Introduction: To evaluate the impact of mother’s literacy on child dental caries based on a
national oral health survey in Iran and to investigate the possibility of ecological fallacy in
aggregate data analysis. Materials and Methods: Existing data were from second national
oral health survey that was carried out in 2004, which including 8725 6 years old participants.
The association of mother’s literacy with caries occurrence (DMF (Decayed, Missing, Filling)
total score >0) of her child was assessed using individual data by logistic regression model.
Then the association of the percentages of mother’s literacy and the percentages of decayed
teeth in each 30 provinces of Iran was assessed using aggregated data retrieved from the
data of second national oral health survey of Iran and alternatively from census of “Statistical
Center of Iran” using linear regression model. The significance level was set at 0.05 for all
analysis. Results: Individual data analysis showed a statistically significant association
between mother’s literacy and decayed teeth of children (P = 0.02, odds ratio = 0.83). There
were not statistical significant association between mother’s literacy and child dental caries in
aggregate data analysis of oral health survey (P = 0.79, B = 0.03) and census of “Statistical
Center of Statistics” (P = 0.60, B = 0.14). Conclusion: Literate mothers have a preventive
effect on occurring dental caries of children. According to the high percentage of illiterate
parents in Iran, it’s logical to consider suitable methods of oral health education which do not
need reading or writing. Aggregate data analysis and individual data analysis had completely
different results in this study.