A tooth cavity is a decayed area in the tooth, forming a hole in the enamel (outer hard surface of the tooth), which gradually proceeds inwards. It is caused by gradual erosion of the tooth and if left untreated for a long period, it can involve the dentin layer of the tooth as well and may finally reach the pulp cavity. A cavity in the tooth may cause severe toothache and could ultimately lead to loss of the tooth.
The formation of cavities, or dental caries, caused by tooth decay is one of the most common tooth disorders that occur not only in children but in people of all ages. Cavities take a long time to form – often months or years – so the aim should be to detect and arrest tooth decay and prevent cavity formation in the very early stage.
Structure of a Tooth
A tooth is divided into 3 parts :
- Crown is the part of the tooth that protrudes out of the gum and is visible.
- Neck is the part of the tooth at the gum line, between the crown and the root.
- Root is the part of the tooth that lies inside the gum. Some teeth, such as the incisors and canine, have one root, while the premolars and molars have 4 roots each.
A tooth is made up of a number of layers, from the outermost hard enamel to the soft innermost part of the tooth, known as the pulp.
- This is the white, outermost layer of the tooth.
- It is the hardest substance in the body (composed mainly of calcium phosphate), which covers the exposed part of the tooth above the gums, forming the crown.
- The enamel helps to protect the dentin which lies beneath it.
- It does not have any nerve endings in the enamel.
- This forms the main mass of the tooth.
- The structure of dentin may be compared to bone and it is less hard than enamel.
- There are tiny tubules within the dentin which connect with the nerves in the pulp cavity, thus making the dentin sensitive to stimuli.
- The covering over the dentum which likes in the gum (over the root).
- It is a hard bone-like substance.
- Periodontal membrane
- This membrane is attached to the cementum and binds the root of the tooth to the jaw bone.
- Elastic fibers in the membrane allow some amount of movement of the tooth within the bony socket.
- This is the soft central area of the tooth.
- Blood vessels and nerves run through the pulp of the tooth.
- Root canal
- This is the extension of the pulp within the root of the tooth.
- An opening in the cementum at the tip of the root connects the root canal to the neighboring tissues.
- The nerves and blood vessels of the tooth enter the pulp through this opening.
How does a Tooth Cavity Form?
There are many types of bacteria normally present in the mouth but certain acid-producing species are commonly involved in causing tooth decay.
When food, especially those high carbohydrates, remain on the teeth for a prolonged period of time, either due to improper brushing or not rinsing the mouth after a meal, these bacteria act on the food and produce acids.
Plaque formation occurs as a result of build-up of food debris and bacteria on the tooth surfaces. Acids produced by the bacteria cause tooth decay by gradually eroding the enamel layer, leading to cavities or caries.
Symptoms of a Tooth Cavity
- In the very early stages, when a cavity is restricted to the enamel, there will be no pain since the enamel does not have any nerve endings.
- In later stages, when the dentin is involved, there will be pain (toothache) on consuming sweet, hot or cold food or drinks.
- When the cavity runs deep and the pulp gets involved, there will be pain even after removal of the stimulus (such as cold water). There may be spontaneous toothache even without any stimulus.
- The pain may stop temporarily in very late stages if the pulp dies. Root infection or inflammation may cause pain on biting or if the tooth is pressed upon by the tongue or a finger.
- If the infection leads to abscess formation, there will be constant pain, made worse on biting.