The correct answer is dental caries. This gross image of the maxilla shows portions of the crown missing from the left maxillary first and second molar teeth (#109 and #110, respectively). Lesions are diagnosed in the clinical setting by the use of a dental explorer; it "sticks" in the soft decaying dentin. Carious lesions result from microbiologic activity on the occlusal surface of teeth: carbohydrates ferment and cause acid production, then acid demineralizes and destroys tooth structures. The most commonly affected teeth are maxillary first molars and mandibular first and second molars. Removal of decayed tissue allows restoration of tooth structure. However, if dental caries progresses into the pulp cavity, endodontic therapy will be required prior to restoration. In severe cases with extensive loss of dental structure, extraction will be required.