Description of cause
Pathogenesis (cause):A multifunctional pathogenesis is assumed, since causes are often not clear. In at least 80 % of the cases occlusion is causative or mainly responsible of CMD. Predisposed, triggering and maintaining factors enclose biological, psychological and social elements.
Assumed and discussed factors:
Earlier experiences of pain
Macrotrauma from accidents
Posttrauma strain dysfunction
Physical malposition and dysfunction of pelvic floor area
The system of bones, joints, muscles, tendons, teeth and other tissue is connected in multi-layers and linked tightly with nerves.
If this regulating circle is disturbed by any cause, there will be a typical reaction of counter regulation at another point as the case may be. If this counter regulation is successful, then it will be without symptoms and is compensated. In case of a futile counter regulation or more common a failing counter regulation caused by overstraining of single system parts, the above mentioned symptoms will occur. There can also be a feedback effect:
the cause effects a counter regulation – if this is not successful, a repercussion of the causal area will take affect, which will lead to a more intense counter regulation etc.
The causes are not clear in many cases. It is certain, that the genesis is multi-causal. Non-influential developmental dysfunctions of the jaw or damages from trauma or tumors are clear causes. Predisposed, effecting or maintaining factors can be related to stress, hormons or postural condition. There are indications that fibromyalgia and CMD have a causal relationship.
Psychological factors manifest in „bruxism“= teeth grinding or unconscious pressing of alignments. This is a typical human way of dealing with stress. It is no wonder that German terms as - “to bite through” meaning to fight through or “to grit one`s teeth” meaning pull yourself together – are common phrases.
Favorizing factors of bruxism are irregular positions of alignments. Considered causes are deformity of teeth, aplasia of teeth, destroyed chewing surfaces from caries, insufficient fillings, insufficient crowns, loss of teeth or insufficient dentures. Furthermore, there are studies of bruxism effected by anti-depressive and neuroleptic medication.
(Drug-Induced Bruxism Vol. No: 30:01 Posted: 1/19/05 Olanrewaju Obisesan,xPharmD Supervising Pharmacist Rite Aid Pharmacy Buffalo,
New York US Pharm. 2005;1)
Influence of occlusia, respectively the bite:The swallowing process can be described as the center: A person swallows 500 to 2500 times per day saliva in small amounts without noticing. This swallowing process is a highly complex and complicated process in which a number of muscles, nerves and organs (lips, cheeks, tongue, soft palate, throat, larynges, vocal cords, gullet…) take part. Thereby the teeth must touch.
Simplified process of swallowing:
The need to swallow arises when enough saliva is collected in the mouth: The tongue pushes the saliva to the throat in the back. Thereafter, the soft palate rises and the throat muscles pull together. With this the nasopharyngeal zone is sealed. Now the alignments close together, since the lower jaw is necessary as stable foundation for the swallowing process. Then the bottom mouth muscles pull together. Thus the larynge entrance moves up and closes, so that no food can enter into the trachea. At the same time the throat muscle draws together in waves and pushes the saliva into the gullet.
With this the involved muscles on the right and left side should work simultaneously and equally. Now the teeth become involved: When the chewing muscles receive the command to close the mouth, the process will be interrupted with the first contact of teeth. As soon as the first tooth pair touches, the control takes place. If this is the case, then the current task of the involved muscles will be completed.
However, often all teeth do not touch at the same time or the lower jaw has to be moved into a new position. So the order for the big chewing muscles is to draw further together until all teeth touch each other. Since the lower jaw is slightly elastically deformable and the teeth are also mounted elastically in their sockets and the lower jaw position can be changed, the subsequent general teeth contact is managed and the swallowing can continue. This process cannot be controlled or guided by intention from us.
These muscles form the bottom of the mouth and are affixed to the lower jaw, on one side, but also to the hyoid bone, the only bone of the human body which hangs loose. This means it is not connected to other bones with a joint.
Since they have to work against the shortened and hardened mouth muscles, they will shorten and harden as well. Due to the shortening, the hyoid bone will be pulled to the front, which results that the muscles which connect the bone directly and indirectly to the sternum, shoulder blade area, the basicranium and the cervical spine, will shorten. This will lead to a malposition or rather false position of the head, neck and shoulders and to pain.
The blood vessels leading to and from the head will be impaired, which will have a negative effect on the blood circulation of the head, caused by the hardening of the muscle structure. This influences migraine and tinnitus and could be the cause for these symptoms in single cases. Furthermore this can enhance or lead to dizziness. Similarely, an influence of the regulation of blood pressure is possible.
The above image shows (a transcription according to anatomist Brodie) the interrelation schematically.
The unbalanced tension of the mouth closing muscles can also effect on the connecting side, that the pressure on the jaw joint is increased and that the cellular connective tissue of the flexible joint disk between joint fovea and the lower jaw joint end is jolted. This will lead to higher deterioration and to rubbing or cracking noises of the jaw joint.
Rubbing noises are a sign of a perforated disc and bones are grinding on one another. Commonly this will lead to chronic pain, which is not necessarily experienced in the jaw joint.
Cracking noises often show that the disc is jammed and does not glide correctly while the mouse is opening and closing. In many cases the disc will be placed extremely forward, which will reduce the natural mouth opening.
Co-factors are all factors, which influence the regularity of the teeth or the relative vertical position of the jaw (the bite):
- missing teeth
- tilted teeth
- loose fitting or worn out pontics or dentures
- worn out fillings
- tooth decay
- orthodontic treatment
- wrong posture
- wrong sleeping position
- one-sided stabilization of head
- telephoning often holding receiver between shoulder and head
- bad shoes
- standing often on one leg