Looking a Horse in the Mouth

Dental maintenance is important when analyzing behavioral problems, be it bucking, stiffness in the neck or lower back, bracing in the jaw, any number of things.  I spent years as a veterinary technician with excellent equine and small animal veterinarians, and my degrees are in psychology, anatomy, and neurobiology, so it is to my favorite textbooks I turn for teaching information about horse teeth and how they affect behavior and training.  Although a quick and somewhat simplified example, here is an explanation of the dental issues with which the new horse is dealing.  These diagrams are taken from Pasquini, Spurgeon, and Pasquini's text, Anatomy of Domestic Animals 9th Ed., and Centered Riding by Sally Swift, the organization in which I hold my instructor certification.  Today's dental work was done by Dr. Allen Landes with Equine Medical Services.  His calm stall-side manner is bettered only by his knowledge of horses and how their complex bodies function!

View of the entire equine skull

Equine skull with teeth more prominently drawn.  Notice how far the teeth go into the horse's head, both front to back and up and down!

This horse in for training this month is a sweetheart, and now that we have his bucking issues resolved I wanted to further investigate why he has a history of being behind the bit and avoiding any contact with the reins and rider's hands when riding.  The veterinarian did a quick oral exam (palpating or feeling inside the gelding's mouth, not asking him to answer questions verbally hee hee) which showed us that he had some sharp points on the edges of his teeth that were irritating his cheeks, so we sedated him and proceeded to do a more thorough exam.

One of the things we check is the occlusal angles, or how the cheek teeth meet each other.  Because horse's teeth continue to erupt, one might think of them as growing throughout the horse's life.  The horse is born with all the tooth he's going to have, and as he chews forage he wears them down, and simultaneously fresh tooth erupts into the oral cavity.  Because of this grinding and the schedule for losing baby teeth, the permanent teeth can come in and develop odd wear patterns.  It's important to have a qualified veterinarian check young horses' teeth every 6 months, and adult horses on the same schedule.  Ideally they won't need dental work, or floating, that often, but the earlier a potential problem is identified the easier it is to correct or maintain.

There are many factors we assess and address in a horse's dental exam, but this is the short list of things directly affecting this particular horse we evaluated today.  We looked at the jaw joint itself for pain or swelling, the teeth and their occlusal angle, or how the cheek teeth meet, the grinding surface since horses chew in a circular motion, the alignment of the incisors to see if they meet evenly, the amount of slide the jaw has forward and backwards, and the amount of slide and quality of grind the jaw has left to right.

As an illustration of this jaw motion, because human's anatomy is comparable to the horse, let your jaw hang loosely with your teeth not touching and then look down.  Do you feel your jaw slide forward?  Put your head in a neutral position again.  Clench your teeth, and try to look down again.  Do you feel how forced and tense you become?  Notice where you feel the tension.  Neck?  Shoulders?  Lower back?  The horse can feel it in all these places if his teeth don't allow his jaw to slide. 

From Centered Riding by Sally Swift

The horse here had very little to no sliding motion forward and backwards because of transverse ridging on his cheek teeth.  There should be some amount of ridging on the teeth so the horse can grind his food, but because of excessive ridging his jaw motion forwards and back was very limited.  Because of this limitation, he would tuck his head down because he thought that was expected of him, but he was flexing at the third cervical vertebrae, and not at the poll.  This resulted in hypertrophy of the neck muscles, or enlarging of the neck muscles.  He didn't want his jaw to hurt, so he compensated by flexing at the third vertebrae, not at the first.  This also can lead to lower back pain since compensating in one area can lead to tension in another.

Diagram of the top teeth and the bottom teeth

Now we have the gelding's teeth sliding more normally after his dental work with hand files (called floats).  We don't have completely normal range of motion yet because it needs to be a gradual process so he can acclimate to this new balance in his mouth, but he has much more motion than he did before today's dental work.  It will be interesting to see how this affects his comfort level when riding, and how he changes his responses to the bit, rein aids, and rider hands.

This blog post is a very over-simplified explanation of what makes up a thorough dental exam and floating, but it gives a general idea of some of the factors that can affect a performance horse from his mouth.

One more site that has excellent photographs of horse skulls and teeth is located at http://www.vivo.colostate.edu/hbooks/pathphys/digestion/pregastric/horsepage.html