Intraoral measurement of tactile and filament-prick pain threshold using shortened Semmes-Weinstein monofilaments.

OBJECTIVES: Semmes-Weinstein monofilaments are too long for use in parts of the oral cavity. The present study used shortened Semmes-Weinstein monofilaments to evaluate reliability and spatial differences in the intraoral tactile detection threshold (TDT) and the filament-prick pain detection threshold (FPT) in healthy volunteers. METHODS: For practical purposes, classic Semmes-Weinstein monofilaments with 20 different diameters were cut to half their length (ie, 19 mm) and the bending forces were measured. Eighteen men and 18 women (age range, 20 to 33 y) were recruited to evaluate the reliability and reproducibility of measurements using half-cut monofilaments. The TDT and the FPT were measured on the labial maxillary gingiva, on the palatal maxillary gingiva, and at the anterior tip of the tongue, using a double random staircase method. RESULTS: According to the forces needed to bend the half-cut filaments, they were renumbered from 2.55 to 6.86. There were significant differences of bending force between the half-cut and original monofilaments (P<0.001), Using half-cut filaments, the following differences could be detected; the labial maxillary gingiva had a significantly higher TDT threshold compared with the other test sites (P<0.001). By contrast, the palatal posterior maxillary gingiva had a significantly higher FPT threshold compared with the other test sites (P<0.001). DISCUSSIONS: The present study illustrated that in healthy participants, half-cut Semmes-Weinstein monofilaments reliably and easily assess TDT and FPT intraorally. A combined examination of sensory and pain thresholds using these filaments contributes to the clinical examination for orofacial pain.

Does eccentric-exercise-induced jaw muscle soreness influence brainstem reflexes?

OBJECTIVE: To investigate the effects of soreness evoked by eccentric jaw exercises on two types of brainstem reflexes: the short-latency stretch reflex and the longer-latency exteroceptive suppression (ES), and to test for possible relationships between magnitude of soreness and reflex responses. METHODS: The brainstem reflexes of jaw-closing muscles were recorded before (Baseline), immediately after (Post-task), and 1 day after (1-day-after) a 30-min eccentric exercise in 15 healthy men. All subjects participated in a control session without exercise. RESULTS: Soreness sensations at rest and during maximum biting were significantly elevated until 1-day-after the eccentric exercise (P<0.014). The ES responses tended to be increased (more inhibition) at Post-task and 1-day-after. There was a significant correlation between the ES response and the soreness sensation during maximum biting (P<0.04). The jaw-stretch reflex did not show significant change after the eccentric exercise. CONCLUSIONS: Muscle soreness associated with eccentric jaw exercises has a differential impact on the jaw-stretch reflex and the ES response. SIGNIFICANCE: Experimentally induced acute muscle pain has previously been shown to influence both the ES and the jaw-stretch reflex, thus, different types of muscle pain and symptoms can be speculated to have different effects on a variety of brainstem reflexes.