title: Reflex responses of the masseter muscle in patients with chronic arthritis or internal derangement of the temporomandibular joint. A comparison with symptomfree subjects.
abstract: Averaged reflex responses in the masseter muscle to transverse taps delivered to the upper central incisor were studied in 13 patients with chronic arthritic temporomandibular joint (TMJ) disease (arthritis group) and 28 patients having internal TMJ derangement (derangement group). The diagnostic assessment of TMJ disease was based on a combination of imaging methods. Fourteen symptomfree subjects served as a control for the electromyographic observations. The tapping force was increased in steps from 0.25 to 6 N. The pattern of the reflex response consisted of various inhibitory and excitatory waves, which were found to change with increasing tapping force. The first inhibitory wave (I-1) increased in duration with increasing tapping force in all subjects. At certain tapping forces, I-1 was of significantly lower amplitude and longer duration in the arthritis group than in the control group, but latency and threshold did not differ. The excitatory wave seemed to have longer latency and higher amplitude in the arthritis group than in the control subjects at some tapping forces. In summary we conclude that the pattern of the reflex response seemed to be similar in patients with different TMJ disorders and in symptomfree subjects. Only the level of inhibition, duration of I-1 and higher excitatory response, might separate the patients with arthritic TMJ disease and internal TMJ derangement from symptomfree subjects, but no specific differences between the groups could be found.
authors.affiliation: Department of Oral Surgery and Oral Medicine, Faculty of Dentistry, University of Oslo, Norway.
authors.forename: T
authors.initials: T
authors.lastname: Bjørnland
authors.forename: P
authors.initials: P
authors.lastname: Brodin
authors.forename: T A
authors.initials: TA
authors.lastname: Larheim
authors.forename: H
authors.initials: H
authors.lastname: Aars
mesh_terms: D000328:Adult; D001168:Arthritis / Q000503:physiopathology*; D002908:Chronic Disease; D004576:Electromyography; D005260:Female; D006801:Humans; D007180:Incisor; D008297:Male; D008406:Masseter Muscle / Q000502:physiology*; D010474:Percussion; D011930:Reaction Time / Q000502:physiology; D012026:Reflex, Stretch / Q000502:physiology*; D013314:Stress, Mechanical; D013705:Temporomandibular Joint Disorders / Q000503:physiopathology*