EFFECT OF A FLUORIDATED TOOTHPASTE ON LESION DEVELOPMENT IN PLAQUE-FILLED DENTIN GROOVES - AN INTRAORAL STUDY

Fluoride can inhibit caries at plaque-retention sites, but some studie s indicate that fluoride is less effective in fissures than on smooth surfaces. To study the efficacy of fluoridated toothpastes at plaque-r etention sites, an intra-oral model was used with bovine coronal denti ne discs, in which grooves of two different widths were sawn. The disc s were mounted in the partial prostheses of 31 participants divided in to two groups. One group brushed with a non-fluoridated toothpaste and a second with a paste containing 1,000 ppm fluoride as NaF. After 3 m onths, the specimens were retrieved and from each a thin section was t aken for microradiographic analysis. Lesions which developed in the gr ooves resembled natural lesions in terms of the presence of a surface layer and the mineral content profiles. Extensive lesions followed the direction of the dentinal tubules. The mineral loss was quantified ha lf-way into and at the base of the grooves and ranged from 0 to 20,000 vol%x mu m. Analysis of variance showed that the mineral loss was sig nificantly influenced by the treatment and the width of the grooves (p <0.001). In the broad grooves the average mineral loss was 19% smalle r in the fluoride group than in the non-fluoride group, in the narrow grooves this value was 7%. Taking the two treatment groups together, t he average mineral loss was largest half-way into the broad grooves (4 ,921 vol%x mu m) and smallest at the base of the narrow grooves (2,289 vol%x mu m). The results with this new intra-oral model indicate that the dimensions of small grooves in dentine, and thus their accessibil ity, determine not only their susceptibility to caries but also the pr otective effect of a fluoridated toothpaste.