The Portland TMJ Clinic - Occlusion and Posture
Abstract. The relationship between stomatognatic and postural system has longtime been investigated among practitioners in healthcare. ABSTRACT. The relationship between occlusion and posture has been a continual source of inter- est to all participants in the delivery of health care. The relationship between abnormaldental occlusion, body posture and development of Temporomandibular Disorders (TMD) has been a controversial subject.
Dentists can contribute to postural treatment by extending or shifting the mandibular bracing position, usually anteriorly or antero-medially, in conjunction with synergistic efforts to improve head posture.
Because of the precise bite registration techniques needed for prosthodontics, dentists have thoroughly documented how body posture can influence the mandibular closing trajectory.
In animals, experimentally changing the occlusion changes the curve of the spine. Without a basis for understanding the connection between occlusal and postural features, the role of dental occlusion in posture is simply not recognized.
Although a change in an integral biological system like the postural system can be expected to involve some change in all its components, the mandible is the only postural component routinely left out of efforts to improve or even analyze overall posture, simply because its role in body posture has never been understood.
In addition, most people have such a steep interdigitation between their teeth that, any adjustment or other attempt to improve body posture is followed by a return of the mandible to its precise pre-treatment position, which tends to return the whole postural system to its pre-treatment position.
The reason for our failure to correlate occlusion and posture is that the parameters we use to measure dental occlusion have no relevance to almost any functional features, including body posture. We quantify and compare occlusions by measuring details of the way the teeth fit and slide together, but those details reveal very little information about relevant features such as the mandible's position relative to the cranial base and the cervical vertebrae or the cross sectional area of the pharyngeal airway.
To understand the role of occlusion in posture requires understanding the role of the mandibular bracing platform in determining mandibular posture, the role of mandibular posture in body posture, and how those roles have changed during the last couple of centuries as our dietary change to highly processed foods has changed facial growth patterns. To mitigate this danger, bracing the mandible immobilized and secured it by clamping it up forcefully and immoveably against the underside of the cranium through the medium of the occlusal table.
Mandibular bracing was especially important for hominids. Canine and simian mandibles are protected from posteriorly directed impacts, even at rest, by overlapping canines. In hominids, the canines withdrew into the occlusal plane, leaving the vital inner ear areas protected only by a thin bony plate and neuromuscular reflexes that respond to danger by rapidly bracing the mandible.
Functional swallowing requires a braced mandible to provide a stable base of operation for the circumhyoid and tongue muscles. Efficient postural maintenance requires the ability to brace the mandible in order to enable the anterior kinetic chain of skeletal muscles to pull down directly on the front end of the cranium by pulling down on the mandible. That resting posture may be located several millimeters beneath the bracing platform or almost pushed up against it, depending on the resting tensions of the elevator muscles.
New Research Shows Relationship Between a Bad Bite and Poor Posture
Still, in a horzontal plane, the postural location of the mandible remains just beneath its bracing position. The accommodation of the posture of the mandible to the location of its bracing platform has been demonstrated in three planes.
Vertically, an immediate increase in freeway space follows the first occlusal contact after placing a bite raising appliance, and an immediate return to the pre-treatment freeway space follows the first occlusal contact after removing the bite raising appliance.
Laterally, children who develop unilateral cross-bite undergo a shifting of the mandible in both bracing and postural positions to the side of the cross-bite motivated by increased resting tension in the posterior temporalis on the side of the cross-bite; and their jaw muscle resting tensions normalize after correction of the cross-bite. In that posture, each skeletal member rests in a neutral zone at an equilibrium between opposing myofascial tensions.
The mandible's posture should occupy a neutral zone within the curtain of myofascial tensions that extends between the front of the head and the clavicles — at least it would occupy that postural position if the teeth were not involved. If the mandibular posture determined by the resting myofascial tensions of the habitual upright stance is not coincident with the mandibular posture determined by the reflex accomodation of the jaw muscles to the occlusion, a strain is shared between the masticatory and postural systems.
In these cases, patients often report that their symptoms switch back and forth between jaw and neck or back muscles.
If body posture is otherwise healthy, the symptoms can be relieved by changing the occlusion to make mandibular posture better fit body posture. If body posture is strained, it needs to be changed together with a change in mandibular posture. However, occlusal change is controversial. Because it is irreversible in some aspects, most dental authorities consider any occlusal treatment to be invasive and only to be used as a last resort.
A change in occlusion is irreversible because of the dentoalveolar adaptation that it triggers, - if an occlusal change causes symptoms, those symptoms cannot always be eliminated by simply reversing the occlusal change, because this is a biological rather than a mechanical system.
Treating the adverse effects of a change in occlusion does not require precisely reproducing all the centric and bracing occlusal contacts that existed before the change - it requires understanding the orthopedic aspects of that occlusion; and treating the occlusion to help improve body posture requires understanding the role of the mandible in head posture.
The spines of quadrupeds are supported at front and back like a suspension bridge - with the skull hanging from the well supported shoulders and the mandible hanging from the skull.
The forward ends of the food and air channels, hanging in sequence from the forward portion of that bridge, are easily kept separated and scarcely affected by movements of the head. The primary involvement of the postural muscles in mandibular movements is just to assist in mouth opening and closing by extending and flexing the head.
Uprighting a quadruped required revamping the skeleton. To absorb the forces of weight bearing, the spine developed alternating curves and the foot acquired a concave arch. The rib cage flattened. The pelvis acquired a concave front surface to support the abdomen and a thick bony crest for enlarged buttock muscles to help balance the weight over the legs. Instead of hanging from its occiput, its connection with the spine had to shift to a location under its center of mass.
Thus its pivot point for articulation with the spine shifted posteriorly, requiring a sharp bend in the cranial base, as illustrated in figure 1. The structural reinforcement for the mandible moved from its inner border, where it limited the size of the airway, to its outer front end where it formed a chin.
Evaluation of the correlation between dental occlusion and posture using a force platform
Mandibular opening moved its center of rotation from an axis between the condyles, which would rotate the chin into the airway space, to an axis between the mandibular foramen, which maintains the stability of the airway borders and the neurovascular bundle entering the mandible. The tongue balled up. Unfortunately the hominid airway was still left vulnerable to obstruction in the pharynx. Between its upper end where it was protected by the bony nasal cavity and its lower end where it was protected by the cartilage of the larynx and trachea, the airway in the pharynx was enclosed in a collapsable tube surrounded by muscles and protected only by neuromuscular reflexes.
Experimentally obstructing the pharynx airway causes all the muscles of the area to acquire unusual firing patterns, often in synchrony with respiration, in order to restore airway patency. The pull down on each side prevents tipping to the opposite side, and selective relaxation of muscles provides the flexibility needed for movement.
From side to side, this tower is symmetrical and stable. A series of parallel transversely extending structural components two feet, a pelvic girdle, a shoulder girdle, a mandible, and a cranium are connected by muscles at varied angles. A change in the orientation of any one of these structural components induces a change in the others.
From front to back, stability is far more difficult for a body so tall and flat. Symmetry is lost right from the top. In back, thick straps of postcervical muscles attach directly onto large bony occipital prominences.
However, in front, thick muscles and large bones could interfere with the freedom of movement necessary for yawning, swallowing, coughing, vomiting, spitting, talking, and turning the head. Thus, the front of the neck contains a series of generally small and nearly parallel bones clavicles, hyoid, and mandible connected by a large number of small muscles with varied directions of pull that maximize their leverage and ensure that each bone is capable of independent but coordinated action.
The balance between this sophisticated pre-cervical kinetic chain and the simple thick post-cervical muscle mass is illustrated below. To prevent the traction from the anterior postural muscles from reaching the face, the long rigid mandibular corpus absorbs it and transfers it all the way around to the sides of the head where the zygomatic arches and temporal fossae provide large areas of bone with sufficient structural support for strong muscle attachments.
The mechanics of this head posture mechanism makes the location of the mandibular corpus and the location of atlas inversely proportional in an antero-posterior direction. Shifting the head posteriorly shifts the corpus anteriorly relative to the head by compressing the tissues behind the ramus.
Shifting the head anteriorly shifts the corpus posteriorly relative to the headbecause traction from the pre-cervical muscles and fascia that tether the mandible to the clavicles prevents it from shifting as far anteriorly as the head. Our jaw muscles are now about half as strong as they used to be. In our ancestors, the use of the jaw muscles stimulated mandibular growth, causing it to elongate throughout life and thereby continuously carry the roots of the mandibular teeth anteriorly into the maxillary teeth enclosing them in front and on both sides in order to continuously supply tooth structure at the occlusal table throughout life and thereby compensate for the occlusal wear that continuously removed tooth structure from the occlusal table throughout life.
Typically, the elongation of the mandible produced enough anterior translation to steadily overcome the overjet and overbite, as illustrated in figure 3.
Because the anterior translation of the corpus was the primary motivator of this change in occlusion, the mandibular teeth moved slightly less far than their roots, causing the incisors to tip backwards on their bony bases. The difference in the way our faces grow today can be seen in the following illustration that compares the craniofacial skeletons of a population of humans before and after discovering agriculture.
The solid line represents the hunter-gathering population, and the dotted line represents the farmers. A very similar change in craniofacial form can be seen all over the planet as people acquire a diet of processed foods.
Today the mandible still elongates throughout life, but some of its growth has been redirected posteriorly and inferiorly. Overbite and overjet usually persist, and they may even increase rapidly in some TMJ disorder patients. Mandibles have become shorter. In population studies, posterior mandibular posture and anterior head posture are well correlated.
Most longitudinal studies have found stronger associations between changes in mandibular growth and subsequent body posture changes than associations between changes in body posture and subsequent mandibular growth.
Because the mandible surrounds the pharynx on three sides and the cervical spine borders its fourth, posterior displacement of the mandible can diminish the cross-sectional area of the pharyngeal airway. In response, all the muscles of the area alter their resting postures to hold the bones in whatever positions are necessary to maintain an adequate airway.
Usually they tip the head back into extension in order to rotate the mandibular corpus anteriorly and superiorly and thereby increase its distance from the cervical spine. When a child's mandible suddenly stops growing anteriorly with the rest of the face due to an injury such as TMJ ankylosis, the resulting severe class 2 malocclusion is accompanied by extreme anterior head posture simply as a result of the extreme posterior mandibular posture.
Forward head posture progressively diminishes and may even reverse the cervical lordosis by shifting its top end atlas forward over its base, as seen from left to right in figure 4. The vertical line rotating from a The descent of the upper horizontal line shows the loss of vertical height that accompanies forward head posture. Because the lateral and inferior aspects of the scapulae do not follow the base of the neck as far anteriorly, the scapulae also tend to rotate around a largely vertical axis, leaving their lateral and inferior aspects sticking out like wings winged scapula.
Lateral displacement of the mandible, which can be approximated by comparing the midlines between maxillary and mandibular central incisors, has been correlated with scoliosis and other postural asymmetries.
Studies of healthy subjects have shown that asymmetric occlusal interferences produce asymmetric firing of neck muscles, lateral displacement of the cervical spine, and increased body sway. The width of the maxilla is determined largely by functional forces.
For example, pre-industrial populations who chewed very forcefully often developed maxillae that were so wide that the mandible could only brace unilaterally on either side.
In contrast, monkeys raised on soft diets develop narrow palates much like modern children. In contrast to the maxilla, the width of the mandibular dental arch is determined mainly by genetics.
As a result, many modern children have a mandibular dentition that is wider than the maxillary dentition. Another common cause of lateral mandibular displacement has been the weakening of our jaw muscles. Experiments have shown that jaw muscle weakening causes increased variability and asymmetry in all the craniofacial components.
The temporalis muscles are responsible for posturing the mandible in a frontal plane. In unilateral cross-bite, the ipsilateral temporalis undergoes increased resting tension. Lateral mandibular displacement is also typically accompanied by a tipping of the head to the same side as the shift of the mandible.
To obtain the ''cotton rolls'' mandibular position, cotton rolls that were 8 mm thick and 37 mm long were positioned between the mandibular teeth distal to the canines. Quiet conditions were maintained during the exam, and disturbing elements were eliminated to avoid any influence on posture.
A force plate was placed cm from a wall such that the subjects were positioned perpendicular to the wall. The subjects were required to remain as stable as possible, relaxed, with their arms hanging free beside their trunk, and facing the wall without concentrating on a precise point.
Moreover, all of the subjects were asked to avoid alcohol, sports and conservative therapies during the 24 h before the clinical recordings. The placement of the subjects on the force plate was standardized; specifically, a hand was placed under the foot of the subject, lifting the foot until it met the following criteria using the markers painted on the surface of the platform Figure 1: Based on the results obtained, four parameters were evaluated: RESULTS A preliminary analysis of the results showed that the values of the postural parameters tended to increase when the subjects' eyes were closed.
Results in Table 1. The variations between the areas recorded in different mandibular position were lower under the same visual conditions mm2. The lowest areas were recorded in mandibular resting position. The mean values of the sway velocity when the eyes were closed were between 7.
In different mandibular positions under the same visual condition, there were variations of 0. The position of the center of the foot pressure on the X and Y axis is affected by wide variations. The dynamic stabilometric parameters area and velocity seem to be influenced by vision, and we observed a loss of postural control when a subject closed his or her eyes, as demonstrated by an increase in the postural parameter values.
This result can be understood if we assume that the vision represents a fundamental component of the tonic postural system and that the exclusion of vision prevents the superior system from controlling the posture. We observed that the position of the center of the foot pressure was not influenced by visual or occlusal components. It can be supposed that the coordinates of the center of the foot pressure are dependent on the patient's positioning on the platform and are not related to the test itself and that the position of the center of the foot pressure on the X axis changes less than on the Y axis because the relationships between the anatomical body parts are more subject to anterior-posterior sway than to lateral sway.
In this study, the mandibular position significantly influenced the sway area parameter, as some authors have previously reported 7,but it did not influence the sway velocity parameter. The influence of the mandibular position on sway area appears to be weak; however, this result is not completely reliable due to the abnormal statistical distribution of its values. In a clinical study conducted by Bracco et al.
All subjects exhibited statistically significant variations of body posture with different mandibular positions according to the asymmetry index and the position of the COP on the X and Y axes 15 ; this result is in contrast to the results of the present study, which did not reveal an influence of the different mandibular positions on the COP values.
A study by Perinetti et al. The sway area, sway velocity and length of the force platform were significantly higher when the subjects had their eyes closed versus open for both mandibular positions. There were no differences between the mandibular rest position and dental occlusion under the different visual conditions.
From a theoretical viewpoint, the absolute displacement of the COP was not correlated with the visual condition or mandibular position 9. This finding is compatible with our results, with the exception that we identified a weak influence of the mandibular position on the sway area.
Finally, Sakaguchi et al. Statistically significant differences were found in the sway length and sway area parameters between five different mandibular positions. It was concluded that changing the mandibular position affected the body posture and vice versa 7, Considering these previous conclusions, it seems probable that, despite the existence of a correlation between dental occlusion and posture, our results are similar to Perinetti's findings.
Dental Occlusion & Body Posture - A Review of Existing Studies | catchsomeair.us
Due to the presence of some significant differences between the results in the scientific literature and in accordance with the conclusion of Perinetti in his review article 19the most reasonable interpretation of our results is that the force platform and its most widely used parameters, although commonly used in gnathopostural clinical practice, do not constitute the most ideal method for the analysis of the correlation between dental occlusion and posture because of the lack of sensitivity of the method, especially in healthy subjects.
We can suppose that, because of the increased compliance among young, healthy subjects especially those without craniomandibular disorders and without occlusal problemsthe influence of dental occlusion on posture was not clearly observed in the lower legs, and the use of a force plate makes this difference even more difficult to detect.
The sway area was the only parameter that demonstrated a weak ability to detect an influence of dental occlusion on posture. The force plate is commonly used by clinicians to analyze posture in healthy, pathological and elderly individuals and athletes undergoing postural changes. It is also frequently used by specialists of a variety of disciplines who are interested in posture e. However, the utility of this instrument for verifying the relationship between occlusion and posture in healthy subjects appears to be less reliable.
Based on the results of this study, gnathologists should be careful in using force platform analysis to modify their therapeutic plans, especially in young patients and those without TMJ disorders, due to its low sensitivity for revealing occlusion-related postural alterations. Thus, the force platform does not seem to be the ideal instrument for use in gnathoposturology.
In fact, despite the results of this study, a correlation between dental occlusion and body posture is suggested by gnathopostural results obtained in clinical practiceby clinical studies that have been conducted without the use of a force platform 23,24 and especially by the important finding of the existence of a reciprocal relationship between dental occlusion and body posture described by Sakaguchi et al.
Contrary to the conclusions of other studies 9the clinical influence of this relationship could be important in gnathopostural approaches to treating painful trunk muscle symptomatology.
Future studies should focus on the development of new experimental protocols based, for example, on 3D analysis to clearly verify the correlation between dental occlusion and posture. These studies should evaluate the importance of this correlation for and its influence on each anatomical segment of the body.
Longoni S conducted the statistical analysis. Cozza P coordinated the study. Principles of Neural Science. Anxiety affects the postural sway of the antero-posterior axis in college students. Dental occlusion and posture: Primary trigeminal afferents to the vestibular nuclei in the rat: