Incisor crowding in untreated persons 15-50 years of age: United States, 1988-1994.
The purpose of this study was to (1) describe the prevalence of mandibular incisor irregularity (II) among untreated adults in the United States and (2) evaluate the factors explaining individual differences in II. Data were derived for a random sample of 9044 individuals (49% male and 51% female; 35% Mexican American, 34% black, and 31% white) between 15 and 50 years of age collected as part of the Third National Health and Nutrition Examination Survey. Although the differences were small (0.5 mm), males had significantly greater II than did females; blacks showed less II than did whites (0.9 mm) and Mexican Americans (1.1 mm). Family income was negatively related with II. Incisor irregularity increased in a curvilinear fashion with age, with the greatest increases occurring during early adulthood. Although the number of premolars and molars (first and second) were positively related with II, the presence of third molars had a negative effect on II. Multivariate Poisson regression analyses showed that the ethnicity, the number of first and second molars, sex, and age combined to explain differences in II. Odds ratios were relatively low, indicating that these factors explained relatively small amounts of between-subject variation. We conclude that (1) approximately 50% of individuals in the United States who were 15-50 years of age have little or no II, 23% have moderate II, and 17% have severe irregularity, (2) erupted third molars are not associated with increased crowding, (3) crowding increases most during early adulthood, and (4) although individual differences in crowding are multifactorial, the primary determinants remain unidentified.
Department of Orthodontics, Baylor College of Dentistry, The Texas A&M University System Health Science Center, 3302 Gaston Avenue, Dallas, Tex 75246, USA. phbuschang@tambcd.edu
Peter H
PH
Buschang
Jay D
JD
Shulman
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D001641:Bicuspid / Q000473:pathology; D044383:Black People / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D007180:Incisor / Q000473:pathology*; D007182:Income; D008297:Male; D008310:Malocclusion / Q000453:epidemiology* / Q000208:ethnology; D008334:Mandible; D017058:Mexican Americans / Q000706:statistics & numerical data; D008875:Middle Aged; D008963:Molar / Q000473:pathology; D008964:Molar, Third / Q000473:pathology; D015999:Multivariate Analysis; D020380:Needs Assessment / Q000706:statistics & numerical data; D016017:Odds Ratio; D015995:Prevalence; D012044:Regression Analysis; D012737:Sex Factors; D014481:United States / Q000453:epidemiology; D044465:White People / Q000706:statistics & numerical data; D001741:Black or African American