Geographic information system and multilevel analysis: gingival status among 12-year-old schoolchildren in São Paulo, Brazil.

OBJECTIVE To evaluate gingival and calculus status among schoolchildren 12 years of age using a geographic information system and multilevel analysis. METHODS A total of 1 002 schoolchildren were selected from 18 municipal districts by means of cluster sampling, from among 25 public and private schools in Piracicaba, São Paulo, Brazil, in 2005. Examinations were carried out by a single calibrated examiner utilizing the criteria of the World Health Organization, as well as the Community Periodontal Index. Social, economic, and behavioral variables were recorded with the use of a questionnaire and were used in the individual analysis (first level). The variables "percentage of heads of families without income" and "percentage of illiterate heads of families" were used in the contextual analysis (second level). RESULTS A geographic information system was constructed for mapping the distribution of gingival bleeding. The variables were visually distinguished in the maps and demonstrated a tendency toward better gingival health in the central areas of the city, which are recognized as more privileged. On the contextual level, only the "percentage of illiterate heads of families" was significantly associated to gingival bleeding. CONCLUSIONS The study confirms better oral health status among schoolchildren from privileged families, but does not confirm the data regarding "income." The individuals from areas in which the heads of family did not have income were not associated to a higher prevalence of gingival problems. This suggests that these individuals are reasonably protected from the impact of social privation due to the actions of public health care services in the municipality.