Factors Affecting Dental Caries

The following factors have an important impact on dental health:

Individual factors

Susceptibility to dental caries varies between individuals and between different teeth within one person’s mouth. The shape of the jaw and oral cavity, tooth structure and the quantity and quality of saliva are all important in determining why some teeth are simply more susceptible to decay than others. For example, some teeth may have pits, small cracks or fissures that allow bacteria and acids to infiltrate more easily. In some cases, the structure of the jaw/dentition renders teeth more difficult to clean or floss.

The quantity and quality of saliva determines the extent to which teeth remineralise. For example relatively fewer caries are generally found in the lower front part of the mouth where teeth are more exposed to saliva.

The type and number of caries-causing bacteria present in the mouth is also relevant. All bacteria can turn carbohydrates into acids but certain families of bacteria such as Streptococci and Lactobacilli are more powerful acid producers. The presence of this type of bacteria in plaque increases the risk of decay. Some people have higher levels of decay-causing bacteria than others due to neglected or inappropriate oral hygiene.

Oral hygiene and use of fluoride

Oral hygiene including regular brushing and flossing to remove plaque and the use of fluoridated toothpaste, combined with regular dental check-ups, is thought to be responsible for the improvement.

Fluoride inhibits demineralisation, encourages remineralisation and increases the hardness of the tooth enamel making it less acid soluble. The proper amount of fluoride helps prevent and control caries. Fluoride can be supplied systemically through fluoridated community drinking water, other fluoridated beverages or by supplementation. Alternatively it can be provided topically direct to the tooth surface via toothpaste, mouth rinses, gels and varnishes.

In some countries, salt, milk or other beverages have fluoride added and supplements in the form of tablets or liquid are also available. The level of fluoride in drinking water and food needs to be taken into account when assessing the need for fluoride supplementation. This is especially important in young children under the age of 6 whose teeth are still developing.

Regular dental check-ups can help detect and monitor potential problems. Regular plaque control and removal can help diminish the incidence of dental caries. If very little plaque is present, the amount of acid formed is insignificant and decay cannot occur.

Dietary factors

Although the decline in tooth decay in many countries has been largely linked to fluoride exposure and improved dental hygiene, eating habits still affect the risk of tooth decay.

Fermentable carbohydrates

For many years the simplified message to prevent tooth decay was ‘don’t eat too much sugar and sugary foods’. Over the last few decades sugar intake in many countries has remained constant whilst caries levels have declined. This suggests that where appropriate oral hygiene is practiced (i.e. regular tooth brushing using fluoride toothpaste) the role of sugars in tooth decay is less manifest.

Advice to replace sugar with starchy foods to avoid tooth decay is of questionable value. It is now known that any food containing fermentable carbohydrates can contribute to tooth decay. This means that as well as sweets and confectionery, pasta, rice, potato crisps, fruits, and even bread can set the scene for demineralisation. For example, a study testing the acid- producing potential of various starchy foods including pasta, rice and bread, found that these foods produced the same amount of acid as a 10% sucrose (table sugar) solution. Another study found that acid formation in plaque after eating soft bread or potato chips was greater and lasted longer than after eating sucrose.

Food characteristics

The physical characteristics of a food, particularly how much it clings to the teeth also influence the tooth decay equation. Foods that adhere to the teeth increase the risk of tooth decay compared to foods that clear from the mouth quickly. For example crisps and biscuits stick to teeth for longer periods than foods such as caramels and jelly beans. This may be because caramels and jellybeans contain soluble sugars that are washed away more quickly by saliva. The longer carbohydrate- containing foods are around the teeth, the more time bacteria have to produce acid and the greater the chance of demineralisation.

Frequency of eating

There is some debate over the relative importance of the frequency of consuming carbohydrate foods and its link with dental caries. As with the relationship between diet and caries, the link appears to have been weakened with the adoption of good oral hygiene and fluoride.

Each time we nibble a food or sip a drink containing carbohydrates, any decay- causing bacteria present on the teeth start to produce acid and demineralisation commences. This continues for 20 to 30 minutes after eating or drinking, longer if food debris is locally entrapped or remains in the mouth. In between periods of eating and drinking saliva works to neutralise the acids and assist in the process of remineralisation. If food or drink is taken too frequently the tooth enamel does not have a chance to remineralise completely and caries can start to occur. This is why nibbling or sipping continuously throughout the day should be discouraged. The best advice is to limit the consumption of food and drink containing carbohydrates to no more than 6 occasions per day and ensure teeth are brushed with fluoride toothpaste twice a day.

Protective foods

some foods help protect against tooth decay. For example hard cheese increases the flow of saliva. Cheese also contains calcium, phosphate and casein, a milk protein, which protects against demineralisation. Finishing a meal with a piece of cheese helps counteract acids produced from carbohydrate foods eaten at the same meal. Milk also contains calcium, phosphate and casein, and the milk sugar, lactose, is less cariogenic (caries causing) than other sugars. Nevertheless caries have been found in children breastfed frequently on demand.

Tooth-friendly products

Tooth-friendly products are formulated using sweetening ingredients that cannot be fermented by the mouth bacteria. Intense sweeteners such as saccharin, cyclamate, acesulfame-K and aspartame, and sugar substitutes such as isomalt, sorbitol and xylitol fall into this category.

Sugar-free chewing gums use these sweeteners. Both the sweet taste and chewing stimulate salivary flow, which contributes to the prevention of caries. Such chewing gums may also contain minerals such as calcium, phosphate and fluoride to enhance the repair process. Studies have reported that chewing sugar-free gum after a meal accelerates the clearance of food debris and reduces the rate of caries development in children.

Toothfriendly products have to comply with a specific test regimen in order to get ‘safe for teeth’ approval.