What was expected to be a routine dental appointment turned into a heartbreaking tragedy for 9-year-old Silvanna Moreno, who died on March 18, 2025, just hours after undergoing a dental procedure at Dreamtime Dentistry in Vista, California.

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

Methemoglobinemia (MetHb) is a rare but potentially life-threatening condition in which hemoglobin — the molecule in red blood cells responsible for transporting oxygen — is altered in such a way that it cannot effectively release oxygen to body tissues. The condition can be triggered by certain medications or chemicals, including nitrous oxide, commonly known as "laughing gas," which is frequently used during dental procedures.

According to the Cleveland Clinic, MetHb can lead to symptoms such as bluish discoloration of the lips, skin, or nails, fatigue, confusion, and — in severe cases — loss of consciousness and death due to oxygen deprivation. Some individuals may exhibit no symptoms, making it difficult to detect without specific testing.

A Seemingly Healthy Child, a Standard Procedure

Silvanna was described by her dentist and anesthesiologist as a healthy child with no prior major medical issues. She had been referred to Dreamtime Dentistry for a root canal on one of her molars. According to reports, the procedure lasted approximately three hours. During the dental visit, multiple teeth were removed, including some baby teeth and one decayed permanent tooth.

People Magazine reported that Silvanna had a mild fever the day before the procedure and was given children’s Tylenol to manage her symptoms. Nothing at the time indicated that she was at heightened risk for complications.

Dr. Ryan Watkins, the trained anesthesiologist who oversaw the procedure, said in a public statement that Silvanna had undergone the office’s standard preoperative evaluation and was determined to be “an appropriate candidate for outpatient general anesthesia.”

Signs of Trouble After the Procedure

Following the dental work, Silvanna was moved to a recovery room. The Medical Examiner’s summary revealed that her mother noticed unusual behavior during this time — Silvanna was groggy, occasionally opened her eyes, and mumbled incoherently. Despite these warning signs, she was allowed to go home.

Once home, the young girl continued to sleep. About 30 minutes later, her breathing became shallow and slow. Alarmed, her family tried to wake her but were unsuccessful. They quickly called 911, and Silvanna was rushed to the hospital.

Despite emergency efforts, Silvanna was pronounced dead shortly after her arrival. Her sudden death left her family — and the local community — in shock and mourning.

“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,” Dr. Watkins said in a written statement.

A Troubling History

Though Silvanna’s death has been classified as accidental, the dentist who oversaw her anesthesia — Dr. Watkins — has a documented history of serious professional concerns.

In 2016, he was investigated in connection with the death of a 54-year-old patient who experienced cardiac arrest under general anesthesia. The Dental Board of California determined that one of the drugs administered should not have been used and was directly linked to the patient's near-death experience.

As a result, Dr. Watkins was placed on probation from 2020 to 2023 under the terms of a decision order issued by the board. He was allowed to continue practicing but under certain restrictions and additional oversight during that period.

Now, in the wake of Silvanna’s death, questions are once again being raised about the safety protocols and decision-making processes within outpatient dental anesthesia — particularly when it involves children.

Remembering Silvanna

Silvanna’s sudden death has devastated her family and community. A GoFundMe campaign was created to help cover funeral expenses and support the grieving family. Messages of condolence have poured in, honoring a young girl who was full of life and had so much ahead of her.

Her case also underscores the rare but serious risks associated with general anesthesia in dental settings — and the importance of transparency, thorough screening, and emergency preparedness.

As of now, no criminal charges have been filed. However, the Dental Board of California is expected to review the case as part of its regulatory oversight, which may lead to further professional action.