Dental hygiene tools sit on a tray. (Michael Nagle/Bloomberg News)

When she left the Children’s Dental Group of Anaheim in California in July, 7-year-old Mimi Morales became one of 800 children this summer to receive a pulpotomy at the clinic — basically, a baby root canal.

Her decaying baby tooth was cleaned out with medication and water and sealed for protection. She was sent home, the Orange County Register reported, and within days seemed back to normal.

But soon the second-grader could feel a bump in her mouth, her grandmother told the newspaper, and she saw blood when she brushed her teeth. Chewing food, she said, made her “silver tooth” hurt. But the symptoms eventually seemed to subside, the grandmother said. There was no cause for concern — until two months later.

In September, the Register reported, Mimi’s grandmother caught a striking snippet of information while watching the news: Nearly a dozen children had developed potentially dangerous bacterial infections that eat at the tooth and jaw after procedures at Children’s Dental Group.

Within days, that number had climbed to 20, and has since peaked at 30, reported CBS News.

When Mimi’s family rushed her in for a checkup, they were dismayed. The girl’s tooth was so badly infected, the clinic immediately ordered its removal and referred her to a hospital, where Mimi was admitted.

The infection had spread enough that doctors had to surgically remove three of her permanent baby teeth and a section of her jaw, reported KTLA 5. She will have to wait more than a decade — when she turns 18 — to fill out her smile with permanent dental implants.

“I want my teeth back,” the girl told her grandmother, according to CBS News, while she looked at her school picture. “The kids are going to laugh at me.”

Sam Gruenbaum, Children’s Dental Group’s chief executive, said in a statement to CNN that he “regrets even one patient has developed this condition” and is working to “make sure every single person is seen for a precautionary examination.”

The 30 cases involve children ages 3 to 9 who visited the clinic between March and July, reported CNN, and health officials at the Orange County Healthcare Agency expect even more cases to surface in the coming weeks and months. The infection, Mycobacterium abscessus, moves slow and can take time to cause symptoms.

The culprit, officials told CNN, appears to be the water lines at Children’s Dental Group.

The bacteria may have grown in low-level stagnant water that isn’t properly flushed, investigators said. In a dental office, this water is used to clean and rinse teeth, allowing the bacteria growing within to be trapped in fillings. To ensure a sterile work environment, the state of California mandates that “at the beginning of each workday, dental unit lines and devices shall be purged with air or flushed with water for at least two minutes” and that “dental unit lines and devices shall be flushed between each patient for a minimum of twenty seconds.”

It’s not yet clear whether the Children’s Dental Group did not follow these guidelines, but the Dental Board of California is investigating.

“We want to make sure they were doing what they were supposed to be doing,” board spokeswoman Joyia Emard told CNN.

Emard told CNN that the clinic is cooperating with the investigation and has agreed to stop using its water lines for the duration. The company told CNN that it plans to replace the lines and monitor its water purity.

Even so, parents of the affected children remain outraged.

“I want their license revoked,” one mother told CNN. “I want that place to be shut down.”

“It kind of just makes you upset because you trust these professionals with your kids,” Mimi’s father, Zachary Morales, told KTLA 5. “I just want to make sure she gets better.”

After Mimi recovers from her infection, which is being treated with antibiotics, she will require extensive dental work and bone grafting for her future implants, the Register reported.

“Thank God for my mom having the common sense to see this on the news and connect the dots,” Zachary Morales told the Register. “That’s my baby. I told her last night I wish I could have gone through the pain instead of her.”

Mimi’s grandmother, also named Mimi Morales, told CBS News that it broke her heart to hear the second-grader fret about her appearance.

“The kids aren’t going to laugh at you,” the grandmother said she told Mimi. “You’re beautiful. Nobody’s going to laugh at you.”