Incisor Reduction In Equine Dentistry

“A New Profit Center” Developed Without Science

Modern equine dentists have recently embraced the removal of material from the front teeth of a horse (nippers, incisors). Some horses have died from this procedure. There is no basis in sound science for performing incisor reduction, and until someone proves to me the necessity for it being done, I will not do it. The veterinary profession has moved away from routinely performing this procedure (AAEP and BEVA – from a seminar at their meetings in 2003).

A question posted on my YouTube site for this video:

“I have found some of your videos interesting but I wanted to discuss this incisor bit with you, purely for curiosity.

If a horse doesn’t need “proper grinding” how can a horse who is over-floated “starve” from lack of nutrition? Do you really believe proper mastication doesn’t increase digestion efficiency?

Also, I just wanted to point out that though “back teeth grind and your front teeth never touch” is it not also true that a horses front teeth are always in occlusion??

What have your results been with a horse who has incisor malocclusion?

Have you looked into “camming?”

When the lateral movement of the mandible takes place, and the horse’s incisors are in occlusion, BUT there is a slant, or a curvature, this HAS to separate the back teeth, and hence you would notice a larger temporal muscle on one side.

This is PROOF of excessive use on one side due to incisors and so I am curious as to your results/thoughts.”

“Mack Horse” on March 21, 2013 on my YouTube page

My Response:

1) Over-floating can remove all points preventing the horse from getting a grip on the food, causing him not to form a swallowable bolus. This is why some horses have difficulty chewing after floating with quid formation. In the worst case, the horse cannot swallow anything, causing starvation.

2) The purpose of chewing is to form a swallowable bolus. Other chewing results include increasing exposed surface area for digestive enzymes and bacteria to do their work. Adding saliva lubricates as well as starts the breakdown of sugar. There is no study to prove that increased chewing causes improved digestion. Instead, a study of 17 horses with various teeth condition were given the same feed. Sampling of digestive contents showed that digestion occurs in the digestive tract, and chewing was not a factor. As every horseman knows, most of the manure in one barn looks the same. Colon condition has the most influence on manure consistency, with horses on high grain diets having colonic ulcers due to dysbiosis, causing loose, watery manure and whole grains to pass undigested. To answer your question, “proper mastication” doesn’t increase digestion efficiency.

3) Incisor occlusion – the only time incisors occlude (and again, there is no study, only assumptions) is when they bite something. Incisors are used as weapons in fighting. They are not used to cut off the grass (harvesting grass), as can be seen in parrot mouth horses (no occlusion) and horses without incisors (lost with EOTRH). All ruminants (cattle, deer, sheep, goats) never have upper incisors. With that in mind, what causes teeth to wear? Specifically incisors? Their enamel is different (seen in electron-microscopy) and softer than the cheek teeth enamel (Dr. Paddy Dixon, personal communication 2003). My theory is that the tongue moving over the teeth causes the most wear. I also believe the constant pressure of the tongue behind the incisors moves them forward in older horses (Please see all the images in the aging project post). Do they come into occlusion? Yes, and anywhere there is no opposition, an overgrowth occurs, such as the upper 3’s forming the seven-year hook. My statement was when chewing, the incisors do not come into occlusion because the bolus of food prevents complete closure of the mouth.

Again, for chewing, the incisors are not required. So, why are horse dentists looking upon incisors with such interest? It is a “profit center,” expressed by the man who invented it in the 1980s (personal communication with another equine dentist who was told this directly). There is no science behind it, and several horses have died from the process as secondary, un-treatable osteomyelitis caused the horse to stop chewing from pain, leading to starvation. If occlusion is necessary, why aren’t we filling in the over-worn teeth of cribbers or stall bar rubbers?

4) My results with horses with incisor malocclusions – Any variance to a perfect horizontal occlusion is secondary to something causing the horse to chew unevenly. The number one reason I have seen for this is sharp points causing buccal ulcers and chronic pain. The horse chews to avoid the pain, like a man walks lopsided if one leg hurts. The second reason for uneven chewing is an over-erupted tooth such as 311 and 411 hooks. Each horse I have seen with uneven incisors has been in good body condition. One of my expressions is, “I have never seen a skinny parrot-mouthed horse.” The same is true for uneven incisors. Smoothing all sharp points of the cheek teeth always improves their chewing. Again, no study has been done involving only reducing the enamel points, reducing only the over-erupted incisors, or both.

5) I have not looked into “camping” as my belief in its theory is doubtful. Cams are mechanical devices that cannot alter their shape or size; however, living tissue will adapt to applied forces.

6) “When the lateral movement of the mandible takes place, and the horse’s incisors are in occlusion, BUT there is a slant, or a curvature, this HAS to separate the back teeth, and hence you would notice a larger temporal muscle on one side.” – This is classic “cart and horse” argument of which came first? Your statement requires that the over-eruption of the incisors, causing the uneven bite, is an active event that forces the jaw out of position. The over-eruption is a passive event secondary to the horse’s chewing movement. Removing incisor growth doesn’t cause the teeth to become re-balanced. However, removing the pain caused by the cheek teeth will allow it to close correctly, and the incisors can self-correct over time. Nobody has taken the time to prove this. The asymmetry of the muscle can be caused by an altered chewing pattern caused by pain, not incisor obstruction. Most horses select one side to chew their food (so do we humans), and in almost every horse, the soft tissue below the left temporomandibular joint (TMJ) is larger than the right, and in some, it is painful to pressure.

Finally, thank you for asking me my opinion on incisors in horses. I believe that horses have survived for many years without our interference. I also believe in doing what is in the horse’s best interest. Reducing incisors and balancing them is something I have looked at for three decades, and I am not convinced that it is the right thing to do. In a personal conversation with Dr. Paddy Dixon in Scotland (co-author of Equine Dentistry with Dr. Easly) in 2003, he said that “the United Kingdom is rapidly moving away from recommending incisor reductions” as they are secondary to a primary event in the cheek teeth area. In addition, they have caused the death of several horses. Later that year, the same thing was said by Dr. Lowder (University of Georgia Veterinary School) at the 2003 AAEP equine dentistry wet lab. That was enough for me to end the discussion on the subject.

Doc T