Dental Tribune Middle East & Africa Edition

D uring the treatment of symp- toms originating from disor- ders of the temporomandibu- lar joint (TMJ) and occlusion, it was found that restoring the TMJ to its normal condition resulted in a change of general body health. In most cases, this change was improved general body health. Owing to similar reports, a con- nection between TMJ status and general body health was therefore hypothesised. However, the mechanism of this relation- ship remains unclear. TMJandmyofascialpain Dental occlusion is the relationship be- tween the maxillary and mandibular teeth when they approach each other.1 The TMJ is the joint of the jaw, which is unique in that it is the only bilateral joint that cross- es the midline.2 As the treatment of den- tal diseases aims to achieve harmony with- in the entire stomatognathic system, teeth could be literally considered to be a set of gears anchored in bone, while the upper and lower jaws are attached to each oth- er by the TMJ.3 The causes of TMJ disorders can be di- vided into five categories: dental, trauma, lifestyle habits, stressful social situations and emotional factors.4 Trauma can be in the form of whiplash, traction appliances and blows to the head, face or jaw.4 Evi- dence of significant trauma to the TMJ has also been found following hyperextension of the cervical spine.5 With regard to hab- its, 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 hyper- algesic trigger points located in skeletal muscle and fascia, is commonly character- ised by persistent regional pain.6 The myo- fascial component has generally been con- sidered to be part of pain syndromes that involve TMJ. Trigger points in masticatory muscles are presumably caused by maloc- clusion, misalignment and habitual para- function of the jaws, abnormal head and neck postures, or trauma.6 RelationshipbetweenTMJand generalbodyhealth There have been several studies on the re- lationship between occlusion/ TMJ and general body health. Among other find- ings, it has been found that lesions in the masticatory muscles or dentoalveolar liga- ments 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 associated with reduced lower extremity strength, agility and bal- ance in elderly people.10 The proper func- tional occlusion of natural or artificial teeth has been shown to play an important role in generating an adequate postural reflex.11 The subgroups of general body conditions associated with TMJ may be divided into the following three categories: 1)Synchronisationofhead&jaw muscleswithothermuscles There is a necessary systematic synchroni- sation of the head and jaw muscles with the other muscles of the body to maintain proper body posture. The functional cou- pling of the stomatognathic system 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 imbalance of sternocleidomastoid muscle activity, often leading to neck pain, can be induced by a unilateral loss of occlusal support.14 The biomechanical impact on cervical ver- tebrae during mastication has been calcu- lated, which confirmed that vertical occlu- sal alteration can influence stress distribu- tion in the cervical column.15 Possible asso- ciations between trunk and cervical asym- metry and facial symmetry have been re- ported. 16 For example, it has been found that visual perception control is most im- portant in orienting the head in the frontal plane.16 A relationship between dental oc- clusion and postural control has also been postulated.17 2)TMJandbodystability Dental occlusion/TMJ condition exerts an influence on body stability. Human be- ings assume a relatively unstable postural state when in the standing position; there- fore, the maintenance of a standing posi- tion is related to fluctuation in the centre of gravity, which is controlled by informa- tion from the ocular region, the three semi- circular canals and anti-gravity muscles.18 It has been suggested that occlusion and head position affect the centre of gravi- ty, resulting in an increased risk of falling when abnormal.19 Poor or absent dental occlusion may decrease proprioception in this area, interfering with the proper sta- bility of the head posture.7 It is thought that tooth loss is a risk factor for postural instability.20 Physiologically, mechanical receptors in the periodontal membrane control mandibular movements and coor- dinate masticatory function,21 and this is related to the motor activity of the neck muscles.22 Fluctuation in the centre of gravity caused by altering the occlusal contact area experimentally was examined ex- perimentally, and the results confirmed that occlusal contact affects gravity fluc- tuation and that appropriate occlusion at- tained by maintaining even occlusal con- tact in the posterior region is crucial for gravity fluctuation.23 3)TMJ&physicalperformance TMJ conditions can influence physical per- formance. Trainers often advise athletes to wear occlusal splints or mouth guards during competitions in order to increase motor performance.24 It has also been re- ported that proper teeth clenching plays an effective role in the enhancement of physical performance.25 The relationship between the presence of occlusal support in edentulous subjects and their capacity for physical exercise has been investigated, and it was conclud- ed that reconstruction of occlusal support holds significance not only for the restora- tion of masticatoryfunctionbutalsoforthe- maintenance of physical exercise.26 Mechanism of relationship between the TMJ and general body health based on the myofascial aspect It is the first hypothe- sis of this article that TMJ and other parts of the body are connected through fasci- ae, which is a connective element between various anatomical structures,27 very sim- ilar to a three-dimensional network ex- tending throughout the whole body.28, 29 This network can be stretched by the con- traction of underlying muscles and trans- mit tension over a distance.30, 31 The fascial tissues are arranged vertically, from head to toe, and four interconnect- ed transverse fascial planes crisscross the body. Therefore, should an injury occur in one part of the body, pain and dysfunction may occur throughout the body.32 Mechanismbasedonqi andthemeridianaspect The second hypothesis is that the TMJ and other parts of the body are connect- ed through the meridian system, which is constituted of the fasciae. Traditional- ly, acupuncture meridians are believed to form a network throughout the body, con- necting 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 fea- tures that differentiate acupuncture points from surrounding tissue.34 One of the his- tological and anatomical associations with the meridians is intermuscular or intra- muscular loose connective tissue (fascia). Ancient acupuncture texts contain sever- al references to “fat, greasy membranes, fasciae and systems of connecting mem- branes” through which the qi is believed to flow.35 In terms of connective tissue as- sociations, several authors have suggested that a connection may exist between the acupuncture meridians, which tend to be located along the fascial planes between muscles or between a muscle and bone or tendon, and the connective tissue.34, 35 In view of experimental evidence, it has been hypothesised that the network of the meridians can be viewed as a represen- tation of a network of interstitial connec- tive tissues. These findings are support- ed by ultrasound images showing connec- tive tissue cleavage planes at the acupunc- ture 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 con- vergence in a network of connective tis- sue permeating the entire body, similar to highway intersections in a network of pri- mary and secondary roads.34 Dental occlusion/temporomandibular joint and general body health Drs Yong-Keun Lee & Hyung-Joo Moon discuss clinical evidence and mechanism of an underestimated relationship 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 con- tacted at ykleedm@gmail.com. Contact Information Correlationbetweentrigger pointsandacupuncturepoints Although separated by two millennia, the traditions of acupuncture and myofascial pain therapies share fundamental similar- ities in the treatment of pain disorders.36 Recent reports have suggested substan- tial anatomic, clinical and physiological overlap of the myofascial trigger points and acupuncture points.36 The analogy be- tween the trigger points and acupuncture points has been discussed since 1977,37 when 100 per cent anatomic and 71 per cent clinical pain correspondences for the myofascial trigger points and acupuncture points in the treatment of pain disorders were reported. A number of similarities between 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 similar to the de qi sen- sation, and the referred pain generated by needling trigger points is similar to the propagated sensation along the meridians. It was pointed out, however, that the acu- puncture points located at the trigger points are not frequently used by acu- puncturists, and do not share the same clinical indications as the trigger point therapy.38 It was further argued that the claim of 71 per cent correspondence be- tween the acupuncture points and the trigger points37 is conceptually impossible. Furthermore, even putting this conceptual problem aside, no more than 40 per cent of the acupuncture points correlated with the treatment for pain and, more likely, only approximately 18 to 19% of the points are actually correlated.39 The correlation be- tween the trigger points and the acupunc- ture points clearly need to be further in- vestigated in the future. The fascial connection theory we propose can explain the functional connection be- tween dental occlusion/TMJ and oth- er parts of the body based on either myo- fascial release or the qi and meridian sys- tem, or a combination of both. Therefore, dental occlusion should be built up and maintained in a normal natural condition, while causes for deterioration of the TMJ status should be treated in an effort to re- store the natural condition. Editorial note - This article is a summary of two review papers recently published in the Journal of Alternative andv Com- plementary Medicine 17 (2011): 995– 1000 & 1119–24. A complete list of refer- ences is available from the authors. 5rESEarchDental tribune Middle East & Africa Edition | November 2012