A Clinical Study On The Effect Of Occlusal Adjustment On Chronic Pain In Patients With Temporomandibular Disorders

Temporomandibular disorders (TMD) are one group of the most common diseases in maxillofacial region. Temporomandibular joint (TMJ) and masticatory muscles disorders are mainly involved. Epidemiological datas show nearly 25 % to 60 % of people suffered with TMD. The main symptoms of TMD are pain in TMJ, associated soft tissues, abnormality or dysfunction of mandible movement, and joint sounds, etc. At present, most domestic and foreign scholars agree that TMD are due to multiple etiological factors. Even though there are many disputes on the etiology of TMD, it can not be denied that occlusal and psychological factors are main etiological factors. Clinically, pain is the most important reason for those patients to visit and ask for treatment. One foreign study reported that about 94% of patients with TMD suffered with pain problems. As we all known, pain is a complex physiological and pathological phenomenon, involved with complicated subjective symptoms.Based on the results of our previous animals and biomechanical experiments, in this study, our unique occlusion adjustment method was applied to eliminate the occlusal interference and achieve a stable occlusal relationship. 73 patients (11 patients failed to follow-up visit)with TMD chronic pain were selected in our TMD clinic. Patients were divided into occlusion adjustment (OD) group(36 patients in all, 29 patients selected and 7 patients lost) and control group (37 patients in all,33 patients selected and 4 patients lost) randomly and single-blindly. OD group were treated with occlusion adjustment, while control group with mock occlusion adjustment (MOD). Visual analog scale (VAS),pressure pain threshold(PPT), TMJ clicking, maximum mouth opening, occlusion contact,bite force,symmetry of occlusion, electromyogram(EMG) amplitude of temporal muscle and masseter muscle,mandibular kinesiography(MKG),etc, were measured and analyzed before and one month after the treatment.Results:1. After one month, the index of VAS in OD patients was lower than that before treatmen(tP～0.000), while no significant changes in MOD paients(P=0.469). There was no difference in the index between OD and MOD group patients before treatment(P=0.716), while the index in OD patients was lower than that in MOD group patients after treatment(P～0.000).2. The pressure pain threshold(PPT) of anterior temporal muscle and masseter muscle in OD patients one month later was higher than that before treatment(P<0.05), while no changes in the control group(P>0.05). The PPT of OD patients in MPP was higher than MOD patients one month later( P<0.05), but no difference in the PPT between OD and MOD group before adjustment(P>0.05).3. After OD treatment, there were still 13 patients with TMJ clicking in all 15 patients with this before treatment. No changes occurred in MOD patients before and after treatment.4. The maximum mouth opening of OD patients improved significantly after treatment(P=0.001),but no difference found in MOD patients before and after treatment(P=0.662). After treatment, the maximum mouth opening of OD patients was larger than that of MOD patients, but no difference before treatment(P=0.881).5. Number of occlusion contact in OD group increased greatly(P～0.000) after treatment, but no significant changes were found in MOD group (P=0.685). After treatment, the number of occlusion contact in OD patients was more than that of MOD patients(P～0.000), but no difference before treatment(P=0.107).6. In the OD group , the average value of︱L-R︱decreased significantly after treatment(P=0.002),but no changes in the MOD group (P=0.377).One month later, the average value of︱L-R︱in OD group was lower than that in MOD group(P～0.000), but no difference before treatment(P=0.653).7. The bite force of patients in OD group elevated after treatment (P～0.000),while no changes in MOD group (P=0.222). One month later, the bite force of patients in OD group was higher than that in MOD group(P=0.001), but no difference before treatment(P=0.574).8. Before treatment, there was no difference in the tracings of chewing cycles between OD group and MOD group(P=0.346). One month later, the tracings of chewing cycles in OD group tended to be normal, but no changes in MOD group.9. One month later, the electromyogram amplitude of anterior temporal muscle and masseter muscle in MPP decreased, while increased when biting tightly in ICP( P<0.05).There were no obvious changes in electromyogram amplitude in MOD group before and after treatment. Before treatment, there was no difference between OD and MOD group(P>0.05), but after treatment, the electromyogram amplitude of OD patients in MPP was lower than control group patients, but higher than control group patients in ICP( P<0.05). Conclusion:Occlusion adjustment could increase the number of occlusion contact, improve the symmetry of occlusion and the chewing cycle, reduce the electromyogram amplitude of anterior temporal muscle and masseter muscle in MPP and elevate that in ICP, lessen the VAS pain index, and strengthen the bite force and the pressure pain threshold. In a word, Occlusion adjustment has evident therapeutic effect on TMD patients with chronic pain.