International College for Research on Equine Osteopathy
EINDWERKEN
EINDWERKEN
Debora Severo:
The temporo-mandibular joint.
Introduction
When I decided to write about TMJ I knew there where many connections between dental problems and the rest of the body, in particular the spine, the one we are more interested in, being osteopaths, because it is the home of the nervous system, the place where everything starts. I’ve read books about TMJ, even if not many, but I haven’t been able to find what I was looking for: the real bone, muscular, neurological connections.
What I found where statements like: “C2 is linked to TMJ” or “molar 9 might be a consequence of a lame hind limb” but nobody would explain why, in which way these structures where connected.
The purpose of this final job, than, was to describe the temporomandibular joint, all the direct and indirect anatomic structures, bones, nerves, musculature, fascia, viscera related to it.
Working this way it has been logic, simple and scientific connecting TMJ with a hind limb dysfunction, for instance, or to a front limb or to a sacral dysfunction.
It is easy now to understand how dental problems, for instance, or a TMJ misalignment can affect the other structures in the body directly or indirectly.
Temporo mandibular dysfunction
TMD stands for Temporomandibular Dysfunction: when the temporal bone and the articular processes of the mandibula are not properly aligned and not articulating properly and the surrounding tissue of TMJ is stressed, the TMJ mechanism is out of balance and cannot function optimally.
This condition known occurs in all horses regardless of discipline. Horses exhibit signs of possible TMD discomfort in several different ways. TMD goes hand-in-hand with the misalignment of the upper and lower incisors and/or any imbalances that may appear in the wear of the teeth, such as hooks or waves, and each perpetuates the other.
TMD shows up in many different shapes and sizes and cases differ in levels of severity. Horses with TMD will clearly show low levels of performance, improper gaits, uneven wear of the teeth, possible head shaking, signs of headaches, cribbing and/or various behaviour problems. In some cases, even a slight retrusion in the lower jaw can be seen - the lower incisors of the mandible come behind the upper incisors of the maxilla. Any horse that has TMD will have some level of difficulty in performance.
Mandibular movement is directly connected to the cranio-sacral rhythm (primary rhythmic impulse). The normal occlusion depends on balance between cranio-sacral system and mandibular system. The occlusion is the result of the dynamic of several cranium bones and the dynamic of sphenobasilar joint. The cranio-sacral and mandibular system are built up by two main systems: a dynamic, functional and adaptive system, represented by TMJ, which is connected with the first cervical vertebra atlas by miofascial tissues and the direct connection to occiput, hyoidal bone and os sfenoid. TMJ is not an independent functional unit, but is interconnected with the rest of the body through the Stomatognathic system. The Stomatognathic system includes the parts of the head, the neck and the upper thorax representing the muscular, osseous, ligamentous, fascial and nervous system. The Stomatognathic system is responsible for control of biting, chewing and swallowing.
In horses with dental problems the mandibular bone in connection with maxilla represent the primary cause for dysfunction of the cranio-sacral system through temporal bones and tentorium cerebelli, which divides the cerebrum and the cerebellum and has a function of maintenance of tension to the basilar cranium bones.
The normal function of mandible depends on correct position and functional balance of temporal bones and normal contact of dental tables producing normal occlusion. The dental occlusion refers to the coming together of the upper and lower teeth, whereas neuromuscular occlusion occurs when the dental occlusion is synchronized with healthy relaxed masticatory muscles.
Any tightness or contraction in the muscles, tendons or ligaments of the TMJ Mechanism will change a normal function of the TMJ. In the event of these muscles tightening and shortening, the body than negatively compensates for the imbalance and equilibrium.
Two kinds of pathologic changes may be diagnosed: primary or secondary occlusive lesions or descending and ascending lesional chains, which will be largely explained.