RESUMEN
Silent period is defined as transient electromyographic activity following a stimulus of some kind during a sustained period of muscle contraction. The exact mechanism of this reflex and the factors that influence it are still unknown. One important unanswered question is the relationship between the length of muscle and duration of silent period. The aim of this study was to compare the silent period duration of masseter muscle before and after placement of an occlusal splint in the mouth. Twenty five persons with complete dentition [28 natural teeth with no prosthesis and class I occlusion, without signs and symptoms of muscle or TMJ dysfunction and without history of orthodontic treatment were chosen for this study. The mean age of subjects was 22.3 years. For each subject, a maxillary occlusal splint with 3mm thickness in premolar area was fabricated and adjusted. Silent duration was measured during maximum muscle activity using chin tap as stimulus. Silent period was evoked and measured 3 times and the mean of the measurements was used as individual SPD. The mean SPD taken without splint was 20.03 +/- 1 and 14.19 +/- 0.83 with splint. Pair Wise Comparison test with use of LSD test showed that the mean SPD with and without splint were significantly [P<0.05] different. The result of this study showed that placement of a splint shortens the SPD of masseter muscle, significantly. Therefore, it is suggested that SPD can be used as a Para clinical factor to evaluate the full mouth restorative treatments that probably change VD. It also shows that muscle and TMJ receptors have a more important role in SPD than periodontal receptors