The cavity will start from enamel. At this stage, you will not feel any pain; therefore it is difficult to notice caries. If you have regular dental check-up, the dentist can detect the caries and treat it at an early stage.   Pain will be felt when eating cold, hot, sour, and sweet food. Cavity may also be found.   Severe pain will be felt that may affect sleep at night. An obvious cavity may appear on tooth. Pulp may also be infected by bacteria and the tooth becomes necrotic, which can even result in an abscess.   Go to a dentist immediately to receive the following treatments: At an early stage of dental caries without obvious cavitations, the dentist will apply topical fluoride to repair the early caries, or give other preventive treatments according to need. Restore the tooth by a filling when the carious lesion is still small, and the tooth is still restorable. Restore the tooth by a crown when the carious lesion is relatively big, and the remaining tooth structure is weak. Carry out pulp treatment (root canal treatment) when the caries have extended into the pulp. Extraction is needed if pulp treatment is not appropriated.