
authors.forename: Britt
authors.initials: B
authors.lastname: Øverland
authors.affiliation: **Department of Orthodontics, Dental Faculty, University of Oslo.
authors.forename: Ingrid E
authors.initials: IE
authors.lastname: Valen
authors.affiliation: **Department of Orthodontics, Dental Faculty, University of Oslo.
authors.forename: Terese A
authors.initials: TA
authors.lastname: Jensen
authors.affiliation: ****Sleep Unit, Department of Otorhinolaryngology/Head and Neck Surgery, Lovisenberg Diakonale Hospital,*****Department of Otorhinolaryngology/Head and Neck Surgery, Oslo University Hospital, Rikshospitalet, Norway.
authors.forename: Harriet
authors.initials: H
authors.lastname: Akre
mesh_terms: D000848:Anodontia / Q000453:epidemiology*; D001641:Bicuspid / Q000002:abnormalities; D002648:Child; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D004314:Down Syndrome / Q000453:epidemiology*; D005260:Female; D006801:Humans; D007180:Incisor / Q000002:abnormalities; D008297:Male; D009664:Norway / Q000453:epidemiology; D011159:Population Surveillance; D015995:Prevalence; D011446:Prospective Studies