What is the difference between cavities, decay and caries?
This is a great question. Tooth decay is the lay term for dental caries. Dental caries is the medical term given to an infectious disease process that results in damage to the enamel, dentin and even the cementum of teeth. Basically, given a susceptible tooth, bacteria will metabolize (convert) ingested sugars producing acids, which damage the tooth structure. This results in, you guessed it, tooth decay.
Although the infective process may vary, acid preferentially attacks the hard to clean areas of teeth, the microscopic pits and fissures on the biting surfaces of the back teeth as well as contacting areas between the teeth where a toothbrush cannot reach. As enamel breaks down (and minerals are dissolved out of the surface), the process eventually penetrates into the underlying dentin, which contains much less mineral than the enamel. The process progresses faster in the dentin where it mushrooms beneath the enamel and causes cavitation (true cavity formation).