Tooth troubles: Tackling equine dental problems

Approaching a dental problem in horses is the same as for any medical issue. Start with the body as a whole, and then work to the specific. Treatment, when possible, should address the primary cause.

"It's important that knowledgeable clinicians perform equine oral examinations, make accurate diagnoses and perform appropriate treatments," says Robert Menzies, BVSc, a resident in dentistry and oral surgery at the Matthew J. Ryan Veterinary Hospital at the University of Pennsylvania's School of Veterinary Medicine.

Armed with preliminary information from the client, as soon as you see the horse, you can begin to take its condition into account, such as how the horse is moving and its character and temperament.

But before focusing on dental matters, perform a general physical examination to assess a horse's overall health, including body temperature, weight, heart rate, lung sounds and respiratory rate. Also assess the mucous membranes, the horse's hydration status and gut sounds.

"A horse always gets a physical exam before it gets an oral exam," says Robert Gregory, DVM, owner of Seattle Equine Dentistry, "since about 4 percent of horses I see have some sort of general physical problem that excludes them from a dental exam or treatment that day."

Overview of a thorough exam

The focus of an equine oral examination should be based on the presenting complaint. Menzies notes an examination should include the following:

• A thorough history involving both a general and an oral history, the latter of which should include a dental history, feeding habits and biting history.

• An extraoral examination, which entails examining the horse's head, including visual assessment of facial symmetry, or the contours created by soft tissues (temporal and masseter muscles, lips, muzzle, parotid and laryngeal regions and skin, and hard tissues around the mandible and maxilla). Also check for discharge and odor from the nose and mouth. Palpate facial structures to help confirm visual facial assessment. Check percussion of the sinuses.

• An intraoral examination, including the assessment of gingiva, teeth (present and absent), bite, occlusal surfaces and occlusion. Palpate the mandibular and maxillary interdental spaces for canine teeth, first premolar teeth, unerupted teeth, bit trauma and bone irregularity.

• The use of an oral speculum to examine all soft tissues, including the tongue (Photo 1) and sublingual mucosa, hard and soft palates, lips, commissures, gingiva, mucogingival junction and alveolar and vestibular mucosa. Use a periodontal probe to check for appropriate attachment around each tooth.

• A thorough check of the teeth within each quadrant and assessment as a functional unit. Closely examine the occlusal surface for abnormal secondary dentin; tertiary dentin; open pulp horns; fissures in the dentin, enamel and cementum; dental fractures; infundibular cemental hypoplasia, infundibular caries and impacted feed matter.

Photo 1: Ulceration of the right dorsal body of the tongue.

Gregory says the oral examination should be consistent—the same procedure every time.

Sedation

Menzies advises that as you perform your basic physical examination, you should assess the patient for suitability for sedation. Some horses may be old or in poor body condition or may have arthritis.

"You can't afford to have these horses to go down on their knees or be oversedated," says Menzies. "The presence of oral pain in such patients can make adequate sedation very challenging. Local nerve blocks are often essential facilitative therapy."

In addition, waiting to perform an oral examination may be prudent. In instances of severe periodontal disease, for example, some horses may allow a more thorough oral examination, diagnostics and treatment only after receiving an appropriate course of anti-inflammatories and antibiotics.

"Coming back a second time, they'll be less cantankerous, and sedation works better," says Menzies. "It's best, depending on the condition of the animal, not to try to fix everything during the first visit. Often, it's a working diagnosis, and response to treatment is going to guide you. If you take a more conservative approach, it may take longer to get where you're going, but you're going to cause fewer welfare issues than by overtreating or inaccurately diagnosing and inappropriately treating a horse."

Assuming a horse is healthy and before beginning the oral examination, Gregory has the horse eat something to assess its manner of eating, which may illustrate the possible problem.

"When I walk into the stall, before I look at a horse's head or in its mouth, I touch the horse and attempt to pick up a foot," says Gregory. "A horse with a significant dental problem most likely will be in pain and therefore unhappy to allow you to pick up its foot. If it stands with its foot planted to the ground, I'll have to take a little more time to get it to relax before I proceed."

Once the physical examination is completed, a sedative is given, and the horse is walked into the stocks or similar restraint.

"The selection of sedative is very important, and the amount is based on the individual patient, procedure and environment you're going to be working in," says Menzies. "I prefer to work with animals in a hospital setting for a number of reasons: It's a controlled environment—one I'm familiar with; I have all the equipment I would need; and I have the assistance of vet techs and other personnel."

The extraoral examination

The next step is to look for asymmetry of the head. "It could be skeletal—maybe a compression fracture of the maxillary sinus or frontal sinus," Menzies says. "You might see a swelling that's discharging from the mandible, a tooth-root abscess, a fractured jaw. A mild skeletal asymmetry might show as a tooth wear pattern that's not within the normal limits but appropriate for that individual. Each horse is assessed according to its specific anatomy."

As he performs an extraoral examination, Gregory uses all of his senses as each gives him information. "I also palpate the head, check muscle and jaw function, check the temporomandibular joint and the mandible for possible fracture or abnormality and note any odor from the nose or mouth," he says.

"Often there might be a lump on the side of the face, a malodor or a nasal discharge that leads you in a direction before you even open the mouth," Gregory continues. "Between the external and internal oral examinations, I open their lips and look at gum color and incisors and again check for odor from the mouth. That gives me a start. If I have a direction—a lump, pain or swelling—I go in that direction."

Menzies says that viewing the incisors can give you an idea of the animal's age as well as abnormal wear patterns, periodontal disease, equine odontoclastic tooth resorption and hypercementosis, which is becoming a well-recognized condition affecting older horses.

He also advises palpating the masticatory muscles as part of the extraoral examination. "An abnormal chewing pattern often will be reflected in myositis because the muscles will be working abnormally or overworking," says Menzies. "They may become swollen and sore."

Be sure to take note of any discharge. An ocular discharge, for example, may be the result of a functionally occluded nasolacrimal duct resulting from inflammation around an infected tooth root as the duct travels down from the eye to the nose, says Menzies. A nasal discharge, whether unilateral or bilateral and no matter the amount or character, warrants further investigation to determine the cause. Appropriate treatment will vary considerably depending on the diagnosis. Dental disease may be implicated. Also monitor air flow for any malodor coming from the nostrils, mouth or oral cavity. And check around the lips—look for wounds caused by a bridle, the bit or vegetation.

The intraoral examination

For the intraoral examination, use a headlamp to provide a good source of bright light. "Prior to the speculum's placement, I look at the incisors and canines, since once you put in the speculum you can't see those any more," says Gregory. "Before rinsing, I see where there might be food within the mouth—food stasis on one side or the other—impacted between the teeth. After rinsing, I look again, noting if there's a diastema—spacing between teeth—or a cavity. With rinsing, food usually washes out but might stick in those places. Such food residues might be indicative of a particular problem."

Gregory says he starts with the arcades: 2, 3, 4, 1. With a dental explorer, he takes a good look at every tooth. He then uses a dental mirror and an oral endoscope to take a better look at problem areas. Next, he puts his hand in the mouth and palpates all the teeth, since, he says, about 25 percent of problems are invisible to the naked eye but might be felt. He begins palpation from the back of the mouth and moves forward. He checks the cheek teeth, bars, diastemata of the cheek teeth, canines in males and incisors in females.

Menzies adds that it's important to count the teeth to assess either supernumerary or missing teeth in the dental arcade. Once the mouth is rinsed, use a dental mirror to get a cursory look throughout the mouth. Then use a rigid endoscope to further examine and record.

"The endoscope is 45 to 50 cm long with a 30- to 90-degree bevel on the end," Menzies says. "The advantage of it is several-fold: The picture comes up on a monitor, so with the clients there to observe, it's a great educational tool to help them understand what the problems are as you go through. And you can examine the most rostral premolar teeth and the most caudal molar teeth with the same degree of accuracy. This is a great advantage, since most of the pathoses are in the more caudal region of the mouth. Diagnostic tests, diagnoses and treatments all get harder to perform as you go more caudally."

Menzies says he goes over each tooth in the lingual and palatal aspect, occlusal surface and vestibular surface, paying particular attention to the interproximal area where diastemata form and food is entrapped (Photos 2A & 2B). Image capture software allows each view to be recorded. "If there's impacted food, it's best to try to get that out before doing endoscopy because it might obscure certain areas," he says. "It might help to use a high-pressure Waterpik and an explorer to get the food out to more properly examine the teeth and periodontium."

Photo 2A: Entrapped feed in a diastema between the left mandibular third and fourth premolar teeth.

After the endoscopic examination, go back and check any areas of concern, Menzies says. Palpate each tooth, and apply percussion or heat and cold. As you apply these provocation tests, look for repeatable responses from the horse, which are possible even with the effects of sedation and analgesia already administered.

Photo 2B: The same diastema in Photo 2A with the feed removed revealing marked periodontal disease.

"Often I'll take a heavy probe to tap on the teeth or lightly push on them to see if there are any loose teeth," Gregory says. "I also inspect the gingiva, both on the vestibular and palatal sides, for discoloration and pockets. I look at the palate, gums, salivary ducts and tongue. Once I get to that point, I move the speculum down to manipulate the mandible, looking for excursions of overcontact, abnormal sounds or squeaking, as an abnormal tooth has a high pitch."

During the examination, Gregory periodically stops to record what he has done, though the endoscope has the ability to record. He also may take photographs, depending on what he finds. "For 50 to 75 percent of the horses I see, I recommend radiographs. I take x-rays and put that together with what I see visually."

Menzies agrees that if areas of concern are found, radiography is the most appropriate next step because most information lies below the gingiva. "It's a challenge because oral radiographs are not the easiest radiographs to do or to interpret. The better your radiographs are, the easier it becomes to diagnose. Though it can be tricky for the neophyte, you really can't do a proper diagnosis without radiography."

Further imaging using computed tomography and scintigraphy can be helpful, he continues, particularly for certain types of fractures and for tumors, especially those of the maxilla.

Oral health just a part of the whole

Menzies notes that veterinarians shouldn't hesitate to refer cases to dental and other specialists when needed. "No one is the ultimate expert, but we can all help out," he says. "We each have varying levels of expertise that are complementary. A horse suspected of an oral problem could end up needing the skills of a radiologist, an internist, an ophthalmologist, a surgeon, an anesthesiologist, a histopathologist, a microbiologist, a parasitologist or a behaviorist—just to name a few—besides those with extra training in dentistry."

A horse's systemic health is important to determine, he continues. For example, conditions such as Cushing's disease may have a marked influence on oral health. "Cushing's affects the body in many ways. In the mouth, the abnormal collagen metabolism decreases immune function and impairs healing abilities. Horses with Cushing's tend to have loose teeth, periodontal disease and a disproportionate amount of oral ulcers. When you're treating a horse with Cushing's for periodontal disease, it's a good idea to treat the Cushing's as well. That's certainly one reason I feel so strongly that dentistry is a veterinary-only activity; the oral health cannot be considered in isolation from the rest of the body."

Ed Kane, PhD, is a researcher and consultant in animal nutrition. He is an author and editor on nutrition, physiology and veterinary medicine with a background in horses, pets and livestock. Kane is based in Seattle.