A routine dental procedure ended in tragedy when 9-year-old Silvanna Moreno of San Diego died just hours after undergoing extensive dental treatment at Dreamtime Dentistry in Vista. Silvanna had suffered from persistent tooth pain for months and was referred for a root canal. On March 18, she underwent a three-hour procedure that included a root canal, crown placement, and the extraction of several decayed teeth. The day before the surgery, she reportedly had a fever that was treated with children’s Tylenol, though the clinic stated it was not informed of any recent illness.

According to the dental practice, Silvanna was continuously monitored during the procedure and showed no signs of distress. She was discharged in stable condition, awake and with normal vital signs. During the ride home, however, she remained drowsy and slept heavily. After arriving home, she continued sleeping and snoring loudly for about 90 minutes before her breathing gradually slowed.

Concerned by the changes, her grandmother checked on her and found her unresponsive. Emergency services were called, and Silvanna was rushed to the hospital, where doctors discovered she was in asystole, a condition in which the heart stops pumping. Despite extensive lifesaving efforts, she could not be revived.

The medical examiner later ruled her death accidental, citing methemoglobinemia linked to recent nitrous oxide administration, along with the effects of multiple anesthetic drugs. The rare blood disorder can interfere with the body’s ability to carry oxygen. An internal review is underway, and the case has drawn additional attention because the dentist involved had previously faced investigation following a separate anesthesia-related incident in 2016.