Dr. James Belcher, December 6, 2025

Fluoride – friend or foe?

Fluoride has been a subject of debate for decades: Is it an essential protection for our teeth – or an underestimated risk? In this article, we take a closer look, debunk myths, and explain how fluoride really works. By the end, you'll know what you can do for your dental health.

Fluorid – Freund oder Feind?

What's behind it?

Fluoride is not all the same. Different salts of this ion exist and have been used in dental care for decades. All of them harden tooth enamel and remineralize teeth after acid attacks, for example, from excessively sweet foods. Many dental care products therefore contain fluoride as a classic active ingredient for protecting teeth (Brambilla, 2001) .

What is being criticized?

Some criticize fluoride: especially in very high concentrations or with incorrect use, it can cause irritation or side effects (Wong et al., 2024). Furthermore, many question whether it makes sense to achieve protection solely through chemical additives—or whether the focus should be on a healthy balance in the oral microbiome. It turns out that while fluoride-containing products are slightly more toxic to bacteria than products without fluoride, foaming agents such as SLS or disinfectants such as triclosan have a significantly greater impact on the microbiome . Unlike fluoride, these can even be irritating to the human mucosa at conventional concentrations (Kasi et al., 2019 & Randall et al., 2015).

Another criticism: Rinsing immediately after brushing with water or mouthwash can reduce the fluoride effect because some of the fluoride is washed away. This makes the protection less effective (Brookes et al., 2025). 


Infobox
Studies show that rinsing immediately after cleaning the fluoride concentration directly on the tooth , reduced by a factor of 4 , thus impairing the remineralization of the enamel , i.e., the  Fluoride protection massively reduced (Duckworth, 1991; Nordström, 2009).

Scientific background

Fluoride acts locally in the mouth: It supports the remineralization of tooth enamel and makes the tooth more resistant to acid attacks by bacteria. It has thus been proven to reduce the risk of caries (Ten Cate et al, 2019 & Walsh et al., 2019). 

However, excessive or improper use — such as frequent use in children — increases the risk of over-supply , which can be problematic (Wong et al., 2024). 

Therefore, new approaches to oral care advocate a combination: fluoride-containing toothpaste to protect tooth enamel and at the same time microbiome-friendly care that maintains the balance of the oral flora — instead of all bacteria to destroy. This also includes refraining from using aggressive foaming agents and disinfectants.

Practical tips for everyday life

  • ✓ Use a fluoride toothpaste — it protects your tooth enamel and prevents cavities.
  • ✓ After brushing your teeth, it's best not to rinse immediately with water: This way the fluoride remains effective for longer .  
  • ✓ If possible, use a toothpaste that also takes oral flora protection into account . 
  • ✓ Use mouthwashes at separate times — not directly after brushing, to avoid washing away the fluoride protection. 
  • ✓ Pay attention to the correct amount and frequency – especially for children – to ensure that fluoride requirements are not exceeded. 

At a glance

ⓘ Fluoride strengthens tooth enamel and protects against cavities. 

ⓘ If used incorrectly, the benefits may diminish or undesirable effects may occur. 

ⓘ The best oral care combines enamel protection with a healthy microbiome.

ⓘ Fluoride offers protection — but balance in the oral microbiome remains crucial. 

Sources

    • Brambilla E. Fluoride – Is It Capable of Fighting Old and New Dental Diseases? An Overview of Existing Fluoride Compounds and Their Clinical Applications. Caries Research . 2001.

    • Brookes Z, Bescos R, Witton R, et al. An Update on Mouthwashes: Advice for Dental Practitioners. British Dental Journal . 2025;239(5):312–315. doi:10.1038/s41415-025-9115-3.

    • Duckworth RM, Knoop DT, Stephen KW. Effect of Mouthrinsing After Toothbrushing With a Fluoride Dentifrice on Human Salivary Fluoride Levels. Caries Research . 1991.

    • Kasi SR, Roffel S, Özcan M, Gibbs S, Feilzer AJ. In Vitro Cytotoxicity (Irritant Potency) of Toothpaste Ingredients. PLOSOne . 2024.

    • Nordström A, Birkhed D. Fluoride Retention in Proximal Plaque and Saliva Using Two NaF Dentifrices Containing 5,000 and 1,450 ppm F With and Without Water Rinsing. Caries Research . 2009.

    • Randall JP, Seow WK, Walsh LJ. Antibacterial Activity of Fluoride Compounds and Herbal Toothpastes on Streptococcus mutans: An In Vitro Study. Australian Dental Journal . 2015.

    • Tadin A, Gavic L, Govic T, et al. In Vivo Evaluation of Fluoride and Sodium Lauryl Sulphate in Toothpaste on Buccal Epithelial Cells Toxicity. Acta Odontologica Scandinavica . 2019.

    • Tavener JA, Davies GM, Davies RM, Ellwood RP. The Prevalence and Severity of Fluorosis in Children Who Received Toothpaste Containing Either 440 or 1,450 ppm F From the Age of 12 Months in Deprived and Less Deprived Communities. Caries Research . 2005.

    • Ten Cate JM, Buzalaf MAR. Fluoride Mode of Action: Once There Was an Observant Dentist… Journal of Dental Research . 2019.

    • Walsh T, Worthington HV, Glenny AM, Marinho VC, Jeroncic A. Fluoride Toothpastes of Different Concentrations for Preventing Dental Caries. The Cochrane Database of Systematic Reviews . 2019.

    • Wong MCM, Zhang R, Luo BW, et al. Topical Fluoride as a Cause of Dental Fluorosis in Children. The Cochrane Database of Systematic Reviews . 2024. 

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