Relative effects of pre- and post-eruption water fluoride on caries experience by surface type of permanent first molars

Abstract

Objectives: To determine the relative pre- and post-eruption exposure effects of fluoridated water on the caries experience of different surface types of first permanent molars. Methods: Parental questionnaires covering residential history of participants were linked to the oral examinations of 6–15-year-old Australian children conducted in 1992 by the School Dental Services of South Australia and Queensland. Percentage of lifetime exposed to optimally fluoridated water pre- (PRE) and post-eruption (POST) was calculated with respect to tooth eruption age. Combined pre- and post-eruption categories were created to test PRE against POST exposure: PRE and POST = 0, PRE < POST, PRE = POST and in the range 0–90% of lifetime exposure, PRE > POST and, PRE and POST ≥ 90% lifetime exposure. These categories were used as indicator variables in linear regression models with PRE and POST = 0 as reference in an analysis of first permanent molar DMFS scores overall and by surface type. Results: Participation rates were 69.7% in South Australia (n = 9690) and 55.6% in Queensland (n = 10 195). Compared with the reference, the categories PRE > POST (b = -0.033), PRE = POST (b = -0.028) in the range 0–90% and, PRE and POST ≥ 90% (b = -0.055) showed significantly lower caries overall (P < 0.01), with a similar pattern for pit and fissure surface caries (b = -0.035, -0.031 and -0.052, respectively). Only a high PRE and POST exposure decreased caries levels significantly in the approximal (b = -0.038; P < 0.01) and free smooth surfaces (b = -0.023; P = 0.03). Conclusions: Pre-eruption exposure was important for a caries preventive effect on first permanent molars in children 6–15 years old since post-eruption exposure alone could not lower caries levels significantly. For pit and fissure surfaces, a high pre-eruption exposure could decrease caries levels significantly. However, for other surface types, only a high pre- and post-eruption exposure produced a caries preventive effect.