How can we know that our teeth has cavities?

See a dentist: The only way to know is to have a professional take a look for you. If it gets big then you can see it easily but small ones you may need xrays and an exam to find. There is no better way. Know that no pain does not equal no problem. Pain however almost always means problem and sometimes its way later than it should have been. See your dentist.

Holes in your teeth: Dental caries/cavities are basically holes in your teeth as seen in picture here. Often you can see the holes yourself, but many times the holes are on the sides or back of the teeth which are not easily visible. Thus, regular dental exam is advised so that your dentist/hygienist can examine your teeth more thoroughly, with/out x-ray etc.. Good dental=good sign of general good health. Good luck.

See dentist: The only way to be certain is to see a dentist. Cavities may be present without pain, and may also only be visible by xray. It just depends on location and extent. Don't wait for pain, that usually means the cavity has progressed beyond an initial depth. Consider a second opinion if you have any doubts.

See dentist: See your dentist for an exam with imaging to check all areas of your teeth. Sometimes you might see the holes (cavities) in your teeth from decay if they are big enough and close enough to the front to be seen.