The relationship between plaque index scores, fluoride content of plaque, plaque pH, dental caries experience and fluoride concentration in drinking water in a group of primary school children.

The aim of this study was to determine the relationship between fluoride in drinking water, plaque and dental caries experience in a sample of primary school children from a fruit farming (mainly grapes) area. The children who qualified for the study (n = 177) were placed into three groups according to the concentration of fluoride in their drinking water namely, less than 0.4 ppm (group A), between 0.4 and 1.6 ppm (group B) and more than 1.6 ppm (group C). Most children (78.5%) did not have a toothbrush. Plaque scores were significantly lower in groups B and C. A statistically significant inverse correlation was observed between plaque scores and fluoride content of plaque (p < 0.05). Plaque pH did not differ significantly between the groups. The concentration of fluoride in plaque was high and increased with increasing concentration of fluoride in the drinking water. Dental caries experience was relatively low in primary (dmft = 2.15; 2.07; 1.79) (p > 0.05) and permanent teeth (DMFT = 1.22; 1.43; 1.38) (p > 0.05). Paradoxically, there was also no significant inverse correlation between dental caries experience and fluoride concentration in drinking water. However, the significant inverse correlation between fluoride content of plaque and caries experience supports the contention that fluoride can be accumulated in plaque and act as a reservoir which provides prolonged elevated levels of fluoride to produce a cariostatic effect. It is postulated that the high fluoride levels in the plaque reservoir is responsible for the relatively low caries experience, the significant differences in caries experience between the groups and the poor correlation between dental caries experience and fluoride concentration in drinking water.