Fluorine levels in in vitro remineralized enamel after treatment with 1000 ppm F as NaF, MFP or mixed solutions.

By means of secondary ion mass spectrometry (SIMS) an investigation has been made of the F uptake and the transport of fluorine-carrying ions in artificially carious human enamel after in vitro remineralization. The fluoridation was effected from solutions of pure Na2FPO3 (MFP), pure NaF, or mixtures of MFP and NaF, always with a total F content of 1000 atom-ppm. The recorded in depth profiles of F concentration show that, after 14 days of remineralization, 1) neither the acquired F levels nor the F distributions are greatly dependent on whether fluoridation is from NaF, MFP or mixtures, 2) the F distribution shape is not strongly influenced by a 3-month storage followed by remineralization, 3) the penetration of F beyond the lesion is generally deeper from NaF than from MFP, and 4) the effect of long storage on penetration depth is mainly noticeable for MFP-treated specimens.

Quantified marginal leakage of composites in vitro.

In this in vitro study the marginal leakage of three composite systems--Sevriton, Consize and Isocap--has been quantified as a function of time. The method used (v.d. Veen et al., 1984) consists of the determination of the amount of nitrogen gas passing through restoration margins at 2 atm. The results show that the marginal leakage of all composites decreased strongly with time and became negligible after about 1 month. If we rank the three systems investigated according to their marginal leakage we have Consize greater than Isocap greater than Sevriton. The data suggest that water uptake and subsequent expansion of the polymers account for the leakage decrease.

An in vivo investigation of the fluoride uptake in partially demineralized human enamel from several different dentifrices.

In this study, the total fluoride uptake in partially demineralized enamel from in situ brushing with six dentifrice systems was investigated in vivo among 22 panelists. Five dentifrices with different fluoride systems were compared with a placebo control. Two demineralized enamel discs were placed in proximal positions on specially fabricated dentures worn by each participant. Each treatment involved use of the placebo dentifrice for one week, followed by two weeks of twice-daily use of the test dentifrice. The F- contents of the dentifrices were: A = 1000 ppm F as Na2PO3F + 450 ppm F as NaF; B = 1100 ppm F as NaF; C = 1000 ppm F as Na2PO3F; D = 1000 ppm F as SnF2; E = 1500 ppm F as Na2PO3F; and P = 0 ppm F (placebo). The F- uptakes from A, C, D, and E were not significantly different from each other but were all significantly higher than the placebo. Statistical analysis showed a significantly higher F- level from the NaF-based paste B than that from all other systems. No differences existed between mesial-distal specimens; there was no correlation between F- uptake and age. Significant uptake differences were found between panelists with full and partial prostheses.

Microharness and lesion depth studies of artificial caries lesions: a comparison of gelatin and HEC based systems.

Microhardness measurements with the indenter load perpendicular to the artificial carious enamel surfaces can be employed to investigate lesion depth in de- and remineralization of fluoridation studies in vitro or in vivo. In this study, microhardness and lesion depth studies were made on bovine enamel subjected to demineralizing solutions on a gelatin base at pH = 4.5 and 37 degrees C. The parameters studied were load, demineralization period and dialysis of the gelatin. All experimental data are compared with lesions formed in acidified 6% HEC solutions under identical conditions. The results show that lesion formation and mechanical properties of artificially carious enamel are comparable for nonchared HEC and charged gelatin based systems. Because of the higher sensitivity, lesions formed in HEC are to be preferred for lesion depth determinations by means of microhardness indentations. Both gelatin - and HEC based systems show a lesion depth proprotional to the square root of the demineralization period. If gelatin or HEC is dialyzed first, and subsequently used in the demineralizing buffers, the results show that no subsurface lesions are formed but "acid-softening" of the enamel takes place.

SnF2 treatment of enamel, hydroxyapatite or brushite at 37 degrees C and 50 degrees C: an infra-red investigation.

The effect of 4% SnF2 on brushite, hydroxyapatite and powdered bovine enamel applied for short, 15 or 30 minute, periods was investigated using infra-red spectroscopy. It was found that brushite was converted into a fluoridated hydroxyapatite, a reaction which was both time and temperature dependent. The reactions of hydroxyapatite and powdered enamel with SnF2 were similar. There was a drop in the OH- peak intesities. X-ray diffraction analysis of these samples showed that F- ions occupied mainly OH positions in the hydroxyapatite lattice structure. In all reactions an increase in temperature from 37 degrees C to 50 degrees C increased the reaction speed by at least a factor 2. The most probable result of in vivi SnF2 application on sound enamel is the formation of a fluoridated hydroxyapatite together wity stannous complexes and amorphous CaF2. In demineralized areas some of the brushite is converted into a fluoridated hydroxyapatite as is some of the remaining hydroxyapatite. In the more protected area of an enamel lesion these reactions may well continue for some time after the topical fluoride application; Sn2F3PO4 may also therefore be formed.