Interactions between the Craniomandibular System and Cervical Spine

Bachelorarbeit von Stephan Klemm

Abstract:

The connections between the mobility of the jaw region and that of the cervical spine have been the subject of research on many occasions in recent decades. For example, Ridder gives an overview of experiments conducted on animals by Japanese scientists in his monograph „Functional impairments in the jaw and tooth malalignment and their effects on the periphery of the body“. In this monograph, he describes investigations that tested the effects of changes in the dental and jaw regions, and that persisted in the long-term, on the periphery of the body. In the quadrant theory, Guzay outlines that the centre of the movements of the jaw does not lie within the temporomandibular joint itself. He describes how the movements of the jaw occur around a region in the upper cervical spine, namely around the atlanto-axial joint. Based on this proposition, he declares (ibid.) that inadequate dental occlusion can result in spinal malalignment, leading to curvature of the body axis. Maehara tested the propositions put forward in the quadrant theory by shortening the right-hand teeth in rats. He subsequently observed scoliosis of the spine and variation in the size of the right and left eyes. In addition, he shortened the teeth in Beagle dogs. As a result, the dogs exhibited bad posture, changes to their fur, watery eyes and cataracts. Maehara & Hashimoto then also shortened some of the teeth in monkeys. They observed that the monkeys suffered from loss of fur, exhibited abnormal behaviour and that their tongues were bent. Following this, a stencil-like splint was fitted to the shortened teeth to restore the original tooth height. This resulted in growth of the monkeys' fur, normal behaviour and a straightening of the tongues. In a further experiment, Maehara & Azuma shortened the teeth in guinea pigs. The guinea pigs lost weight after two weeks. Weight loss was greater in these animals than in control animals that were starved. After one week, electro-cardiograms of the guinea pigs exhibited a negative T wave, indicating cardiac insufficiency. The researchers then also shortened the teeth in the control group, which resulted in the negative T wave being exhibited by all animals.

Based on these results, the question arises as to whether functional connections in the dental and jaw regions also exert effects on the periphery of the body in humans. Several publications indicate that this may be so.

For example, Stiesch-Scholz et al. also make connections between impairments to the craniomandibular system (CMS) and postural changes in the region of the cervical spine (CS) and shoulders. Rocabado demonstrated that pain in the CMS can be caused by changes to the cervical spine. Fink et al. induced functional restrictions in the region of the cervical spine as well as peripherally in the iliosacral joint through artificial unilateral changes to dental occlusion.

The biological development and evolution of the CMS also suggest systemic observation of the dental / jaw region may be appropriate. The neurological and biomechanical connections to adjacent areas can be illustrated based on its genesis. The CMS, for example, serves the purpose of taking in food as well as obtaining specific information about our environment through tactile oral perception. There are also connections to the digestive tract, for the regulation of our wake state (attentiveness), as well as to the cervical spine for the „orientation“ of our „tactile organ“, the temporomandibular joint.

The biological development and evolution of the craniomandibular region will therefore be investigated first, in order to provide information on the theoretical and empirical background to this research. The neurological, functional as well as biomechanical and muscular relationships resulting from this will then be illustrated for adult humans and will form the basis of this research.

Functional relationships between the craniomandibular system and adjacent structures were therefore the subject of intensive research. However, the question has not yet been satisfactorily answered of whether a change in dental occlusion can affect the degree of mobility in the cervical spine, and if this is the case, how this occurs. A closer investigation of this question is the subject of this research.

More specifically, the current research project will investigate whether an artificially produced, short-term, unilateral impairment of dental occlusion also produces changes in the mobility of the cervical spine.

Table of Contents:

1.	INTRODUCTION	7
2.	THEORETICAL BACKGROUND	9
2.1	EMBRYOLOGY	9
2.1.1	BIOLOGICAL DEVELOPMENT AND EVOLUTION OF THE JAW, FACIAL AND CERVICAL REGIONS	10
2.1.1.1	THE GILL SYSTEM	10
2.1.1.2	DIFFERENTIATION OF TISSUES IN HUMAN GILL ARCHES	10
2.1.1.3	GILL ARCH INNERVATION IN HUMANS	13
2.1.1.3.1	CMS AND ANTERIOR CS REGION	13
2.1.1.3.2	PINNA AND POSTERIOR CS REGION	14
2.2	ANATOMY OF THE HUMAN TEMPOROMANDIBULAR JOINT	16
2.2.1	NEUROANATOMICAL RELATIONSHIPS BETWEEN THE CMS AND THE UPPER PORTION OF THE CS	17
2.2.1.1	THE NERVUS TRIGEMINUS PATHWAY	17
2.2.1.2	THE AREA INNERVATED BY THE NERVUS TRIGEMINUS	18
2.2.1.3	NERVUS TRIGEMINUS CONVERGENCES WITH OTHER AREAS	19
2.2.1.4	PLEXUS CERVICALIS AND ITS RELATIONSHIP TO THE UPPER CS	21
2.2.2	MUSCULATURE IN THE CMS REGION	22
2.2.2.1	THE CMS MUSCULATURE	22
2.2.2.1.1	„TRUE“ MASTICATORY MUSCLES	22
2.2.2.1.2	SUPRAHYOID MUSCULATURE, MUSCULI SUPRAHYOIDEI	23
2.2.2.1.3	MIMIC MUSCULATURE IN THE ORAL REGION	23
2.2.2.2	MUSCULATURE IN THE CS REGION	24
2.2.2.2.1	PREVERTEBRAL, LATERAL AND POSTERIOR CERVICAL SPINAL MUSCULATURE:	24
2.2.2.2.2	SUBOCCIPITAL MUSCULATURE	26
2.2.2.3	FUNCTIONAL INTERACTIONS BETWEEN THE MASTICATORY MUSCULATURE AND THE ANTERIOR AND POSTERIOR NECK MUSCULATURE.	28
2.2.3	FUNCTIONAL CONNECTIONS BETWEEN THE CMS, CS AND SHOULDER GIRDLE REGIONS	29
2.2.3.1	HEAD POSTURE	30
2.2.3.2	MANDIBULAR POSTURE	31
3.	EMPIRICAL SECTION	31
3.1	INVESTIGATIONS ON NEURONAL INTERACTIONS BETWEEN AREAS INNERVATED BY THE TRIGEMINUS AND THE INNERVATION OF THE UPPER CERVICAL AREAS.	32
3.1.1	SENSORY NEURONAL INTERACTIONS BETWEEN THE CMS AND CS REGIONS	32
3.1.2	NEURONAL MOTOR INTERACTIONS BETWEEN THE CMS AND CS REGIONS	34
3.2	CRANIOMANDIBULAR DYSFUNCTION	36
3.2.1	HISTORICAL BACKGROUND FOR CMD	36
3.2.2	DEFINITION AND DIAGNOSTICS FOR CMD	37
3.2.3	OVERVIEW OF INVESTIGATIONS IN CASES OF FUNCTIONAL IMPAIRMENT OF THE CMS.	39
3.3	PATHOPHYSIOLOGY OF THE CMS AND THE UPPER CS REGION IN HUMANS	41
3.4	BIOMECHANICAL CONNECTIONS BETWEEN THE CCS AND CMS	43
4.	AIMS OF THE CURRENT STUDY AND HYPOTHESES	44
5.	MATERIAL AND METHODS	45
5.1	DEFINITION OF THE EXCLUSION CRITERIA	46
5.2	SAMPLE	47
5.3	QUESTIONNAIRE AND CLINICAL INVESTIGATION OF THE CS REGION	48
5.3.1	QUESTIONNAIRE A: SOCIODEMOGRAPHIC DATA, PAIN ASSESSMENT AND MEASUREMENT OF THE MAXIMUM OPENING OF THE MOUTH	48
5.3.2	QUESTIONNAIRE B: DETERMINATION OF THE EXCLUSION CRITERIA (B1) AND QUESTIONING OF THE SUBJECTS ON SUBJECTIVELY PERCEIVED TENSION (B2)	49
5.4	EXPERIMENTAL DESIGN AND MEASUREMENTS	49
5.4.1	EXPERIMENTAL DESIGN	50
5.4.2	CHRONOLOGICAL SEQUENCE OF THE ENTIRE EXPERIMENTAL DESIGN DEPICTED USING A FLOW CHART	52
5.4.3	DESCRIPTION OF AN INDIVIDUAL MEASUREMENT	53
5.4.3.1	INTRODUCTION, FITTING OF THE METAL FOIL, WARMING UP	53
5.4.3.2	CONDUCT OF ANALYSIS OF MOBILITY IN THE CS	53
5.4.3.2.1	PREPARATIONS FOR THE MEASUREMENT	54
5.4.3.2.2	THE CMS 70 P HARDWARE	54
5.4.3.2.3	EXPERIMENTAL PROTOCOL USING THE CMS 70 P	56
5.4.3.2.4	SOFTWARE	57
6.	RESULTS AND INTERPRETATION	58
6.1	DEMOGRAPHIC DATA	58
6.2	INTERGROUP COMPARISON OF DEMOGRAPHIC DATA	59
6.3	GENERAL EVALUATION OF THE RAW DATA ON BASELINE MEASUREMENTS	59
6.4	EVALUATION OF THE BASELINE MEASUREMENTS FOR EACH GROUP	60
6.5	STATISTICAL ANALYSIS OF MEASUREMENTS MADE UNDER EXPERIMENTAL CONDITIONS	61
6.6	RESULTS FROM THE QUESTIONNAIRES ON SUBJECTIVE PERCEPTION OF TENSION	65
6.7	EVALUATION OF THE HYPOTHESES	66
7.	DISCUSSION	66
7.1	DISCUSSION OF THE FINDINGS WITH REFERENCE TO THE THEORETICAL AND EMPIRICAL RESEARCH BACKGROUND AND THEIR CLINICAL RELEVANCE	67
7.2	DISCUSSION OF ERRORS	68
7.3	COMPARISONS WITH OTHER STUDIES	71
8.	CONCLUSIONS	74
8.1	STUDY DESIGN	74
8.2	RESULTS OF THE CURRENT INVESTIGATION	74
9.	REFERENCES	76
	APPENDIX A: QUESTIONNAIRE A FOR A STUDY OF THE MAXILLARY JOINT	83
	APPENDIX B: RAW DATA 1 FROM QUESTIONNAIRE A AND FROM THE MOTION ANALYSIS OF THE UPPER CS WITH THE ZEBRIS-CMS 70 P DEVICE	84
	APPENDIX C: QUESTIONNAIRE B1: ACQUISITION OF EXCLUDING CRITERIA	85
	APPENDIX D: RAW DATA 2 FROM QUESTIONNAIRE B1	86
	APPENDIX E: QUESTIONNAIRE B2: ESTIMATES FROM THE SUBJECTS ABOUT THE FLEXIBILITY OF THE SPINE AND THE TENSION IN THE MAXILLARY REGION	87
	APPENDIX F: RAW DATA 3 FROM QUESTIONNAIRE B2	88
	APPENDIX G: INTRODUCTION AND WARMING-UP OF THE PROBATIONERS IN ORDER TO ADAPT THE BODY FOR THE MEASUREMENT OF THE OCCLUSION.	89
	APPENDIX H: INSTRUCTION TO THE MEASUREMENT OF THE MOBILITY OF THE CS	90
	APPENDIX I: LIST OF FIGURES	91
	APPENDIX J: LIST OF TABLES	92

Text Sample:

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.