Cavities don't always announce their presence via pain. In fact, a cavity may be present in a tooth for a long time before you experience any pain. However, you never wait until a cavity causes pain before visiting your dentist for treatment. Doing so may result in the need for a root canal and crown. If your dentist can get to the cavity before you begin to feel pain, then a simple filling should prevent any further damage from occurring.
To get a good idea of why this is so, you need to understand the process of tooth decay.
A Tooth is Comprised of Two Outer Layers
The reason a cavity, which is essentially just a hole, does not cause you any pain at first is because the bacteria that cause the cavity must first get through two layers of protection. The first layer, enamel, is the hardest substance in the human body, even harder than bone. However, tooth decay is a lengthy process that takes months or years depending on your diet and oral hygiene practices.
If your diet is high in sugar, which happens to be the favorite food of the bacteria present in your mouth, then your teeth will erode at a much faster rate. When well fed and allowed to multiply on your teeth due to poor oral hygiene, these bacterial organisms secrete acid which slowly but surely eats away at the enamel surface. No pain is felt, however, because enamel is composed of minerals such as calcium. However, once a cavity reaches the underlying layer, you may begin to feel the presence of the cavity.
Sensitivity is Felt before Pain
Once a cavity reaches the layer of dentin under the enamel, you may begin to feel sensitivity in the tooth. Temperature fluctuations brought about by drinking hot and cold drinks will cause bouts of sensitivity as will breathing in cold air, and even consuming foods high in acidic content such as lemon juice. However, sensitivity isn't pain, so you may still not believe that you have a cavity.
Pay attention however, because sensitivity is a signal that your enamel may have already been compromised. The dentin layer of tooth contains microscopic tubules responsible for transferring nutrients and oxygen throughout the tooth. Once a cavity reaches this layer then, the tubules may transmit sensation to the centre of the tooth. At this stage, the pulp (nerve) of the tooth can still become infected if the cavity is not filled by your dentist.
Don't wait for a cavity to cause you pain. Pain means your tooth has become infected. The only way to remove the infection is root canal therapy. If you spot what you think is a cavity, book an appointment with your dentist immediately.