Most horse owners are well aware how important it is to ensure their horses receive regular dental and oral exams. In some cases, however, our animals may require more advanced care beyond the scope of a routine checkup. New and improved technologies, equipment, techniques, diagnostic imaging and a more thorough understanding of a horse’s teeth and oral structures have made certain complex procedures more practical and possible over the past 20 years or so, but many are still largely experimental, expensive, and require the services of equine dental specialists.
Dr. James Carmalt is a board-certified professor of equine surgery at the University of Saskatchewan’s Western College of Veterinary Medicine. He also Canada’s only veterinarian board-certified in equine dentistry by the American Veterinary Dental College and one of only 18 in North America. Carmalt gives us a glimpse into emerging equine dental procedures, their benefits and drawbacks.
Root Canals and Fillings for Horses
Endodontics is the branch of dentistry relating to the dental pulp, the central part of the tooth, which is comprised of blood vessels, nerves, and connective tissues. If a tooth becomes damaged due to injury, wear, trauma or even overzealous floating, decay can set in, causing pain, nasal discharge, and swelling, among other clinical signs. Root canal surgery may save the tooth, preventing the need for extraction.
With the horse under standing sedation or general anesthesia, the veterinarian removes diseased and dead pulp, fills the space and caps it with restoration material to prevent entry of food material. Similarly, fractures, breaks, chips, or decay that may ultimately compromise the tooth structure can be “restored” or filled with same amalgam or composite materials used for human cavities.
In humans, even dogs and cats, this is all pretty straightforward, but not so with horses, in large part due to their hypsodont tooth anatomy, meaning their long, permanent teeth continually erupt from the gum and wear evenly (in ideal situations) as the horse eats the majority of the day on coarse grasses or hay.
“In humans, the teeth don’t move up into the mouth. They’re not worn down in the same way as a horse’s tooth. In a human tooth that’s not erupting, that restoration will stay there forever, assuming it’s put on correctly and is otherwise normal. The problem with horses is you’ve got a type of filling in the tooth and a restoration at the top of the tooth that will not stand up to abrasion,” says Carmalt.
“In the horse, because two to three millimetres of tooth is worn away every year, at some point that restoration will all be worn away. That restoration covers an opening that is filled with the material that you’ve put in [the pulp chamber], but it’s not designed to stop bacteria.”
In canines and incisors, the root canal success rate is relatively high because they don’t erupt quite as much as cheek teeth, explains Carmalt. They also have single pulp chambers, similar to human teeth, whereas cheek teeth possess a more complicated pulp structure with up to seven chambers situated both vertically and horizontally. Access to the vertical chambers to clean and remove diseased pulp is complicated but doable, he says, but the horizontal aspects are more difficult to reach. “Ultimately, I may seal in bacteria in the little communications between the pulp chambers.”
During root canals, the tooth is generally accessed from the root end, meaning the veterinarian has to bore through bones in the face or sinus. “Now you’ve got a complication of a second approach because you’re doing something to the surrounding tissue in addition to the tooth.” He mentions a novel way around this called a re-implantation procedure. The tooth is removed from the mouth entirely and a root canal performed from the top of the tooth, which is then pushed back into the mouth to re-implant. However, he notes, “These teeth are diseased, which means they’re not as strong as normal teeth. You have a greater chance of damaging them upon extraction. As soon as you damage them, then you’ve reduced the chance of successful re-implantation even further.”
Extracting Horses’ Teeth
So why not just remove the tooth in the first place? Carmalt says this comes with a host of other longer-term complications, especially in terms of cheek tooth extraction.
There are six cheek teeth in each arcade (top and bottom rows, both left and right), each of which acts as a single chewing, grinding unit. When a gap appears on one side, the opposing cheek tooth doesn’t wear as it would normally and instead develops a downward or upward spike on the portion of the tooth opposite the gap. This acts like “a screwdriver” packing feed in the hole.
The other difficulty is that equine cheek teeth have adapted to have no gaps between them. “Even if horses could use their hooves to hold tooth floss, they wouldn’t be able to floss between their cheek teeth because there is no space,” jokes Carmalt.
If you remove one tooth, the rest shift to close the gap. Over months or years, narrow spaces – called diastemata – appear between the other teeth. Food gets trapped in these spaces and eventually putrefies, leading to gum recession and periodontal disease, a painful inflammation of the periodontium, the tissues surrounding and anchoring the teeth within the jaw bone. In addition to bad breath, quidding (dropping feed), weight loss, colic, choke and other symptoms, if left untreated, periodontal disease can lead to infection of the roots and underlying bones and tissues.
Management of these issues will include a life-long commitment to providing regular dental exams possibly involving extensive rasping of opposing tooth hooks and widening of the spaces between teeth to allow food and saliva to flush through naturally.
Dental Implants for Horses
We all know someone with a dental implant. This involves the replacement of tooth roots with metal posts onto which an artificial tooth is attached. (Interestingly, many human dental implants are constructed from equine bone!) Surely horses could benefit from the same type of components?
“As long as it’s stronger than the material around it and it is possible to design it right, a fake tooth can be put in place of a diseased tooth and it will do the job of holding the other teeth apart. We’ve got 3D printing technology now, that’s easy.” However, although equine implants are currently being studied, as is the case with so many veterinary innovations, it’s a matter of researchers like Carmalt finding “the right client with the right horse who is willing to take the risk to let me try it.”
He adds, “You can’t replicate infected teeth in five hundred horses because it’s not ethical, but if I can try it on two or three client-owned horses, then all of a sudden we might get some research money and we can try different things.”
Procedures like those mentioned here and many more are being honed and advanced at research centres and in private equine dental clinics around the world. One major development is the refinement of sedation, local anesthetics and equipment that allow horses to remain standing during procedures. Not only does this make life easier and safer for both practitioner and patient, it’s generally less expensive than general anaesthesia.
Another significant advancement is the ability to remove teeth via the cheek in a technique called minimally invasive transbuccal screw extraction. The majority of equine teeth removed by persons who specialize, or have a particular interest, in equine dentistry are now being removed through the mouth. The success rates are higher and the complication rates lower than that caused by cheek tooth surgical “repulsion,” which involves boring through facial or sinus bone to drive the tooth from its socket.
It’s certain that what’s considered cutting-edge today in equine dentistry will, within the next couple of decades, be standard offerings and we’ll be looking toward an entirely new slate of oral health techniques and technologies.
