The easiest way to mechanically stimulate teeth is by means of tapping the labial surface of incisor teeth with a probe (orthogonal stimulation). 1983), and the vibration-sensitive receptors in the inner ear ( van Steenberghe et al. However, tooth stimulation can also activate vibration-, stretch- and position-sensitive receptors in and around the jaws ( Lund et al. the mechanoreceptors in the gingiva and the periodontal space (the PMRs). Forces applied to a tooth can stimulate receptors in the area of application, i.e. Mechanical stimuli activate a number of receptors that may have different synaptic connections to the motoneuronal pool. The nature of the resulting feedback is unclear due to the difficulty in stimulating the PMRs without activating other receptors in the peri-oral region at the same time ( Sato et al. An additional aim was to test the reproducibility of the results by retesting the subjects on a second occasion.Äuring mastication, the forces that are applied to the teeth displace them in their sockets, thus stimulating PMRs. To this end, changes in the surface electromyogram (SEMG) of masseter and digastric muscles to a number of different mechanical stimulus profiles were investigated. The main aim of the present study was to investigate the contribution of PMRs to human masseter and digastric muscles using axial stimulation. The current study differs from previous studies as it involves a novel stimulation technique, axial stimulation. mechanically stimulating the labial surface of the incisor ( van der Glas et al. Previous studies on humans have involved orthogonal stimulation of teeth, i.e. However, due primarily to limitations in methods, this is yet to be confirmed in humans. This indicated a difference in jaw reflexes to forces applied in different directions, possibly due to the activation of different receptor types when stimulating the tooth in either the orthogonal or axial directions.Ä®xperiments in animals indicate that a large amount of feedback for jaw-closing muscles comes from periodontal mechanoreceptors (PMRs) ( Morimoto et al. Unlike during orthogonal stimulation, slowly rising stimuli did not produce any excitatory reflex activity. As the application of a local anaesthetic block removed or significantly reduced both of these responses, it was concluded that they originated from the PMRs. However, it is possible that this late excitation could be due to delayed action potentials and hence be artefactual. The results indicate that the most common response of the masseter muscle to brisk axial stimulation of the incisor is a reflex inhibition at 20 ms, followed by a late excitation at 44 ms. The reflex responses obtained were significantly different between subjects however retesting the same subject on a different occasion yielded similar results. There was little detectable change in the activity of the digastric muscle under the tested conditions and what was found could be attributed to cross-talk with the masseter. It was found that the reflex response in the masseter was modulated by the rate of rise of the stimulus used and, to a lesser degree, the level of background muscle activity. Ten neurologically normal young adult females were tested, each on two separate occasions to confirm the reproducibility of the results. The purpose of this study was to investigate the response of the masseter and digastric muscles in humans to controlled axial stimulation of the upper left central incisor, both before and during a local anaesthetic block of the PMRs. To date, the work that has been done on humans has been limited and confined to orthogonal stimulation of the labial surface of the tooth. The role of periodontal mechanoreceptors (PMRs) in the reflex control of the jaw muscles has thus far been mainly derived from animal studies.
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |