MAXILLOFACIAL PROSTHETICS TEMPOROMANDIBULAR JOINT DENTAL IMPLANTS I.
KENNETH
ADISMAN,
Bioiagic move
laws
LOUIS
governing
the mandible.
Nibs F. Guichet, Anaheim, Calif.
J. BOUCHER,
Section editors
functions
of rnW&s
Part II. Condykw
that
pas&ion
D.D.S.
M
any factors other than the proprioceptive inputs originating from occlusal contacts of teeth program jaw position and functions of the muscles that move the mandible. Proprioceptive stimuli received from anatomic structures1-5 plus those resulting from gravity”-’ and those of psychic origins*-‘3 all have an effect on muscle function. However, once the mechanism by which the occlusion programs muscle function is clearly understood, it becomes a relatively simple matter to make an accurate diagnosis and select the most direct approach to treatment. This is the second of a series of four articles on the biologic laws governing functions of muscles that move the mandible. The series deals with the specific muscle responses programmed by specific types of occlusal contacts. Much of the information presented in this series is based on clinical observation of modified muscle responses related directly to occlusal treatment procedures and interpretation of this information to produce a useful clinical tool in diagnosis antd treatment. The laws are stated on the basis that there is no medium between the teeth and the mandible is being manipulated by the dentist. When evaluating the clinical observations reported in this article, the reader must first assume that the “patient” has a full complement of teeth in good alignment. The patient is seated in the dental chair in a slightly reclining position with the head in normal postural position in relation to the body. The patient reports no pain or inflammation in any of the tissues of the gnathostomatic system, and none can be elicited on clinical examination. The patient is considered to be “normal.” The only variable in the patient will be modified proprioceptive stimuli which result from modifications in the character of the occlusion. All other proprioceptive input.c are considered to be fixed. Presented
before
the
Academy
of Denture
Prosthetics,
Washington,
D.
C.
35
36
J. Prosthet. Dent. July, 1977
Guichet
2 +
2 UNIT LOAD
Fig. 1. A diagrammatic stress-bearing unit. Fig.
2. A diagrammatic
UNIT LOAD
representation
of the
representation
of the
100 20
UNIT
UNIT
1
single
2 UNIT LOAD
periodontal
proprioceptive
3. A diagrammatic
Fig. 4. The direction tively governs functions
or
bundle-the
basic
mechanism.
LIMIT
LOAD
0 Fig.
fiber
0 representation of the resultant of the muscles
MODEL TO QUANTIFY
of the stress-bearing
ability
force vector to occlusal that move the mandible.
of the periodontal loading
determined
apparatus. propriocep-
MUSCLE RESPONSE
A diagrammatic representation (model) of the basic stress-bearing unit, the single typical periodontal fiber or ligament, is seen in Fig. 1. This unit has a capacity to withstand stress. However, there is a physiologic limit to the amount of stress which it can withstand. Let us assign a value of 2 units to that limit. This means that if the ligament is stressed with a load of 2 units, it will return to normal; if it is stressed with a load in excess of its physiologic limit, 2 units, it will not return to normal-it will be damaged. In order to prevent damage during the physiologic functions of chewing, swallowing, and speech, periodontal ligaments are equipped with an alarm system, the proprioceptive mechanism.14-18 Sensors within the periodontal ligament are illustrated as contacts in Fig. 2. When the ligament is stressed to its physiologic limit, the sensors are brought into contact, sounding the alarm that the physiologic limit or maximum load-carrying ability of the ligament has been reached. This signal in turn induces a protective muscle response such as an opening reflex or inhibited movement.*4s *Q-22
Volume Number
38 1
Fig. 5. The gramming.”
Biologic
process
by which
the
laws
occlusion
governing
programs
mandibular
muscle
functioc.
muscles.
Part
II
37
is termed “occlusal pro-
The periodontal ligaments are analogous to firemen around a fire ring which is used to catch people who jump from burning buildings. The inner circle represents the canvas of a fire ring (Fig. 3, A). Each of the 10 bars about the ring represents a fireman having a load-carrying capacity of 2 units. That apparatus can withstand a load of 20 units applied perpendicular to the center of the ring without exceeding the load-carrying capacity of the system. If a load in excess of 20 units were applied, the system would fail and damage would result. The supporting structures of the teeth are analogous to the fire ring in that the periodontal ligaments can be thought of as a system of fire rings (Fig. 3, B) . The amount of axial stress a tooth can withstand is directly proportional to the number of basic stress-bearing units in the supporting structures of the teeth-in other vvords, the area of periodontal ligament. If occluding forces are applied parallel to the long axis of a tooth, the tooth has maximum load-bearing ability without proprioceptive sensors signaling for inhibition of the application of load (Fig. 4). However, if applied forces are not in the direction of the long axis of the tooth upon application of a relatively minor load, certain periodontal ligaments will be stressed to their physiologic limits, initiating a proprioceptive signal to inhibit further application of load (inhibited mandibular movement). When pressures are applied to the chewing surfaces of the teeth by a bolus or the opposing occlusion, the direction and degree of the applied loads are perceived by the proprioceptive mechanism. In turn, this mechanism programs the most physiologic muscle response in consideration of the prevailing conditions within the total system (Fig. 5). This is the basic protective reflex mechanism which prevents damage of the system in the functions of chewing, swallowing, and speech. Understanding the mechanism by which mechanical contacts of teeth program muscle response enables the dentist to quantify the muscle response elicited by occlusal contacts (occlusal switches) and express it as laws governing muscle functions. In presenting the five laws which govern functions of the mandible-moving musrles, I will (1) state the law, (2) present the clinical observations upon which the law is based sometimes along with an analogy, and (3) discuss its clinical application.
38
J. l’rosthet. Dent. July, 1977
Guichet
Table I. Analogy extensor removal resulting
of an electromyographic analysis comparing the response of the and flexor muscles of the right and left legs as a result of introduction and of an irritant to the response of the muscles that move the mandible from occlusal irritation
A. Most physiologic condition B. Irritation induced C. Irritation and extension D. Irritation eliminated
Right
Left
4 8 16 4
4 4 4 4
CONDYLAR POSITION (LAW NO. 11 In the absence of inflammation in the temporomandibular joints or muscles of mastication, the condylar positions of the mandible at rest and as it moves to maximum intercuspation (centric occlusion) are programmed (or influenced) by the prevailing occlusal scheme. Clinical observation. The ability of the dentist to modify the occlusion and reprogram the condylar position and muscle response is easily demonstrated clinically and mandibular clutches in occlusal treatment procedures. *, I59 23-28 When maxillary which include a central bearing screw are removed from the mouth after hinge axis location or pantographic recording, the patient frequently demonstrates alarm, because the teeth do not intercuspate properly. This modification occurs, because during the time that the clutches were held between the teeth, they provided a new occlusal program which induced a complementary muscle response and condylar position. When the clutches were removed, the teeth did not fit together properly. After several jaw closures, the muscles reprogrammed the condylar position to complement the prevailing occlusion. This phenomenon illustrates the potential of the dentist, in the absence of inflammation in the temporomandibular joint or associated musculature in the patient, to almost instantly reprogram the musculature and condylar position by occlusal treatment. An analogy. The physiologic basis for Law No. 1 governing condylar position can be presented with an analogy. Consider an electromyographic analysis of the extensor and flexor musculature of the right and left legs. Assume that both appendages are in the most physiologic state and exhibit minimum stress or contractions of the musculature. An electromyographic analysis of these appendages would exhibit a minimum reading on the electromyographic scale. Let us assign a value of 4 to this reading (Table I). Now, let us introduce an irritation in the right knee. The irritation in the right knee is perceived by the proprioceptive mechanism, and signals are transmitted to master control (central nervous system) which in turn programs the most physiologic muscle response in consideration of the prevailing conditions. The right leg flexes. Basically, the flexor muscle in the right leg becomes more contracted or stressed so as to fix the leg in a more favorable postural position in consideration of the prevailing conditions. When the leg assumes this adjusted postural position, there is a condition of increased stress or tension in the muscles of the right leg. Any attempt by the patient to extend or to flex the leg from this ad-
Volume Number
38 1
Biologic
laws governing
mandibular
muscles.
Part
II
39
justed postural position requires effort. This is the minimum, stress possible in the musculature as long as the irritation in the knee prevails. An electromyographic analysis of the right and left legs at this time would reveal a condition of increased stress in the muscles of the right leg. On the electromyographic scale, let us assign a value of 8 to this condition of increased contraction in the muscles of the right leg (Table I), The left leg is unchanged. At this time, in order to extend the right leg so that it assumes the postural position it had before the irritation was introduced, effort on the past of the patient would be required. This is a strained relation, because it is necessary for the extensor muscles to contract sufficiently to overcome the chronically contracted flexors programmed by the irritation in the knee. An electromyographic analysis at this time would reveal a condition of further increased stress or tension in the muscles of the right leg. Let us assign a value of 16 to this electromyographic reading (Table I j . If at this time the irritation from the right knee could be totally removed, the leg would be restored to the condition which prevailed prior to the time the irritation was introduced, showing a reading of 4 on the electromyographic scale (Table 1:~. This is basic muscle physiology. Now, let us compare this response to the responses to occlusal irritation shown by the muscles that move the mandible. Assume that the muscles that move the mandible are in the most physiologic position and that they exhibit minimum stress or tension. For purposes of discussion, let us say there is simultaneous, even contact of the teeth when the condyles are in centric relation.” An electromyographic analysis of the musculature of this patient, who exhibits absence of irritation in the occlusion, would reveal minimal tension in the musculature. Like the leg, let us assign a value of 4 to that electromyographic reading (Table I). Now let us introduce an irritation between the teeth, a deflective contact in centric relation. Because of the introduction of an irritation, there is an adjusted postural position, as with the irritation in the knee. The leg flexes; the jaw comes forward or assumes another adjusted postural position depending on the type of occlusal irritation introduced. The occlusal irritation is perceived by the proprioceptive mechanism, and signals are transferred to master control (nervous system) which in turn programs the most physiologic muscle response in consideration of the prevailing conditions. An electromyographic analysis of the jaw musculature at this time, as with the leg, will reveal a condition of increased stress or tension in the musculature-a reading of 8 on the electromyographic scale (Table I) . This is the minimum tension possible in the musculature under the prevailing conditions. If at this time we ask the patient to move his jaw forward or backw& to centric relation, effort would be required. For the patient to move the jaw backward, the retractor muscles must overcome the tensions of the chronically contracted protractor muscles which are programmed by the prevailing occlusal irritant. An electromyographic analysis of the musculature with the patient maintaining his condyles in centric relation would show increased tension in the musculature. Analogous to the leg, a
*This specification for occlusion being in the most physiologic position discussion only, and it should not be construed that the author feels that this logic mandibular position at which maximum intercuspation should occur.
is for the sake of is the most physio-
40
Guichet
reading ever, if muscles troduced existing
J. Prosthet. Dent. July, 1977
of 16 would be recorded on the electromyographic scale (Table I). Howat this time the occlusal irritant were completely removed, the tension in the would return to the condition present prior to the time the irritant was in(Table I) . This physiologic response of the neuromuscular system to the occlusal condition is termed “occlusal programming.“2”. 8”
CENTRIC RELATION RECORDS The ability of the occlusion to program condylar position accounts for the patient’s repeated ability to avoid damage and close in the position of maximum intercuspation of the teeth.“0-“2 The teeth are brought together in that position where they fit best. Patients avoid occlusal contact on prematurities and close in maximum intercuspation (centric occlusion) . One can readily appreciate the clinical significance of the foregoing discussion as it applies to obtaining a centric relation record. The challenge in obtaining an accurate centric relation record is not so much one of obtaining an indexing registration of the mandibular teeth to the maxillary teeth as it is one of how to relieve stress in the muscles or reprogram them so they will allow the condyles to seek and retain the position of centric relation (or the potentially most optimum position) at the time the record is obtained. It is easy for the dentist who does not understand the physiology of occlusal programming to obtain an interocclusal record with the condyles splinted in a position other than centric relation (or the most optimum position) in his attempts to obtain a centric relation record.
SUMMARY A model to quantify muscle response to occlusal contacts is useful in developing an understanding of the mechanism by which the occlusion programs muscle function. A knowledge of how the occlusion programs muscle function enables the dentist to develop manipulative skills of the mandible which are necessary for diagnosis and effective occlusal treatment. This article presents complicated neuromuscular responses (reflexes) to occlusal contacts in an oversimplified way and with analogies so that the clinical significance of these neuromuscular reflexes in diagnosis and treatment can be more easily understood.
References 1. Gill, H. I.: Neuromuscular Spindles in Human Lateral Pterygoid Muscles, J. Anat. 109: 157-167, 1971. 2. Thilander, B.: Innervation of the Temporomandibular Joint Capsule in Man, Trans. Roy. Schools Dent. Stockholm Umea, No. 7, pp. 9-67, 1961. 3. Storey, A. T.: Sensory Functions of the Temporomandibular Joint, J. Can. Dent. Assoc. 34: 294-300, 1968. 4. Wyke, B. D.: Neurophysiological Aspects of Joint Function With Particular Reference to the Temporomandibular Joints, J. Bone Joint Surg. 43B: 396-397, 1961. 5. Griffin, C. J., Sharpe, C. J., and Gee, E.: Inhibition of the Linguo-Mandibular Reflex. I. Golgi Type Organs of the Pes Menisci, Aust. Dent. J. 10: 376-379, 1965. 6. Garnick, J., and Ramfjord, S. P.: Rest Position, J. PROSTHET. DENT. 12: 895-911, 1962. 7. Preiskel, H. W.: Some Observations on the Postural Position of the Mandible, J. ProsTHET. DENT. 15: 625-633, 1965.
Biologic 8. 9. 10. 11. 12. 13. 14. 1.5. 16. 17. 18.
19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 3n. :i 1.
:12.
laws governing
mandibular
mu.trles.
Part
II
41
Ramfjord, S. P.: Bruxism, a Clinical and Electromyographic Study. J. Am. Dent. Assoc. 62: 21-44, 1961. Livingston, R. B., and Hernandez-Peon, R.: Somatic Functions of the Nervous System, Ann. Rev. Physiol. 17: 269-292, 1955. Pavlov, I.: Lectures on Conditioned Reflexes, ed. 2, Muenchen, 1’328, J. F. Bergman, Kraus, H.: Muscle Function and the Temporomandibular Joint, J. PROSTHET. DEST. 13: 950-955, 1963. Schwartz, L.: Disorders of the Temporomandibular Joint, Philadelphia, 1959, W. B. Saunders Company. Svein, E.: Temporomandibular Joint Disorders, Dent. Digest 60: 361, 1954. Sessle, B. J., and Schmitt, A.: Effects of Controlled Tooth Stimulation on Jaw Muscle Activity in Man, Arch. Oral Biol. 17: 1597-1607, 1972. Jerge, C. R.: Neurologic Mechanism Underlying Cyclic Jaw Movements, J. PROSTHET. DENT. 14: 667-681, 1964. Lewinsky, W., and Steward, D.: The Innervation of the Periodontal Membrane, J. Anat. 71: 98-102, 1936. Griffin, C. J.: The Fine Structure of End-Rings in Human Periodontal Ligament, Arch. Oral Biol. 17: 78.5-797, 1972. Kizior, J. E., Cuozzo, J. W., and Bowman, D. C.: Functional and Histologic Assessment of the Sensory Innervation of the Periodontal Ligament of the Cat, J. Dent. Res. 47: 59-64, 1968. Beaudreau, D. E., Daugherty, W. F., and Masland, W. S.: Two Types of Motor Pause in Masticatory Muscles, Am. J. Physiol. 216: 16-21, 1969. Goldberg, L. J.: Masseter Muscle Excitation Induced by Stimu!ation of Periodontal and Gingival Receptors in Man, Brain Res. 32: 369-381, 1971. Yemm, R., Hannam, A. G., and Matthews, B.: Changes in the Activity of the Masseter Muscle Following Tooth Contact, J. Dent. Res. 48: 1131, 1969. Hannam, A. G., Matthews, B., and Yemm, R.: The Response in the Masseter Muscle Following Tooth Contact in Man, J. Physiol. 203: 25-26, 1969. Jerge, C. R.: Comments on the Innervation of Teeth, Dent. Clin. North Am., March. 1965, pp. 117-127. Jarabak, J. R.: An Electromyographic Analysis of Muscular and Temporomandibular Joint Disturbances Due to Imbalances in Occlusion, Angle Orthod. 26: 170-190, 1956. Krogh-Paulsen, W. B.: Facial Pain and Mandibular Dysfunction, Philadelphia, 1968, W, B. Saunders Company. Posselt, U.: Physiology of Occlusion and Rehabilitation, Philadelphia, 1962, F. A. Davis Company. Ramfjord, S. P., and Ash, M. M.: Occlusion, Philadelphia, 1966: W. B. Saunders Company, p. 167. Kabcenell, J. L.: Effects of Clinical Procedures on Mandibula,r Position, J. PROSTHET. DENT. 14: 266-278, 1964. Guichet, N. F.: Applied Gnathology, Why and How, Dental Clinics of North America, Philadelphia, 1969, W. B. Saunders Company. Guichet, N. F. : Gnathology-Everyday Dentistry, i\naheim. 1964, Denar Corporation, p. 30. Pameijer, J. H. N., Glickman, I., and Roeber, F. W.: Intraoral Occlusal Telemetry. Part II. Registration of Tooth Contacts in Chewing and Swallowing, J. PROSTHET. DENT. 19: 151-159, 1968. Jones, R. G.: The Physiological Role of Dental Occlusion in the Masticatory System. Master’s Thesis, Indiana University, 1965, p. 146. 320 OL.YMPIA PLACE ANAHEIM, CALIF. 92806
KENNETH
ADISMAN,
Bioiagic move
laws
LOUIS
governing
the mandible.
Nibs F. Guichet, Anaheim, Calif.
J. BOUCHER,
Section editors
functions
of rnW&s
Part II. Condykw
that
pas&ion
D.D.S.
M
any factors other than the proprioceptive inputs originating from occlusal contacts of teeth program jaw position and functions of the muscles that move the mandible. Proprioceptive stimuli received from anatomic structures1-5 plus those resulting from gravity”-’ and those of psychic origins*-‘3 all have an effect on muscle function. However, once the mechanism by which the occlusion programs muscle function is clearly understood, it becomes a relatively simple matter to make an accurate diagnosis and select the most direct approach to treatment. This is the second of a series of four articles on the biologic laws governing functions of muscles that move the mandible. The series deals with the specific muscle responses programmed by specific types of occlusal contacts. Much of the information presented in this series is based on clinical observation of modified muscle responses related directly to occlusal treatment procedures and interpretation of this information to produce a useful clinical tool in diagnosis antd treatment. The laws are stated on the basis that there is no medium between the teeth and the mandible is being manipulated by the dentist. When evaluating the clinical observations reported in this article, the reader must first assume that the “patient” has a full complement of teeth in good alignment. The patient is seated in the dental chair in a slightly reclining position with the head in normal postural position in relation to the body. The patient reports no pain or inflammation in any of the tissues of the gnathostomatic system, and none can be elicited on clinical examination. The patient is considered to be “normal.” The only variable in the patient will be modified proprioceptive stimuli which result from modifications in the character of the occlusion. All other proprioceptive input.c are considered to be fixed. Presented
before
the
Academy
of Denture
Prosthetics,
Washington,
D.
C.
35
36
J. Prosthet. Dent. July, 1977
Guichet
2 +
2 UNIT LOAD
Fig. 1. A diagrammatic stress-bearing unit. Fig.
2. A diagrammatic
UNIT LOAD
representation
of the
representation
of the
100 20
UNIT
UNIT
1
single
2 UNIT LOAD
periodontal
proprioceptive
3. A diagrammatic
Fig. 4. The direction tively governs functions
or
bundle-the
basic
mechanism.
LIMIT
LOAD
0 Fig.
fiber
0 representation of the resultant of the muscles
MODEL TO QUANTIFY
of the stress-bearing
ability
force vector to occlusal that move the mandible.
of the periodontal loading
determined
apparatus. propriocep-
MUSCLE RESPONSE
A diagrammatic representation (model) of the basic stress-bearing unit, the single typical periodontal fiber or ligament, is seen in Fig. 1. This unit has a capacity to withstand stress. However, there is a physiologic limit to the amount of stress which it can withstand. Let us assign a value of 2 units to that limit. This means that if the ligament is stressed with a load of 2 units, it will return to normal; if it is stressed with a load in excess of its physiologic limit, 2 units, it will not return to normal-it will be damaged. In order to prevent damage during the physiologic functions of chewing, swallowing, and speech, periodontal ligaments are equipped with an alarm system, the proprioceptive mechanism.14-18 Sensors within the periodontal ligament are illustrated as contacts in Fig. 2. When the ligament is stressed to its physiologic limit, the sensors are brought into contact, sounding the alarm that the physiologic limit or maximum load-carrying ability of the ligament has been reached. This signal in turn induces a protective muscle response such as an opening reflex or inhibited movement.*4s *Q-22
Volume Number
38 1
Fig. 5. The gramming.”
Biologic
process
by which
the
laws
occlusion
governing
programs
mandibular
muscle
functioc.
muscles.
Part
II
37
is termed “occlusal pro-
The periodontal ligaments are analogous to firemen around a fire ring which is used to catch people who jump from burning buildings. The inner circle represents the canvas of a fire ring (Fig. 3, A). Each of the 10 bars about the ring represents a fireman having a load-carrying capacity of 2 units. That apparatus can withstand a load of 20 units applied perpendicular to the center of the ring without exceeding the load-carrying capacity of the system. If a load in excess of 20 units were applied, the system would fail and damage would result. The supporting structures of the teeth are analogous to the fire ring in that the periodontal ligaments can be thought of as a system of fire rings (Fig. 3, B) . The amount of axial stress a tooth can withstand is directly proportional to the number of basic stress-bearing units in the supporting structures of the teeth-in other vvords, the area of periodontal ligament. If occluding forces are applied parallel to the long axis of a tooth, the tooth has maximum load-bearing ability without proprioceptive sensors signaling for inhibition of the application of load (Fig. 4). However, if applied forces are not in the direction of the long axis of the tooth upon application of a relatively minor load, certain periodontal ligaments will be stressed to their physiologic limits, initiating a proprioceptive signal to inhibit further application of load (inhibited mandibular movement). When pressures are applied to the chewing surfaces of the teeth by a bolus or the opposing occlusion, the direction and degree of the applied loads are perceived by the proprioceptive mechanism. In turn, this mechanism programs the most physiologic muscle response in consideration of the prevailing conditions within the total system (Fig. 5). This is the basic protective reflex mechanism which prevents damage of the system in the functions of chewing, swallowing, and speech. Understanding the mechanism by which mechanical contacts of teeth program muscle response enables the dentist to quantify the muscle response elicited by occlusal contacts (occlusal switches) and express it as laws governing muscle functions. In presenting the five laws which govern functions of the mandible-moving musrles, I will (1) state the law, (2) present the clinical observations upon which the law is based sometimes along with an analogy, and (3) discuss its clinical application.
38
J. l’rosthet. Dent. July, 1977
Guichet
Table I. Analogy extensor removal resulting
of an electromyographic analysis comparing the response of the and flexor muscles of the right and left legs as a result of introduction and of an irritant to the response of the muscles that move the mandible from occlusal irritation
A. Most physiologic condition B. Irritation induced C. Irritation and extension D. Irritation eliminated
Right
Left
4 8 16 4
4 4 4 4
CONDYLAR POSITION (LAW NO. 11 In the absence of inflammation in the temporomandibular joints or muscles of mastication, the condylar positions of the mandible at rest and as it moves to maximum intercuspation (centric occlusion) are programmed (or influenced) by the prevailing occlusal scheme. Clinical observation. The ability of the dentist to modify the occlusion and reprogram the condylar position and muscle response is easily demonstrated clinically and mandibular clutches in occlusal treatment procedures. *, I59 23-28 When maxillary which include a central bearing screw are removed from the mouth after hinge axis location or pantographic recording, the patient frequently demonstrates alarm, because the teeth do not intercuspate properly. This modification occurs, because during the time that the clutches were held between the teeth, they provided a new occlusal program which induced a complementary muscle response and condylar position. When the clutches were removed, the teeth did not fit together properly. After several jaw closures, the muscles reprogrammed the condylar position to complement the prevailing occlusion. This phenomenon illustrates the potential of the dentist, in the absence of inflammation in the temporomandibular joint or associated musculature in the patient, to almost instantly reprogram the musculature and condylar position by occlusal treatment. An analogy. The physiologic basis for Law No. 1 governing condylar position can be presented with an analogy. Consider an electromyographic analysis of the extensor and flexor musculature of the right and left legs. Assume that both appendages are in the most physiologic state and exhibit minimum stress or contractions of the musculature. An electromyographic analysis of these appendages would exhibit a minimum reading on the electromyographic scale. Let us assign a value of 4 to this reading (Table I). Now, let us introduce an irritation in the right knee. The irritation in the right knee is perceived by the proprioceptive mechanism, and signals are transmitted to master control (central nervous system) which in turn programs the most physiologic muscle response in consideration of the prevailing conditions. The right leg flexes. Basically, the flexor muscle in the right leg becomes more contracted or stressed so as to fix the leg in a more favorable postural position in consideration of the prevailing conditions. When the leg assumes this adjusted postural position, there is a condition of increased stress or tension in the muscles of the right leg. Any attempt by the patient to extend or to flex the leg from this ad-
Volume Number
38 1
Biologic
laws governing
mandibular
muscles.
Part
II
39
justed postural position requires effort. This is the minimum, stress possible in the musculature as long as the irritation in the knee prevails. An electromyographic analysis of the right and left legs at this time would reveal a condition of increased stress in the muscles of the right leg. On the electromyographic scale, let us assign a value of 8 to this condition of increased contraction in the muscles of the right leg (Table I), The left leg is unchanged. At this time, in order to extend the right leg so that it assumes the postural position it had before the irritation was introduced, effort on the past of the patient would be required. This is a strained relation, because it is necessary for the extensor muscles to contract sufficiently to overcome the chronically contracted flexors programmed by the irritation in the knee. An electromyographic analysis at this time would reveal a condition of further increased stress or tension in the muscles of the right leg. Let us assign a value of 16 to this electromyographic reading (Table I j . If at this time the irritation from the right knee could be totally removed, the leg would be restored to the condition which prevailed prior to the time the irritation was introduced, showing a reading of 4 on the electromyographic scale (Table 1:~. This is basic muscle physiology. Now, let us compare this response to the responses to occlusal irritation shown by the muscles that move the mandible. Assume that the muscles that move the mandible are in the most physiologic position and that they exhibit minimum stress or tension. For purposes of discussion, let us say there is simultaneous, even contact of the teeth when the condyles are in centric relation.” An electromyographic analysis of the musculature of this patient, who exhibits absence of irritation in the occlusion, would reveal minimal tension in the musculature. Like the leg, let us assign a value of 4 to that electromyographic reading (Table I). Now let us introduce an irritation between the teeth, a deflective contact in centric relation. Because of the introduction of an irritation, there is an adjusted postural position, as with the irritation in the knee. The leg flexes; the jaw comes forward or assumes another adjusted postural position depending on the type of occlusal irritation introduced. The occlusal irritation is perceived by the proprioceptive mechanism, and signals are transferred to master control (nervous system) which in turn programs the most physiologic muscle response in consideration of the prevailing conditions. An electromyographic analysis of the jaw musculature at this time, as with the leg, will reveal a condition of increased stress or tension in the musculature-a reading of 8 on the electromyographic scale (Table I) . This is the minimum tension possible in the musculature under the prevailing conditions. If at this time we ask the patient to move his jaw forward or backw& to centric relation, effort would be required. For the patient to move the jaw backward, the retractor muscles must overcome the tensions of the chronically contracted protractor muscles which are programmed by the prevailing occlusal irritant. An electromyographic analysis of the musculature with the patient maintaining his condyles in centric relation would show increased tension in the musculature. Analogous to the leg, a
*This specification for occlusion being in the most physiologic position discussion only, and it should not be construed that the author feels that this logic mandibular position at which maximum intercuspation should occur.
is for the sake of is the most physio-
40
Guichet
reading ever, if muscles troduced existing
J. Prosthet. Dent. July, 1977
of 16 would be recorded on the electromyographic scale (Table I). Howat this time the occlusal irritant were completely removed, the tension in the would return to the condition present prior to the time the irritant was in(Table I) . This physiologic response of the neuromuscular system to the occlusal condition is termed “occlusal programming.“2”. 8”
CENTRIC RELATION RECORDS The ability of the occlusion to program condylar position accounts for the patient’s repeated ability to avoid damage and close in the position of maximum intercuspation of the teeth.“0-“2 The teeth are brought together in that position where they fit best. Patients avoid occlusal contact on prematurities and close in maximum intercuspation (centric occlusion) . One can readily appreciate the clinical significance of the foregoing discussion as it applies to obtaining a centric relation record. The challenge in obtaining an accurate centric relation record is not so much one of obtaining an indexing registration of the mandibular teeth to the maxillary teeth as it is one of how to relieve stress in the muscles or reprogram them so they will allow the condyles to seek and retain the position of centric relation (or the potentially most optimum position) at the time the record is obtained. It is easy for the dentist who does not understand the physiology of occlusal programming to obtain an interocclusal record with the condyles splinted in a position other than centric relation (or the most optimum position) in his attempts to obtain a centric relation record.
SUMMARY A model to quantify muscle response to occlusal contacts is useful in developing an understanding of the mechanism by which the occlusion programs muscle function. A knowledge of how the occlusion programs muscle function enables the dentist to develop manipulative skills of the mandible which are necessary for diagnosis and effective occlusal treatment. This article presents complicated neuromuscular responses (reflexes) to occlusal contacts in an oversimplified way and with analogies so that the clinical significance of these neuromuscular reflexes in diagnosis and treatment can be more easily understood.
References 1. Gill, H. I.: Neuromuscular Spindles in Human Lateral Pterygoid Muscles, J. Anat. 109: 157-167, 1971. 2. Thilander, B.: Innervation of the Temporomandibular Joint Capsule in Man, Trans. Roy. Schools Dent. Stockholm Umea, No. 7, pp. 9-67, 1961. 3. Storey, A. T.: Sensory Functions of the Temporomandibular Joint, J. Can. Dent. Assoc. 34: 294-300, 1968. 4. Wyke, B. D.: Neurophysiological Aspects of Joint Function With Particular Reference to the Temporomandibular Joints, J. Bone Joint Surg. 43B: 396-397, 1961. 5. Griffin, C. J., Sharpe, C. J., and Gee, E.: Inhibition of the Linguo-Mandibular Reflex. I. Golgi Type Organs of the Pes Menisci, Aust. Dent. J. 10: 376-379, 1965. 6. Garnick, J., and Ramfjord, S. P.: Rest Position, J. PROSTHET. DENT. 12: 895-911, 1962. 7. Preiskel, H. W.: Some Observations on the Postural Position of the Mandible, J. ProsTHET. DENT. 15: 625-633, 1965.
Biologic 8. 9. 10. 11. 12. 13. 14. 1.5. 16. 17. 18.
19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 3n. :i 1.
:12.
laws governing
mandibular
mu.trles.
Part
II
41
Ramfjord, S. P.: Bruxism, a Clinical and Electromyographic Study. J. Am. Dent. Assoc. 62: 21-44, 1961. Livingston, R. B., and Hernandez-Peon, R.: Somatic Functions of the Nervous System, Ann. Rev. Physiol. 17: 269-292, 1955. Pavlov, I.: Lectures on Conditioned Reflexes, ed. 2, Muenchen, 1’328, J. F. Bergman, Kraus, H.: Muscle Function and the Temporomandibular Joint, J. PROSTHET. DEST. 13: 950-955, 1963. Schwartz, L.: Disorders of the Temporomandibular Joint, Philadelphia, 1959, W. B. Saunders Company. Svein, E.: Temporomandibular Joint Disorders, Dent. Digest 60: 361, 1954. Sessle, B. J., and Schmitt, A.: Effects of Controlled Tooth Stimulation on Jaw Muscle Activity in Man, Arch. Oral Biol. 17: 1597-1607, 1972. Jerge, C. R.: Neurologic Mechanism Underlying Cyclic Jaw Movements, J. PROSTHET. DENT. 14: 667-681, 1964. Lewinsky, W., and Steward, D.: The Innervation of the Periodontal Membrane, J. Anat. 71: 98-102, 1936. Griffin, C. J.: The Fine Structure of End-Rings in Human Periodontal Ligament, Arch. Oral Biol. 17: 78.5-797, 1972. Kizior, J. E., Cuozzo, J. W., and Bowman, D. C.: Functional and Histologic Assessment of the Sensory Innervation of the Periodontal Ligament of the Cat, J. Dent. Res. 47: 59-64, 1968. Beaudreau, D. E., Daugherty, W. F., and Masland, W. S.: Two Types of Motor Pause in Masticatory Muscles, Am. J. Physiol. 216: 16-21, 1969. Goldberg, L. J.: Masseter Muscle Excitation Induced by Stimu!ation of Periodontal and Gingival Receptors in Man, Brain Res. 32: 369-381, 1971. Yemm, R., Hannam, A. G., and Matthews, B.: Changes in the Activity of the Masseter Muscle Following Tooth Contact, J. Dent. Res. 48: 1131, 1969. Hannam, A. G., Matthews, B., and Yemm, R.: The Response in the Masseter Muscle Following Tooth Contact in Man, J. Physiol. 203: 25-26, 1969. Jerge, C. R.: Comments on the Innervation of Teeth, Dent. Clin. North Am., March. 1965, pp. 117-127. Jarabak, J. R.: An Electromyographic Analysis of Muscular and Temporomandibular Joint Disturbances Due to Imbalances in Occlusion, Angle Orthod. 26: 170-190, 1956. Krogh-Paulsen, W. B.: Facial Pain and Mandibular Dysfunction, Philadelphia, 1968, W, B. Saunders Company. Posselt, U.: Physiology of Occlusion and Rehabilitation, Philadelphia, 1962, F. A. Davis Company. Ramfjord, S. P., and Ash, M. M.: Occlusion, Philadelphia, 1966: W. B. Saunders Company, p. 167. Kabcenell, J. L.: Effects of Clinical Procedures on Mandibula,r Position, J. PROSTHET. DENT. 14: 266-278, 1964. Guichet, N. F.: Applied Gnathology, Why and How, Dental Clinics of North America, Philadelphia, 1969, W. B. Saunders Company. Guichet, N. F. : Gnathology-Everyday Dentistry, i\naheim. 1964, Denar Corporation, p. 30. Pameijer, J. H. N., Glickman, I., and Roeber, F. W.: Intraoral Occlusal Telemetry. Part II. Registration of Tooth Contacts in Chewing and Swallowing, J. PROSTHET. DENT. 19: 151-159, 1968. Jones, R. G.: The Physiological Role of Dental Occlusion in the Masticatory System. Master’s Thesis, Indiana University, 1965, p. 146. 320 OL.YMPIA PLACE ANAHEIM, CALIF. 92806
