OBJECTIVETo analyze the masseter inhibitory reflex (MIR) and the recovery cycle of the MIR reflex after magnetic stimulation in normal subjects.

METHODSIn 30 healthy subjects we studied the MIR evoked by single magnetic stimulation in the mental territory. Masseter electromyographic activity, latency and duration of the early silent periods (SP1) and late silent periods (SP2), and SP2 amplitude percent were recorded. Paired stimuli technique was used, conditioning and test stimuli were delivered at different interstimulus intervals (ISI), ie.100, 200, 300, 400, 500, and 600 ms, then the recovery cycle of the MIR was analyzed.

RESULTSLatency of SP1 was 12.1 (11.1, 14.4) ms, and duration of the SP1 was (17.3 ± 2.9) ms. Latency of SP2 was (47.7 ± 6.0) ms, and duration of the SP2 was (39.7 ± 13.3) ms. SP2 amplitude percent was 100.0%. With the paired stimuli technique, SP1 of the inhibitory reflex evoked by the test stimuli was found to be stable at every ISIs, but SP2 of the inhibitory reflex evoked by the test stimuli, instead, varied according to different ISI. With the short ISI, the area of SP2 evoked by the test stimuli was reduced, and with the increase of the ISI, the recovery degree of the area of SP2 evoked by the test stimuli was ascending, at 100 ms the SP2 amplitude percent was 17.1%, at 400 ms it was 93.4%, and it was close to 100% at 600 ms.

CONCLUSIONSThe study indicates that the use of the MIR elicited by the single and paired magnetic stimulation may be useful to examine or quantify some craniofacial diseases.