Why do dentists apply fluoride to my teeth?

Why do dentists apply fluoride to my teeth

A lot of people are always asking, why do dentists apply fluoride to my teeth? Is it necessary? Well, here’s a quick explanation of what’s going on.

How it works:
Our teeth have an outer layer known as enamel. It is one of the hardest structure in our body, thin as it is. It consists primarily of minerals known as calcium hydroxyapatite. The adult teeth generally start forming from a young age, with the permanent front teeth forming from as early as 1 year old.

Why decay happens is due to acid production by bacteria on our teeth. In the initial stages, one may notice a white, opaque discolouration first. This is from loss of minerals (demineralization).
At this early stage, if good brushing is introduced, calcium and phosphate minerals from the saliva can be introduced back into the enamel to help restore it. However, once too much demineralization has happened, or a cavitation occurs, the tooth is said to have a decay, and a filling would be required.

What fluoride does is that it helps the process of restoring calcium and phosphate into the enamel. Also, it actively replaces some calcium in the mineral structure, resulting in a fluoridated hydroxyapatite, or even fluorapatite. This mineral can resist acid attack better than regular calcium hydroxyapatite.

In Singapore, fluoride was introduced into the water system, following guidelines from the World Health Organization (WHO). It was initially at 0.7mg per litre (or 0.7ppm). It has since been revised down to 0.4-0.6ppm.

This is one major source of the fluoride to help prevent decay in Singapore. With regular exposure to fluoride from young, it can help strengthen the teeth by being incorporated into the teeth early.*

The next step would be using fluoridated toothpaste and mouthwash. One should take note that the toothpaste should contain about 1450ppm of fluoride to be effective in preventing decay. Brushing twice a day, with flossing, would greatly help reduce decay.

For fluoridated mouth rinse, one should actually try using it during the day, in between the times when you brush. There is already fluoride exposure when brushing, so using it during the day (eg after lunch or dinner) would be more beneficial to ‘top up’ the fluoride exposure.

Another source would be professionally applied fluoride. Usually, this is in the form of fluoride varnish or gel. This is usually in the range of 22 000ppm of fluoride. This high concentration helps greatly in protecting the teeth, and its effect usually lasts for a long duration (assuming one helps by maintain good oral hygiene and not snacking on sweets).

So, there we have it! We will apply fluoride for patients, sometimes routinely, because the patient might be at high risk of getting decay. We do hope to see you only for regular cleaning, and not have to subject you to terribly sensitive fillings, or even more invasive root canal treatments and such.

*The major concern a lot of people have, is whether or not having fluoride in the water is toxic. Here’s the math:

A person need to ingest an average of 0.2mg/kg before they experience some symptoms of stomach discomfort. For a 60kg person, that means 12mg of fluoride. At 0.6mg per litre, one has to consume nearly 20 litres at a go, to start experiencing stomach discomfort (To note, this is not at the level where one is likely to die. Also, one is likely to actually suffer from serious side effects from ingesting that much water). For a 10kg child, that would mean about 2mg of fluoride, or 3.3 litres of water. Again, the child is not likely to drink that much.

Also, a short term research has been done in Calgary, USA, after the removal of fluoride in the water, and it appears that there has been a marked increase in the amount of decay the children are experiencing. [Lindsay M., Steven P., Salima T., Peter F, Deborah M., Melisa P., Luke S. (2016) Measuring the short-term impact of fluoridation cessation on dental caries in Grade 2 children using tooth surface indices. Community Dentistry and Oral Epidemiology, 44 (3) 274-282]