Enamel fluoride uptake from mouthrinse solutions with different NaF concentrations.

OBJECTIVES: The influence on enamel fluoride uptake of reducing the NaF concentration of a mouthrinse solution by half, from 0.05-0.025%, was examined in elementary school children. METHODS: The participatory elementary school had employed school-based fluoride mouthrinse with 0.05% NaF solution since 1983, and in 1993, the NaF content was lowered to 0.025%. Dental examination and enamel biopsy of maxillary central incisors were performed just before the NaF content reduction for children who had received the daily 0.05% NaF mouthrinse for 2-5 years since 6 years of age. During 1993-95, dental examination and enamel biopsy were undertaken for newly enrolled 6-year-old children, and the same subjects were re-examined after 2 years. The same series of examinations were conducted for the control group, which consisted of children belonging to another elementary school without a fluoride program. RESULTS: The enamel fluoride concentration of 8-year-old children who used the 0.025% NaF mouthrinse for 2 years was 1810 +/- 535 ppm, reaching the same order as that in children who continued using the 0.05% NaF mouthrinse (1863 +/- 1358 ppm), and was significantly higher than that of children without fluoride programs (1113 +/- 303 ppm). There was no considerable increase of mean DMFT values due to the NaF content reduction. CONCLUSIONS: It was concluded that a daily 0.025% NaF mouthrinse provides the similar fluoride content for enamel as 0.05% NaF mouthrinse as long as the rinsing frequency is maintained.

Phylogenetic associations of ISAa1 and IS150-like insertion sequences in Actinobacillus actinomycetemcomitans.

The distribution and number of two insertion sequences (ISs), ISAa1 and an IS150-like element, in the genomes of a collection of Actinobacillus actinomycetemcomitans strains previously subjected to population genetic analysis were determined to obtain information about their stability and biological significance. The hybridization patterns revealed that these IS elements are widespread in the genome of A. actinomycetemcomitans strains and that their occurrence agrees with the overall population structure of the species. While the patterns of ISAa1 showed significant evolutionary stability, the IS150-like element showed evidence of intra-genomic variability even within members of the previously identified high-toxicity JP2 clone. Searching of the available genome sequence of strain HK1651 of the JP2 clone (www.genome.ou.edu/act.html) revealed close proximity of the IS elements to housekeeping genes, but no evidence of structural disruption of genes or integrations that may be presumed to influence pathogenic potential.