Introductory notes:
1) The TMJ is a convex-concave and concave-convex joint between mandibular condyle, disk and temporal bone.
2) The muscles called "masticatory muscles" acting upon this joint are the masseter, the temporalis, the medial and lateral pterygoid.
3) In functional terms, these muscles bestow stability to the joint and permit to fit the teeth together (to close the mouth).
4) Though being monoarticular muscles, they can interact with the whole skeletal muscle architecture.
The physical laws governing complex systems have shown that whenever several forces are acting upon a system (skeletal bones), these forces are joint and interacting with each other. 5. (Correct) posture means a correct skeletal sequence of articulations, irrespective of the spatial position of the body .

The physiology of deglution
Swallowing is an unvoluntary reflex movement which is evoked several times per minute; to enable us to swallow, the muscles of mastication contract and make our teeth come in contact.
If dentition is physiologically correct, the masticatory muscles have the same intensity of action, since they utilize the minimum bite force required. The bite shall be such as not to affect other body areas, that is to say following a physiological pattern. No relationship between temporomandibular joint and posture will result.

Relation between temporomandibular joint and posture
Physiologically, there should be no relation between temporomandibular joint and posture; nevertheless, this connection will occur if dentition is pathologically positioned in the dental arch. Three events may be more frequently observed, namely:
a) teeth of different length (pre-contact)
b) excessive freeway space
c) reduction or absence of freeway space
Teeth of different length (pre-contact) If the teeth in a dental arch are too long or too short, the masticatory muscles will function asymmetrically (right-left) and with more intensity than physiologically required when closing the mouth. The first result will be that the condyle of the temporalis on the side of the "short" teeth will extend beyond its physiological position towards the mandibular fossa to allow teeth contact. The mandible will then make a twisting movement. This event may trigger painful symptoms especially affecting the TMJ, the ear and the head, since many receptors are located inside the mandibular fossa. Furthermore, with reference to the statements made in para. 4 of the introduction, an asymmetric and excessively intense activation of muscles will involve other muscle regions, starting from the muscles of the neck. Overstraining or tension of the muscles will not be restricted to the masticatory muscles, but other joints, too, will be subject to the traction force of the muscles, the cervical vertebrae will lose their symmetric position, which may also result in a raised shoulder and involve a variety of complex skeletal alterations if this pathological issue should perpetuate over time. .
The result will be an altered body posture.
Excessive freeway space
At rest, that is to say when the muscles of mastication are relaxed, the teeth should not fit together but show an about 2-mm "freeway space".
This is considered by our brain circuits as the proper physiological rest condition.
In case of excessive freeway space, for example because of generally "too short" teeth, the muscles of mastication should be constantly tense to maintain a correct freeway space. To counterbalance this continuous fatigue, the muscle system and particularly the muscles positioned anteriorly to the cervical spine, inserting into the third thoracic vertebrae, will cause the whole head to move forward. The dental arches will then meet and unload the overwork of the masticatory muscles.
However, a forward displacement of the head also means displacement of the barycentre of the body. To prevent us from losing our balance, the underlying muscle zones will be activated by modifying the pattern of the whole vertebral spine, thus accentuating or reducing physiological lordoses and resulting in an altered vertical sequence of the body segments.
In this case, too, the result will be a postural alteration.
Reduction or absence of freeway space
This problem is opposite to the foregoing.
In this case, the post-cervical group of muscles will be activated so as to draw the head back. The dental arches will then be slightly apart, thus unloading the work of the hyoid muscles. Again, the barycentre of the body will be displaced this time posteriorly and the underlying musculature must be activated to keep the balance by acting on the whole spine, which will lead to an altered vertical sequence of the body segments.
The result will be an altered posture.
All postural disorders taken into examination may cause, in turn, orthopedic pathologies (e.g. scoliosis, lumbago, cervicodynia, etc), that may be defined as subsequent to a primary pathologic involvement of the buccal system .