The aim of the study was to assess the association between past fluoride exposures from ingested toothpaste and current fluorosis manifestations in 10- 11 year old index subjects. Fluorosis was assessed with the Dean’s Index in 1343 10-11 year old index subjects. Two hundred index subjects who had younger 4-5 year old siblings were sub sampled and fluoride exposures from ingested toothpaste in their younger siblings (proxy subjects) were determined. The values for the fluoride ingested per brushing of the proxy subjects were utilised together with past frequency of toothbrushing of index subjects to extrapolate on the past exposure of index subjects. The mean extrapolated past fluoride exposure from ingestion of toothpaste was highly variable; 671.7 ug ± 739.3 ug (sem= 56.9). It was higher in the subjects with fluorosis (697.3 ug) than in those without fluorosis (646.89 ug) but differences were not of statistical significance. This approach of extrapolation has not been reported elsewhere and need to be validated. The implications of the present methodology to estimate past fluoride exposure is discussed.