title: Monozygotic twins are discordant for chronic periodontitis: clinical and bacteriological findings.
abstract: OBJECTIVE
  The aim of this study was to assess, in monozygotic (MZ) and dizygotic (DZ) twin pairs in whom the proband of the twin pair was suffering from moderate to severe chronic periodontitis, the contribution of genetics, periodontal pathogens and lifestyle factors towards the clinical phenotype.
  
  
  METHODS
  For this study, 18 adult twin pairs were selected on the basis of interproximal attachment loss (AL) >or=5 mm in >or=2 non-adjacent teeth in one twin member. The study included 10 MZ and eight DZ twin pairs, in whom the periodontal condition, presence of periodontal pathogens, educational level, smoking behaviour and body mass index (BMI) were evaluated.
  
  
  RESULTS
  Both MZ and DZ twins were discordant regarding AL and alveolar bone loss. Discordance was greater in DZ compared with MZ twins. In MZ twins, the discordance could not be explained by education, smoking, BMI and periodontal pathogens. In DZ twins, 45.6% of the discordance could be explained by more pack-years of the probands.
  
  
  CONCLUSIONS
  The results confirm a possible role of genetic factors in periodontitis. However, the magnitude of the genetic effects on disease severity may have been overestimated previously.
authors.affiliation: Department of Periodontology, Academic Center for Dentistry Amsterdam (ACTA), Amsterdam, The Netherlands.
authors.forename: Gaudy L
authors.initials: GL
authors.lastname: Torres de Heens
authors.forename: Bruno G
authors.initials: BG
authors.lastname: Loos
authors.forename: Ubele
authors.initials: U
authors.lastname: van der Velden
mesh_terms: D000328:Adult; D015992:Body Mass Index; D016022:Case-Control Studies; D055113:Chronic Periodontitis / Q000150:complications / Q000235:genetics* / Q000382:microbiology / Q000473:pathology; D004200:Diseases in Twins; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D008019:Life Style; D008297:Male; D008875:Middle Aged; D017622:Periodontal Attachment Loss / Q000150:complications / Q000235:genetics* / Q000382:microbiology / Q000473:pathology; D012720:Severity of Illness Index; D012907:Smoking; D018709:Statistics, Nonparametric; D014429:Twins, Dizygotic / Q000235:genetics / Q000502:physiology; D014430:Twins, Monozygotic / Q000235:genetics / Q000502:physiology