Cavities begin as relatively minor dental issues, but left untreated they can decay the tooth to the point where restoration is virtually impossible without a procedure called crown lengthening. Crown lengthening is a routine surgical procedure, which remodels the contour of the gum line. The procedure does not actually lengthen the crown, but rather lowers the gum line. When there is not enough tooth structure to affix a crown, this is the only option available. Sometimes a tooth has been broken below the gum line. In this situation, crown lengthening is very successful in exposing the tooth, so the dentist can administer treatment.