How Tooth Decay Occurs
For most people, the first sign of a cavity is pain, but the actual start of tooth decay begins much earlier, with the accumulation of minute amounts of a sticky film, called plaque, on the tooth's surface.
Plaque contains bacteria, which feed on carbohydrates in the mouth. As a result of their feeding frenzy, the bacteria produce acids, which can attack the tooth enamel -- the outermost layer of the tooth. If the plaque isn't removed, it continues to build, creating more acid that continues to damage the tooth enamel. There usually is no pain until the acids eat through to the tooth's underlying dentin and pulp layers, where the nerves are located. This decay, technically known as dental caries, is the point at which treatment is needed to prevent further tooth damage and loss.
Cavities usually form:
- in depressions and grooves of chewing surfaces
- between teeth
- on the root surfaces of people whose gums have receded
Dental decay usually occurs in the back teeth, where it is more difficult to remove food debris and plaque. There are two notable exceptions: early childhood decay in bottle-fed babies and root decay in older adults.
Baby-bottle decay usually occurs in the upper front teeth as a result of continuous feeding on sweet liquids, including milk, formula and fruit juice. Nighttime use of a bottle is the most dangerous because the sugars sit on the baby's teeth for an extended time. Tooth loss can result, causing spacing and development problems when the permanent teeth erupt.
"It's very nasty," says Cleveland dentist Matthew Mecini, D.D.S. "You don't see it too often, but when you do, it's severe. The amount of damage that can be done to children's teeth in a short time is amazing."
Root decay occurs on the exposed root surfaces of older adults whose gums have receded as a result of gum disease. Many types of medicines older people typically use decrease saliva production, which can aggravate the problem. Saliva is important in preventing tooth decay because it can wash away food particles and bacteria and help neutralize acids formed by bacteria in the mouth.
The first sign of a cavity forming may be a white spot that in time may turn brown. Most patients, however, remain unaware of the decay until it is well advanced. Common signs that people notice include sensitivity of the tooth when exposed to hot or cold and brief pain after eating a sugar-containing food.
The dentist can diagnose decay with x-rays or by probing the tooth with a sharp instrument. Decayed enamel or dentin will feel soft.