You go to your dentist for a checkup…and SURPRISE! You have a cavity, and your dentist says it’s a BIG ONE! How is it possible you didn’t know about this? You may have been missing some signs along the way that a cavity was growing!

First, what IS a cavity anyway?

A cavity is literally a hole in your tooth. Some of the foods we eat contain sugar or break down to sugars, and certain types of bacteria (called Streptococcus Mutans) in our mouths like to use these sugars as food. This food provides energy and allows bacteria to burrow into microscopic cracks and crevices in your teeth, leaving decayed and mushy stuff as they go. Sugars and acids, if allowed to stay on the teeth for a while, can also weaken the tooth surface and make it even easier for bacteria to eat away at what should be the hardest surface in our body.

So, how do I know if I have a cavity starting?

Here’s the kicker…most of the time…you don’t know you have a cavity starting.  In fact, most patients never know they have a cavity until a tooth breaks or a dentist finds a cavity during a checkup! You might think that bacteria digging its way into your tooth would be painful, but it’s usually a completely painless disease. Why? Pain in teeth is most often caused by touching the inside part of the tooth, called dentin, with a tool or cold or hot foods. While the cavity is growing, the mushy and decayed tooth stuff left behind by bacteria covers the inside part of the tooth. However, if you could push a toothpick into the hole, you would definitely feel pain! As the cavity gets bigger, the hard tooth structure is weakened by the cavity growing underneath, and it will break. Now is a time when the inside part of the tooth is exposed and you might start to have sensitivity to touch or to hot and cold foods.

Sometimes a cavity starts right near the gum line of the tooth. Food can get stuck in the developing cavity, which irritates the gums. They may start to bleed when you brush and floss your teeth, and the tooth may also be sensitive to temperature changes. As a cavity grows, it can get deeper into the tooth and reach the nerve of the tooth, which is in the center of the tooth and runs down the roots. If the cavity goes very close to the nerve, or even into the nerve, the bacteria can cause a deeper infection around the tooth called an abscess.  Once this happens, a regular filling will not be enough to solve the problem, and often more complicated treatment like root canal may be needed.

If I don’t have any pain, how does my dentist know I have a cavity?

Dentists use x-rays of your teeth to find cavities in certain areas while they are still small. It’s usually possible to find small cavities between the teeth this way which is why we recommend x-rays every 1-2 years even when you DON’T have pain. However, we can’t see everything on an x-ray because it doesn’t show us a three-dimensional view of the tooth! Your dentist will also feel the grooves in the teeth and also all the places you have fillings already to be sure they fit the tooth well. However, even this is not a foolproof method because bacteria is much smaller than the tip of the instrument we use. Modern dental offices also use magnifiers on their eyeglasses and can take digital photographs of teeth to make our view much larger.  There are also lasers we can use in dentistry to help us find cavities when they are just starting on the outer surface of teeth so we can stop them before more healthy tooth is destroyed.

The bottom line is this: your dentist trained for a long time and likely has many years of experience with diagnosing and treating cavities. We can do this when cavities are small (easy and relatively inexpensive to fix) or large (more difficult and costly), and the timing is up to the patient!

Dr. Andrea Stevens is a cosmetic and family dentist in practice in Kanata, Ontario. If you have dental questions, you can call her at 613-271-7091 or visit her at Please also feel free to leave comments or questions below, and Dr. Stevens will be happy to answer.