Joel Berg calls himself a “Halloween nerd” because he hands out toothbrushes to the costumed kids who ring his doorbell that day.

Some youths might see this as a trick rather than a treat, but Berg, a Bellevue resident, isn’t trying to be the Halloween Scrooge. He’s just your typical dentist concerned about teeth.

And why shouldn’t he be? The holiday may seem like a candy dream for youngsters, but it’s a nightmare for the mouth.

There’s a tendency for kids to snack on candy throughout the day until their supplies are depleted, or at least until their favorites are gone. But Berg, chair of the University of Washington Department of Pediatric Dentistry, says people need to give their mouths a break.

“I’m not saying ‘don’t go trick-or-treating and don’t have fun,'” Berg said. “They can still have the candy. The problem is having one piece of candy after another all day long.”

That’s because constant snacking provides a continuous supply of sugar, which feeds the acid-generating bacteria that causes cavities.

Berg says kids can prevent tooth decay with thoughtful consumption. The most important factors to keep in mind are the types of candy and how it’s being eaten, he said.

Sticky treats, like taffy and gummy worms, tend to get stuck on teeth, exposing them to sugars and bacteria for longer periods of time. Chocolate on the other hand melts in the mouth.

In terms of how to eat the sweets, Berg recommends that kids indulge only during mealtimes to limit their frequency of exposure to sugars.

Children with braces have even more to be concerned about. Hard candy can cause brackets to pop off, leading to longer treatment times.

Bellevue orthodontist Wisanu Charoenkul is doing something about the dangers posed by Halloween sweets. He’s offered to buy back candy at a rate of $1 per pound.

Charoenkul will also make matching monetary contributions to the Bellevue Boys and Girls Club, while the candy will get shipped out to soldiers in Iraq and Afghanistan by way of Operation Gratitude. The goal is to bring in at least 300 pounds of treats this Halloween.

“We need to get this stuff off the streets to protect those braces,” he said. “This is one of those things where everyone wins.”

Charoenkul got the idea for his candy buyback from a dentist friend in Maryland, and he’s hoping to start a network of buyers in the Puget Sound region.