A cavity is when bacteria in your mouth destroy the areas of your tooth. A cavity can start out as a tiny area on the enamel of a tooth, but left untreated it will work its way through the enamel and into the actual structure of the tooth. Eventually, if left untreated, it will reach the nerve of the tooth causing pain and infection. A cavity can destroy the entire structure of a tooth, and then the tooth must be pulled.
We all have bacteria in our mouths. This is simply part of life. The bacteria feed on sugar, and when left unchecked, they secrete acids that can eat into a tooth and cause a cavity. This is the simple version of the answer. The actual process is complicated.
First, the bacteria eat the sugar that we eat. Whenever we eat sugary foods or drinks, this fills our mouths with sugar. The bacteria consume the sugars and then they secrete an acid. This acid sits on the surface of the tooth until it is washed away by saliva, brushed away when we brush our teeth or flossed away. If allowed to sit for any period of time, the acids begin to eat away at the enamel surface of the tooth.
Colonies of bacteria form a gooey substance called plaque. This plaque can be easily washed or brushed away if it is done soon enough after forming. If it is not gotten rid of, the plaque absorbs calcium and other minerals from our saliva and then forms a hard substance called tartar. Tartar protects the bacteria and allows acid to eat into our tooth. Tartar is much harder to get rid of than plaque is.
When a cavity begins to form, it is so small that it is virtually invisible to the eye. When the acid is allowed to remain on the tooth, it begins to eat a hole in the tooth. Bacteria enter the hole, consuming more sugar and secreting more acid, and the process continues until the hole can eat right through the enamel and reach the dentin of the tooth.
Once the bacteria have established itself in the dentin of the tooth, it then spreads out. On the surface of the tooth, there may still be nothing visible, or it may appear as just a tiny brown spot on the surface. Yet damage is being done deep within the tooth. Eventually a ‘hole’ or cavity will be visible. If it is still left untreated, eventually the bacteria will reach the nerve of the tooth. When this happens, it causes great pain and can cause a nasty infection.
It takes time to form a cavity. The best defense against getting one is to limit the amount of sugar you consume. When you do eat or drink something sugary, either brush your teeth afterwards or at least rinse your mouth with water. Brush your teeth three times a day, floss every day and see a dentist on a regular basis.