My tooth aches but i have no rotting or cavities, what could it be?

Tension?: Often it is hard to tell if a tooth has a cavity. The cavity could be a small hole near the gum line or between the adjacent teeth and thus hard to see. If you have been told by a dentist that there is not tooth decay present in your aching tooth, it could be clench or grinding of your teeth due to tension. Are you under any additional stress lately? Do you catch yourself clenching your teeth?

How do you know ?: How do you know you don't have any carious lesions? Did your dentist tell you, or is it because you can't see any? If you don't have any cavities, you may have traumatized the tooth, or you may be grinding. Consult with your dentist to be sure.