This prospective, randomized, double-blind investigation evaluated the influence of a short-time artificial change of occlusion to the upper cervical spine mobility. Twenty 14-19 aged female dancers were investigated in a cross-over-design on head movement rotation in anteflexion with a three-dimensional ultrasonic measurement device, the Zebris 3D Motion Analyzer (CMS 70 P). A change of the occlusion was produced by positioning a 0.75mm foil of tin between premolar and first molar of the right side. Towards the current theory of convergence of cervical and trigeminal nerves the change of occlusion should enlarge tensions in the suboccipital muscles and consequently decrease the mobility of the upper spine. The results of this investigation are: There were no significant differences in measuring movements of the upper cervical spine in dependence of changes of the occlusion. Assessments of the probationers to the changes in tension or motion support these results.

Chapter 2.2.2.3, Functional interactions between the masticatory musculature and the anterior and posterior neck musculature: There is no direct muscular connection between the mandible and the CS. However, an indirect connection between the CS and CMS is revealed if the overlapping functions of the musculature of the CMS region with the posterior cervical musculature of the CS exists. This connection is important for the integrated functioning of the head and jaw. Muscular connections are due to a closed chain of muscles in the CMS. Anteriorly, muscles connect the skull to the mandible (the masticatory muscles, see above). Inferiorly, the mandible is anchored to the shoulder girdle via the hyoid (supra and infrahyoid muscles, see above). Posteriorly, the cervical muscles connect the cranium to the shoulder girdle. Therefore, contraction of one muscle will pull on the neighbouring muscle/bone and set up a chain of force disturbing the balance of the whole system. This demonstrates that disorders of the masticatory apparatus, e.g., hyper- or hypotonicity, can disturb the balance of the posterior cervical musculature and vice versa. Since dysfunction of the CMS or cervical spine can cause dysfunctions in related musculature and disturbance of the musculature can cause altered functioning in the joints, these two areas are quite intimately linked by virtue of this muscular chain. Within the framework of their study Craniomandibular system and spinal column , Stiesch-Scholz & Fink describe the interactions between CMS and CS musculature through the movements for extension and flexion. This includes the fact that when the CS is extended by the infra- and suprahyoid musculature as well as by the increased tension in the soft tissue of the anterior neck, retraction of the mandible occurs and the interocclusal distance is increased in the resting position. In contrast, a flexion of the CS and protrusion of the mandible results in a decrease in the interocclusal distance. Therefore, the integrated functioning of this chain model is also an important demonstration of interactions between CMS and the craniocervical system (CCS) (see Fig. 9, page 29). Functional connections between the CMS, CS and shoulder girdle regions: A description of the numerous neuroanatomical and biomechanical anatomical connections between the CMS and the cervical spine has been given and now the connections within the functioning system will be discussed. Much of the integrated functioning occurs because of the close anatomical relationships and the essential requirement for appropriate head movements whilst talking, eating, swallowing etc. It is doubtful if the human lineage would have got very far in its evolution if the heads had been allowed to bob up and down at the neck due to jaw movements every time the individual talked or chewed. Sherrington stated: Posture is the basis of all movement and all movement begins and ends in posture”. In other words, if posture is faulty, then any subsequent movements will be faulty. It is therefore necessary to first describe the functional interactions between the postural/main musculature of the CMS and CCS according to different postures of the head. Then the effects of the mandibular position on the CCS region will be illustrated. Furthermore, the effects of occlusion on the CMS and CS regions will be highlighted. Head posture: The ideal posture of the head places the centre of gravity slightly anterior to the occipital condyles and, therefore, anterior to the cervical spine. The head tends to nod anteriorly on the spine, as when a person falls asleep in a sitting position. Therefore, the head has to be actively held upright, a function performed by the powerful posterior cervical muscles, which support the weight of the head against gravity. The anterior cervical muscles are much smaller and more weakly developed as gravity aids in their functioning. This may not seem a very efficient form of functioning, but it is the price we pay for adopting an upright posture. The head may be said to teeter” on the atlanto-occipital joint. Any structure anterior to this joint will add to the load already produced by gravity on the posterior cervical muscles. These structures include the mandible and oral structures, facial muscles, masticatory muscles and hyoid muscles. Any increase in tension of these muscles requires a balancing increase in posterior cervical muscle tension. This occurs physiologically during chewing, talking and swallowing and pathologically in CMD. If we use the example of a very common anomalous posture, namely the forward head posture, the mandible is retruded by the pull of the hyoid muscles from the sternum. Stiesch-Scholz & Fink state that the forward positioning of the head results in increased infra- and suprahyoid muscular activity, as well as increased activity in the musculi masseter und musculi temporalis. In turn, this increased muscular activity leads to retraction of the mandible and condyles into a dorsocranial position. The forward positioning of the head also results in an increase in the activity of the dorsal cervical musculature. Therefore, a shift in the position of the head as described above by just one cm can lead to a substantial increase in the isometric postural work carried out by the muscles on the back of the neck. Retroversion of the atlanto-occipital joint occurs in order to maintain the eyes on a level with the labyrinth. This is then maintained by increased concentric work carried out by the short, deep muscles on the back of the neck. The more forward the position of the head, the more retruded the mandible. Mandibular posture: The mandible is supported in a muscular sling, which adds its weight to the anterior load on the cervical spine. Opening of the jaw is assisted by gravity and the mandible is at rest at an opening of 2-3 mm, when the jaw-closing muscles are not active. As the head extends backwards, the jaw tends to open due to the pull of the hyoid muscles. In fact, the mouth can be opened fully by fixing the mandible and extending the head, so called ‘head opening’. As the head is flexed, the mouth tends to close as the mandible is compressed against the sternum and the maxilla pushed down. Mandibular posture is greatly influenced by occlusal contact of the teeth. Malocclusion results in uneven tension in the musculature bilaterally which can lead to dysfunctions in the craniomandibular system. Furthermore, and also by this mechanism, uneven tension in the posterior cervical muscles results in predisposition to cervical lesions. Changes in the postural positions of the head and neck affect the mandibular resting posture and consequently also affect occlusion. As with the forward posture of the head and the correlated mandibular retrusion, the occlusal contact pattern will be altered, causing heavier contact in the posterior molar region. Therefore, prolonged postures of this nature will require permanent adaptation of the teeth to the new occlusal pattern. In summary, it is clear that the head, CS, CMS and shoulder girdle regions cannot be regarded as individual entities with regard to function. Any increase in tension in the facial and masticatory musculature must be compensated for by an increase in tension in the posterior cervical musculature. Furthermore, postural changes of the head on the shoulder girdle require changes in mandibular position, which also results in changes to occlusion. The following section will focus on linking the results of empirical studies to theory.

• Zahnokklusion

• Kiefergelenk

• Atlas (Halswirbel)

• Wechselwirkung

• Bewegungsanalyse

• Ultrasonic Measurement

• Upper Cervical Spine

• Jaw region

• Craniomandibular System

• Zebris 3D Motion Analyzer

Stephan Klemm, Physiotherapeut, Osteopath D.O., BSc.(Hons.) Ost., Osteopathie Studium an der Internationalen Akademie für Osteopathie in Gent, Belgien. Abschluss zum Diplom Osteopathen 2005, Abschluss zum BSc. (Hons.) Ost. 2007 an der University of Westminster, London. Leiter der Abteilung Physiotherapie von 1998-2006 in der Rehberg-Klinik St. Andreasberg, ab 2007 Ltd. PT in der Fachklinik Erbprinzentanne. Dozententätigkeit an der Internationalen Akademie für Osteopathie sowie der Muschinsky Schule für Physiotherapie. Selbständige Tätigkeit in eigener Praxis.