SECTION EDITOR Electromyographic and computer analyses of patients suffering from chronic myofascial pain-dysfunction syndrome: before and after treatment with immediate complete anterior guidance development Robert B. Kerstein, DMD, and N. R. Wright Boston, Mass. Seven women patients at Tufts University School of Dental Medicine were evaluated for the subjective symptoms of a myofaseial pain dysfunction. Each patient was evaluated by an occlusal analysis of the T-Scan computer to determine posterior disclusion time during excursive movements, and EMG analysis of the masseter and temporalis muscles. Each patient was then treated occlusally by developing immediate complete anterior guidance. This adjustment process involved the removal of all lateral and protrusive interferences prior to habitual closure adjustments. No attempt was made to retrude the mandible in centric relation, and splints were not used to deprogram the musculature before adjust- ment, In this study, protrusive movements and interferences were not examined, and there was no control group. Posttreatment EMG and T-Scan computer analyses revealed that by shortening disclusion times to less than 0.5 second in any lateral excursions, muscle function returned to normal in all seven patients in approxi- mately 1 month’s time. A direct correlation seemed to exist between contractile muscle activity and disclusion time. Lengthy disclusion time leads to excessive muscle activity that introduces spasm and fatigue of the masseter and temporal muscles. These results indicated that a partial explanation of the etiology of MPDS may be the time the molars and nonworking premolars remain in contact during excursive movements-a phenomenon termed “disclusion time.” (J PROSTHET DENT 1991;66:677-66.) c omplete anterior guidance has been described by Kerstein and Farrell as a successful method of reducing the chronic symptoms of myofascial pain-dysfunction syn- drome (MPDS) for 53 patients. This occlusal adjustment technique involved no attempt to adjust centric relation or habitual centric closure contacts until after the class I, II, and III interferences described by Glickman2 have been removed from the existing occlusal scheme. After success- ful development of complete anterior guidance, the habit- ual closure position is balanced during a sequence of ap- pointments. Identical molar interferences were observed in all 53 pa- tients with documented MPDS symptoms. The relief of symptoms was reported by 51 of the patients in approxi- mately 5 to 7 days after removing these interferences. This study attempted to identify, using the T-Scan computer (Tek-Scan Inc., Boston, Mass.), the occlusal in- terference pattern in seven long-term MPDS patients, and determine its relationship to the electromyography (EMG) of their masseter and temporalis muscles. After developing the complete anterior guidance, a posttreatment set of T- 10/l/28631 Scan computer and EMG recordings were compared witb the preoperative data. LITERATURE REVIEW EMG studies have repeatedly shown the relationship between eccentric tooth contact and increases in muscular activity. In 1967, Schaerer et al3 stated that balancing in- terferences caused a high percentage of inhibitory muscle pauses during chewing. Ramfjord described marked aber- rations in muscle function patterns in patients with retruded contact position (RCP) and balancing side inter- ferences. This study demonstrated that occlusal adjust- ment improved muscle function. Riise and Scheikholeslam5 inserted a “high” interim amalgam restoration in the distobuccal cusp of a maxillary molar of 11 dental students and then studied their muscu- lature using EMG. Seven students reported an immediate increase in pain and muscle fatigue 1 hour after the inser- tion of the restoration. Most of the patients were aware that they had started bruxing. The EMG study revealed a dis- tinct elevation in muscle activity that required approxi- mately 7 days to reduce after removing the interference. Ingervall and Carlson measured muscle activity before and after balancing interferences were removed from THE JOURNAL OF PROSTHETIC DENTISTRY 677