The most effective fluoride formulation for preventing root surface caries is Stannous fluoride (SnF₂).

- Root surface caries occurs primarily in the elderly and individuals with gingival recession, exposing the root dentin which is more susceptible to demineralization.
- Among various fluoride preparations, stannous fluoride (SnF₂) has been shown to possess unique properties that enhance its effectiveness in this context.

- Antimicrobial Action: Stannous fluoride exhibits potent antimicrobial effects against cariogenic bacteria, reducing plaque formation and bacterial acid production.

- Dentin Tubule Occlusion: It promotes the occlusion of dentinal tubules, which decreases sensitivity and protects root surfaces.

- Increased Fluoride Uptake: Stannous fluoride results in a higher uptake of fluoride ions in the root dentin compared to sodium or amine fluoride.

- Enhanced Remineralization: It facilitates remineralization of demineralized root surfaces, thus preventing progression of root caries.

While sodium fluoride (NaF) and amine fluoride are effective in general caries prevention, their efficacy on root surfaces is less pronounced due to limited antimicrobial properties. Silver diamine fluoride is primarily used for arresting active caries lesions, rather than broad prevention.

In summary, the multifactorial benefits of stannous fluoride – antimicrobial, tubule occlusion, and remineralization enhancement – make it the superior choice for preventing root surface caries.

Reference: Sullivan, J. L., *Contemporary Oral Chemistry*, Volume 2, Chapter 7, Pages 145-150