The reliability of interview data for age at which infants' toothcleaning begins

A number of studies have reported on the age at which toothbrushing started and drawn important conclusions. Such studies often relied on parental recall of a particular event that occurred some years previously, assuming the quality of retrospectively reported data. The present study aimed to investigate consistency of reporting the age at which toothcleaning began. Mothers from two different cultural backgrounds, 100 Caucasian and 150 Asian living in a deprived inner city area, were interviewed in their homes on two separate occasions, when the sample child was 6-24 months old and again at 3-4 years. Of the 39 Caucasian and 31 Asian mothers who specified an age at which toothbrushing commenced at both interviews, complete agreement occurred among 4 (10%) Caucasian and 2 (6%) Asian mothers, with a variation of +/- 2 months among 12 (31%) and 5 (16%) respectively. Intraclass correlation coefficients were -0.01 for Caucasian and -0.46 for Asian mothers. Kappa values were 0 and -0.09 respectively. Of the 139 mothers who stated that their children's teeth were not cleaned at the time of the first interview, 17 claimed an earlier age than this at the second interview. It was concluded that there was little agreement between the two interviews, although the extent of the variation differed between the two cultural groups. Although these findings represent relatively deprived population groups, caution is recommended in unquestioningly accepting the accuracy of retrospective reporting of oral hygiene practices in dental surveys until evidence of better reliability is available.