9-Year-Old Girl Dies After Routine Dental Visit; Medical Examiner Rules Death an Accident

Vista, California — What began as a routine dental procedure ended in tragedy for 9-year-old Silvanna Moreno, who died just hours after her appointment at Dreamtime Dentistry on March 18, 2025.

More than two months later, the San Diego County Medical Examiner’s Office has ruled her death an accident. The official cause was listed as “methemoglobinemia in the setting of recent nitrous oxide administration.”

Rare Blood Condition Linked to Nitrous Oxide

Methemoglobinemia is a rare condition in which hemoglobin is altered, reducing its ability to carry oxygen throughout the body and leading to hypoxia. According to the Cleveland Clinic, symptoms can include blue or purple discoloration of the lips, skin, or nails. In some cases, however, it presents without visible warning signs.

Silvanna reportedly had a fever the day before the procedure and was given children’s Tylenol, People reported. The three-hour treatment included a root canal on a molar, the extraction of several baby teeth, and one decayed permanent tooth.

Dentist’s Office and Anesthesiologist Respond

Dr. Ryan Watkins, the office’s anesthesiologist, said in a statement that Silvanna had undergone the practice’s standard preoperative evaluation and was deemed “an appropriate candidate for outpatient general anesthesia.” He described her as “a healthy 9-year-old with a history of regular medical checkups.”

Following the procedure, Silvanna was moved to a recovery room. According to the medical examiner’s summary, her mother told investigators that her daughter appeared “out of it,” intermittently opening her eyes and mumbling incomprehensibly.

On the way home, and later at home, Silvanna remained asleep. Within 30 minutes, her breathing slowed. When attempts to wake her failed, her family called 911. She was rushed to the hospital, where she was pronounced dead.

“We are profoundly saddened by the tragic loss of Silvanna Moreno, and our hearts continue to go out to her family during this incredibly difficult time,” Watkins said in a statement.

History of Prior Investigation

Dr. Watkins has previously faced scrutiny. In 2016, he was investigated in connection with the death of a 54-year-old man who suffered cardiac arrest under general anesthesia. The Dental Board of California later determined that one of the medications administered should not have been used, as it contributed to the patient’s cardiac arrest.

As a result, Watkins was placed on probation from 2020 until 2023, according to state records.

Community Response

Silvanna’s unexpected death has shaken the Vista community. A GoFundMe page was created to support her family as they mourn the loss of a child whose life was cut tragically short during what was supposed to be a routine dental visit.