No abstract

The aim of this study was to investigate the relationship between thickness of sample food and bite force. We designed a new sensor that can detect the pressure distribution between the incisor and molar teeth on one side, and the contact area between the food samples and the teeth. The force and contact area were directly measured in real time using the multiple-point sheet sensor, which is a very thin and flexible pressure-sensing device. Silicone rubber blocks were used as a sample food and were chewed with incisors and molars by 10 healthy women. The peak force, contact area, duration and impulse were greater between the incisors for a thicker specimen. The active pressure, defined as the ratio of the force to contact area, at peak was similar for different thicknesses. In contrast, with a 2 mm thick sample, the peak force and force related parameters were greatest in molar chewing. The force, contact area and duration were greater for molar chewing cycles than incisor ones. We verified that the thickness of samples influenced the chewing force of humans and the effects differed between incisors and molars.

The aim of the present study was to compare and characterize the secretory and vasodilator effects induced by chorda lingual nerve (CLN) stimulation (i.e., direct parasympathetic stimulation) and reflex parasympathetic stimulation in the submandibular gland (SMG) of sympathectomized cats. The increase in blood flow and salivary secretion in response to electrical stimulation of the central cut ends of the vagus and inferior alveolar nerves, as well as to stimulation of the CLN at a site approximately 5 mm distal to the intersection of the CLN and the SMG duct (site D) was completely abolished by section of the chorda tympani nerve (CTN). Neither response to CLN stimulation at a site nearly 5 mm proximal to the intersection of the CLN and the SMG duct (site C) was affected by CTN section. Section of the CLN at a site approximately 5 mm distal to the intersection of the CTN and the CLN abolished the submandibular salivary and vasodilator responses elicited by CLN stimulation at site D but had no effect on the two responses evoked by CLN stimulation at site C. The blood flow increases evoked by electrical stimulation of the CLN at site D were greatly reduced by prior treatment with the autonomic ganglion blocker hexamethonium, but the vasodilator responses evoked from site C were reduced much less. These data suggest that the secretory and vasodilator responses elicited by CLN stimulation at site D and those by vagus and inferior alveolar nerve stimulation are mediated largely via a parasympathetic reflex mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)

(1) The purpose of the present study is to investigate whether or not the vasodilatation evoked by intradermal (I.D.) injection of nicotine is mediated through axon reflex mechanism, and to examine the involvement of histamine receptors or capsaicin-sensitive C-fibers in nicotine-induced vasodilator response, using a band method and a laser Doppler technique. (2) The vasodilator response, whether it was caused by nicotine or histamine, developed as quickly on the uninjected side as on the injected side of the band, while the wheal reaction was elicited only by histamine and was localized in the injection side of the band. (3) Pretreatment with either a local anesthetic (lidocaine) or 1% capasaicin markedly reduced the nicotine- and histamine-induced blood flow responses, whereas pretreatment with antihistaminergic agent (diphenhydramine) showed inhibitory effect to the blood flow response only to histamine. (4) These data suggest that two types of chemical receptors, i.e. the nicotinic and the histamine-sensitive receptors, exist in capsaicin-sensitive C-fibers to elicit axon reflex vasodilatation in human skin.

SUMMARY1. Electrical stimulation of the infra-orbital nerve and the maxillary buccal gingiva caused an increase in ipsilateral lip blood flow in a stimulus intensitydependent manner in anaesthetized cats.2. The reflex vasodilator response was resistant to blockade by antimuscarinic (atropine), antiadrenergic (phentolamine and propranolol) and antihistaminergic (tripelennamine) but sensitive to ganglionic blocking agent (hexamethonium).3. The reflex vasodilator response was unaffected by section of the ipsilateral cervical sympathetic trunk and facial nerve root, but was completely abolished by ipsilateral section of the glossopharyngeal nerve root.4. The vasodilator response elicited by stimulation of the facial and glossopharyngeal nerves was never affected by lesion of the ipsilateral pterygopalatine ganglion.5. Local anaesthesia or section of the inferior alveolar nerve abolished the vasodilator effects of stimulation of the facial and the glossopharyngeal nerves.6. These results suggest that there is a somato-autonomic reflex vasodilator system mediated via final neurons that are not cholinergic, and that the parasympathetic vasodilator fibres emerge from the brain stem with the glossopharyngeal nerve and reach the blood vessels via the otic ganglion and the inferior alveolar nerve in the cat mandibular lip.