BACKGROUND Oral transmucosal fentanyl citrate lozenges (lollipops) are indicated for the oral management of breakthrough cancer pain. When abused, these sucrose-containing lozenges can cause rampant dental caries. CASE DESCRIPTION The authors examined a 19-year-old man whose dentist referred him because of total dental coronal destruction. After the authors questioned the patient, they concluded that his frequent oral use of sucrose-containing opioid fentanyl citrate lozenges across a three-year period caused the dental condition. CLINICAL IMPLICATIONS Dentists should be aware that oral transmucosal fentanyl citrate lozenges are being prescribed off-label for the control of pain from nonmalignant sources. Fentanyl citrate's effective analgesic potency can lead to misuse and potential abuse. Early recognition of its misuse could prevent severe dental caries and the need for extensive dental restoration.