Investigation 006
The Fluoride Decision
A quarter of a tooth, and everything it was traded for
Environment & exposure
Nano-hydroxyapatite
The fluoride-free alternative is the mineral your enamel is already made of — which is both the case for it and the reason to ask what a nanoparticle of it does elsewhere.
What we are reading
Gathered for the investigation and not yet written up. Each note says what the paper does and does not show.
- Epple M. Review of potential health risks associated with nanoscopic calcium phosphate.10.1016/j.actbio.2018.07.036 · PMID 30031162
The safety review the whole nano-hydroxyapatite question turns on, and it does not say what either camp wants. Findings: no inherent toxicity; particles taken into the cell are digested in the lysosome and raise intracellular calcium, which cells clear within hours unless the dose is very high; observed cytotoxicity in culture is mostly agglomeration and sedimentation producing a huge LOCAL dose. Crucially for toothpaste: 'there is NO RISK from an oral uptake of calcium phosphate nanoparticles due to their RAPID DISSOLUTION IN THE STOMACH' — stomach acid takes the nanoparticle apart before it can be a nanoparticle. Dermal and mucosal risk very low. The one real exposure route is INHALATION, which is an aerosol and occupational question, not a brushing question. He also names the origin of the scare: a 2016 EU SCCS statement about non-spherical nano-hydroxyapatite in cosmetics, and a 2016 US argument about nano-calcium-phosphate in baby food.
- Cocco F, Salerno C, Wierichs RJ, Wolf TG, Arghittu A, Cagetti MG, Campus G. Hydroxyapatite-Fluoride Toothpastes on Caries Activity: A Triple-Blind Randomized Clinical Trial.10.1016/j.identj.2024.09.037 · PMID 39971658
The largest clinical trial in this space: 610 children aged 4-7, 518 completing, 24 months, triple-blind. Hydroxyapatite-plus-fluoride pastes beat conventional monofluorophosphate pastes on enamel lesions (p<0.01); of 78 active lesions at baseline in the hydroxyapatite arm, 58 were inactive at two years. NOTE WHAT IT IS AND IS NOT: both arms contained fluoride. This trial tests hydroxyapatite as an ADDITION, not as a replacement — which is the question most people asking about it actually want answered.
- Amaechi BT, Alshareif DO, Azees PAA, Shehata MA, Lima PP, Abdollahi A, Kalkhorani PS, Evans V, Bagheri A, Okoye LO. Anti-caries evaluation of a nano-hydroxyapatite dental lotion for use after toothbrushing: An in situ study.10.1016/j.jdent.2021.103863 · PMID 34743963
Randomised, double-blind, crossover, 30 adults wearing intra-oral appliances with real human enamel blocks. 5% nano-hydroxyapatite toothpaste remineralised early lesions and completely prevented demineralisation of sound enamel; adding a 5% lotion afterwards raised remineralisation from 37.7% to 58.4%. Real mechanism, real measurement — and an in-situ appliance study on 64 enamel blocks, which is a long way from a caries outcome in a population.
- Butera A, Gallo S, Pascadopoli M, Montasser MA, Abd El Latief MH, Modica GG, Scribante A. Home Oral Care with Biomimetic Hydroxyapatite vs. Conventional Fluoridated Toothpaste for the Remineralization and Desensitizing of White Spot Lesions.10.3390/ijerph19148676 · PMID 35886524
40 patients, three months, hydroxyapatite against 1450 ppm fluoride. Hydroxyapatite beat fluoride on sensitivity and pain; erosive wear scores did not move in either arm. Forty patients and one outcome that is not caries — this is a signal, not a verdict, and should be labelled that way on air.
Connected on the map
Also in Environment & exposure