Estimation of the caries-related risk associated with infant formulas.

PURPOSE Baby bottle tooth decay (BBTD) affects 6% of children under three years of age and is associated with inappropriate bottle use. The objective of this study was to estimate the caries-related risk associated with 26 infant formulas and whole milk. METHODS First, the plaque pH of adult volunteers was monitored before and after an oral rinse with infant formula to determine the minimum pH obtained in response to each formula. Second, Streptococcus sobrinus 6715 was cultured in each infant formula, and the increase in the number of colony forming units was measured. Third, each infant formula was incubated with powdered enamel and the solubility of enamel mineral was calculated in the absence of bacteria. Fourth, each formula was mixed with standardized concentrations of acid to determine the buffering capabilities. Finally, enamel windows were created on extracted permanent molars and exfoliated primary incisor crowns that were then colonized with mutans streptococci and incubated with infant formula. Caries was assessed visually and radiographically for 18 weeks. The length of time required for the development of enamel caries, dentinal caries and pulpal involvement was recorded. RESULTS One-way or two-way ANOVA of these five assays demonstrated that 1. Plaque pH varied in response to oral rinsing with infant formula and most formulas did have the ability to reduce the pH significantly below the pH obtained after rinsing with water 2. Some infant formulas supported significant bacterial growth 3. Enamel mineral was dissolved by incubation with certain infant formula 4. The buffer capacity varied among the infant formulas tested 5. The length of time required for caries to reach dentin or pulp differed for the formulas, with some formulas causing dentinal caries by 3.4 weeks and pulpal involvement by 7.2 weeks.