Cavity Fighting Compounds: Calcium Fluoride and Sodium Fluoride

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Fluoride Compounds

Fluoride is the negatively charged ion of the element fluorine. Sodium fluoride, stannous fluoride and sodium monofluorophosphate are fluoride-containing compounds approved by the FDA for anti-cavity toothpaste. Each is synthesized from hydrofluoric acid, which is derived from the mineral fluorite (calcium fluoride) through a chemical reaction with sulfuric acid. When examining calcium fluoride vs. sodium fluoride and teeth, the effectiveness of the compound is essential because it serves as a delivery vehicle for the active ingredient fluoride. The target of fluoride is the tooth enamel and bacteria within the mouth.

Reducing Bacterial Acid Secretions

Naturally occurring bacteria that reside in the mouth produce a film on the surface of teeth called plaque. It releases acid after the consumption of carbohydrates. The acid can wear down the tooth enamel and leave it susceptible to decay. Fluoride prevents tooth decay by reducing acid secretions from the bacteria. It accomplishes this by targeting the metabolic processes of the bacteria. This reduces the amount of food consumed by the bacteria and thus the amount of waste produced, in the form of acid.

Strengthening Tooth Enamel

Fluoride helps to re-mineralize tooth enamel. The major constituent of tooth enamel is a mineral called hydroxyapatite, which consists of calcium hydroxyphosphate. It is constantly degraded by bacterial acid. The hydroxyl ion is lost, which weakens the tooth enamel. Hydroxyapatite is re-mineralized by the hydroxyl ion in saliva. The presence of fluoride during the re-mineralization process produces another constituent within the enamel called fluorapatite, in which fluoride takes the place of the hydroxyl ion. It is resistant to acid wear and reduces the amount of mineral lost from the tooth enamel.

Differences Between Cavity-Preventing Fluoride Compounds

For fluoride to be effective, it must properly disassociate from its compound. Manufacturers devise chemical combinations that increase the solubility of the fluoride compound. When examining calcium fluoride vs. sodium fluoride and teeth, in terms of efficient delivery of fluoride to the teeth, sodium fluoride is the desired choice because of its solubility. In aqueous solution, sodium fluoride has a solubility of 18,000 ppm, while calcium fluoride only has a solubility of 8 ppm.

Another factor which determines the disassociation of the fluoride is the abrasive that is paired with the fluoride compound in the toothpaste. The abrasive is designed to clean the teeth, without interfering with the absorption of fluoride. Hydrated silica and gel formulations are usually paired with sodium fluoride. Calcium pyrophosphate works well with stannous fluoride.

Reference

https://pubs.acs.org/cen/whatstuff/stuff/7916sci4.html McCoy, Mike. “What’s That Stuff? Fluoride.” Chemical & Engineering News. Vol. 79 No. 16. Apr. 16, 2001.

https://hyperphysics.phy-astr.gsu.edu/hbase/Minerals/fluorapatite.html Nave, C.R. “Fluorapatite.” Hyperphysics. Georgia State University.

https://www.cdphe.state.co.us/pp/oralhealth/fluoridation/fl-145.pdf Reeves, Thomas G. “The Fluoride Ion.” Colorado Department of Public Health & Environment.

https://journals.cambridge.org/action/displayFulltext?type=1&fid=784036&jid=PNS&volumeId=22&issueId=01&aid=784028 Jenkins, G.N. “Theories on the Mode of Action of Fluoride in Reducing Dental Decay.” Proceedings of the Nutrition Society. Vol. 22 pg. 97-104 doi:10.1079/PNS19630020.