Panel Expert: Dr. Heather Mack
Submitted by member: Nancy
I have heard you mention somewhere that the Temporo-Mandibular Joint (TMJ) is the “Master Link” to a horses balance and wellbeing. What are some of the things I can look for to see if my horse is affected by it?
Answer by Heather
Thanks for that wonderful question Nancy! I actually did a series of topics on TMJ for Equestrian Coach. You can view those by clicking here. I also did an extensive article on my website, which you can read by clicking here.
But let me give you a quick rundown here on evaluating for TMJ Pain or Temporo-Mandibular Dysfunction (TMD):
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 stems of hay? 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 a good time to evaluate the forehead or temporalis muscle and the cheek or masseter muscle for symmetry also. The pterygoid muscle is equally important but less noticeable on visual inspection.
2. Incisor Evaluation: The incisor pattern, length and angle directly affect the biomechanics of the TMJ. Look straight at your horse’s incisors; they should be aligned top to bottom. There is pathology in the mouth and TMJ if they are off center or there is a wedge sending them one direction and not the other.(figure 1) Now look from the side is there an overbite or an overjet which is really an incomplete overbite? (figure 2) If so chances are your horse cannot put his head down and drop his mandible into a comfortable or neutral position because anterior motion of his jaw is impeded. Check for anterior and posterior motion visually 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 horses head the lower incisors should move forward if they have healthy anterior motion of the jaw. The lack of anterior/posterior motion indicates the biomechanics of the jaw can be improved.
3. Listen: There is a harmonic resonance in a healthy jaw that one can hear. Listen to your horse grazing or eating hay with his head down. All horses should be fed at ground level. With their head down the atlanto-axial joint opens (C1-C2), 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 the perfect balance of tension and relaxation for proper chewing and neurological input. Wild horses graze for 15-20 hours a day. All of the wild horse skulls I’ve found have nearly perfect incisor and molar patterns. When you listen to your horse chewing there should be a clear, clean sound if everything is healthy. It is a resonance, which is also a frequency or vibration that is like a lullaby to the nervous system. Squeaks, or pops or clicking sounds could indicate TMJ or dental pathology.
4. Gentle palpation of the TMJ joint space can indicate asymmetry or pain. One side may feel shallow and open while the other side might feel tight and pinched. Palpation and observation of the muscle on the forehead, the cheek muscle and the pterygoid muscle which is difficult to observe but can be palpated on the medial aspect of the mandible.
5. Palpation of acupoints – TH17, ST7, Bao-Sai, the facial crest trigger points and the medial pterygoid muscle attachment- (see figure 3) for those familiar with acupuncture or acupressure.
After doing the above evaluation if you suspect your horse has some TMJ dysfunction, please have a vet or a qualified equine dentist perform an exam with a full mouth speculum. Many problems in the rear molars cannot be assessed without one. It is important to consult with a professional so that he/she can help suggest the best course of treatment for your horse.
Hope that helps!
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Dr. Mack teaches Balanced Mouth Dentistry and Holistic Horse Health at Balanced Equine Wellness. She has a particular interest in balancing the mouth to affect a positive change in the Temporo-Mandibular Joint (TMJ). She considers the TMJ the “Master Link” in the chain of the horses’ balance. Heather was one of the first women accepted at Columbia University in NYC and received her B. S. there. Visit her website: www.balancedequinewellness.com