Very few people choose a horse for its winning . . . smile. But in horses, as in humans, an unhealthy mouth is more than just a cosmetic concern. A horse with a dental problem can get ornery with a bit in its mouth and is more prone to throw a rider. A rotten tooth or infected gum can cause an equine to stop eating and lose weight. It can also lead to more serious ailments, including some that are deadly. But, unlike humans, four-legged beasts can’t tell their owners when they’ve got a nagging toothache — Mr. Ed aside.

Amber — her real name — has had extensive dental work done in the last three years, though you’d never know it by the way she acts around horse dentist Duncan MacPhail. The 6-year-old, chestnut-colored Haflinger is as gentle as a lamb when MacPhail begins his biannual exam in Diane Wyatt’s West Newbury barn. MacPhail is there to check up on the mare’s troublesome underbite.

MacPhail, 31, has been practicing equine dentistry throughout New England for about five years. Sometimes his work calls for a delicate touch; other times, only a fair amount of muscle will get the job done. Either way, MacPhail, who stands 6-foot-3, exudes quietness, almost serenity. His demeanor helps put the animal at ease, he says, but it also keeps him attuned to the subtle, nonverbal cues a horse gives when it’s frightened, angry or in pain. That’s key, because when you’re elbow-deep in the mouth of a half-ton draft horse with an inflamed abscess, cooperation is 90 percent of the battle. “They’ve all got a finite amount of patience,” he says, “because this can be fairly invasive.”

Unlike a human dentist, MacPhail has to take a more roundabout approach to his patients than just asking them to “open wide.” Even though he’s worked on Amber before, MacPhail begins at her right flank, pats her neck and lets her sniff his hands. “A lot of people will be aggressive with horses and really back them into a corner and get after them. I don’t do that,” he says. “I’ve found that if I move with them, it’s a good experience for them and it’s much easier the next time.”

When MacPhail hasn’t worked on a horse before, he avoids its head entirely for the first five to 10 minutes. Then he starts gently leaning against its body and gradually works his way up toward its ears.

“When I get to the head, I’m looking for symmetry,” he explains, staring into Amber’s eyes while palpating the outside of her jaw. He’s looking for anything that seems out of the ordinary, such as bumps along the jaw line or retained caps, which are baby teeth that horses are supposed to shed. MacPhail also examines the horse’s forehead muscles, which tell him whether the animal is chewing equally on both sides of its mouth.

If the horse doesn’t react violently, MacPhail gives its head a few quick, firm squeezes to make sure there aren’t any tender spots. Amber doesn’t flinch. “Then, I’ll just slip my finger into the horse’s mouth, like this,” he explains, poking his fingers through Amber’s black, rubbery lips. “That has two purposes. It lets them know what’s coming. Also, I can feel how sharp the outside edges of the molars are.”

A healthy horse jaw functions like a mortar and pestle, MacPhail explains, grinding food to aid the horse in digesting it. In nature, where wild horses eat a diet full of grit, their molars constantly wear down to a smooth, flatter surface. But domesticated horses eat a cleaner diet of hay and grains, which wear down their teeth much more slowly. Horse teeth continue to grow over most of the animal’s life — they can add between an eighth and a third of an inch of enamel per year — making for some very uneven chompers.

As a result, most domestic horses need to have their teeth filed periodically. To do this, MacPhail feels inside Amber’s mouth for sharp enamel points on the outer edges of the molars. He’s also looking for “ramps,” or enamel bumps at the rear end of the molars that can grow as high as an inch, and “hooks,” which are similar bumps on the front end of the tooth. These Academy of Equine Dentistry [1] in Glenns Ferry, Idaho. During this intense, two-month program, he spent 16-hour days in class and working on horses. Still, much of his expertise was learned on the job.

Ironically, many horse owners will spend thousands of dollars trying to fix a “problem horse,” MacPhail says, and never think to look in its mouth. Yet many behavioral and physical problems can be traced to poor dental health.

“I’ve worked on horses that have had real problems for years,” he says, rinsing his instruments under a water pump outside the barn. “I can spend an hour with them, and they’re a brand new horse. That’s pretty cool.”

CLICK HERE TO WATCH AN AUDIO SLIDESHOW OF THIS EXAM. [2]