Fluoride retention in clean and plaque‐covered demineralized enamel in vivo after application of monofluorophosphate

Abstract

– The retention of fluoride in clean and plaquc‐covcred demineralized enamel in vivo was measured 1 wk after a single application of a MFP solution with low or high content of free fluoride. Demineralization of the enamel was induced in vivo during a 4‐wk period prior to application of fluoride by applying orthodontic bands on a pair of premolars scheduled for extraction of orthodontic reasons. The band from one tooth of each pair was then removed and the tooth cleaned (clean enamel lesion). The band on the contralateral tooth (plaque‐covered enamel lesion) was left in place. The MFP solutions were applied and the teeth extracted after one more week. The chemical form of fluorine in the lesions was analyzed by conventional acid etching of the enamel combined with KOH dissolution and by a nondestructive surface analysis using ESCA to detect intact monofluorophosphate ions. The ESCA measurements showed that MFP was only present in the clean enamel lesions, indicating complete hydrolysis by dental plaque. Alkali soluble fluoride could be extracted from both plaque‐covered and clean enamel lesions. Conflicting results regarding the amount of fluoride uptake in the lesions were obtained with the acid etching and the ESCA technique. It was thus not clearly established whether plaque enhanced fluoride uptake in carious lesions after MFP application.

Reactivity of Fluoride Dentifrices with Artificial Caries

“…In particular, the por osity of the lesions could have been an important fac tor, since the lesions used by Mellberg and Mallon [1984a] were probably more porous than the lesions used in this study. In any case, it is difficult to extra polate the in vivo efficacy of monofluorophosphate from in vitro studies, since plaque hydrolysis plays such an important role in the anticaries activity of this ion [Rolla, 1983: Ogaard et al, 1985. The results of the present study would, however, suggest that cleav age of covalently bound fluoride is a prerequisite to significant MFP remineralization efficacy.…”

“…Unfortu nately, there is little data available as yet on the fluo ride distribution in completely remineralized inci pient lesions. One way to obtain information on this phenomena would be to examine the pattern and spe cificity of fluoride topical efficacy in caries progres sion studies (such as the in vivo orthodontic banding methods [Ogaard et al, 1985;O'Reilly and Featherstone, 1985] or in vitro pH cycling models [Featherstone et al, 1986a;ten Cate and Duijsters, 1982]) where the effect of fluoride on developing le sions can be measured from the outset to more ad vanced stages.…”

Enhanced Uptake of Monofluorophosphate by Hydroxyapatite (Short Communication)

“…It would be difficult to explain the dif ferential reactivity of MFP in the presence of group IIA metal ions based on the limited data presented here. The interaction of MFP with HAp probably in volves (1) adsorption onto HAp, (2) diffusion into HAp [Jongebloed et a!., 1975;Mellberg, 1980;Borggreven et al, 1981;de Rooij et al, 1981;Ogaard et al, 1985], and (3) reaction [Ericsson, 1963] at the HAp surface. In addition, MFP uptake onto HAp in the presence of the group IIA metal ions may involve other interactions between MFP, metal ion, and HAp.…”