Abstract:
A model for demonstrating referred pain. A human cranium and jaw are jointed to show a temporomandibular joint and tensionable connectors show muscles such as a trapezius muscle, neck muscle and jaw muscle. Tension can be regulated to demonstrate the effect on muscle stress and subsequent pain when the temporomandibular joint is in central relation or is out of central relation with the teeth maintained in central occlusion. The model allows a patient, student or clinician to visualize and demonstrate the concept of muscle tension resulting from jaw position and referred pain. A method and apparatus is disclosed.

Description:
FIELD OF THE INVENTION 
     The invention relates to a physical model for demonstrating relief of pain, particularly referred pain, in the craniofacial region. 
     BACKGROUND OF THE INVENTION 
     Physical models are helpful to simulate the cause and effect of various orthopedic and neuromuscular processes. Abnormalities in these processes often result in pain. Because of the complex physical and physiological relationships among the vascular, neuromuscular, and orthopedic systems, models are useful to locate and visualize the intricate interplay among these systems in an attempt to correct the abnormality and thus relieve the pain. 
     Models are particularly useful to demonstrate relationships in the craniofacial and upper body areas, where structures are more compact and the interdependence of these structures is more readily visualized. For example, craniofacial muscle stress is a result of changes in torque or force vectors in the muscles and ligaments between the jaw and cranium. An example of one such muscle that may be stressed is the trapezius muscle. A stressed trapezius muscle refers pain to the head, leading to symptoms such as headache and joint pain. The trapezius muscle, located in the shoulder and neck and serving to support the head from the back, contains trigger points. Trigger points are one or more sites of irritable muscle tissue which are especially tender to squeezing or pressure. The trigger points usually cause the phenomenon of referred pain recognized at a position removed from their own location. 
     Referred pain is defined as pain in which an abnormality in a particular location results in pain being felt in a location distant from the source. The concept is complicated and is difficult for many individuals to comprehend. An example of referred pain is the pain in the left arm that is felt by an individual suffering a heart attack. While it is cardiac muscle (that is, the heart) that is deprived of oxygen, the pain is experienced in the arm. Less drastic muscle aggravation than that provoking a heart attack, for example skeletal muscle aggravation, can result from strenuous exercise, sudden movement, improper positioning for an extended duration, and so on. The aggravated muscles in one area of the body thus lead to muscle tension and pain in other areas of the body resulting from a complex series of elements, culminating in referred pain. If these elements can be relieved, the tension in muscles having trigger points will also be relieved and therefore will not refer pain to other areas of the body. The end result is that pain in other areas of the body, or referred pain, will be relieved. 
     Physical models of various body regions in general, and of the craniofacial region in particular, are well known. However, all suffer from the drawback that they do not demonstrate the phenomenon of referred pain. For example, U.S. Pat. No. 3,376,645 discloses a demonstration device that simulates proper and improper dental occlusion and its effect on the temporomandibular joint. The device includes bas-relief planar facsimiles of the human upper and lower jaws which are mounted on a planar support. The upper jaw is fixed while the lower jaw is removable and is adapted to pivot about the temporomandibular joint. By substituting alternative lower jaw facsimiles representing various malformations, including improper bite or occlusion, sliding or shifting of the lower jaw fore and aft can simulate the effect of the temporomandibular joint and muscles and ligaments in the face, head and neck. 
     Similarly, U.S. Pat. No. 3,616,537 discloses a demonstration device that includes upper and lower plates having representations of an upper and lower jaw and temporomandibular joint. The plates include slots and pins which may be adjusted to simulate different occlusions and their effect on the function of the temporomandibular joint. 
     As another example, U.S. Pat. No. 4,541,807 is a planar demonstration device similar to that disclosed in the aforementioned &#39;645 patent but including a series of rubber bands to simulate various muscles that support the lower jaw. The device also includes a series of replaceable inserts to represent different improper bites or occlusions, and which cause movement at the temporomandibular joint. Another series of inserts function to correct an improper bite or occlusion and to move the temporomandibular joint back to its proper position. 
     As still another example, U.S. Pat. No. 4,948,373 discloses a three-dimensional model of the human craniomandibular system. A cranium is pivotally mounted to the first cervical vertebra, and a series of rubber bands simulate various muscle functions. Insert or enlargement pieces may be added to or removed from the lower jaw to simulate Angle Class I, II and III situations. Inserts may also be used to simulate patients in which the lower jaw is either horizontal or parallel to the upper jaw, or is upwardly or downwardly inclined with respect to the upper jaw. 
     Each of these models fails to account for the common effects leading to referred pain. For example, one source of referred pain is pain triggered by a trigger point in the trapezius muscle which is tensed or aggravated due to the non-coincident central occlusion of the teeth and central relation of the temporomandibular joint. The cranium in each of these models is fixed and cannot pivot or tilt downwardly, thus the models do not take into account, and hence do not simulate, normal and abnormal trapezius muscle function. Although the &#39;373 patent uses rubber bands to simulate the effect of various muscles, it is a complicated three-dimensional device that does not account for the effects of coincident central relation and central occlusion, and furthermore does not show the effect of treatment of this problem. Because the concept of referred pain is difficult for many individuals to grasp, a visual model would be particularly useful in demonstrating the physiology underlying this complex phenomenon. 
     Muscles are cumulatively the largest single body organ and account for over forty percent of the body weight. Given the amount of stress and strain muscles endure, it is not surprising that many individuals suffer muscle pain. However, X-rays and other imaging techniques do not provide images of muscles. Thus, models demonstrating these complex relationships would have advantages in educating patients, physicians, therapists and other professionals who institute and monitor patient treatment, and in treating the patients who endure referred pain. 
     While a patient may not be able to grasp the complexities inherent in standard medical models, a model that clearly depicts the interrelatedness between abnormalities in craniofacial structures and sites of referred pain would facilitate a patient&#39;s understanding and education. This, in turn, would likely motivate and assist a patient in taking corrective action to alleviate the problem. Such a model is therefore needed. 
     SUMMARY OF THE INVENTION 
     The invention includes a model of a human craniofacial region functional to demonstrate relief of referred pain. A head comprises a cranium that is pivotally joined to a neck supported on a base. A jaw is connected to the cranium at a joint that simulates the temporomandibular joint. Tensionable connectors, for example rubber bands or springs, represent muscles such as the trapezius muscle and jaw muscle. Tension can be varied in these connectors to demonstrate effects between the positions of the cranium, jaw and muscles that can result in pain. The model also contains teeth and can demonstrate the teeth and temporomandibular joint in various positions. The model may be a physical model and may also include a device such as a splint inserted between the teeth to demonstrate how pain may be relieved. 
     The invention also includes a method for physically demonstrating a source of pain, particularly referred pain. A model is provided of a human cranium hinged to a base and a jaw jointed to the cranium to simulate the temporomandibular joint, containing teeth, and having tensionable connectors representing a state of muscle tension. The method includes varying the position of the head and teeth, varying the tension on the connectors, and/or inserting a splint to demonstrate the effect of jaw position and trapezius irritation as a source of pain, and the relief thereof. 
     There is thus briefly summarized a craniofacial model that is both easy to use and easy to understand, and methods of using the model to demonstrate the effect of source and relief of pain involving these structures. The invention will be further appreciated in light of the following drawings and detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front view of a model profile of a normal head. 
     FIG. 2 is a front view of a model profile of a head having non-coincident central relation and central occlusion. 
     FIG. 3 is a front view of a model profile of a head during treatment for non-coincident central relation and central occlusion. 
    
    
     DETAILED DESCRIPTION 
     With reference to FIG. 1, a model  10  demonstrating the normal position of the craniofacial region is shown. The model  10  comprises a human head  12  and neck  14  in profile. The head  12  and neck  14  are generally planar (i.e., ½″ to 1″ or so thick, for example) but could be of lifelike three dimensional configuration. 
     The model  10  is supported on a base  16  by neck member  14 . Head  12  is pivoted to neck support member  14  by hinge  13 . The hinge  13  defines a space S between members  13   a ,  13   b  at an angle A of about 45°. The space S permits the head  12  of the model  10  to tilt forward decreasing angle “A”, for example, when it is desired to have the model simulate a stressed state of the muscles. 
     The model head  12  has at least a jointed jaw  18  separably connected to a replica cranium  20 . The jaw  18  and cranium  20  are connected at the temporomandibular joint, illustrated at  22 , by any type of tensionable connectors  24  such as rubber bands, elastic members, springs, etc. The tensionable connectors  24   a-h  represent muscles or muscle groups and can simulate either an uncontracted or relaxed state of the muscle, as well as a contracted or tensed state of the muscle. When trigger points in the neck muscles, such as the trapezius muscle, are activated, they refer pain as described above. In many cases the tension is caused by contraction of the jaw muscles such as represented by tensionable connectors  24   b ,  24   d  by, for example, a “bad bite”, nighttime clenching of the jaw  18 , nighttime grinding of the teeth  26 , or other actions causing the jaw muscles to contract. The result is that the model head  12  reacts as a physiological specimen would react and tilts forward (F) as illustrated in FIG. 2, causing the neck muscles to contract even more to offset the extra tension in the jaw muscles to hold the head level. This extra tension in the neck muscles activates the trigger points in the neck  14 , which then refer pain to the head. Manipulation of the model  10  fully demonstrates these relationships and the relief of pain caused thereby by reason of return to the central occlusion (CO) and central relation (CR) positions of the elements described above, respectively. For example, the model  10  may be used to demonstrate dysfunction in the craniofacial region  25  (with jaw and teeth in respective noncoincidental CR and CO positions, as will be described), which can spark trigger points in a muscle of the neck  14  and/or shoulder to then refer pain to the temple, side of the head, and/or above the eyes. 
     Any desired amount of tension in the muscles may be illustrated by tension in the respective tensionable connectors  24   a-h , up to the point at which the stretched tensionable connector  24   a-h  will snap. This type of model  10  is thus useful when instructing patients in the consequences of their actions and/or craniofacial positions in terms of a partial or total relief from pain. As will be described with respect to FIG. 3, a splint returning the jaw and teeth to CR and CO eliminates excess muscle tension and trigger point activation, alleviating or relieving referred pain. 
     In one embodiment of the model of FIG. 1, upper teeth  26   a  and lower teeth  26   b  are included in the mouth  27 . The top of the head  12  is substantially horizontal (horizontal line (T 1 )) when angle A is about 45°. In the normal state of the craniofacial region  25 , the temporomandibular joint  22  assumes a CR position, where the joint  22  is centered and the upper and lower teeth  26   a ,  26   b  are meshed or engaged, defining a CO position. This results in the CO position of teeth  26   a ,  26   b  and CR position of the temporomandibular joint  22  being coincident, i.e., the joint  22  is properly seated in its socket and the teeth  26   a ,  26   b  are properly meshed. There is no muscle pain, since the muscles represented by tensionable connectors  24   a-h  need not strain in an attempt to attain these positions, and likewise there is no referred pain. 
     FIG. 2 illustrates the physical condition of body components wherein the upper and lower teeth  26   a ,  26   b  are not meshed in CO but overlapped, the joint  22  is unseated or out-of-socket and there is noncoincidental CR and CO. FIG. 2 illustrates the same muscle set as depicted in FIG. 1 but shows the increased amount of tension placed on the tensionable connectors  24   a ,  24   b  and a slackening of tension on the tensionable connectors  24   e ,  24   h , just as in the human circumstance. This may be caused, for example, by stress and stress induced lower jaw positioning away from the unstressed position, illustrated in FIG.  1 . As shown in FIG. 2, this tension in the jaw muscles modeled at  24   a ,  24   b  causes the head  12  to tilt forward F, decreasing angle A and increasing tension in tensionable connector  24   g  representing the trapezius muscle of the neck  14  and back in stretch or strain. 
     The trapezius muscle normally helps to stabilize the head  12  during head and neck movements such as chewing. It also pulls the head  12  backward and helps lift the arms. When the muscle is tensioned, such as by the tilting of the head  12  described above, it aggravates trigger points therein and pain is referred to the lateral portion of the head  12 . The tension in the neck muscle, simulated as tension in the tensionable connectors  24   f ,  24   g , activates the trigger points in the neck  14 , which in turn refer pain to the temple, side of the head and above the eyes. Thus, to offset the tension in the tensionable connector  24   b  simulating the jaw muscle, and in an effort to return the head from a forward tilted position (T 2 ) back to a substantially horizontal position (T 1 ), the tensionable connector  24   g  simulating the trapezius muscle in the back, and the tensionable connector  24   f  simulating the muscle in the side of the neck are observed to contract. The forward tilt (T 2 ) reaction of the head in response to noncoincidental CO and CR resulting from jaw muscle stress results in tension of connectors  24   f  and  24   g  illustrating the resulting tension in the neck and trapezius muscle. As shown in FIG. 2, this is clearly illustrated in the model  10  by the head  12  tilting forward (T 2 ), stretching the tensionable connectors  24   g  in the back of the neck  14  representing the trapezius muscle and  24   f  representing the neck muscles. 
     Thus, in summary, when the CR and CO are not coincident, as when the teeth  26   a ,  26   b  are unmeshed and the joint  22  is unseated, the abnormal condition places a stress on the trapezius muscle, represented in the model as the tensionable connector  24   g . While a natural urge in an unstressed position is to have the upper and lower teeth  26   a ,  26   b  mesh, meshing of the teeth  26   a ,  26   b  in a stressed condition results in the temporomandibular joint  22  being pulled out of CR. The temporomandibular joint  22  out of CR stresses muscles and causes the head  12  to tilt forward (T 2 ). This position of the head  12  places a stress or tension on the tensionable connectors  24   g  and  24   f  representing the trapezius muscle and the neck muscle respectively, which in turn sets off trigger points to refer pain to the head  12 . 
     With reference to FIG. 3, to relieve the tension on the trapezius muscle and concomitantly to relieve the cause of the pain, a splint  30  is inserted into the mouth  27 . The splint  30  allows the upper and lower teeth  26   a ,  26   b  to return to a mesh position (CO), with the temporomandibular joint  22  being in CR. Thus, the splint  30  restores the normal state of having a coincident CO and CR. As is easily visualized by the model  10  as shown in FIG. 3, the head  12  is horizontal (T 1 ) and is not torqued or forced to tilt forward, so that the trapezius muscle and the neck muscle, represented by the tensionable connectors  24   g  and  24   f  respectively, are not tensed. Since the trapezius and neck muscles are not tensed, their trigger points are not aggravated, no pain is referred, and the referred pain that was manifested as a headache or a joint ache is relieved. 
     The model  10  may be a physical model that is life sized, less than life sized, or greater than life sized. The model  10  may be made out of any material that can be easily and fixedly connected by tensionable connectors  24  such as rubber bands to simulate muscles in a contracted, relaxed or normal state. Such materials include but are not limited to natural products such as wood, synthetic products such as hard plastic, styrofoam or other suitable material, and combinations of the above. The connections  32  that secure the tensionable connectors  24  to the model  10  or base  16  may be secured by any means that allow maximum elasticity of the tensionable connectors  24  without destroying their integrity. Examples of connectors  32  include, but are not limited to, hooks, pins, staples, clips, etc. 
     Furthermore, the model may be a computer-generated model depicting normal and stressed conditions of muscles graphically or visually. 
     From the above disclosure of the general method of the present invention and the preceding summary of the preferred embodiments, those skilled in the art will readily comprehend the various modifications to which the present invention is susceptible without departing from the scope of the invention. Therefore, applicant desires to be limited only by the scope of the following claims.