Caries can develop on chewing surfaces, proximal surfaces of adjacent teeth or cervical surfaces. Brown spots or cavities can be detected easily on the surfaces visible to eye. But caries without these symptoms needs to be identified by radiography.
Untreated caries on enamel tissue progresses to dentinal tissue. Dentin is a structure that can dissolve more rapidly compared to enamel thus caries of dentin is progressive. Sensitivity to cold, hot, sour or sweet can be present in caries progressed to dentin tissue. Pain ceases when the causing effect disappears.
If the pain is constant, tooth decay is progressed to pulp tissue where the vessels and nerves of tooth are present, and the root canal therapy is necessary in such cases.