What's in Your Mouth?
To understand what happens when your teeth decay, it's helpful to know what's in your mouth naturally. Here are a few of the elements:
Saliva — Your mouth and teeth are constantly bathed in saliva. We never give much thought to our spit, but this fluid is remarkable for what it does to help protect our oral health. Saliva keeps teeth and other parts of your mouth moist and washes away bits of food. Saliva contains minerals that strengthen teeth. It includes buffering agents. They reduce the levels of acid that can decay teeth. Saliva also protects against some viruses and bacteria.
Plaque — Plaque appears as a soft, gooey substance that sticks to the teeth a bit like jam sticks to a spoon. It is, in fact, colonies of bacteria, protozoa, mycoplasmas, yeasts and viruses clumping together in a gel-like organic material. Also in the mix are bacteria byproducts, white blood cells, food debris and body tissue. Plaque grows when bacteria attach to the tooth and begin multiplying. Plaque starts forming immediately after a tooth is cleaned; it takes about an hour for plaque to build up to measurable levels. As time goes on, different types of microorganisms appear, and the plaque thickens.
Calculus — If left alone long enough, plaque absorbs minerals from saliva. These minerals form crystals and harden the plaque into calculus. Then new plaque forms on top of existing calculus. This new layer can also become hard.
Bacteria — We have many types of bacteria in our mouths. Some bacteria are good; they help control destructive bacteria. When it comes to decay, Streptococcus mutans and Lactobacilli are the bacteria that cause the most damage to teeth.
How Your Teeth Decay
The bacteria in your mouth need food to live and multiply. When you eat sugary foods and other carbohydrates, the bacteria use them as food, too. The bacteria then produce acids that can dissolve tooth enamel (outer layer of the tooth).
It's not just candy and ice cream we're talking about. All carbohydrate foods eventually break down into simple sugars. These include glucose and fructose. Some of this process begins in the mouth.
Foods that break down into simple sugars in the mouth are called fermentable carbohydrates. These include the obvious sugary foods, such as cookies, cakes, soft drinks and candy. But they also include pretzels, crackers, bananas, potato chips and breakfast cereals.
Bacteria in your mouth turn the sugars in these foods into acids. These acids begin to dissolve the mineral crystals in teeth. The more times you eat each day, the more times your teeth are exposed to an acid attack.
This attack can lead to tooth decay, also known as dental caries. First, the acid begins to dissolve calcium and phosphate crystals inside a tooth. A white spot may appear on the enamel in this weakened area. But the loss of minerals develops beneath the surface of the enamel. The surface may still be smooth.
At this stage, the tooth can be repaired with the help of fluoride, proteins and minerals (calcium and phosphate) in the saliva. The saliva also helps reduce the acid levels from bacteria that attack the tooth.
Once the decay breaks through the enamel to cause a cavity, the damage is permanent. A dentist must clean out the decay and fill the cavity. Left untreated, the decay will get worse. It can destroy a tooth all the way through the enamel, through the inside dentin layer and down to the pulp or nerve of the tooth. That's why it is important to treat caries at a very early stage, when the process can be reversed.
Types and Stages of Decay
Young children can get a type of decay called baby bottle tooth decay or early childhood caries. It destroys enamel quickly. This type of decay is common in children who are put to sleep with a bottle of milk or juice. The bottle exposes the teeth constantly to carbohydrates through the night. Bacteria can grow rapidly and produce acid that decays teeth.
Decay can become worse if the parent does not clean the child's teeth. It can eat through enamel and leave a large cavity in a matter of months.
In older adults, the exposed roots of teeth can develop cavities. This is called root caries. Older adults are more likely to have receding gums caused by years of hard brushing or periodontal disease. They also are more likely to have dry mouth (xerostomia). The decrease in saliva results in less protection of the teeth. This increases the risk of decay. Many common medicines can cause dry mouth. Be sure to ask the doctor or pharmacist if any of your medicines cause dry mouth.
Decay can form beneath fillings or other tooth repairs, such as crowns. Sometimes bacteria and bits of food can slip between the tooth and a poorly placed filling or crown. This also can happen if the filling cracks or pulls away from the tooth, leaving a gap.
Do you or your family members get cavities often? Dental research has found out that certain factors can affect your risk of tooth decay. These factors include
- The current number of decayed or filled teeth
- Your fluoride exposure
- Family history of decay
- How well you take care of your teeth
- The amount of saliva and the balance of minerals, enzymes and buffering agents it contains
- How often and what types of foods you eat (especially carbohydrates)
- Ask your dentist about the best ways to reduce your risks and limit dental decay.
To prevent your teeth from decaying, you can do two things:
- Strengthen your teeth's defenses with fluoride, sealants and agents that contain calcium and phosphateions.
- Reduce the number of bacteria in your mouth.
Fluoride penetrates into teeth. It strengthens them by replacing minerals that acid has destroyed. The benefits of fluoride to teeth were first discovered in the 1930s. Dentists started to notice that people who drank water that naturally contained fluoride had less tooth decay. In 1945, communities started to add fluoride to water supplies. Adding fluoride to water systems has been the most successful cavity prevention method to date.
In the early 1960s, fluoride also began to be added to toothpaste. This also had a major impact on cavity prevention. Now almost all toothpastes contain fluoride. Everyone should brush with a fluoride toothpaste every day. Dental offices sometimes recommend higher levels of fluoride in toothpastes, gels and mouth rinses for both children and adults.
More recently, agents containing calcium and phosphate have been developed. MI Paste and MI Paste Plus both contain Recaldent (the calcium-phosphate ingredient). Your dentist can apply them to your teeth. Recaldent also can be found in chewing gum (some Trident products) and toothpaste. These agents help prevent and reverse early decay that has not yet led to a cavity.
Sealants are protective coatings placed over the tops of the back teeth — molars and premolars. They block bacteria and acids from sticking in the tiny grooves on the chewing surfaces of these teeth. Sealants can be placed in adults and children. Children can have sealants on their baby molars, and also on the permanent molars once they come in. Dentists can put sealants on molars with signs of early decay, as long as the decay hasn't broken through the enamel.
You can never get rid of all the bacteria in your mouth. But you can take steps to control bacteria:
- Brush twice a day.
- Floss daily.