Search for:

It seems there is some confusion about fluoride. A friend recently rejoiced to me, “I found a great charcoal toothpaste, it’s even fluoride free!”. I then went on to explain to them that fluoride is not one of these chemicals to avoid when choosing oral products. It is quite the opposite.

Additionally, it is a very controversial topic. Many having strong feelings for and against systemic fluoride. Here, we will break down the benefits and risks of fluoride.

What is fluoride?

Fluoride is a natural mineral which helps to prevent tooth decay. It is added to toothpaste and mouthwash to combat caries.

Systemic vs topical fluoride

Fluoride can be used systemically or topically.

Systemic fluoride is ingested, for example via drinking water. This means it is helping remineralise and strengthen the existing teeth. Remineralisation occurs by the fluoride slowing down bacterial metabolism. Due to the fluoride being incorporated into the body, it will also be present in saliva, so can act topically too.

Topical fluoride is fluoride which has been added to toothpaste and mouthwash. The optimal and most effective fluoride content in toothpaste is approximately 1,350-1,500 ppm. Mouthwash usually contains lower concentrations of fluoride than toothpaste. Using mouthwash straight after brushing teeth can actually wash away the fluoride. Hence, this is why it is advised not to brush and rinse at the same time.


Sources of fluoride include:

  • Tea
  • Water
  • Chicken
  • Rice
  • Fish
  • Fluoride supplements
  • Toothpaste
  • Mouth-rinse
  • Gels
  • Varnishes
  • Some floss brands

What does fluoride do?

During childhood, systemic fluoride can help strengthen developing teeth by replacing the top tooth surface with a stronger alternative. The outer layer of the tooth, composed of hydroxyapatite, can be replaced with fluorapatite. This changes the structure of the teeth, allowing them to be much more resistant to decay. Topical fluoride kills decay-causing bacteria, with levels above 20ppm being lethal to the S.mutans strain.

Fluoride is toxic to bacteria as it inhibits enzymes required for their metabolism to function.

Fluoride in Water

In England, 40,000 children and young people are admitted to hospital each year to have their teeth removed due to decay. It has been found that those with less severe tooth decay are drinking water in areas with more concentrated fluoridated water.

In Manchester, UK, there is no added fluoride in drinking water. In Birmingham, UK, there is fluoridation in their water. According to the ‘Community Practitioner’, Manchester children are 23 times more likely to be admitted to hospital for tooth extraction than those in Birmingham.

Am I drinking fluoridated water?

Countries that fluoridate their water include:

  • United States
  • Australia
  • Singapore
  • Brunei
  • Chile
  • Canada
  • Israel
  • New Zealand
  • United Kingdom
  • Hong Kong
  • Malaysia

Different counties in the UK have differing water fluoridation levels. This is also the case for other areas such as the United States.


There is some controversy on whether it is ethical to add fluoride to drinking water. Some people feel like this is against their free will, and others believe it is imperative in order to maintain cavity-free. Some people would like to control how much fluoride they are consuming, for example if they are pregnant it may cause adverse effects.

Benefits of Fluoride

Fluoride is beneficial as it:

  • strengthens teeth
  • reverses early signs of cavities
  • saves money on dental treatments due to reduced possibility of cavities
  • is natural
  • is effective

You are more likely to benefit from systemic fluoride than others if you:

  • snack frequently
  • have poor oral hygiene
  • do not have regular dental checkups
  • have a diet high in sugars and carbohydrates, or
  • have a history of tooth decay

That being said, everyone will reap the benefits from regularly using toothpaste that contains fluoride (topical fluoride).

Risks of Fluoride

Fluoride accumulates in the body, as only 50% of it is excreted.

Neurological problems

As fluoride is swallowed, it travels through the bloodstream and enters vital organs such as the brain. Studies have shown that fluoride can have adverse effects on neurotransmitters like increased serotonin and histamine. It has also been found that exposure to higher levels of fluoride before birth are linked to a lower IQ. High fluoride is also linked with ADHD.

Immune response

High fluoride levels have also been shown to have a toxic effect on immunological processes, such as a decrease in some types of white blood cell.

Thyroid problems

Some people also claim that fluoride can affect your thyroid, leading to weight gain and hair loss. This can also lead to a decrease in calcium within bones, and an increase in calcium in the blood. As a result, bones become more brittle and easily fractured.

Side Effects of Fluoride

As we know, fluoride is toxic to bacteria as it wreaks havoc on their metabolism. However, did you know that humans share the same metabolic process that the fluoride targets? Yup, that means it is toxic to us too! This is why you were told not to swallow your toothpaste as a kid. In small amounts this is not going to be a problem. However, fluorosis is a thing.


This is a cosmetic condition -not a disease. Fluorosis can occur during the development of permanent teeth. It is the result of a high intake of fluoride.


There may be no symptoms if the fluorosis is mild.

The effects can be:

  • White or brown discolouration on enamel
  • Tooth surface irregularity
  • Small colour change
  • Streaks/pots/pits on tooth surface

Do not worry, as these effects are often subtle and normally it is your dentist who detects it first. They are permanent, however they are not a cause for concern. Fluorosis is not detrimental to your child’s oral health.

At what age does the fluorosis risk stop?

During adulthood, it is highly unlikely that an individual will consume too much fluoride. Although, there has been a case of skeletal fluorosis where a woman drank from a pitcher containing 100-150 tea bags a day for 17 years…so maybe avoid doing that. Skeletal fluorosis results in brittle bones which can lead to pain and discomfort.

At the age of six, dental fluorosis risk terminates as a threat.

Preventing Fluorosis

In order to monitor your child’s fluoride intake, help them use a pea-sized amount of toothpaste when brushing their teeth. Encourage them to spit the toothpaste out and ensure they don’t swallow it. Furthermore, you can buy toothpaste with a lower fluoride content for your children. Additionally, be careful when taking fluoride supplements.

Recommended dose

The World Health Organisation (WHO) recommends that drinking water should contain no more than 1.5 ppm fluoride. This is the limit at which negative health effects begin to be seen.

Fluorosis Treatment

Treatment for fluorosis consists mainly of a cosmetic treatment. Treating the staining and discolouration would be the main focus. Whitening may be necessary, and in more serious cases, further cosmetic dentistry such as veneers and crowns are available.

However, some people find that there is no need to treat their fluorosis as it is barely noticeable.

Final thoughts

My recommendation is: opt for fluoride toothpaste. Ensure to spit it out after brushing and you will be able to sleep well at night, knowing that you are looking after both your teeth and your health. If you are concerned about the level of fluoride that you or your child consumes, do not hesitate to contact your dentist or other health professional for advice.


Hi! I'm Lara Phillips - a second-year dental student at Cardiff University. I created to further expand my knowledge and consolidate my learning throughout my course as well as to help people understand the complex nature of teeth!