Finn Brudevold

A study of acidulated fluoride solutions—I: In vitro effects on enamel

Abstract A search for acid fluoride solutions which provided maximal fluoride uptake while causing minimal demineralization prompted a detailed study of solutions of sodium fluoride in acid sodium phosphate. Prolonged exposure of enamel to these solutions failed to cause etching. The fluoride was readily available and acquisition by enamel increased with increase in concentration and decrease in pH. There was appreciable penetration of fluoride into intact enamel after a 20 min exposure to a solution of phosphate-fluoride at pH 3. The deposited fluoride is present primarily as fluorapatite. Acid dissolution of powdered enamel was decreased after treatment with acid phosphate, and this effect was enhanced when fluoride was present in solution. These findings and the fact that acid phosphate-fluoride solutions are stable and cause no discoloration of teeth, suggest that they may be suitable for topical application treatments.

Solubility Rate and Natural Fluoride Content of Surface and Subsurface Enamel

THE surface enamel is more resistant to acid than is subsurface enamel, the rate of dissolution of phosphate from the surface being less than that from the subsurface enamel.1-3 With ordinary and polarized light microscopy, as well as with soft x-rays, it has also been shown that it is possible for demineralization of the subsurface enamel to occur without any apparent change in the enamel surface,4 5and when ground sections of teeth were exposed to EDTA the outer portion of enamel was the last to be demineralized.6 The reason for this difference between surface and subsurface enamel has not been established. That fluoride may play a role, at least at the level of 2 ppm in the water supply, is suggested by the work of Jenkins, Armstrong, and Speirs,2 who found that the solubility rate of surface enamel of teeth from areas with 2 ppm fluoride in the water supply was less than that from areas with 0.25 ppm, although there was no difference in the solubility rate of the bulk of the enamel. Since fluoride accumulates in the surface enamel, even in teeth from areas low in fluoride,7 it was considered that fluoride acquisition might generally be responsible for the decreased solubility rate of surface compared to subsurface enamel. Therefore, in the present study an attempt was made to correlate the solubility rate and fluoride concentration of successive layers of enamel from areas with different levels of fluoride in the drinking water.

Caries increments, tooth discoloration, and state of oral hygiene in children given single annual applications of acid phosphate-fluoride and stannous fluoride

Abstract One hundred and ninety-five children who received topical applications of an acidic fluoride and phosphate solution once a year for 2 years had approximately 50 per cent fewer carious surfaces than 197 children who served as a control group at the end of 2 years. Development of carious surfaces was less in children with good oral hygiene than in those with poor oral hygiene, and the caries reducing effect of topical fluoride was greater in the former group. Two hundred and eleven children treated with stannous fluoride had the same caries surface increment as the control group at the end of 1 year. Identifiable enamel staining developed in 60 per cent of the children treated with stannous fluoride.

A microroentgenographic investigation of demineralized enamel, comparing natural and artificial lesions.

Abstract 1. 1. The microroentgenographic appearance of initial carious lesions occurring as white spots has been described. 2. 2. Artificially produced lesions were also investigated by a microroentgenographic technique and confirmed several of the findings on natural lesions. 3. 3. Saliva-glucose incubation for periods of eight to thirteen days at 37° C. confirmed the resistance of the surface layer and the greater solubility of the subsurface enamel. 4. 4. Acid-etched areas produced by exposure of sound enamel to 1 M lactate buffer at a pH of 3.7 to 5.1 simulated a later stage of natural demineralization. The palisade structure observed implied an inward invasion of acid affecting the interprismatic material more than the prisms. The “stepped” character of the floor of these areas emphasized the different solubility of the incremental layer.