Caries–Preventive Effect of Topical Amine Fluoride in Children with High and Low Salivary Levels of Mutans Streptococci

The aim of the study was to assess the relationship between the salivary mutans streptococci (SMS) level and the effectiveness of a preventive intervention based on a biannual application of an amine fluoride solution (AmF). A total of 284 schoolchildren aged 6 years were recruited from eleven classes of a primary school in Milan and randomly assigned to an experimental (A) and a control group (B). SMS counts were obtained at baseline and caries incidence data (diseased, missing, filled teeth, DMFT) were recorded every 6 months for 5 years. The participants of the experimental group received application of an AmF 1% F^– solution twice a year on the enamel surfaces of the first permanent molars for 5 years. Control group subjects received application of a placebo solution twice a year on the enamel surfaces of the first molars for the same period. The mean DMFT in the experimental and control groups were 0.56 and 0.22, respectively, at the beginning and 1.14 and 2.06 after 5 years. SMS data allowed children to be classified into low– (0–10⁵ CFU/ml of saliva) and high– (>10⁵ CFU/ml of saliva) SMS subjects. Survival analysis, performed on the first molar data split by SMS group, showed a significantly higher caries reduction in low–SMS experimental group subjects compared to low–SMS control group subjects after 5 years. No significant differences were found between the two high–SMS experimental and control groups. These findings indicate that the preventive effects of the treatment were significantly lower in subjects who had high SMS. It is concluded that the effectiveness of a simple and economical topical fluoride intervention applicable at a community level is significantly influenced by the SMS level of the subjects involved. Simple AmF preventive interventions, applied on low–SMS subjects, can give significant results in terms of caries reduction.