articles

Equine Dentistry

By  | 

Equine dentistry is practiced by veterinarians and veterinary technicians as well as certifi ed and uncertifi ed laypersons all over the world. There are many levels of consciousness in the way it is being taught and practiced. The intention of this article is to bring higher awareness to how the temporo-mandibular joint (TMJ), and therefore the entire health of the horse, can be positively or negatively affected by the way the animal’s teeth are fl oated.

The goal of dentistry is to maintain an ideal relationship of anatomical alignment of the TMJ, molars and incisors with the body. When teeth are properly fl oated from a young age through the fi nal stages of life, there will be fewer medical and behavioral conditions.

The TMJ is a convergence point for six acupuncture meridians – three to the front legs, and three that go through the entire body and down the pelvic limb. More importantly, it is the closest joint proprioceptor to the brain and brainstem. Proprioception is a natural defense mechanism that prevents injury, and the immediate interaction between the brain and the voluntary muscle response. Poor proprioception leads to an imbalance in sympathetic and parasympathetic responses, placing inordinate stressors on the entire system. The TMJ is the most highly innervated joint in the body. Dysfunction of the jaw affects the facial and trigeminal cranial nerves. The TMJ’s proximity to the auditory tube or acoustic meatus directly affects the vestibular system.

While it’s important to eliminate the rims and sharp points of the teeth, it’s critical to consider the comfort and biomechanics of the TMJ. Restoring proper function and neurology to the jaw joint is key to physical and mental health in the horse. When horses are over-fl oated (common with power tools) to the point where there is no molar contact, they clench hard to get their molars together. This causes articular pain and even dysfunction (TMD), which involves more muscular, myofascial and ligamentous pain. What can start out as a bit of imbalance and discomfort can lead up to a raging headache, an unpleasant and potentially dangerous horse to handle or ride, tail wringing, head tossing, running backwards and more behavioral problems.

Dental exam – listen, look and feel First, relax and take a deep breath. You cannot rush this exam.

1. LISTEN and LOOK: Listening is receptivity. Listen with your whole body, not only with your ears but with your hands, face, even the back of your neck. You can listen and look at the same time. Observe the horse eating at ground level, which is where all horses should be fed. There should be a clean, clear, almost hollow sound of molars grinding. This resonance is a frequency or vibration that is a lullaby to the nervous system. This horse will have a contented expression and manner of foraging. With limited molar contact or dental pathology, you may hear nothing or you may hear strange squeaks, pops and crepitus in the joint. The horse is anxious, tense and perturbed in his effort to forage. You will see it in his eyes and his hurried “I can’t get enough food” attempt to masticate. This horse will often have asymmetric gaits, unidentifi ed lameness, abnormal posture and possibly a compromised immune and nervous system.

2. LOOK and FEEL: First, look for symmetry of the nostrils, eyes, ears, facial crests and muscles. Note the spacing between the atlas and the ramus of the mandible. Second, begin to palpate the TMJ by feeling the energy fi eld around it. Pain will cause fear and worry in the horse’s eyes as you move your hands toward his jaw. Then palpate the soft tissue. The masseter and temporalis muscles are easy to palpate for tone and/or atrophy. Although the pterygoid muscle is diffi cult to palpate it has a very obvious trigger point – two fi ngers’ width dorsal to the angle of the mandible on the medial aspect. I also take great care to palpate the hyoid apparatus, the gyroscope of the body. I regularly do a hyoid release taught me by Dr. Kerry Ridgeway (see video at balancedequinewellness.com).

Next, palpate the joint space itself; it should be bilaterally even. Challenge the TMJ by applying pressure to the front of the coronoid process of the mandible across the joint, and to the caudal aspect of the zygomatic process of the temporal bone. The horse’s reaction will be crystal clear!

Finally, check the anterior and posterior motion of the mandible. This may be the single most important indicator of proper TMJ biomechanics. Run your fi ngers along the incisor line, feeling for any changes when you lift and lower the head. Alternatively, you can part the lips and observe changes in the incisor bite as you elevate and lower the head. The change in the bite need only be 3mm to 5mm to allow the jaw to move into the desired neutral position. With good anterior motion of the mandible the horse can lower his head, fl ex at the poll, lift his lower cervicals and withers, elevate the spine and engage his hindquarters. This is the balance a horse needs for walking up and down hills, jumping over jumps, performing reining maneuvers, cutting cows, etc.

Proper use of dental instruments The wave of power instruments on the market, and schools or courses training equine dentists to use them, has been enormous in the last decade. “Time is money,” say many power fl oat practitioners. But at what cost? Whose cost? Some highly skilled dentists use power instruments with care and do a good job balancing horses’ mouths. I have power instruments myself and use them judiciously when I come across extreme pathology. But I always fi nish my work with hand instruments.

I usually start by balancing the incisors. One goal is to have the horse aware of the subtle changes to the nervous system as we make adjustments to the teeth (so minimize sedation). This also allows the horse’s head to be in a natural position. I often fi nd myself on my knees and up close and personal with the mouth to best determine the most appropriate angles for that individual, especially for the incisors. The goal is to have a three point balance between the incisors, molars and TMJ. I fi nd that proper length and angle on the incisors is key to holding this balance together.

Most horses are so content with the improvements to their incisors that they allow us to do the molar work without more sedation. I may titrate more sedation at this point or simply use some Bach Flowers and/or essential oils to continue with the dental work. The angles on the molar arcades are responsible for guidance of the jaw joint and proper neurological input. Having the horse’s head in a neutral position is important, so again minimum sedation is best. Evaluation of the fl oating is best when using minimal sedation and allowing the head to be in a normal position. Each horse is unique, so it is not just about taking points off the teeth. Concerns with power tools are that the horse has to be heavily sedated to even get these loud vibrating instruments into his mouth. The head needs to be propped, held or tied up to allow the practitioner to work because the horse is too drugged to hold his head up. Usually, the speculum is open quite wide, and there may even be a very bright light shining in his eyes while he is overextended at the poll. All this rigging is tedious to let down so the horse is often in this unnatural position for as long as it takes to get the job done! If the horse should shake his head or move suddenly, it is easy to mistakenly put an incorrect angle on one or several teeth since many of these instruments are quite aggressive. Evaluation of the results may not be as accurate.

Potential problems with power instruments While inaccurate fl oating can be done with hand tools, I generally see many more problems when power tools are used.

1. Putting the same angle on the near and far side molar arcades is essential for good balance. With small tooth-specifi c hand instruments, we use both the left and right hand for the corresponding arcades. Often, power tool operators use their dominant hand on both sides, creating different angles. Usually a right-handed person will fl atten the horse’s left molar arcade and leave the right side steeper.

2. Far too often, teeth fl oated with power tools have had the molar tables completely fl attened in an attempt to eliminate buccal and lingual rims, and the surface is left smooth. The amount of tooth is limited, especially in the older horse with an attrition rate of around 2mm or 3mm per year. One pass of the more aggressive power instruments will take that off in 20 seconds. There needs to be texture to the molars for grinding.

3. When molar tables have been over-fl oated, the incisors are often untouched. This leaves the horse riding on his incisors with little or no contact between the molars. These horses are in severe myofacial pain as they clench in an attempt to get molar contact. Food boluses are not being cut and sheared properly. The temporalis muscle often over-develops and a vertical mastication pattern ensues, causing extreme body soreness as the horse’s nervous systems are fi ghting minute by minute for their balance.

4. Power tools can create thermal damage because the cementum absorbs the heat, altering the chemical structure. The surface becomes too hard, preventing the necessary vibration in the periodontal ligament that stimulates proper eruption of the tooth. Therefore, the tooth does not wear normally. While adding a water cooling system may help, proper hand floating is better.

Healthy teeth = healthy horse We humans have the responsibility to do what is best for the animals, not what is easiest for ourselves. Take the time to look, listen and feel. Keep the horse’s head in natural positions. Change the way you look at things, and the things you look at change. Keep blades sharp and use fl oats that are ergonomically correct and designed to fi t in the horse’s mouth. Use minimal sedation. If power is needed, do it with great care and consideration. See each horse as an individual needing a tailored approach.

Horses frequently perform brilliantly after TMJ awareness dentistry. Recently, I treated a meter 40 horse with chiropractic and acupuncture because she “just wasn’t powering up from behind.” After the show, I did dentistry. Three days after the dental, her owner rode her by my treatment stalls and said, “Hey Doc, she’s jumping the top of the standards, I’m going to see if I can qualify for Young Riders on her!” I get this kind of response more regularly from my dentistry than from any other form of treatment. It is so satisfying!

REFERENCES

Baker, Gordon J. & Easley, Jack (2002) Equine Dentistry W.B. Saunders Co. Ltd.

Dacre, Ian, T. PhD, MRCVS, Histological and Ultra structural Anatomy of Equine Teeth (2002) Gellman, Karen, DVM, PhD. 2007 Veterinary Dental Forum. Living with Gravity: Posture and the Stomatognathic System.

Lytle, Larry, M.D. Proprioception to the Brain, proper dental muscle alignment is the key. Laserlightinstitute@earthlink.net

May, Kevin J., DVM. (2008) Interrelationships Between Equine Acupuncture, Chiropractic and Dentistry, Prick. Of 34th IVAS 2008 International Congress, Keystone, Co.

Rooney, James R. Clinical Neurology of the Horse. KNA Press Inc. 1971 June, First Edition.

Upledger, John E., D.O., F.A.A.O. Craniosacral Therapy II, Beyond the Dura. Eastland Press Inc. 1987

Dr. Heather Mack graduated from the University of Pennsylvania with a VMD in 1991. She was certified by IVAS in 1992 and AVCA in 1995. She has practiced, raised, trained and lived holistically with horses on her Mystic Canyon Ranch in Idaho since 1994. Dr. Mack has maintained an equine sports medicine practice in Southern California for 12 years. She also teaches holistic horse health clinics and takes people on wilderness horse retreats.