The Effect Of Occlusion On Orofacial Pain-A Primary Clinical Trial

Orofacial pain is a common clinical condition in orofacial area.The temporomandibular disorders(TMD)and trigeminal neuralgia(TN)were different diseases but with orofacial pain.In the details,TMD have three main symptoms,orofacial pain in the temporomandibular joint and/or masticatory muscles area,joints sounds and limited mouth opening.TN is characterized of sudden,brief sharp or/and electric shock-like pains in distribution of trigeminal nerve area and can be triggered by innocuous stimuli.At present,the role of occlusion in TMD was widely focused,but significance of occlusal contact in TN was seldom reported.In the clinics,our group found a lot of TN patients also had abnormal occlusal contacts obviously.So this study was to explore the relationships between occlusion and TMD as well as TN by methods of case analysis and clinical intervention.MethodIn this study,routine dental examinations were not only used,but also special tests for occlusion and functions of orofacial system including: MPQ(McGill Pain Questionnaire)values,VAS(visual analogue score)and attack frequency score for orofacial pain evaluation,electrognathography system for mandibular movements,electromyography for surface electromyographic(SEMG)activity of masseter muscle(MM),T-scan system for occlusal force,and silicon rubber for occlusal print when maximal voluntary clenching(MVC)at intercuspal position(ICP).This study including two parts as followings:1.Eighteen patients with a unilateral mandibular over-erupted third molar were selected from a sample of patients with complaints of temporomandibular disorders(TMD)symptoms.A unilateral gum-chewing trace was recorded separately for left and right side chewing by an electrognathography system.The average chewing pattern(ACP)was created based on segments from the recorded chewing trace to represent the chewing movement characteristics of each individual.The medial amplitude,the lateral amplitude,the vertical amplitude,and the anterior-posterior amplitude of ACP and the cross zero point value of ACP(the segment sequence number of the ACP where the opening path crosses the central sagittal plane from the balancing side to the chewing side)were acquired.Two factors,the TMD symptomatic side and the over-eruption side,were analyzed for their associations with values of difference in the parameters(?value)regarding the ACP between chewing with right and left side.Further,the side differences of the three dimensional amplitudes and the cross zero point value of the ACP were analyzed.2.The 25 participants meeting the trigeminal neuralgia diagnosis(the International Classification of Headache Disorders 3rd beta edition)were treated by occlusal adjustment.The aim of treatment was to rebuild the stable occlusal relationship in the centric postion and eliminate occlusal interference in the centric and eccentric positions,and finally the occlusal relationship conformed to regularity of the force distribution.The VAS,MPQ score and attack frequency score were taken from the patients at different time points in pretreatment,1 week-,1 month-,3 months-,6 months-after occlusal treatment.Also,tests including SEMG activities,T-scan and occlusal print were taken in the pretreatment and 1-month after treatment.The data of occlusal penetrated number and area in molar,premolar and posterior arch(including molar and premolar)and MM SEMG activities in the 100%-,75%-,50%-and 25%-maximal voluntary clenching at intercuspal position(ICP),protrusive edge to edge position(Pro),lateral cuspal to cuspal position of no-pain side and pain side were analysed.Further,we analyzed the averaged SEMG activity in the 3.3s sustained ICP-clenching.Results1.The over-eruption side had associations with the ?value of the medial amplitude,the lateral amplitude,and the cross zero point(P < 0.05),but the symptomatic side didn't(P > 0.05).When chewing on the over-eruption side,the medial amplitude was shorter,the lateral amplitude was larger,and the cross zero point value,which related to ACP,was smaller than those when chewing on the other side(P < 0.05).2.Occlusal treatment had an effect on the MPQ score,VAS and attack frequency score(P<0.05).The pain scores went down from 1 week after occlusal modification to 6 months.The VAS went down from 7.2±1.7 before treatment to 2.8±2.9 in the 6 months.The MPQ score went down from 59.1±19.8 before treatment to 21.8±25.3 in the 6 months.The attack frequency score went down from 2.7±1.6 before treatment to 1.1±1.4 in the 6 months.The results of occlusal print were as followings: The occlusal penetrated areas of molar,premolar and posterior arch deceased after occlusal treatment(P<0.05).The occlusal treatment decreased the striked occlusal contact area.The results of T-scan and SEMG activity after occlusal treatment were as followings: In the 100%-and 50%-ICP-MVC,the bilateral MM SEMG difference of pretreatment were different from that after treatment(P<0.05).In the sustained ICP-clenching,the averaged bilateral MM SEMG difference of pretreatment were different from that after treatment(P<0.05).Totally,MM SEMG of pain side lower than that of non-pain side in pretreatment,but this difference decreased after treatment.Conclusion1.The present data indicate that there is an association of the side of an over-erupted mandibular third molar with chewing pattern,the TMD symptom(s)is not related to over-erupted third molar in side-distribution.2.Occlusal treatment can relieve symptom of TN and this effect should be confirmed in further study.