Experimental intra-oral caries models in fluoride research.

The use of experimental intra-oral caries models has increased in fluoride research. This paper focuses on the pre-clinical intra-oral models, the in situ and in vivo models, the various types, their benefits and disadvantages. Both preparation and sterilization of the hard tissue substrates can affect the substrates and therefore the results. Care needs to be taken that dentine samples are not exposed to drying and consequently shrinking during preparation and evaluation. Sterilization by gamma-radiation is at present the least tissue-damaging method. The most realistic experimental model is the in vivo model, followed by the in situ model using specimens with natural surfaces. The most accurate and direct evaluation technique for demineralization and remineralization studies is quantitative transversal microradiography, whereas confocal laser scanning microscopy (CLSM) is the most sensitive qualitative evaluation technique. Other evaluation techniques discussed are microhardness testing and the iodine permeability test. In light of the present skewed caries situation in western countries we suggest that fluoride research focuses on experimental caries models that can mimic severe cariogenic challenge. Testing of fluoride combinations and dosages that can prevent lesion development rather than promote remineralization would then be a practical consequence.

Analytical and ultrastructural studies of pellicle on primary teeth.

The pellicle on permanent enamel has been thoroughly studied. The aims of this study were to compare the chemical composition, rate of formation, and ultrastructural appearance of pellicle formed on deciduous enamel in children with those on permanent teeth. This was done by amino acid analyses, Auger analyses, and transmission electron microscopy. The amino acid composition of 2-h pellicle on deciduous and permanent enamel had an overall similar pattern, but the contents of serine, glycine, and tyrosine were statistically significantly different. An initially slower pellicle formation and a thinner 2-h pellicle without a globular structured second layer was observed on deciduous enamel. The results indicated therefore distinct differences in chemical composition, rate of formation, and ultrastructural appearance between pellicle on primary teeth and that on permanent teeth.

Caries development in fluoridated and non-fluoridated deciduous and permanent enamel in situ examined by microradiography and confocal laser scanning microscopy.

The aim of the study was to compare initial caries development in fluoridated and non-fluoridated deciduous and permanent enamel in situ. Enamel slabs were mounted in removable appliances and worn for 4 wks. Significantly larger lesions developed in deciduous than in permanent enamel when no topical fluorides were used. Fluoride mouthrinsing partly prevented lesion development in deciduous and completely in permanent enamel. Initial enamel caries not detected by microradiography can be visualized by CLSM (confocal laser scanning microscopy).

Quantitative determination of type A and type B carbonate in human deciduous and permanent enamel by means of Fourier transform infrared spectrometry.

Caries progression has been shown to be faster in the deciduous than in the permanent dentition. Several factors influence caries progression. Among these are variations in the chemical composition of the two enamel types. The carbonate ion is known to occupy two different positions in the hydroxyapatite structure of the enamel, the hydroxide position (A) and the phosphate position (B). Carbonate may be of different chemical importance in the two lattice positions. In the present study, a quantitative determination of the carbonate in the two different positions (type A and type B) in deciduous and permanent enamel was performed by FTIR spectrometry. Calibration curves, made with synthesized hydroxyapatites with carbonates in either position, were used to determine the quantity of type A and type B carbonates in both enamel types. The deciduous enamel contained significantly more type A carbonate than permanent enamel. The total carbonate content (sum of type A and type B carbonates) was also significantly higher in deciduous than in permanent enamel. TG analysis of enamel samples confirmed the quantitative carbonate determinations by FTIR spectrometry. The difference in carbonate content between deciduous and permanent enamel may be one of several factors contributing to faster caries progression in deciduous teeth.

A comparison of the anticaries effect on the primary dentition of two dentifrices containing 250 ppm and 1450 ppm fluoride.

The purpose of the study was to compare the anticaries effects of two dentifrices containing sodium fluoride with fluoride concentrations of 250 ppm and 1450 ppm on the primary dentition of kindergarten children. A total of 319 children participated in the study (155 in the low-fluoride and 164 in the high-fluoride group) and brushed their teeth daily under supervision in their kindergartens. The children were examined by one dentist trained according to the procedures of O'Mullane et al., and carious lesions were recorded at the cavitation level according to the WHO criteria. At the final examination after 22 months, the groups comprised 83 (low-fluoride group) and 89 (high-fluoride group) children. The differences in mean dmfs and dmft increments between the two groups were not statistically significant. In both groups about 57% of the children remained caries free. Excluding these children from the analyses, the mean dmfs increment was significantly lower in the high-fluoride group, but not the mean dmft increment. The mean dmfs increment excluding occlusal surfaces was significantly lower in the high-fluoride group.

Caries prevalence of kindergarten children in Salzgitter and Oslo.

In a comparable epidemiological study of kindergarten children, 455 4- and 5-year-olds in Salzgitter (FRG) and 171 4- and 5-year-olds in Oslo (Norway) were examined. Caries was scored at the cavitation level according to WHO criteria. The percentage of caries-free children was higher and the dmfs scores were lower in Oslo than in Salzgitter. It is postulated that this was the result of different levels of fluoride exposure, nutritional habits and dental treatment provision.