title: Patterns of incisor-premolar agenesis combinations: A retrospective study.
abstract: BACKGROUND
  Tooth agenesis is the most common dental anomaly which causes serious problems in humans. Many theories were asserted to explain the main etiologic factor of this anomaly, and genetic factors were considered as primary reasons.
  
  
  OBJECTIVE
  The aim of the present study was to evaluate the relationship between incisor and premolar tooth agenesis and to reveal a considerable data about combinations of incisor-premolar agenesis and their frequency.
  
  
  METHODS
  According to inclusion and exclusion criterion, archived panoramic radiographs of nonsyndromic 6535 patients (4077 females and 2058 males) ranging in age from 7 to 18 years old were retrospectively examined to find the presence of tooth agenesis. Panoramic radiographs showing at least one tooth agenesis were recorded, and the missing tooth or teeth excluding third molars were noted.
  
  
  METHODS
  Combinations of incisor-premolar tooth agenesis were listed, and the most affected teeth groups were noted.
  
  
  METHODS
  Collected data were statistically analyzed using Chi-square test or Fisher exact's Chi-square test.
  
  
  RESULTS
  Three hundred and eight patients (4.7%) who had at least one tooth agenesis and 648 missing permanent tooth, excluding third molars, were detected. Although the sample size of females was bigger than males in all examined patients, tooth agenesis was detected significantly more in males than females (P = 0.021). Thirty-two patients (10.4%) had both incisor and premolar agenesis, and of all patients, twenty patients (6, 5%) were found to have both maxillary lateral incisor and mandibular second premolar agenesis.
  
  
  CONCLUSIONS
  Combinations of tooth agenesis are an issue which has begun to take attention recently. The results of the present study may provide empirical data for further genetic studies.
authors.affiliation: Department of Pedodontics, Faculty of Dentistry, Bulent Ecevit University, Zonguldak, Turkey.
authors.forename: Levent
authors.initials: L
authors.lastname: Demiriz
authors.affiliation: Department of Pedodontics, Faculty of Dentistry, Bulent Ecevit University, Zonguldak, Turkey.
authors.forename: Ebru Hazar
authors.initials: EH
authors.lastname: Bodrumlu
authors.affiliation: Department of Biostatistics, Faculty of Medicine, Bulent Ecevit University, Zonguldak, Turkey.
authors.forename: Furuzan
authors.initials: F
authors.lastname: Kokturk
mesh_terms: D000293:Adolescent; D001641:Bicuspid / Q000002:abnormalities* / Q000000981:diagnostic imaging; D002648:Child; D005260:Female; D006801:Humans; D007180:Incisor / Q000002:abnormalities* / Q000000981:diagnostic imaging; D008297:Male; D015995:Prevalence; D011862:Radiography, Panoramic; D012189:Retrospective Studies; D017678:Sex Distribution; D014071:Tooth Abnormalities / Q000000981:diagnostic imaging / Q000453:epidemiology*; D014421:Turkey / Q000453:epidemiology