07 September 2023

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Root caries: effect of fluoride toothpastes and bioactive F-glass

Lara Figini

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Root caries is one of the main causes of tooth loss in the aging population. Toothpastes containing fluoride are considered inexpensive anti-caries agents due to their remineralization effect which is attributed to fluoride-enhanced precipitation of calcium phosphate in the form of fluorapatite. Therefore, more than 95% of the population in developed countries use fluoride toothpastes.

High fluoride toothpaste (5000ppm-F) has been reported to block 51% of primary root caries compared to toothpaste containing 1100ppm-F. However, the bioavailability of fluoride after tooth brushing is limited to a short time as the level of fluoride in saliva decreases rapidly due to salivary flow. Calcium fluoride phospho-silicate glass (bioactive F-glass) is a new bioactive component containing low concentration fluoride and has been incorporated into toothpastes to increase the bioavailability of fluoride in the oral cavity for up to 12 hours.

Bioactive F-glasses are amorphous silicate glasses, which degrade in aqueous solutions and are a source of calcium, phosphate and fluoride ions.

Materials and methods

In an in vitro study, published in June 2023 in the Journal of Dentistry, the authors analyzed the effect of different toothpastes containing 5000 ppm fluoride (F), 1450 ppm F or bioactive glass (BG) with 540 ppm-F on carious lesions artificial roots (ARCL).

The crowns of 23 extracted healthy teeth were removed leaving only their roots. Subsequently, each root was divided into four parts. ARCLs were obtained using a demineralizing solution (pH-4.8).

The 15-ARCL samples were left untreated, and the rest of the samples were divided into four groups:

• Group 1, treated with BG with 540 ppm-F
• Group 2, treated with 5000 ppm-F
• Group 3, treated with 1450 ppm-F, and
• Group 4, treated with deionized water.

Samples were demineralized for 6 hours, and then the samples were placed in the remineralization solution (pH-7) for 16 hours. Each sample was brushed with their assigned toothpaste twice daily over the 13-day study cycle.

The fluoride concentration at each time point was measured using F-ISE, while the release of calcium (Ca2+) and phosphorus (P) ions was determined using ICP-OES, KHN, XRD, 19F-MAS-NMR analysis.

Results

KHN showed significant surface changes for each group (p < 0.001). Ca2+ uptake occurred on days 1-2, phosphorus ion loss was high relative to uptake in all groups.

XRD showed the presence of sharp diffraction lines highlighting the formation of apatite for Groups 1-3. 19F-MAS NMR confirmed the presence of fluorapatite in Groups 1-3.

Conclusions

From the data of this study, it can be concluded that all dentifrices are promising in the formation of fluorapatite. BG with 540 ppm-F toothpaste releases more ions (Ca2+ and P) and remineralizes the carious lesions of the artificial roots more than other Groups.

However, the 1450 ppm-F dentifrice showed more fluorinated apatite formation while the 5000 ppm-F dentifrice showed more fluorapatite formation.

Haoran Chen, Robert Hill, Aylin Baysan, "The effect of different concentrations of fluoride in toothpastes with or without bioactive glass on artificial root caries," Journal of Dentistry, Volume 133, 2023, 104499, ISSN 0300-5712, https://doi.org/10.1016/j.jdent.2023.104499.