title: Third molars and periodontal pathology in American adolescents and young adults: a prevalence study.
abstract: OBJECTIVE
  To assess the association between visible third molars and the prevalence of periodontal inflammatory disease of non-third molars.
  
  
  METHODS
  Subjects aged 14 to 45 years with 4 asymptomatic third molars were enrolled in an institutional review board-approved study. Subjects were classified based on whether at least 1 third molar was visible or all third molars were not visible. Full-mouth periodontal probing depth (PD) data, with 6 sites per tooth, were obtained as a measure of a subject's periodontal status. At least 1 non-third molar PD of 4 mm or greater was indicative of periodontal inflammatory disease. Outcomes for the respective groups were compared by use of Cochran-Mantel-Haenszel row mean score statistics. The level of significance for differences was set at .05.
  
  
  RESULTS
  The 342 subjects in the visible group were significantly older, with a median age of 26 years (interquartile range, 22.4-32.2 years), as compared with the 69 subjects in the not visible group, with a median age of 21 years (interquartile range, 18.8-24.9 years) (P < .01). The proportion of males and females was not statistically different between groups (P > .05). Most subjects were white. Significantly more subjects with at least a college education were in the visible group than in the not visible group (P < .01). The rate of tobacco use was low and did not differ between groups. Subjects in the visible group were significantly more likely to have at least 1 PD of 4 mm or greater on non-third molars than those in the not visible group: 59% versus 35%. In both groups, first/second molars were more affected than nonmolars when we controlled for differences in age between groups.
  
  
  CONCLUSIONS
  The visible presence of third molars in adolescents and young adults was significantly associated with periodontal inflammatory disease of non-third molars.
authors.affiliation: Department of Oral and Maxillofacial Surgery, School of Dentistry, University of North Carolina, Chapel Hill, NC, USA.
authors.forename: George H
authors.initials: GH
authors.lastname: Blakey
authors.forename: Savannah
authors.initials: S
authors.lastname: Gelesko
authors.forename: Robert D
authors.initials: RD
authors.lastname: Marciani
authors.forename: Richard H
authors.initials: RH
authors.lastname: Haug
authors.forename: Steven
authors.initials: S
authors.lastname: Offenbacher
authors.forename: Ceib
authors.initials: C
authors.lastname: Phillips
authors.forename: Raymond P
authors.initials: RP
authors.lastname: White
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008963:Molar; D008964:Molar, Third; D010514:Periodontal Pocket / Q000209:etiology*; D014481:United States; D055815:Young Adult