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Dental Tribune Untited Kingdom Edition

D uring the treatment of symptoms originating from disorders of the tem- poromandibular joint (TMJ) and occlusion, it was found that restor- ing the TMJ to its normal condi- tion resulted in a change of gen- eral body health. In most cases, this change was improved general body health. Owing to similar re- ports, a connection between TMJ status and general body health was therefore hypothesised. How- ever, the mechanism of this rela- tionship remains unclear. TMJ and myofascial pain Dental occlusion is the relation- ship between the maxillary and mandibular teeth when they ap- proacheachother.1 TheTMJisthe joint of the jaw, which is unique in that it is the only bilateral joint that crosses the midline.2 As the treat- ment of dental diseases aims to achieveharmonywithintheentire stomatognathicsystem,teethcould be literally considered to be a set of gears anchored in bone, while the upper and lower jaws are at- tached to each other by the TMJ.3 The causes of TMJ disorders can be divided into five catego- ries: dental, trauma, lifestyle hab- its, stressful social situations and emotional factors.4 Trauma can be in the form of whiplash, trac- tion appliances and blows to the head, face or jaw.4 Evidence of significant trauma to the TMJ has also been found following hyper- extension of the cervical spine.5 With regard to habits, bad posture, bad ergonomics at work, oral and childhood habits, as well as poor diet and strenuous activities such as heavy lifting, have been cited.4 Myofascial pain, deriving from the hyperalgesic trigger points lo- cated in skeletal muscle and fas- cia, is commonly characterised by persistent regional pain.6 The myofascial component has gener- ally been considered to be part of pain syndromes that involve TMJ. Trigger points in masticatory muscles are presumably caused by malocclusion, misalignment and habitual para-function of the jaws, abnormal head and neck postures, or trauma.6 Relationship between TMJ and general body health There have been several studies on the relationship between oc- clusion/TMJ and general body health. Among other findings, it has been found that lesions in the masticatory muscles or dento- alveolar ligaments can perturb visual stability and thus generate postural imbalance.7 The position and functioning of the mandible also have an effect on the centre of gravity.8, 9 Dental occlusion is associ- ated with reduced lower extrem- ity strength, agility and balance in elderly people.10 The proper functional occlusion of natural or artificial teeth has been shown to play an important role in generat- ing an adequate postural reflex.11 The subgroups of general body conditions associated with TMJ may be divided into the following three categories: 1) Synchronisation of head & jaw muscles with other muscles There is a necessary systematic synchronisation of the head and jaw muscles with the other mus- cles of the body to maintain proper body posture. The functional cou- pling of the stomatognathic sys- tem with the neck muscles is well known. Patients suffering from occlusal or TMJ disorders have reported dysfunction and pain in their neck muscles.12, 13 An imbal- ance of sternocleidomastoid mus- cle activity, often leading to neck pain, can be induced by a unilat- eral loss of occlusal support.14 The biomechanical impact on cervical vertebrae during masti- cation has been calculated, which confirmed that vertical occlusal alteration can influence stress dis- tribution in the cervical column.15 Possible associations between trunk and cervical asymmetry and facial symmetry have been re- ported.16 For example, it has been found that visual perception con- trol is most important in orienting the head in the frontal plane.16 A relationship between dental oc- clusion and postural control has also been postulated.17 2) TMJ and body stability Dental occlusion/TMJ condition exerts an influence on body sta- bility. Human beings assume a relatively unstable postural state when in the standing position; therefore, the maintenance of a standing position is related to fluctuation in the centre of grav- ity, which is controlled by infor- mation from the ocular region, the three semicircular canals and anti-gravity muscles.18 It has been suggested that oc- clusion and head position affect the centre of gravity, resulting in an increased risk of falling when abnormal.19 Poor or absent dental occlusion may decrease proprio- ception in this area, interfering with the proper stability of the head posture.7 It is thought that tooth loss is a risk factor for pos- tural instability.20 Physiologically, mechanical receptors in the peri- odontal membrane control man- dibular movements and coordi- nate masticatory function,21 and this is related to the motor activity of the neck muscles.22 Fluctuationinthecentreofgrav- ity caused by altering the occlusal contact area experimentally was examined experimentally, and the results confirmed that occlusal contact affects gravity fluctuation and that appropriate occlusion at- tainedbymaintainingevenocclus- al contact in the posterior region is crucial for gravity fluctuation.23 3) TMJ & physical performance TMJ conditions can influence physical performance. Trainers often advise athletes to wear oc- clusal splints or mouth guards during competitions in order to increase motor performance.24 It has also been reported that proper teeth clenching plays an effective role in the enhancement of physi- cal performance.25 The relationship between the presence of occlusal support in edentulous subjects and their ca- pacity for physical exercise has been investigated, and it was con- cluded that reconstruction of oc- clusal support holds significance notonlyfortherestorationofmasti- catoryfunctionbutalsoforthemain- tenance of physical exercise.26 Mechanism of relationship between the TMJ and general body health based on the myo- fascial aspect It is the first hypothesis of this ar- ticle that TMJ and other parts of the body are connected through fasciae, which is a connective element between various ana- tomical structures,27 very similar to a three-dimensional network extending throughout the whole body.28, 29 This network can be stretched by the contraction of underlying muscles and transmit tension over a distance.30, 31 The fascial tissues are ar- ranged vertically, from head to toe, and four interconnected transverse fascial planes criss- cross the body. Therefore, should an injury occur in one part of the body, pain and dysfunction may occur throughout the body.32 Mechanism based on qi and the meridian aspect The second hypothesis is that the TMJ and other parts of the body are connected through the merid- ian system, which is constituted of the fasciae. Traditionally, acu- puncture meridians are believed to form a network throughout the body, connecting peripheral tissues to each other.33 Studies that seek to understand the acu- puncture point/meridian systems from a Western perspective have mainly focused on identifying distinct histological features that differentiate acupuncture points from surrounding tissue.34 One of the histological and anatomical associations with the meridians is intermuscular or intramuscular loose connective tissue (fascia). Ancient acupuncture texts contain several references to “fat, greasy membranes, fasciae and systems of connecting mem- branes” through which the qi is believed to flow.35 In terms of con- nective tissue associations, sev- eral authors have suggested that a connection may exist between the acupuncture meridians, which tend to be located along the fascial planes between muscles or be- tween a muscle and bone or ten- don, and the connective tissue.34, 35 In view of experimental evi- dence, it has been hypothesised that the network of the meridians can be viewed as a representation of a network of interstitial connec- tive tissues. These findings are supported by ultrasound images showing connective tissue cleav- age planes at the acupuncture points in human beings.34 Rather than viewing acupuncture points as discrete entities, it has been proposed that these points might correspond to sites of conver- gence in a network of connective tissue permeating the entire body, similar to highway intersections in a network of primary and sec- ondary roads.34 Correlation between trigger points and acupuncture points Although separated by two millen- nia, the traditions of acupuncture and myofascial pain therapies share fundamental similarities in the treatment of pain disorders.36 Recent reports have suggested substantial anatomic, clinical and physiological overlap of the myo- fascialtriggerpointsandacupunc- turepoints.36 Theanalogybetween the trigger points and acupunc- ture points has been discussed since 1977,37 when 100 per cent anatomic and 71 per cent clini- cal pain correspondences for the myofascial trigger points and acu- puncture points in the treatment of pain disorders were reported. A number of similarities be- tween them were also suggested. The two structures have similar locations and needles are used at either point to treat pain. The pain associated with the local twitch response at trigger points is simi- lar to the de qi sensation, and the referred pain generated by nee- dling trigger points is similar to the propagated sensation along the meridians. It was pointed out, however, that the acupuncture points lo- cated at the trigger points are not frequently used by acupunctur- ists, and do not share the same clinical indications as the trigger point therapy.38 It was further ar- gued that the claim of 71per cent correspondence between the acu- puncture points and the trigger points37 is conceptually impos- sible. Furthermore, even putting this conceptual problem aside, no more than 40 per cent of the acu- puncture points correlated with the treatment for pain and, more likely, only approximately 18 to 19% of the points are actually cor- related.39 The correlation between the trigger points and the acu- puncture points clearly need to be further investigated in the future. The fascial connection theory we propose can explain the func- tional connection between dental occlusion/TMJ and other parts of the body based on either myofas- cial release or the qi and meridian system, or a combination of both. Therefore,dentalocclusionshould be built up and maintained in a normal natural condition, while causesfordeteriorationoftheTMJ statusshouldbetreatedinaneffort to restore the natural condition. DT Editorial note - This article is a summary of two review papers recently published in the Journal of Alternative and Complementary Medicine 17 (2011): 995–1000 & 1119–24. A complete list of refer- ences is available from the authors. Dental occlusion/temporomandibular joint and general body health Drs Yong-Keun Lee & Hyung-Joo Moon discuss clinical evidence and mechanism of an underestimated relationship Contact Information Drs Yong-Keun Lee and Hyung-Joo Moon are practicing dentistry at the Moon Dental Hospital and ICPB in Seoul in South Korea. They can be contacted at ykleedm@gmail.com. March 5-11, 201210 Feature United Kingdom Edition