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 ">deformities can cause painful and ineffective chewing. An affected horse may lose weight, even if it’s eating the same amount of food it always has.

When MacPhail finds a ramp or hook, he ventures into the horse’s mouth with a metal instrument that looks like a truncated golf club, only with a carbide rasp on one end. Known as a “float,” this tool is used to file down the excess enamel. MacPhail may keep a pail full of floats beside him, depending on the type of work he needs to do.

Though some equine dentists use power tools for this task, MacPhail says he prefers manual instruments; he claims they give him more dexterity and are less apt to spook the horse and potentially injure it, or him. And, unless a horse has a serious behavioral problem or needs several teeth pulled, MacPhail generally does this work by hand. By law, he’s not permitted to sedate an animal; only a veterinarian can.

Clearly, “floating” horse teeth is strenuous work. With the float in the horse’s mouth, MacPhail files back and forth with short, rapid strokes, all the while holding the horse’s head firmly by its halter. The float emits a deep rasping sound, like a saw blade ripping through a dry log. A fine yellowish slobber appears along Amber’s lower jaw, a mixture of saliva and tooth dust.

“She’s doing pretty well,” MacPhail says, breaking into a sweat in the cold barn. “I’m staying in her line of sight so she knows where I am and what I’m doing.”

Surprisingly, MacPhail says he rarely gets bitten. “I’ve lost a couple fingernails, but no digits yet,” he says, one hand soaked in spittle. “I’m totally convinced that they don’t want to hurt you. And they could if they wanted to.”

After filing Amber’s upper and lower teeth, MacPhail needs to access her rear-most molars. To do so, he pulls out a shiny metal speculum — yup, that contraption — which fits over the horse’s head and ratchets open its mouth. With the device strapped on, Amber resembles Hannibal Lecter in The Silence of the Lambs. “It’s pretty medieval-looking,” MacPhail says, with a chuckle.

When all the back teeth have been filed smooth, MacPhail removes the speculum. Amber whinnies and shakes her mane, but seems none the worse for wear. The entire process takes about a half-hour.

When he’s finished, Wyatt asks him to check “Sonya,” her 9-year-old solid brown paint. Wyatt has obvious faith in MacPhail’s dentistry. “Duncan has really improved Amber’s bite in the three years he’s worked with her,” she says. “I’m really pleased with him.”

Amber and Sonya are well-tended horses, as any visitor to this 34-acre family farm can see. Wyatt keeps the barn immaculate and provides her animals with clean water, fresh hay and new bedding. Though such details may seem insignificant to an untrained eye, an equine dentist must extract information about his patients however he can. And a clean barn speaks volumes about the animals’ health and overall quality of life.

Unfortunately, that’s not the case for all the horses MacPhail sees. “The hardest part of my job is doing a horse that has major problems because it hasn’t been done in years,” he says. “Basically, the horse is living with the situation, and it’s up to the owner to get it help.” Once, MacPhail had to pull five molars from an unsedated horse because its owner steadfastly refused to allow it to be anesthetized. Needless to say, MacPhail worked as quickly as possible.

“That was tough,” he recalls. “But I felt that if they didn’t come out, the horse was going to die.”

Such cases are rare, however. These days, MacPhail says, 80 percent of his work can be done without sedation. And — in case you’re curious — he doesn’t do fillings, crowns or cosmetic dentistry, though he claims some horse dentists in Florida now offer teeth whitening.

Curiously, neither the State of Vermont nor the federal government regulates equine dentistry. In effect, anyone can hang out a shingle and claim to be a qualified horse dentist. “That leads to a lot of problems,” MacPhail admits. “It makes it hard for practitioners who are sincere, educated and dedicated to making it their specialty when there are people out there who aren’t doing what they’re supposed to be doing.”

For his own training, MacPhail attended the Academy of Equine Dentistry 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.”

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