SANTIAGO, Chile (AP) - Diego Rosales was so terrified during his dental appointments when he was 4 that he kept biting his dentist.

Today, the 9-year-old is far calmer, soothed by the presence of “Zucca,” a black Labrador that helps children like him with autism face one of their worst fears.

A visit to the dentist can be daunting for any child, but it’s especially so for many with autism. They can be upset by the lights in their faces or frightened by the noises of the instruments. Some have to be sedated.

Therapy dogs have been used in many countries to calm autistic children and aid people with numerous other conditions. Raul Varela began the practice in Chile after noticing that his autistic child’s social interactions improved after spending time with the family’s black Labrador.

Varela quit his job and got certified by Spain-based Bocalan as a therapy dog trainer for children with autism.

He started a non-profit organization called Junto a Ti (“Next to You”) that specializes in visits to the dentist for autistic children. It uses six dogs, all female, because the organizers say they are more docile. And the dogs get specialized training.

“Zucca had already been trained to be around children with autism, but taking her to the dentist was different,” Varela said. “She needed to be able to resist the screaming, the noise from the drill and to stay still in the lap of the children, even when they pull their hair or their ears.”

So far, the dogs have aided about 50 children visiting a single university-run dental clinic on the southern edge of Chile’s capital. The clinic pays the equivalent of $67 for a session with a dog, though its charge for a child’s visit varies, depending on the family’s economic level.

On a recent day, Diego sat in the dentist’s chair with Zucca on his lap. There was no biting and no screaming this time. Instead, Diego continued to pet Zucca long after the dentist had plucked out one of his teeth, and he smiled when he got to take the tooth home inside a tiny box for the tooth fairy.