What is the commonest disease in the world?” This is a trick question and the answer is not obesity, heart disease or diabetes. It is dental caries!

Tooth decay or caries occurs in a staggering 98 per cent of the world’s population. Age is no bar — caries or cavities can occur in childhood in the deciduous (milk) teeth as well. In adults cavities may appear in the early twenties.

Unfortunately, cavities are not symptomatic in the early stages. There may only be pits in the teeth that are detected during a regular dental check-up (which, sadly, not many take seriously). The diagnosis may be established at that time by probing the enamel surface or with an X-ray.

As the cavity progresses, there may be pain or tooth sensitivity while eating or drinking sweet, hot or cold items. Discoloured pits may then form, finally leading to pus formation around a tooth.

Caries develop because teeth, particularly at the back of the mouth, are often not properly cleaned. Food debris and dead cells build up in the form of dental plaque. Bacteria, normally present in the mouth, begin to grow and flourish in this nutritious medium. And the enamel of the tooth gets damaged.

Poorly calcified teeth are more susceptible to caries. Decalcification occurs when the pH of the mouth falls below 5.5. Cola drinks and sweetened acidic fruit juices can lower the pH of the mouth, making way for caries. Toffee and caramelised sweets are less likely to cause cavities than hard foods like potato chips. This is because saliva washes away sugars, but the chips tend to stick stubbornly to the teeth.

Caries tends to occur in families. The mothers may harbour the caries-producing bacteria in their mouths. They have close contact with the children and often taste the food or bite off a portion of it before feeding it to them, thus spreading the infection. Some young children have a mouth full of discoloured, cavity-filled milk teeth. This may be part of the “bottle mouth” syndrome. Such children are often lulled to sleep with a bottle of milk. The milk remains on the teeth all night, causing much harm.

The elderly are prone to caries because of age-related recession of the gums and subsequent exposure of the root surfaces, and decreased salivation.

Poor dental hygiene with plaque formation and caries causes pain, difficulty in eating and bad breath. It also predisposes people to coronary artery disease and heart attacks. If a person has untreated caries, there is a 25 per cent higher risk of the first heart attack being fatal. The bacteria that live in these decayed teeth may be aspirated at night during sleep. This can cause bronchitis and even abscesses in the lungs.

Prostheses are now fitted everywhere. Stents are placed in blood vessels. Heart valves, knees and hips can be replaced. Dangerous life-threatening infections can occur in these artificial parts by bacteria from dental caries.

Regular dental check-ups are needed to detect cavities early. If pain and swelling have developed, it means the cavity has progressed to the tooth pulp and complications have set in. You may then need a root canal treatment and may eventually lose the tooth.

Once a cavity has developed, the primary treatment is drilling and filling. If the cavity is very deep, a temporary filling can be left in place for six to eight weeks in the hope that the tooth itself will begin to produce restorative dentin. Permanent fillings can be made of many materials. The most common is amalagam, a combination of silver, tin, copper and mercury. A well-done filling can last anywhere from 15 to 40 years. Fears about mercury poisoning have resulted in the use of other materials like porcelain and colourless resins. But these materials tend to harden, soften, shrink or expand when exposed to heat and cold. They do not last as long as amalagam does. If the tooth is badly damaged, a root canal treatment may have to be done and a crown fashioned of porcelain or gold.

Dental caries is preventable with care, time and effort

• Brush your teeth at least twice a day to prevent build-up of plaque. Electric toothbrushes are useful, but a soft toothbrush used for three to four minutes is equally effective.

• Use a toothpaste containing fluoride. A small quantity is sufficient. Excess paste may itself damage the tooth enamel.

• Floss at least once a day to remove food debris that may be stuck between teeth.

• Rinse your mouth after every meal.

• Avoid colas and unhealthy snacks.

• Have regular dental check-ups. If cracks and fissures are detected in the enamel, they can be sealed with dental sealants.

• Do not put children to sleep with milk bottles in their mouths.

Dr Gita Mathai is a paediatrician with a family practice at Vellore. Questions on health issues may be emailed to her at yourhealthgm@yahoo.co.in