Kids are being outfitted with braces at an ever-younger age. (Associated Press)

The trend toward outfitting kids with braces at an ever-younger age isn't always effective and could even lead to a second round of braces in the awkward teenage years, studies show.

Children as young as eight are getting braces and are sometimes free of them by age 10. Many dentists and parents say the earlier a child can get braces, the better, because pre-teens are not so self-conscious about a mouthful of metal.

However, for children with Class II malocclusion, commonly referred to as an overbite or buck teeth, there is no advantage to starting early, according to Dr. William Proffit, a professor at the University of North Carolina's School of Dentistry in Chapel Hill.

Proffit said that was the conclusion of "three major, randomized clinical trials comparing the outcomes of treatment" for younger versus older children.

"Early treatment is more costly both in terms of the amount of money you have to pay and the number of visits you make, and there is a greater burden of treatment with no benefit for most children," he said.

Proffit was the author of one of the three studies that looked at early treatment for Class II malocclusion, with the other two done by researchers at the University of Florida and in the United Kingdom.

Proffit emphasized that early treatment is beneficial for other conditions, such as a Class III malocclusion, commonly referred to as an underbite, where the lower jaw is too big or the upper jaw is too small.

"You're trying to change growth, and your window of opportunity has run out by age 10," Proffit said. "The ideal time to start would be as early as age seven."

The largest group of children getting orthodontic treatment in the U.S. are those with Class I malocclusion, with crowded teeth that are either crooked or protrude. For this group, Proffit said, "early treatment works, but you have to do two phases of treatment.

So, they're going to be in treatment for four years — a first phase, then a vacation and a second phase."

With files from The Associated Press