A toothbrush? Who knew the toothbrush market hadn't already been fully developed.

Like most people, you probably think everything that could be invented has been invented, except cold fusion, seedless avocados and comfortable bike seats.

That's what Heather Phillips, a 37-year-old stay-at-home mother of four in Herriman, thought. Now, she is an official, patent-holding inventor. Her invention: a toothbrush.

A toothbrush? Who knew the toothbrush market hadn't already been fully developed.

Not that Heather ever set out to be an inventor. This was a happy accident, and another case of necessity being the mother of invention. About nine years ago, she worried about the dangers of toothbrushes in the hands and mouths of children. Apparently, a loaded toothbrush in the hands and mouths of children can be dangerous. That's because they have a habit of playing and running around the house while brushing their teeth.

"A toothbrush can go through the back of the throat and sever the carotid artery, or it can puncture the soft palate — that actually happened to my nephew," says Heather, who at the time was a recently graduated dental hygienist. "I thought, there's got to be a better toothbrush for kids."

She was wrong. She visited various stores to find a flexible toothbrush for kids. Nothing. She searched online. Nothing. She decided that if she couldn't buy one, she would make one. She wrote the design on paper — a toothbrush made of material so flexible that it could bend in half, nubs on one end for teething, soft bristles on the other end and a handle shaped like a banana with the peel pulled back to be used as a handle and to prevent it from going down the child's throat.

Between family and work responsibilities, she spent the next few years turning the brush into reality. She researched materials, ultimately settling on silicone for the handle and the bristles. She took out a patent. She found engineers to produce computer drawings. With the help of family, she found a manufacturer in Taiwan to make the brush.

Voila, the Baby Banana Brush for 12- to 24-month-olds and the Baby Banana Brush teether were born.

In 2007, the brush was introduced at various conventions on the East Coast and trade shows around the country, including the ABC Convention in Las Vegas. "It was such a big hit there that it gave us confidence," says Heather. Hundreds of people stopped at their booth each day. Among the visitors were buyers from Toys R Us, Wal-Mart and Bye, Bye Baby.

Since the product was launched in 2008, the Baby Banana Brush has gone bananas. Heather and her husband, Ryan, have already paid off the $80,000 debt they incurred in developing the brush.

"Our first year after the trade show, sales grew 200 percent," says Heather. "We are going to hit a million brushes sold very soon. We are expected to double our sales every year after this."

There are so many orders that their manufacturer cannot meet the demand, forcing the Phillips to find a second manufacturing facility in Albany, N.Y. "We have several thousand brushes on back order," says Ryan.

Half of their sales are overseas — the brush is sold in 30 countries, largely in dental offices and boutiques, with the largest distributors in China, Japan and Korea. Their biggest domestic sales come from Toys R Us and Babies R Us; Bye, Bye Baby; Bed, Bath and Beyond; and Amazon.

"There is no sign of slowing down," says Ryan.

The market for the brush keeps expanding. It has been found to be effective in helping kids with Down syndrome and autism, as well as in children with an oral aversion (they don't want anything in their mouths), which leads to the loss of the sucking and eating instinct, which in turns means they don't develop facial muscles for speech and don't eat well.

"The brush has really helped those kids," says Heather, whose third child, ironically, has severe speech delay and uses the brush for therapy. "They suck on the brush. It's very soft and comforting to them."

This is all a strange turn of events for the Phillipses, who never saw any of this coming. "Heather never planned to be an inventor," says Ryan. "She just tried to buy a soft, flexible toothbrush."

"It's crazy," says Heather. "You dream about things like this. You just don't think it's going to happen."

The Baby Banana Brush company has become a family business. Sandra Phillips, Ryan's mother, is the official owner of the company that produces the brush, and Ryan works weekends for the company. In his day job, he is a manager in his father-in-law's precious-metals refining business, but he foresees a time when he'll have to work full time for Banana Brush. Heather The Inventor can afford to stay home with her children — but for how long?

"I've got other ideas I want to develop now that I know how to do this," she says. "It's put a fire under me and given me a big boost of confidence."