DENTISTRY. Food and dental health interact, with each having effects on the other. Patterns of eating affect the health of the teeth and other tissues in the mouth, while the ability to chew a variety of foods without discomfort influences a person's nutritional state as well his or her enjoyment of eating.

Sugar and Dental Caries

The clearest link between food and dental health is between sugar consumption and caries (cavities). A study in the 1940s compared the dental health of children in an area of northern India, where food was scarce and malnutrition common, to that of better-nourished children in Lahore and in Rochester, New York. The poorly nourished children had the fewest cavities. Subsequent research confirmed that populations who enjoyed a good nutritional status had more caries than less well-nourished populations.

Researchers then looked at the mechanism of caries development to discern the role of diet. Cavities are the end result of a process that involves bacteria and sugars in the mouth over time. Streptococcus mutans, bacteria that are normally present in plaque, a very fine film which covers the surfaces of the teeth, metabolize sugar and form acid. When a person consumes sugar in foods or beverages, acid is formed that can dissolve minute amounts of minerals from the enamel surface of the tooth. When this happens repeatedly over time, enough minerals are lost for a cavity to form.

This relationship between sugar consumption and caries was tested in a classic study conducted at Vipeholm, a mental institution in Sweden, and reported in 1954. Although modern ethical standards would preclude a study in which subjects were unable to give informed consent, it remains a landmark piece of research. Residents were assigned to several groups. All ate the standard diet of the institution, but some were given additional sweets in varying quantities and frequency, up to twenty-four sticky toffee candies per day. After five years of observation, the researchers concluded that the stickiness of the sweets and the frequency with which they were consumed, both increasing the amount of time that the bacteria in plaque could produce acid, were more important than the total amount of sugar.

Streptococcus mutans can feed on any carbohydrate, not just sugars. The bacteria make no distinction between "natural" carbohydrates, such as the sugars in fruit, and refined sugars; they make acid from any of them.

Oral bacteria also make acid from sugar in liquids. This can lead to a particular pattern of caries called "baby-bottle caries," which develops when a baby is put to bed with a bottle filled with sugar-containing liquid, including milk. When the baby falls asleep, the liquid pools in the mouth, leading to decay, most often of the front upper teeth.

Since sugar has been shown to play such a significant role in the development of tooth decay, a basic preventive measure is to limit the frequency of sugar consumption. Because it is the action of bacteria on the sugar that is of concern, minimizing the bacteria by careful attention to oral hygiene is equally important. Fluoride, a mineral that is naturally present in water in some areas, has a strong protective effect as well. It binds to the other minerals to become part of the enamel, making the enamel harder and more resistant to decay. It also slows acid formation and promotes repair of places on the teeth where acid has dissolved some of the minerals.

In areas where the naturally occurring level of fluoride in water is low, it is often added during water treatment. Although there have been controversies about water fluoridation, public health authorities, including the American Dental Association, the United States Public Health Service, and the World Health Organization, all support it as a safe and effective preventive measure. One can see its effectiveness in the fact that, although sugar consumption in the United States has been increasing, children have fewer cavities than they had in the years before fluoridation became widespread.

Sugar substitutes are used to produce candies, chewing gum, and beverages that taste sweet without harming the teeth. Chewing gum containing xylitol, one of these alternative sweeteners, has been shown to be protective.

Diet and Periodontal Disease

Gingivitis, or periodontal disease, is the other common dental disorder. The bacteria in dental plaque cause an infection of the gums and structures that hold the teeth in place. The gums become red, swollen, and tender. Food does not play an important role in the development of gum disease, as it does in the formation of caries. Good oral hygiene is the most important preventive measure. A nutritious diet, which supplies generous amounts of vitamins and minerals, can offer some benefit by helping to maintain the immune system's ability to fight the infection.

Dental Status and Eating

The other side of the food and dental health interaction is the importance of healthy dentition in enabling people to eat and enjoy a wide variety of foods. The absence of a significant number of teeth or a condition such as periodontal disease or poorly fitting dentures, which makes chewing uncomfortable, may limit a person's food choices and compromise his or her nutritional status. This problem occurs most frequently in elderly and low-income populations, who are more likely to be at risk for nutritional problems.

Some researchers do not find this effect, possibly because the subjects with poor dentition have chosen nutritious foods that are easy to chew, or because the comparison population ate no better in spite of good dental status. In general, however, poor dental health increases the risk of poor nutritional health. Good dental care can correct most of these problems and enable individuals to enjoy eating a nutritious diet.

See also Digestion; Fluoride.

Mona R. Sutnick