Fluoride toothpaste is sometimes recommended because fluoride

Fluoride is recommended in toothpaste primarily because it strengthens and hardens tooth enamel, making it more resistant to decay. Tooth enamel is naturally composed of calcium hydroxyapatite, which can be corroded by acids produced by oral bacteria when the mouth's pH drops below 5.5 [2]. When fluoride is introduced via toothpaste, fluoride ions (F–) replace the hydroxyl groups (OH–) in the hydroxyapatite structure to form fluorapatite. This new mineral phase, fluorapatite, is inherently less soluble and more resistant to acid attacks than the original enamel [1]. Furthermore, fluoride enhances the remineralization process by attracting calcium and phosphate ions back to the enamel surface, effectively repairing early-stage demineralized lesions. While fluoride can inhibit some bacterial metabolic activity, its primary clinical function in toothpaste is the structural reinforcement and hardening of the enamel.

Sources

1. [2] https://pmc.ncbi.nlm.nih.gov/articles/PMC6749882/
2. [1] Science , class X (NCERT 2025 ed.) > Chapter 2: Acids, Bases and Salts > pH change as the cause of tooth decay > p. 27