The Relationship Of Occlusion Contact, Surface Electromyograph And Temporomandibular Disorders

There was an interdependence and mutual restriction relationship between occlusion,masticatory muscles and temporomandibular joint(TMJ). When one of three factors changes, the other two factors will also change correspondingly. Malocclusion and occlusal interference may cause the change of surface electromyographic(SEMG) activity and temporomandibular disorders(TMD). But there is controversy about the relationship between occlusion and temporomandibular disorders. The present study used the synchronized T-Scan III and BioEMG III systems to evaluate the interrelationships amang the TMD symptom, occlusal contact and jaw-closing muscles activity by simultaneously recording of occlusion and surface electromyographic(SEMG) activity of anterior temporalis(TA) and masseter(MM) muscles. The purpose of this study was to analyze the association amang the TMD symptom, occlusal contact and jaw-closing muscles activity. We also aimed to detect the occlusion status between orofacial myalgia patients and controls by using a new simple methods.Firstly,seventeen female and 5 male patients(mean age: 19.59±2.51; scope: 16-25) with unilateral scissors-bite and unilateral TMJ sounding symptom, fifteen female-patients(mean age: 23.73±3.08; scope: 19-28) with unilateral orofacial pain and unilateral scissors-bite, were selected to simultaneously record occlusal contacts, biting force distribution and SEMG activity of the anterior temporalis and masseter muscles with BioEMG III electromyographic recording system during maximal voluntary clenching(MVC) in the maximum intercuspal position(ICP), protrusive edge-to-edge contact position(Pro), left and right edge-to-edge positions(LP and RP).Secondly, fifteen female subjects(mean age: 22.93±2.57; scope: 18-27) with complaint of orofacial myalgia were enrolled from the consecutive recording during the period from March 2014 to June 2015 in stomatology hospital and Sex-matched controls(mean age: 23.33±2.25; scope: 19-28) were enrolled from asymptomatic college students. Occlusal contact recordings were taken by the bite imprint when the subject was asked to close freely but as fast as possible into the maximum intercuspation position(ICP). The digital pictures of the bite imprint and model casts were taken and the numbers of the colored sites, representing the contact at different tightness levels(Black as impact, red as medium and blue as loose contact) were counted and the sizes of the color area were measured using photoshop software.We get the results as the following:1. Biting force level and scissors-bite showed an effect on the Occlusal Contact Number, Biting Force Distribution and SEMG values(P<0.05) while TMJ sounding/Orofacial pain did not. The smaller number of occlusion contacts, lower biting force distribution and lower SEMG value of the masseter was associated with scissors-bite side compared to the non-scissors-bite side. The anterior temporolis did not show such an association. The SEMG value of the masseter and the anterior temporolis were significantly increased from the 25%-ICP to 50%-ICP, while no such difference was found from the 50%-ICP to 100%-ICP.2. When bitting on the left and right edge-to-edge positions, the SEMG value of the anterior temporolis of working side and the masseter of balancing side were significantly higher than the opposite side whenever the scissors bite side or the TMJ sounding/Orofacial pain side were as the working side.3. The SEMG value of the masseter of scissors bite side was significantly lower than the non-sicssors bite side when bitting on the protrusive edge-to-edge contact position(Pro).4. The orofacial pain patients group had more impact contact number(4.93) and larger impact contact area(1779.46), less loose contact number(17.93) and smaller loose contact area(15901)than the controls(impact contact number: 1.53, impact contact area: 886.66; loose contact number: 23.13, loose contact area: 18330). The impact contact in patients group were more concentrated on the guiding cusp and the controls were contra verse. The occlusal contact of Orofacial pain patients was more asymmetry than healthy controls.The results indicated that:1. In unilateral TMJ sounding/orofacial pain patients the SEMG activity of the masseter, but not TA, is associated with occlusion like scissors-bite relation rather than TMD symptom.2. Occlusal contact tightness analysis is a new and simple method and has a favourable prospect for clinic application. The orofacial pain patients group had more impact contact than the controls.3. To establish a stable and balanced occlusal contact as the goal of occlusal therapy is expected to become a way to improve the function of chewing muscles and releive the symptoms of temporomandibular joint disorders.