In ten states, respondents reported loss of any permanent teeth because of tooth decay or gum disease, excluding teeth lost because of injury or orthodontics.
All teeth (excluding wisdom teeth) were recorded for agenesis of tooth and developmental dental defects using the Developmental Defects of Enamel Index (Fédération Dentaire Internationale 1992).
For each subject the number of retained teeth, excluding wisdom teeth, was counted according to a modified World Health Organization checklist [ 28].
A total of 12.5% of the zone ABR subjects (three males, three females) had missing permanent teeth (excluding wisdom teeth), compared with 4.6% of the zone non-ABR residents (two males, one female).
We also excluded missing teeth variables from this analysis because tooth loss may be a consequence of periodontal disease rather than a confounder.
Dentition status (tooth loss) was assessed by asking "How many of your own teeth do you still have (excluding baby teeth)?" with response categories (1) all (28 32 teeth), (2) missing some teeth, (3) missing many teeth, (4) almost no teeth left and (5) edentulous.
Although in this study maxillary molars were excluded, 34 teeth had two roots, and in some roots of premolars and mandibular molars, two canals could have existed.
Dentition status (tooth loss) was assessed by asking "How many of your own teeth do you still have (excluding baby teeth)?" The variable was categorized as (1) all (28 32 teeth), (2) missing few teeth, (3) missing quite many teeth, (4) almost no teeth left and (5) edentulous.
They used the tooth and the bracket to determine the interbracket distance; later, they excluded both tooth and brackets and just considered the wire for study.
