The influence of mandibular stretching on athletes subjected to high intensity workout.

The use of oral appliances is considered effective in improving sport performance. Jaw clenching or stretching, improved breathing or positioning of the jaw have been proposed to explain the improvement. In this study, we reported the effects of regularly practiced mandibular stretching at submaximal opening of the jaw in Crossfit athletes. Seventeen test subjects undergoing mandibular stretching (MS) showed significantly reduced (p0.001) performance time in a high-intensity workout measured before and after seven days of 10-minutes stretching practiced twice daily, while no improvement was observed in control subjects who did not perform the stretching. Additionally, blood lactate levels appeared to recover more quickly in MS subjects.Crossfit is a type of training regimen that pushes the limits of bodily recovery processes. Jaw stretching, eliciting the trigeminocardiac reflex (a reflex decrease in heart rate and blood pressure following trigeminal stimulation) and central oxygen-conserving mechanisms could help relieve post-training stress and improve training recovery.

Learning effect and repeatability of stabilometric measurements: "standard" vs. usual foot placement.

The existence of a learning effect by which subjects progressively reduce body sway over the course of repetitive stabilometric measurements is currently debated. Also, the position and orientation of the feet on the platform can have a substantial influence on the outcome measurements. The aim of the present work was to assess the effect of feet positions on mean total velocity (V) of the center of pressure and the area (AR) covered by its displacements during quiet standing. A group of 35 healthy young subjects was examined during two successive sessions consisting of five recordings with their feet placed either in the recommended (standard, SP) or their usual most comfortable (UP) position. Results show a slight decreasing trend that failed to be statistically significant checked with Friedman's ANOVA (SP AR, χ2(4)=6.10, p=0.19 and V, χ2(4)=8.66, p=0.07 and UP AR, χ2(4)=2.32, p=0.68 and V, χ2(4)=1.19, p=0.88). Nonetheless, values of AR and V showed a notable decrement especially evident in the SP exam reaching, respectively, 24% and 11% from baseline, whereas variability measured by the coefficient of variation was the same in the two exams. Given the results, a learning effect should not be ruled out with confidence. Also, usual foot placement would be preferable to avoid this effect. Further research is needed to take into consideration the great variability of stabilometric measurements and the fact that different subjects could adapt more readily to the test conditions than others.

Changes of sensory and pain thresholds in healthy subjects after mandibular extension at maximum mouth opening: implications for temporomandibular disorders therapy.

There is evidence showing that increasing the vertical dimension of occlusion, or interocclusal distance, reduces pain symptoms in patients with temporomandibular disorders (TMD) and bruxism. The mechanism underlying the analgesic effect is still under investigation. Some researchers propose either a gate mechanism or the activation of the trigemino-cardiac reflex. In this study, sensory and pain thresholds changes in the mandibular district have been evaluated in twenty healthy subjects immediately after 5 minutes of mandibular stretching at maximum opening of the jaw. Results showed a 60% increment in sensory threshold and a 70% increment in pain threshold (p<0.001) compared with the baseline values. The magnitude of the analgesic effect seems proportional to the extent of mandibular opening. These and similar results are discussed as for the implication in the treatment of TMD related symptoms.

An observational study of the effects of using an high oral splint on pain control

Increasing occlusal vertical dimension (OVD) by means of oral splints is a practice widely used in the treatment of temporomandibular disorders (TMD), specifically myofascial pain, although the results are still uncertain. Oral splints with a vertical height that significantly exceeds the clinical rest position are considered by some researchers to be a better therapeutic solution in alleviating TMD symptoms than are "low" splints. In our observational study, 21 patients suffering from myofascial pain were examined for the effects of wearing a "high" oral splint while sleeping for 3 months. To ensure proper splint making, a mandibular stretching procedure was used to induce a relaxation of the patients' masticatory muscles and allow the correct alignment of the jaws. Results showed a marked increase of the interocclusal distance or "free space" (hence of OVD; from 0.64±0.53 mm to 1.42±0.76 mm, p<0.0001) measured by a kinesiograph, followed by a substantial reduction of the intensity of pain in oral and extraoral regions after using the splint. These results support the view that increasing OVD beyond the clinical rest position is not detrimental to patients' health. More importantly, high oral splints has been shown to be a promising therapeutic aid for the treatment of TMD and correlated pain syndromes. This clinical trial was registered on clinicaltrials.gov (Identifier: NCT02908568).

Persistent effects after trigeminal nerve proprioceptive stimulation by mandibular extension on rat blood pressure, heart rate and pial microcirculation.

The trigemino-cardiac reflex is a brainstem reflex known to lead to a decrement in heart rate and blood pressure, whereas few data have been collected about its effects on the cerebral hemodynamic. In this study we assess the in vivo effects of trigeminal nerve peripheral stimulation by mandibular extension on pial microcirculation and systemic arterial blood pressure in rats. Experiments were performed in male Wistar rats subjected to mandibular extension obtained inserting an ad hoc developed retractor between the dental arches. Mean arterial blood pressure and heart rate were recorded and the pial arterioles were visualized by fluorescence microscopy to measure the vessel diameters before (15 minutes) during (5-15 minutes) and after (80 minutes) mandibular extension. While in control rats (sham-operated rats) and in rats subjected to the dissection of the trigeminal peripheral branches mean arterial blood pressure, heart rate and pial microcirculation did not change during the whole observation period (110 minutes), in rats submitted to mandibular extension, mean arterial blood pressure, heart rate and arteriolar diameter significantly decreased during stimulation. Afterward mean arterial blood pressure remained reduced as well as heart rate, while arteriolar diameter significantly increased evidencing a vasodilatation persisting for the whole remaining observation time. Therefore, trigeminal nerve proprioceptive stimulation appears to trigger specific mechanisms regulating systemic arterial blood pressure and pial microcirculation.