How does toothpaste work?
We all realise that brushing our teeth with toothpaste is necessary for healthy teeth and gums. Evidence has been found that even prehistoric man cleaned his teeth - using grasses as an early form of dental floss. But do we understand what is in our toothpastes, and why they work?
In the section 'about our teeth' we saw that teeth are composed of layers. Damage to these layers and to the gums can lead to oral problems such as tooth decay. In particular the enamel outer layer is constantly under attack. It can be chipped or damaged and can be dissolved by acid. Dental plaque is a mixture of bacteria firmly adhering to the tooth surface. Bacteria from the plaque in our mouths feed off the carbohydrates/sugars we eat and produce two things:
- acid - which eats into tooth enamel to produce cavities
- volatile sulphur molecules - which can give breath an unpleasant odour
Toothpastes contain mild abrasives which physically scrub away the plaque and food debris without damaging the tooth enamel. Most toothpastes contain fluoride which protects the tooth enamel. Some also contain antimicrobial ingredients to reduce the formation of plaque which could lead to tartar build-up and further problems.
How does fluoride work?
It is found naturally in some foods such as tea, fish, vegetables and fruit juices, but its inclusion into toothpaste has been a major public health advance. Fluoride has been the major factor in reducing the incidence of dental decay and has been used in toothpastes for almost 50 years.
It works by promoting a chemical reaction in tooth enamel that draws in replacement minerals including calcium. Fluoride incorporates itself into enamel weakened by acid attack, making the tooth more resistant to future acid attacks.
What other ingredients are necessary in toothpaste?
Each make of toothpaste has a slightly different formulation, to appeal to different consumer needs. However, most will contain the following ingredients:
abrasives: these remove stains and plaque, and polish the teeth. They must be abrasive enough to do this without damaging the enamel or any exposed dentine. Examples include calcium carbonate, silica and alumina.
detergents: these create the foaming action which helps dislodge food debris and bacterial plaque as well as providing a pleasant mouth feel. A common detergent is sodium lauryl sulphate.
Humectants (eg. glycerin): these give toothpaste its texture and retain moisture so the toothpaste doesn't dry out.
thickeners (such as cellulose gum) are also used for texture. They help the toothpaste to stay on the brush when squeezed from the tube/pump.
preservatives: prevent the growth of bacteria or other micro-organisms in toothpaste.
flavouring and colouring agents: without these, toothpaste would look and taste less palatable.