Six-year-old Ryan Coutinho was not used to smiling. He felt embarrassed after losing almost all his teeth at the age of three.
Now he does. And can not stop showing it.
But getting here was not easy, says dentist Amanda Mattos.
The boy lives in a rural area near Guajeru, a poor town in north-eastern Brazil. He had his teeth pulled out as a result of early cavities. Only a few on his lower arch remained.
Dr Mattos, 25, met Ryan for the first time two years ago, during a social project at the boy's school.
"I had never seen something like this," she told the BBC. Ryan's teacher told her that he avoided smiling and did not engage much with other students.
Dr Mattos offered to treat the boy after contacting the boy's mother through the teacher. But the mother refused, believing that her son would be reliving the drama of his operation.
"They are all very modest, live outside the town and didn't understand the procedures," the dentist said. "They were still shaken by the process that removed all his teeth."
Ryan's story could have ended here. But two years later, by coincidence, his mother got a job as a cleaner at the public clinic where Dr Mattos works.
Soon afterwards, the boy had a pain in one of his remaining teeth. He went to the clinic for treatment and met Dr Mattos again.
"I asked him what he wanted. He smiled and said: 'a smile like my friends'," the dentist said.
The mother was still reluctant to accept the treatment. But she later talked to the father and they finally agreed to take up the offer.
The town's public health service did not pay for the procedure, so Dr Mattos, who owns a private clinic in a nearby town, brought equipment and offered to do it for free.
For several weeks, Ryan visited her after school to take X-rays and impressions. He was disappointed every time he returned home without his new teeth, Dr Mattos said.
Then, on 14 October, two days after Brazil's Children's Day, he finally got a new smile - a denture for his upper arch.
"We all cried. It was very moving," the dentist said.
Dr Mattos says X-rays show Ryan's permanent teeth will not come out. When he reaches 18, he can opt for dental implants. She says she will continue to assist him.
The dentist shared the story on Facebook, and it has gone viral in Brazil. She has become a guest on TV programmes and many other parents have approached her with similar cases.
"I'm really surprised by the reaction, it's unexpected," she said.
"I guess all the reaction has to do with the complexity of the case. And because people aren't used to generosity any more. So when they see cases like this, there's commotion."
And Ryan, she says, cannot stop smiling.