Tooth decay is also called caries, it is caused by unclean surface of the tooth bacteria attached, corrosion of the tooth, this corrosion of the tooth will become deeper and deeper, until the nerve of the tooth to cause pain, and may have to extract the tooth. Therefore, in order to treat caries, it is necessary to deal with as early as possible, the tooth corruption of the stains, and bacteria to clean up the filling. If the caries is so severe that the nerve has been exposed, then root canal treatment is needed to stop the pain and then restoration treatment. If the decayed area is large and the tooth is no longer retained, it can only be considered to be extracted and then restored by choosing a removable denture, a fixed bridge or an implant denture to restore the tooth. Therefore, tooth decay should be treated as early as possible, so that the teeth can be preserved, the trauma is also smaller, and the final result is also better.