Wednesday 29th January 2020

Tooth Decay

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The journey from food to dental caries

To sum it up, every time you feed yourself you also feed the bacteria in your mouth, that demineralize and erode your teeth, leading to tooth decay. Although some foods and drinks are more likely to cause dental caries than others, the key to preventing it is less in your diet than in your dental care, in particular cleaning your teeth twice a day with fluoride toothpaste, flossing and visiting your dentist regularly.

The two most common oral diseases are tooth decay and gum disease.

Bacteria, mostly Streptococcus mutans, living in the mouth metabolize any sugars and starches by a process of fermentation into lactic acid, the acid commonly found in milk. As we've seen above, high concentrations of acid may appear on the surface of a tooth, causing tooth demineralization.

The mouth of all human beings is inhabited by microorganisms, so many that a single mouth can contain more bacteria than all the humans in the world. To minimize your risk of dental caries you must not let the oral bacteria to form organized colonies, which is basically what dental plaque is. Plaque provides a home for microorganisms and at the same time acts as the sticky medium making the acid that they produce adhere directly to a tooth's surface.

The bacteria causing caries use carbohydrates as their food source, and the waste products they create during the digestion of these sugars and starches are the acids causing tooth decay. Since the microorganisms living in our mouth eat every time we do, when we consume foods containing carbohydrates (chocolate, soda drinks, candy, ice-cream, milk, even fruits and vegetables) these bacteria get a meal too. And in minutes they begin producing the acids so harmful to our teeth.

All six-carbon sugars, i.e. glucose, galactose and fructose, and disaccharides based on six-carbon sugars, i.e. sucrose, lactose and maltose, and starches can be converted by Streptococcus mutans into acid demineralizing teeth. But sucrose is considered to have a unique usefulness for oral bacteria. Sucrose is possibly the sugar best converted into dextran, with which the microorganisms glue themselves to the surface of the tooth, clinging more strongly and making their removal more difficult. Besides, dextran is a reserve food supply for Streptococcus mutans.

This special role of sucrose in causing tooth decay is particularly important, since sucrose is almost universally used as the number one sweetener. Sucrose and invert sugar (a mixture of glucose and fructose) are used in many food and drink products, among which confectionery, ice cream, desserts, baked goods, intermediate-moisture foods (e.g. jams, jellies, flour, molasses, dried fruit), and soft drinks. Its use in the latter has gone down due to increased use of high-fructose corn syrups more cheaply available.

Sucrose is what is known as table sugar, lactose is the sugar found in milk, while fructose, or fruit sugar, is in many foods including tree fruits, honey, melons, berries and a few root vegetables, generally combined with glucose and stored in the form of sucrose.


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Are all sugars harmful to tooth health?

A lot of people are confused about what kinds of carbohydrates have the potential to be fermented by bacteria and lead to tooth decay. Some scientists have made this unclear picture even more complicated by dividing sugars into “intrinsic” and “extrinsic”.

Intrinsic sugars are sugars naturally present within the cellular structure of food; they are principally in fruits and vegetables.  

Extrinsic sugars are sugars which are free in food or added to it. Extrinsic sugars are further divided into milk sugars, i.e lactose, and non-milk extrinsic sugars, found mostly in honey, fruit juices, foods with added sugars.

Research shows that dental bacteria can ferment both intrinsic and extrinsic sugars to teeth-attacking acids so all foods containing carbohydrates (all sugars and starches) can potentially contribute to dental caries. Concepts often used in the public discussion of the subject, such as "natural" as opposed to "added", have no relevance to this issue. In fact, while "natural" sugars can be harmful to teeth, "artificial" sweeteners are a means of tooth decay prevention.

So, as in everything relating to diet, avoid the excesses rather than single out a particular food or ingredient as the main culprit. While it's true that, just to give an example, chocolate and sweets are foods very high in sugar content and so they should be eaten in moderation, the most important thing is that an enjoyable, healthy nutrition accompanied by consistent and thorough oral hygiene is the winning formula for both teeth and overall health. 


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What to do to prevent dental caries

The most important factor in dental caries prevention is good oral hygiene, as described in this document on dental care.

Starches and sugars are found in a myriad of foods, some of which are important for health like fruits, cereals, vegetables, grains.

For a long time the simplified message to prevent tooth decay was 'don't eat too much sugar and sugary foods'. In the last three decades sugar intake in many Western countries has remained more or less the same while dental caries' incidence has gone down. This indicates that, when thorough oral hygiene is followed, in the form of regular tooth brushing with fluoride toothpaste, the contribution of sugars to tooth decay is less important then previously thought.

Advice to replace sugary foods like confectionery, sweets, biscuits and cakes with starchy foods to avoid dental caries is debatable. It is now established that any food containing fermentable carbohydrates can play a role in causing tooth decay. This means that not just sweets and confections, but also bread, rice, pasta, potato crisps, potato chips and fruits can help bring about teeth demineralisation. A study researching the acid-forming potential of several starchy foods found that foods like rice, pasta and bread created the same amount of acid as a 10% solution of sucrose, or table sugar. Another study upsetting received wisdom and stereotypical assumptions found that acid production in dental plaque after eating bread or French fries was greater and lasted longer than after consumption of table sugar.

Foods that are more likely to remain attached to the teeth, like sticky foods, and those that are prone to leave more debris in the mouth, like crisps, are best limited not so much for their content as for the length of time of their contact with teeth. What is also important is the overall picture and balance of what you eat over a period of time.

Despite the recent discoveries in this field, it still remains advisable to limit consumption of sugar. Read the list of ingredients on food packages: the higher on the list sugar appears, the higher the proportion of sugar in the product. Keep foods high in sugar to mealtimes, thus reducing the length of time your teeth are at risk. This is anyway true of all foods: don't nibble food, snack or drink often, but allow time between eating occurrences by eating only during main meals.

Dental authorities believe that we should encourage the use of tooth-friendly products, containing sweetening agents that cannot be fermented by the oral bacteria. These are intense sweeteners, e.g. aspartame, saccharin, acesulfame-K and cyclamate, and sugar substitutes, e.g. xylitol, sorbitol and isomalt. 'Safe for teeth' products must comply with specific test standards to obtain the 'tooth-friendly' approval.

Use artificial sweeteners, such as xylitol and aspartame, rather than sugar in your coffee or tea, and use products containing artificial sweeterners rather than sugars.

Sugar-free chewing gums contain such sweeteners. Both the chewing and the sweet taste stimulate the production of saliva, which helps in the prevention of tooth decay. These chewing gums may contain minerals as well, like fluoride, phosphate and calcium, to increase the remineralization of teeth. Studies have found that chewing sugar-free gum after a meal speeds up the clearance of food debris and reduces caries development in children.

There is much solid research in particular on xylitol. Studies have shown that xylitol has beneficial effects for teeth in virtue of its anticariogenic (anticaries) properties. The Journal of the Dental American Association says:

In summary, sugar substitutes can play an important role in shifting the caries process in favor of maintaining dental health, and they should be recommended as part of an overall preventive treatment plan for patients at high risk of developing caries. Although xylitol has anticariogenic properties, there is not sufficient evidence to recommend xylitol as a first-line anticaries strategy in light of the large body of evidence on the effectiveness of topical fluoride and dental sealants. However, xylitol-containing chewing gum and mints can be recommended as an adjunct to other preventive intervention strategies if cost considerations do not outweigh effectiveness.

The presence of fluoride, be it in water, chewing-gum or salt, is also very beneficial to teeth. All major dental and health organizations support water fluoridation. The British Medical Association says:

"Fluoride has been found to be highly protective against dental caries, and there is no convincing evidence of any adverse risk to human health by the introduction of water fluoridation."


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