Over the last ten years, the horse market has been flooded with medications for gastric ulcers, neurologic diseases, inflammatory conditions and all kinds of other issues. Why are our horses so out of balance and in need of all these medications? Is it environmental pressure? Increased travel to shows?
It’s All Related: How the TMJ affects bodily health
1. Chewing food properly is the first step to healthy digestion. In order to chew his food, a horse must be able to move his jaw from side to side, forward and back, and up and down. When dysfunction occurs, a horse will make many adaptations, but these changes affect the entire body.
2. The jaw joint is highly innervated and surrounded by structures that dictate the horse’s balance and equilibrium. It is anatomically the closest joint in a horse’s body to the brain and brainstem. Its proprioceptors tell the horse where he is in space, or what his posture is. The neurology is intricate and beyond the scope of this article, but be aware that the hyoid and cranial nerves are intricately connected with the jaw. The hyoid apparatus in the throatlatch is a group of ten bones that give biomechanical form and function to the larynx, pharynx and tongue.
3. The TMJ is also part of the stomatognathic system, a neurological system that governs balance and equilibrium. All components of this system are located from the shoulder forward. They include the eyes, hyoid apparatus, proprioceptors and dural connections from the cervical spine, which connect all the way to the sacrum and pelvis. Changes in muscle tone in the head and neck increase dural tension all the way to the sacrum.
4. Vital life force or Chi energy flows along the acupuncture meridians or channels to maintain health. If this energy is blocked or altered in any way, it can create dis-ease or dysfunction. Six different acupuncture channels converge on, or are very close to, the TMJ. Three travel to the front legs (LI, SI, and TH), and three to the hind legs (GB, ST, and BL). This is another way of understanding how the hind legs, pelvis and sacrum can be adversely affected by TMJ or TMD.
The TMJ connection
These factors can add to the picture, but I believe many horse people (the veterinary community included) are unaware of how important the TMJ (temporomandibular joint) is to a horse’s balance, digestion, biomechanics and overall wellbeing. I consider this joint the “Master Link.” Restore it to optimal wellness and many other psychological and physical issues, internal organ imbalances and body compensations simply disappear.
The TMJ is critical for a horse’s health and survival. It has two primary functions:
1. Grinding food
2. Balance (a horse’s relationship with the ground, or posture)
Anatomy of the TMJ
The TMJ connects the temporal bone, which expands across the horse’s forehead, to the mandible, the lower portion of the skull. It consists of two parts – an upper sliding joint, and a lower hinge joint. An articular disc separates the two compartments, and the entire joint is encapsulated and contains synovial fluid. It is a very tight joint, reinforced by tendons and ligaments and supported by an intricate array of muscles.
Many horses suffer from articular TMJ pain, but perhaps even more insidious is temporomandibular dysfunction (TMD). This involves myofascial and ligamentous pain. Horses adapt as the inflammatory process slowly progresses, but what starts as a bit of discomfort will become a raging headache. Once you know what to look for, you’ll be able to recognize it:
1. Observation: Watch your horse chewing. Look for symmetry or balance side to side. Does he swing his jaw to both sides? Does he hold his head with a tilt while he eats? Is he dropping food? Does he leave the hay stems?
Observe his head when he is not eating and look straight at him face to face. Are the ears, eyes and nostrils even or asymmetric? How about the bony prominence of the jaw joint or the facial crest that runs down the side of the head? Is one more prominent than the other? This is also a good time to evaluate the forehead and the cheek muscles for symmetry.
2. Incisor evaluation: The pattern, length and angle of the incisors directly affect the TMJ’s biomechanics
•Look straight at your horse’s incisors. They should be aligned top to bottom. If they are off center or there is a wedge sending them one direction and not the other (below), there’s pathology in the mouth and TMJ.
•Now look from the side – is there an overbite or overjet (below)? If so, chances are your horse cannot put his head down and drop his mandible into a comfortable or neutral position, because the anterior motion of his jaw is impeded.
•Visually check for anterior and posterior motion, or by gently placing your finger at the incisor occlusal line (where the front teeth meet). When the head is raised, normal posterior motion should pull the lower incisors slightly back. When you lower the horse’s head, the lower incisors should move forward. A lack of anterior/posterior motion indicates the biomechanics of the jaw can be improved.
3. Listen: A healthy jaw has a harmonic resonance you can hear. Listen to your horse grazing or eating hay with his head down. All horses should be fed at ground level. With his head down, a horse’s atlantoaxial joint opens; the mandible comes down and forward; the upper and lower cheek teeth meet at the optimal occlusion; and the muscles and soft tissues in the head and neck go into a perfect balance of tension and relaxation for proper chewing and neurological input.
When you listen to your horse chewing, there should be a clear, clean sound if everything is healthy. It provides a frequency or vibration that is like a lullaby to the nervous system. Squeaks, pops, or clicking sounds could indicate TMJ or dental pathology.
4. Palpation: Gentle palpation of the TMJ joint space can indicate asymmetry or pain. One side may feel shallow and open, while the other might feel tight and pinched. Palpate and observe the muscles on the forehead and cheek, and the pterygoid muscle, which is difficult to observe but can be palpated on the medial aspect of the mandible.
For those familiar with acupressure, palpating acupoints TH-17, ST-7, Bao-Sai, the facial crest trigger points, and the medial pterygoid muscle attachment can help indicate TMD.
If, after doing this evaluation, you suspect your horse has some TMJ dysfunction, have a vet or qualified equine dentist perform an exam with a full mouth speculum.
TMJ Awareness Dentistry is a holistic approach to dentistry. I feel equine dentistry has advanced too far toward the dentist’s comfort and less toward the horse’s comfort and safety. The overuse of power dental instruments is the primary reason I see and treat so many TMD horses. Although a true artist can do the work correctly with power instruments, it is so easy to over-float with them. I have found a more accurate balance can be achieved with hand instruments.
If I find extreme pathology I will use my power instruments judiciously, but I always finish with hand instruments. My colleagues and I use hand instruments that are ergonomically correct, designed specifically for a horse’s mouth. We use minimal sedation, and are willing to add more if necessary. However, our goal is to have the horse as aware as possible of the subtle changes occurring to his nervous system as we make adjustments to the teeth. This kind of dentistry is really adjusting the “gyroscope”, and is often my first step in treating neurologic diseases.
Many power floaters take off too much clinical crown, and often obliterate the horse’s natural molar table angles. More sedation is required to allow these instruments into the oral cavity, then the head is hoisted or tied up in a very unnatural position. Power floating can be so excessive that it decreases the natural surface contact between the molars. This leads to severe myofascial pain syndrome (TMD) because the horse clenches his jaw and constantly compresses his muscles, tendons, and ligaments to get that molar contact. Sometimes it takes years for the clinical crown to come back.
I believe power tools have allowed dentists to become overly aggressive in equine dentistry. With one quick head shake the proper table angles can be altered. Many dentists are more concerned with eliminating sharp edges than restoring proper biomechanics to the jaw joint. Practitioners often float the molars and either leave the incisors untouched or follow up by adjusting them to fit the work done on the molars.
TMJ awareness dentists start with a thorough examination of the head, hyoid, poll and whole body for asymmetries and symptoms of TMD. We address the incisors first. The length, angle, and balance of the incisor tables are directly related to the TMJ. Sometimes incisor pathology can only be reduced in increments while the horse adjusts to the new TMJ alignment. Some pathology should not be corrected, especially in aged horses that have been compensating for years and have adapted. In these cases we do minimal work, mostly to allow more comfort and maximum surface-to-surface contact between the teeth.
Once we achieve optimum incisor alignment, we put the speculum on and move to the molar tables. Remember we want the horse’s participation and integration during the process, so we don’t hoist his head up. It is easy to create inappropriate changes to the molar table angles when the head is held high and the neck hyper-extended. All the wild horse skulls I’ve found have nearly perfect incisor and molar patterns.
We are willing to kneel on knee pads so the horse’s head is in a natural position. We leave as much clinical crown and table surface as possible on the molars and pay close attention to table angles. This is critically important in the rearmost molars because they are losest to the TMJ, brain, and central nervous system. The occlusal surface and angle is critical to proper guidance, body biomechanics and balance. We always complete our dentistry with some stretching, myofascial and trigger point release work, essential oils, homeopathy, and sometimes chiropractic and acupuncture.
Even with the best of dental care, it takes a total holistic approach to completely treat TMD issues. Dental work alone is a very important starting point, but will not completely resolve many TMJ/TMD issues. We often pull in the help of craniosacral therapists, body workers who do extensive soft tissue work, and farriers to properly balance the feet. We use cyma therapy, microcurrent, laser, chiropractic, acupuncture, homeopathy, bit changes, saddle changes, oral or injectable chondro protective agents, and sometimes anti-inflammatories to get the horse back to total balance and wellness.
I urge you to take a close look at how your horse’s TMJ is functioning. I see far too many hocks and backs being injected when the problem is actually TMD. Although injections will often provide some temporary improvement, the imbalance shows up somewhere else after awhile, often in the feet or neck.
Esure your horse’s feet are balanced, and you will see the life force flow through his entire body. You may still have bodywork to do and old postural compensations to correct, but a healthy TMJ makes it much more possible for your horse to achieve self perpetrating wellness, vitality, and strength.
Heather Mack, VMD, graduated from Pennsylvania in 1991. Shortly after, she received certification from both the IVA S and the AVCA . She has been a member of the AHVMA for 15 years, and is on a continual path of studying holistic health. She is turning her Mystic Canyon Ranch in Idaho into a Balanced Equine Wellness Center and also has a very busy Equine Sports Medicine practice on the West Coast. She is as much a healer as a doctor, teaches this art in Balanced Equine Wellness courses, and considers apprentices from time to time. Contact 760-447-0776 or www.balancedequinewellness.com.