Статья №2 про прикус и осанку от клиники в Портланде - оригинал
Оригинал https://www.portlandtmjclinic.com/tmj-disorders/the-role-of-body-posture
THE ROLE OF BODY POSTURE
The following paper descibes the unappreciated but vital relationship between body posture, TMJ disorders, and the teeth. A more detailed description of the role of the bite in both TMJ disorders and body posture, along with extensive footnotes, can be found in BITES AND BODY POSTURE under the FOR DOCTORS tab. https://www.portlandtmjclinic.com/for-doctors/bites-and-posture (https://healthy-back.livejournal.com/473519.html, https://healthy-back.dreamwidth.org/458122.html), Перевод https://healthy-back.livejournal.com/473792.html (https://healthy-back.dreamwidth.org/458377.html)
BACKGROUND
The mandible (the lower jawbone) is an integral member of the head posture mechanism, and head posture affects body posture; because the position of the big weight on the top of the spinal column reflexively determines how that column aligns beneath it to support the weight on top. In this manner, the posture of the mandible affects the posture of the rest of the body. However, the mandible is the only postural component routinely left out of postural evaluations, because nobody seems to know what to do about it. Dentists are more concerned with tooth mechanics than the function of the whole jaw system, and orthopedists don't know how to deal with joint surfaces composed of jagged rocks. To understand the role of posture in TMJ disorders, it must be recognized that mandibular posture is under two different and sometimes competing influences - one from the tonus of the postural system and one from the neuromuscular reflexes designed to protect the teeth. When there is a discrepancy between the mandibular posture that would be preferred by myofascial forces and the mandibular posture that is determined by the reflex protective mechanisms associated with the bite, mechanical strain is shared between the jaw and postural systems, and successful treatment requires addressing both systems. Treatment that simply enhances adaptability in the muscles undergoing the symptoms often just transfers the symptoms to a different set of muscles.
MYOFASCIAL TONUS is a network of light steady tensions,normally about one percent of each muscle's maximum voluntary contractile force, that maintains a habitual weight bearing postural stance in which each bone has resting place, a neutral zone, in balance between opposing tensions.The mandible rests in a neutral zone within the curtain of muscles draping from the front of the top of the cranium down onto the shoulder girdle and clavicles. At least it would rest there if teeth were not involved.
PROTECTIVE REFLEXES - The myofascial influence on mandibular posture is normally overridden by neuromuscular reflexes that were designed to protect the teeth. During our evolution, the jaw muscles were strong, and the teeth were fragile; therefore the jaw muscles are programmed to protect the teeth by only closing the mandible where the teeth fit in a stable central bite position and to hold the mandible in a resting posture just beneath that stable central bite position so they can rapidly and securely brace the mandible at the first hint of danger by clamping it immovably up against the underside of the cranium through the medium of the bite. As a result, the postural location of the mandible in a horizontal plane is controlled by the location of its central bite position.
Many studies have demonstrated this relationship between the bite and mandibular posture. An immediate increase in freeway space (the space between the teeth when the jaw muscles are at rest in their postural position) follows the first bite contact after inserting a bite raising appliance, and an immediate return to the pre-treatment freeway space follows the first bite contact after removing the bite raising appliance. Children who develop a bite with a side shift (unilateral cross-bite) also undergo a shift of mandibular posture to the same side, maintained by increased resting tension in the posterior temporalis muscle of that side; and their jaw muscle resting tensions rapidly normalize and become symmetrical after correction of the cross-bite. Monkeys experimentally fitted with crowns that force the mandible forward or to one side also undergo a parallel shift in the posture of the mandible to keep it located just beneath the shifted bite position.
BACKWARD MANDIBULAR POSTURE - resulting from a backwardly shifted bite, is almost always found in TMJ disorder patients on at least one side, usually the side of the most damaged TMJ. In most of these cases, the mandible has acquired a backwardly located position relative to the rest of the cranium, because its normal forward translation (advancement) has been blocked by a bite that locks it to the upper jawbone, which cannot translate forward but can only expand. As a result, the mandible and its biting platform gradually shift backward relative to the rest of the cranium and the cervical spine.
FORWARD HEAD POSTURE - results from backward mandibular posture, because the backwardly shifting mandible constricts the airway against the cervical spine (middle illustration below), which triggers the airway protective reflexes to extend (tip back) the head to rotate the mandible and hyoid bone forward out of the airway space. However, the head cannot just tip as in the middle illustration below, because the righting reflexes keep it level for operation of the visual and balance systems. Therefore, in response to backward mandibular posture, the head shifts forward while tipping back, as seen in the right side illustration below.
Of course, the causal chain goes both ways. Forward head posture can cause the posture of the mandible to shift backward relative to the head, because the mandible cannot shift as far forward as the head, because it is still tied to the clavicles and shoulder girdle by the muscles of the front of the neck. However, the few longitudinal studies that have looked at the shifting relationship between head posture and mandibular posture have indicated that the shift in mandibular posture usually comes first.
The forward shifting of the head diminishes the normal cervical curve (lordosis) by bringing its top end forward over its base, as seen in the progression below, where the cervical lordosis flattens (middle illustration) and eventually reverses (right side illustration). In the illustration, the 15 degree rotation of the vertical line shows the cervical spine bending forward and rotating clockwise from a 12:00 position to a 1:00 position relative to the shoulder girdle in order to support the forward head posture, and the descent of the upper horizontal line shows the loss of vertical height that occurs when the head rotates forward.
The tilting of the lower horizontal line in the illustrations above is due to the rotation of the inner and upper aspects of the shoulder blades as these areas follow the forward shifting of the base of the neck. Since the outer and lower portions of the shoulder blades do not follow the forward movement of the base of the neck as closely as their upper and inner portions, the shoulder blades also tilt, leaving their outer and lower portions sticking out like wings.
THE EFFECTS ON THE LUMBAR AND THORACIC SPINE
The head is a heavy weight perched on the top of the spinal column like a bowling ball on a broomstick. When it shifts forward relative to the long axis of the spine, (when the ball hangs off one side of the broomstick), it applies torque to the whole length of the spine, which triggers neuromuscular reflexes that reflexively act to restore physical balance by shifting structural support forward beneath the forwardly shifted head. Usually the hip joints rotate forward (clockwise in the illustration below) to thrust the abdomen forward under the head, while the thoracic curve (kyphosis) increases as the chest sinks backward. These changes in the spine can be seen in the illustrations below.
SIDEWAYS (LATERALLY SHIFTED) MANDIBULAR POSTURE
In some TMJ disorder patients, the mandible is also laterally displaced, because it has grown toward one side, usually accompanied by backward mandibular posture on that side. This lateral mandibular displacement commonly begins in adolescence when a large canine or other permanent tooth erupts into a position that forces the mandible to shift sideways in order to close fully. Subsequently, the closing pathway and bracing position of the mandible quickly adopt the new laterally displaced location, which guides the rest of the erupting permanent teeth into positions that also fit only when the mandible is in the same laterally displaced position. The sideways shift into that displaced location will feel normal, because the jaw muscles become programmed to always use that position to protect the teeth.
TILTED HEAD POSTURE - Because the lateral mandibular shift is maintained by increased tonus of the temporalis muscle on the side of the shift, the head tips toward the side of the shift, making the opposite eye look higher in photographs. It also lengthens that side of the face oppposite the shift while compressing the face on the side of the shift, which often makes the eye look smaller on the side of the shift.
IDENTIFYING DISPLACED MANDIBULAR POSTURE - requires wearing a front flat bite plate appliance nightly for a period of time during sleep in order to deprogram the jaw closing muscles that control mandibular position by removing the flow of signals that constantly programs them to always close the mandible wherever the teeth fit. Instead, while wearing the front flat bite plate appliance, the jaw muscles can hold the mandible in any position they choose. If they choose a position and posture that is different from your normal bite, your bite is probably strained, and your jaw muscles would function better if your bite (and consequently your jaw posture) were located in the new position they have chosen.
CORRECTING DISPLACED MANDIBULAR POSTURE - Correcting a displaced mandibular posture usually requires making small adjustments to the bite, in conjunction with muscle retraining to synergistically reposition head posture back over the long axis of the spine, strengthen the muscles needed to hold the new mandible and head postures, and stretch the fascial restrictions that maintained the old mandible and head postures. People with strong muscles will need more stretching, and people with weak jaw muscles will need jaw muscle strengthening, which requires a stable bite.
EXTENDING THE BITE TABLE - can be accomplished by shaving down portions of teeth that are too high (and therefore collide when the mandible shifts toward the improved position), building up portions of teeth that are too low (and therefore leave a gap when the mandible shifts toward the improved position), or orthodontically moving teeth. When a deep or steep overbite is responsible for backward mandibular posture, the contact between the top front edges of the lower front teeth and the backs of the upper front teeth is usually the feature that locks the mandible back, therefore short-term relief can be obtained by shaving down those contacts; and long-term relief can be obtained by wearing a front flat bite plate that redirects nocturnal clenching forces onto the front teeth to slowly reduce the overbite. In deeply curved (front to back) dental arches, the rear ends of the second molars may also get in the way and need to be shaved down.
MOVING THE BITE TABLE - In some cases, the bite table cannot be easily extended as far as necessary without losing some chewing capacity, and thus the whole bite may need to be altered by rebuilding the teeth or by removing tooth structure from the path of the mandibular shift. This usually requires adding artificial tooth structure (crowns or onlays) behind the shift in bite position.
CONCLUSION - Mandibular posture and head posture function together and should be treated together to get the head centered over the long axis of the spine while getting the mandible centered under the head. Dentists performing multiple crowns should recognize that stabilizing the existing natural bite also stabilizes the existing body posture, and some patients may be best served by incorporating a period of time for improving body posture before locking it in by finalizing the bite. Orthodontists treating class 2 malocclusions should recognize that postural treatment to shift the head back to a position more nearly over the top of the spinal column could be helpful in keeping the mandible properly aligned during the treatment process. Postural adjustments should be undertaken with the awareness that the steep interdigitation of upper and lower teeth can return the mandible exactly to its pre-adjustment biting position, which can cause other postural adjustments to relapse.
THE ROLE OF BODY POSTURE
The following paper descibes the unappreciated but vital relationship between body posture, TMJ disorders, and the teeth. A more detailed description of the role of the bite in both TMJ disorders and body posture, along with extensive footnotes, can be found in BITES AND BODY POSTURE under the FOR DOCTORS tab. https://www.portlandtmjclinic.com/for-doctors/bites-and-posture (https://healthy-back.livejournal.com/473519.html, https://healthy-back.dreamwidth.org/458122.html), Перевод https://healthy-back.livejournal.com/473792.html (https://healthy-back.dreamwidth.org/458377.html)
BACKGROUND
The mandible (the lower jawbone) is an integral member of the head posture mechanism, and head posture affects body posture; because the position of the big weight on the top of the spinal column reflexively determines how that column aligns beneath it to support the weight on top. In this manner, the posture of the mandible affects the posture of the rest of the body. However, the mandible is the only postural component routinely left out of postural evaluations, because nobody seems to know what to do about it. Dentists are more concerned with tooth mechanics than the function of the whole jaw system, and orthopedists don't know how to deal with joint surfaces composed of jagged rocks. To understand the role of posture in TMJ disorders, it must be recognized that mandibular posture is under two different and sometimes competing influences - one from the tonus of the postural system and one from the neuromuscular reflexes designed to protect the teeth. When there is a discrepancy between the mandibular posture that would be preferred by myofascial forces and the mandibular posture that is determined by the reflex protective mechanisms associated with the bite, mechanical strain is shared between the jaw and postural systems, and successful treatment requires addressing both systems. Treatment that simply enhances adaptability in the muscles undergoing the symptoms often just transfers the symptoms to a different set of muscles.
MYOFASCIAL TONUS is a network of light steady tensions,normally about one percent of each muscle's maximum voluntary contractile force, that maintains a habitual weight bearing postural stance in which each bone has resting place, a neutral zone, in balance between opposing tensions.The mandible rests in a neutral zone within the curtain of muscles draping from the front of the top of the cranium down onto the shoulder girdle and clavicles. At least it would rest there if teeth were not involved.
PROTECTIVE REFLEXES - The myofascial influence on mandibular posture is normally overridden by neuromuscular reflexes that were designed to protect the teeth. During our evolution, the jaw muscles were strong, and the teeth were fragile; therefore the jaw muscles are programmed to protect the teeth by only closing the mandible where the teeth fit in a stable central bite position and to hold the mandible in a resting posture just beneath that stable central bite position so they can rapidly and securely brace the mandible at the first hint of danger by clamping it immovably up against the underside of the cranium through the medium of the bite. As a result, the postural location of the mandible in a horizontal plane is controlled by the location of its central bite position.
Many studies have demonstrated this relationship between the bite and mandibular posture. An immediate increase in freeway space (the space between the teeth when the jaw muscles are at rest in their postural position) follows the first bite contact after inserting a bite raising appliance, and an immediate return to the pre-treatment freeway space follows the first bite contact after removing the bite raising appliance. Children who develop a bite with a side shift (unilateral cross-bite) also undergo a shift of mandibular posture to the same side, maintained by increased resting tension in the posterior temporalis muscle of that side; and their jaw muscle resting tensions rapidly normalize and become symmetrical after correction of the cross-bite. Monkeys experimentally fitted with crowns that force the mandible forward or to one side also undergo a parallel shift in the posture of the mandible to keep it located just beneath the shifted bite position.
BACKWARD MANDIBULAR POSTURE - resulting from a backwardly shifted bite, is almost always found in TMJ disorder patients on at least one side, usually the side of the most damaged TMJ. In most of these cases, the mandible has acquired a backwardly located position relative to the rest of the cranium, because its normal forward translation (advancement) has been blocked by a bite that locks it to the upper jawbone, which cannot translate forward but can only expand. As a result, the mandible and its biting platform gradually shift backward relative to the rest of the cranium and the cervical spine.
FORWARD HEAD POSTURE - results from backward mandibular posture, because the backwardly shifting mandible constricts the airway against the cervical spine (middle illustration below), which triggers the airway protective reflexes to extend (tip back) the head to rotate the mandible and hyoid bone forward out of the airway space. However, the head cannot just tip as in the middle illustration below, because the righting reflexes keep it level for operation of the visual and balance systems. Therefore, in response to backward mandibular posture, the head shifts forward while tipping back, as seen in the right side illustration below.
Of course, the causal chain goes both ways. Forward head posture can cause the posture of the mandible to shift backward relative to the head, because the mandible cannot shift as far forward as the head, because it is still tied to the clavicles and shoulder girdle by the muscles of the front of the neck. However, the few longitudinal studies that have looked at the shifting relationship between head posture and mandibular posture have indicated that the shift in mandibular posture usually comes first.
The forward shifting of the head diminishes the normal cervical curve (lordosis) by bringing its top end forward over its base, as seen in the progression below, where the cervical lordosis flattens (middle illustration) and eventually reverses (right side illustration). In the illustration, the 15 degree rotation of the vertical line shows the cervical spine bending forward and rotating clockwise from a 12:00 position to a 1:00 position relative to the shoulder girdle in order to support the forward head posture, and the descent of the upper horizontal line shows the loss of vertical height that occurs when the head rotates forward.
The tilting of the lower horizontal line in the illustrations above is due to the rotation of the inner and upper aspects of the shoulder blades as these areas follow the forward shifting of the base of the neck. Since the outer and lower portions of the shoulder blades do not follow the forward movement of the base of the neck as closely as their upper and inner portions, the shoulder blades also tilt, leaving their outer and lower portions sticking out like wings.
THE EFFECTS ON THE LUMBAR AND THORACIC SPINE
The head is a heavy weight perched on the top of the spinal column like a bowling ball on a broomstick. When it shifts forward relative to the long axis of the spine, (when the ball hangs off one side of the broomstick), it applies torque to the whole length of the spine, which triggers neuromuscular reflexes that reflexively act to restore physical balance by shifting structural support forward beneath the forwardly shifted head. Usually the hip joints rotate forward (clockwise in the illustration below) to thrust the abdomen forward under the head, while the thoracic curve (kyphosis) increases as the chest sinks backward. These changes in the spine can be seen in the illustrations below.
SIDEWAYS (LATERALLY SHIFTED) MANDIBULAR POSTURE
In some TMJ disorder patients, the mandible is also laterally displaced, because it has grown toward one side, usually accompanied by backward mandibular posture on that side. This lateral mandibular displacement commonly begins in adolescence when a large canine or other permanent tooth erupts into a position that forces the mandible to shift sideways in order to close fully. Subsequently, the closing pathway and bracing position of the mandible quickly adopt the new laterally displaced location, which guides the rest of the erupting permanent teeth into positions that also fit only when the mandible is in the same laterally displaced position. The sideways shift into that displaced location will feel normal, because the jaw muscles become programmed to always use that position to protect the teeth.
TILTED HEAD POSTURE - Because the lateral mandibular shift is maintained by increased tonus of the temporalis muscle on the side of the shift, the head tips toward the side of the shift, making the opposite eye look higher in photographs. It also lengthens that side of the face oppposite the shift while compressing the face on the side of the shift, which often makes the eye look smaller on the side of the shift.
IDENTIFYING DISPLACED MANDIBULAR POSTURE - requires wearing a front flat bite plate appliance nightly for a period of time during sleep in order to deprogram the jaw closing muscles that control mandibular position by removing the flow of signals that constantly programs them to always close the mandible wherever the teeth fit. Instead, while wearing the front flat bite plate appliance, the jaw muscles can hold the mandible in any position they choose. If they choose a position and posture that is different from your normal bite, your bite is probably strained, and your jaw muscles would function better if your bite (and consequently your jaw posture) were located in the new position they have chosen.
CORRECTING DISPLACED MANDIBULAR POSTURE - Correcting a displaced mandibular posture usually requires making small adjustments to the bite, in conjunction with muscle retraining to synergistically reposition head posture back over the long axis of the spine, strengthen the muscles needed to hold the new mandible and head postures, and stretch the fascial restrictions that maintained the old mandible and head postures. People with strong muscles will need more stretching, and people with weak jaw muscles will need jaw muscle strengthening, which requires a stable bite.
EXTENDING THE BITE TABLE - can be accomplished by shaving down portions of teeth that are too high (and therefore collide when the mandible shifts toward the improved position), building up portions of teeth that are too low (and therefore leave a gap when the mandible shifts toward the improved position), or orthodontically moving teeth. When a deep or steep overbite is responsible for backward mandibular posture, the contact between the top front edges of the lower front teeth and the backs of the upper front teeth is usually the feature that locks the mandible back, therefore short-term relief can be obtained by shaving down those contacts; and long-term relief can be obtained by wearing a front flat bite plate that redirects nocturnal clenching forces onto the front teeth to slowly reduce the overbite. In deeply curved (front to back) dental arches, the rear ends of the second molars may also get in the way and need to be shaved down.
MOVING THE BITE TABLE - In some cases, the bite table cannot be easily extended as far as necessary without losing some chewing capacity, and thus the whole bite may need to be altered by rebuilding the teeth or by removing tooth structure from the path of the mandibular shift. This usually requires adding artificial tooth structure (crowns or onlays) behind the shift in bite position.
CONCLUSION - Mandibular posture and head posture function together and should be treated together to get the head centered over the long axis of the spine while getting the mandible centered under the head. Dentists performing multiple crowns should recognize that stabilizing the existing natural bite also stabilizes the existing body posture, and some patients may be best served by incorporating a period of time for improving body posture before locking it in by finalizing the bite. Orthodontists treating class 2 malocclusions should recognize that postural treatment to shift the head back to a position more nearly over the top of the spinal column could be helpful in keeping the mandible properly aligned during the treatment process. Postural adjustments should be undertaken with the awareness that the steep interdigitation of upper and lower teeth can return the mandible exactly to its pre-adjustment biting position, which can cause other postural adjustments to relapse.