Prevalence of Visible Third Molars in the United States Population: How Many Individuals Have Third Molars?

Abstract

To determine the prevalence of third molars in the US population and to report the differences in prevalence of visible third molars in the most recent National Health and Nutrition Examination Survey (NHANES) population of 2011 through 2012 by participant, jaw, and demographics. The number of visible third molars in the NHANES data was assessed in nonclinical settings by trained, calibrated dental hygienists by decade of age beginning in the 20- to 29-year-old cohort through the 70- to 79-year-old cohort. Cross-sectional analyses of third molar data were conducted by the authors from the NHANES databases of 2001 through 2002, 2009 through 2010, and 2011 through 2012 to compare data for similarity of outcomes on third molar prevalence in the US population. Outcomes on third molar prevalence also were assessed from the NHANES of 2011 through 2012 by participant, jaw, and demographics: gender, race or ethnicity (Caucasian, African American, other), and education (less than high school, high school graduate, some college, college graduate). Data on the mean number of third molars from NHANES of 2001 through 2002, 2009 through 2010, and 2011 through 2012 were similar. The number of visible third molars in the NHANES of 2011 through 2012 decreased progressively from a mean of 1.48 in the 20- to 29-year-old cohort to 0.81 in the 60- to 69-year-old cohort, No visible third molars were observed in 47% of the 20- to 29-year-old cohort compared with 53% in the 50- to 59-year-old cohort. Participants who were male, non-Caucasian, and had less than a high school education were more likely to have a visible third molar in all age cohorts. No data were collected by NHANES examiners to determine why third molars were absent. Third molar prevalence did not appear to differ in the US population during the first decade of the 21st century. Numbers of visible third molars, prevalent in young adults, decreased progressively through each successive age cohort. Demographic differences exist for prevalence of third molars in the US population.