Key Topics

• • Overview of fluoride, its sources, metabolism and toxicity and its role in caries prevention
• • Different fluoride preparations and their use in dentistry
• • Different types of toothpastes

Learning Objectives

• • To be able to list different fluoride preparations
• • To be able to describe safe and effective use of fluoride containing products
• • To be familiar with different types of toothpastes

Introduction

Fluoride is a trace element that is of particular interest to dentists due to its role in the prevention of caries. Fluoride is present in most foods, including drinking water, however the content of fluoride varies significantly. About 90% of ingested fluoride gets absorbed in the stomach and small intestine. It reaches the peak concentration in blood in 20–60 minutes. In plasma fluoride binds to protein and this is not regulated by the body. Adults retain less fluoride than growing children and the excess is excreted via kidneys. The majority, 99%, of fluoride concentrates in mineralized tissues and only 1% is found in the soft tissues. Fluoride can be passed via the placenta and can be found at low concentrations in breast milk.

The role of fluoride in caries prevention became clear in the last century when an inverse relationship between fluorosis and caries intensity was observed in US cities with different fluoride concentration in the drinking water. However, over the past decades it has become clear that the most anti-caries effect of fluoride is from topical rather than systemic use.

Fluoride prevents demineralization of enamel and plays a role in remineralization by forming fluorhydroxyapatite, which is more resistant to an acidic environment. Fluoride ions also directly affect cariogenic bacteria by inhibiting cellular enzymes.

High systemic intake of fluoride in the first six years of the life when the permanent dentition is developing can lead to fluorosis, a developmental disturbance of developing enamel. Enamel becomes more porous and looks opaque, clinically presenting as white horizontal lines or even white or light brown spots on the crowns of the teeth.

Excessive doses of fluoride are toxic and can lead to stomach pain, vomiting, diarrhoea, shallow breathing, weakness, weak pulse, clammy skin, dilated pupils, cyanosis, muscle paralysis and spasms. It causes hypocalcaemia and hyperkalaemia and can lead to death within 2 to 4 hours. From the literature, the probable toxic dose, that can trigger life threatening symptoms and signs and require immediate hospitalization, is 5 mg/kg. In practice, it means a 20 kg child can get seriously ill after ingesting 75 ml of 1000–1450 ppm toothpaste.

Water fluoridation

The fluoride content in drinking water can vary significantly. The optimal fluoride concentration in drinking water that has been found to be most beneficial in reducing dental decay is 0.7–1.2 ppm. If the fluoride concentration exceeds 2 ppm, people are advised to consider an alternative water supply to avoid fluorosis in young children. In the UK about 10% of the population have drinking water with either naturally or artificially achieved optimal fluoride levels.

If the water fluoride concentrations are low in some areas community water fluoridation is practised by adding small amount of fluoride to the water supply. It is considered a safe, efficient and cost-effective way of reducing the caries rate. It works both systemically and topically and is shown to reduce dental decay by up to 29%, however it continues to be a controversial and emotional issue.

Fluoridated milk