'A Trip to the Dentist'

UNLIKE most of her friends, Gemma always looked forward to seeing her dentist. She wasn't particularly fond of having someone probing around inside her mouth with sharp implements, but she loved Dr. Meg, who was always kind and gentle. She was also one of the smartest people Gemma had ever met.

"Open wide and let's have a look," said the always-smiling Dr. Meg, as Gemma sat down in the big, leather dentist chair. "Everything looks good," said Meg after a few minutes of poking around.

"But there's one tooth I'd like to examine with an X-ray." Dr. Meg could tell by the puzzled look on Gemma's face that she wasn't sure about this X-ray thing. "I'm going to take a picture with a special camera," said Meg, in her reassuring tone. "When the film is developed, we can see a picture inside your tooth and tell if it has a cavity."

"Is this going to hurt?" asked Gemma, who had never before been X-rayed.

"You won't feel a thing. An X-ray is just a form of light that can travel right through many solid objects," said Meg.

"Where do X-rays come from?" asked Gemma.

"Certain substances that are radioactive produce X-rays," said Meg. "Did you know that one of the first people to study radioactive materials and use them in medicine was Marie Curie? Have you heard of her? She was one of the most famous scientists who ever lived."

"I thought most scientists were men," answered Gemma.

"Not at all! There are a lot of women scientists today. But certainly a hundred years ago, fewer women studied science. Marie Curie did," said Meg. "Let me tell you about her while I set up the X-ray machine. Marie was born in Poland, in 1867, and much of her early laboratory work was done in an old shed at a local school. She worked for years trying to extract new metals from tons of rock she had dumped there. In 1898, she succeeded in making about one-tenth of a gram of a new metal called radium- that's less than the size of a match head."

"Wow! But what was so special about radium?" asked Gemma.

"It did something remarkable: It was so radioactive that it glowed in the dark and produced a beautiful greeny-blue light. In fact, Marie kept a sample of the radium beside her bed so she could see its wonderful glow during the night. And all the test tubes and flasks that she had worked with in her lab also glowed in the dark. Many visitors came to see the wonderful sight. During World War I, Marie helped train nurses to use radium X-ray machines to look for bullet and bomb fragments in wounded soldiers."

"So is radiation dangerous?" asked Gemma.

"Oh sure, at high levels it can be very harmful to people and animals. But Marie didn't know it at first," said Meg.

Gemma's eyes opened wide, showing obvious concern as Dr. Meg prepared to take the X-ray. "Don't worry, Gemma, at the low levels found in medical X-rays, the radiation is not harmful. You would have to have hundreds of X-rays before you got a large dose."

After taking Gemma's X-ray, Dr. Meg returned with the developed film. "Good news: no cavity in that tooth! So just keep brushing and flossing after each meal and you'll keep your teeth healthy," she said.

But Gemma still looked worried.

"What's the matter?" asked Dr. Meg. "I thought that would please you."

"Yes, but I'm confused. Until today, I always wanted to study to be a dentist like you. But being a scientist like Marie Curie sounds like fun too," said Gemma.

Dr. Meg smiled and helped Gemma from the chair.

"Don't worry. You've got plenty of time to make up your mind on a career. Just study hard at science and math, and you can be anything you want!"

This story will be on The Times' website at latimes.com/kids.