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At least 1,153 records · Page 64Linked to original sources
PubMed2000

Effects of lingual nerve afferents on swallowing in sheep.

We investigated in sheep the effects of stimulation of the thick afferent fibers running through the lingual nerve (LN) upon the activity of some of the muscles and medullary interneurons or motoneurons which are active during swallowing. Using electromyography (EMG), and extra- and intracellular neuronal recording, we demonstrated that LN stimulation inhibited triggering and/or distal progression of deglutition reflexly induced by stimulation of the superior laryngeal nerve (SLN). This inhibition appeared as a delay, or the interruption or total suppression, of the EMG and neuronal swallowing activities, depending on the interval between SLN and LN stimulation. It was apparent at the level of the muscles and motoneurons of the nucleus ambiguus, as well as at the level of the interneurons of the dorsal medulla within or around the nucleus of solitary tract, which are assumed to be the core of the organizing system for swallowing, the so-called central pattern generator (CPG). Taking into account the stimulation parameters used in our experiments, it was likely that only LN-mechanosensitive fibers were excited. These fibers were involved in the jaw-opening reflex, and possibly in mastication regulation. Therefore, inhibition of swallowing could result from interactions between the hindbrain mastication and swallowing CPGs. However, it was also possible that mechanosensitive afferents acted upon the swallowing CPG directly or indirectly through supramedullary, especially cortical, loops.

Afferent Pathways↗
PubMed2002

Jaw opening and swallow triggering method for bilateral-brain-damaged patients: K-point stimulation.

The aim of this study was to confirm the response in patients stimulated at the trigger point (K-point). Since we have already clinically encountered patients with hyperactive bite reflexes who were able to open their mouth and swallow after stimulation of the trigger point, we investigated this response in other brain-damaged patients. The trigger point lies on the mucosa lateral to the palatoglossal arch and medial to the pterygomandibular fold at the height of the postretromolar pad. A total of 57 brain-damaged patients, including patients with pseudobulbar palsy due to bilateral upper motor neuron disease and bulbar palsy due to medulla oblongate. Other supratentorial brain-damaged patients and 20 non-brain-damaged subjects were also examined. The subjects were gently stimulated at the trigger point by a finger or a tongue depressor. We found that the pseudobulbar palsy patients with a hyperactive bite reflex responded by mouth opening and swallowing after a jaw movement similar to mastication elicited by the stimulation. The other pseudobulbar palsy patients, who did not have hyperactive bite reflexes and could open their mouth spontaneously, responded by swallowing with jaw movements similar to mastication after the stimulation. The bulbar palsy patients and the supratentorial brain-damaged patients showed no response to the stimulation. The non-brain-damaged subjects also did not respond, but all of the subjects reported a strange sensation after the stimulation. We concluded that stimulating the trigger point was useful for opening the mouth and facilitating swallowing in pseudobulbar palsy patients and that this technique may be of help in these patients in terms of oral health care and feeding.

Adolescent↗
PubMed2001

The effect of bolus size on the chewing cycle in humans.

No general agreement exists regarding the effect that bolus size has on masticatory movement, probably because both the size and texture of food change during mastication. In this experiment, in order to clarify the effect of bolus size on masticatory movement, a food that does not change in size and texture--chewing gum--was chosen, and the relationship between bolus size and the chewing cycle was analyzed. Ten healthy subjects in their twenties were asked to chew pieces of softened chewing gum of four different sizes. For ten cycles, beginning with the fifth cycle of mastication, gape and masticatory width were calculated for the spatial parameter of the chewing cycle, and cycle time was calculated as the temporal parameter. The relationship between these parameters and the bolus size was investigated. As the bolus size increased, the spatial and temporal parameters increased. In addition, there was a positive correlation between the bolus size and each parameter. The influence of the bolus size was as follows: gape, r = 0.91; masticatory width, r = 0.79; and cycle time, r = 0.74 (all, P < 0.001). From these results it was concluded that the shape of the chewing cycle was altered by the size of the food bolus, and that the changes in sensory input from the peripheries greatly affected the masticatory movement.

Journal Article↗
PubMed1996

A study of personal and area airborne asbestos concentrations during asbestos abatement: a statistical evaluation of fibre concentration data.

Data were collected and analysed on airborne concentrations of asbestos generated by abatement of different asbestos-containing materials using various removal practices. Airborne concentrations of asbestos are dramatically variable among the types of asbestos-containing material being abated. Abatement practices evaluated in this study were removal of boiler/pipe insulation in a crawl space, ceiling tile, transite, floor tile/mastic with traditional methods, and mastic removal with a high-efficiency particulate air filter blast track (shot-blast) machine. In general, abatement of boiler and pipe insulation produces the highest airborne fibre levels, while abatement of floor tile and mastic was observed to be the lowest. A comparison of matched personal and area samples was not significantly different, and exhibited a good correlation using regression analysis. After adjusting data for outliers, personal sample fibre concentrations were greater than area sample fibre concentrations. Statistical analysis and sample distribution of airborne asbestos concentrations appear to be best represented in a logarithmic form. Area sample fibre concentrations were shown in this study to have a larger variability than personal measurements. Evaluation of outliers in fibre concentration data and the ability of these values to skew sample populations is presented. The use of personal and area samples in determining exposure, selecting personal protective equipment and its historical relevance as related to future abatement projects is discussed.

Air Pollutants, Occupational↗
PubMed1993

Protein synthesis in the major salivary glands of the rat and the effects of re-feeding and acute ethanol injection.

Rates of protein synthesis in the major salivary glands of the rat were accurately determined in vivo using the 'flooding dose' technique and the effects of reflex stimulation through feeding or acute ethanol treatment were assessed. Rats were divided into three groups. The control group was fasted overnight, the re-fed group was also fasted then re-fed the following morning and the third group received an intraperitoneal injection of ethanol after an overnight fast. In control rats the sublingual gland had a higher rate of protein synthesis than the other glands. After a feed the rate of protein synthesis in parotid glands was approximately double that of controls whilst that of the submandibular glands had increased by 24% and the sublingual glands remained unchanged. Acute ethanol injection led to a reduced rate of protein synthesis in all glands. The higher rate of protein synthesis in sublingual glands under fasting conditions may be related to the spontaneous secretion of fluid and protein from this gland, which would require a constant replenishment of secretory protein by synthesis. Protein synthesis in the parotid gland, like secretion, appears to be closely linked with the reflex stimulation caused by mastication. The smaller increase in rate of protein synthesis seen in the submandibular gland after a re-feed does not appear to have been recorded before. It could be mediated by the increased reflex stimuli caused by mastication or by some circulating factor. The mechanism by which ethanol reduces protein synthesis in all glands is uncertain.

Analysis of Variance↗
PubMed1983

The use of an interim protective prosthesis during cancer chemotherapy.

The use of an interim protective prosthesis during cancer chemotherapy allows immediate patient comfort and function by protecting ulcerated mucosa and providing a platform against which to masticate. Chemotherapeutically induced lesions can be exacerbated by trauma from the remaining natural dentition during mastication and parafunctional habits. The interim prosthesis protects ulcerated tissue from further injury, and healing is promoted. The greater the integrity of the oral tissues, the more resistant they become to microbial invasion, subsequent microbial colonization, and infection during periods of granulocytopenia. By the use of a conservative technique, the patients's quality of life is improved during cancer treatment, and definitive prosthodontic treatment is deferred until therapy can be better tolerated by the patient.

Equipment Design↗
PubMed1991

Osseous and muscular changes after vertical ramus osteotomy. A magnetic resonance imaging study.

Magnetic resonance (MR) imaging was performed about 2 years after vertical ramus osteotomy of 10 patients to study changes in the mandibular condyle, cortical and cancellous bone of the proximal fragment, and muscles of mastication. MR imaging observations of the surgically treated patients were compared with findings in 10 asymptomatic untreated control subjects. The results showed that the MR appearance of bone marrow of the mandibular condyle was normal in all patients and in all control subjects. No MR evidence of avascular necrosis of the mandibular condyle was found. MR imaging artifacts from microscopic metallic particles were seen in all surgically treated regions. Thickening of the buccal and lingual cortical bone with narrowing of the bone marrow space was seen bilaterally in eight patients and unilaterally in two patients. Slight medial tipping of the mandibular condyle was seen unilaterally in two patients. Atrophic changes with decreased muscle volume and fatty replacement of muscle tissue was seen unilaterally in eight patients. None of these alterations were seen in the control subjects. MR imaging appears to be an excellent method to study morphologic changes of the muscles of mastication and osseous fragments after orthognathic surgery of the mandible. Thickening of the cortical bone and narrowing of the bone marrow space of the proximal fragment was frequently seen after vertical ramus osteotomy of the mandible and most likely represents remodeling associated with normal healing.

Adolescent↗
PubMed1995

The effects of orthodontic treatment on isometric bite forces and mandibular motion in patients before orthognathic surgery.

PURPOSE: Little is known about the effects of orthodontic treatment on oral motor function. The objective of this report is to evaluate changes in mandibular motion and maximum bite force that occur between the initiation of presurgical orthodontics and its completion before surgery. PATIENTS AND METHODS: Fifteen patients (9 women, 6 men) with a variety of dentofacial deformities were examined before and after presurgical orthodontics. Mechanical advantage of the muscles and bite points, mandibular range of motion, maximum isometric bite force, and levels of electromyographic (EMG) activity in the anterior and posterior temporalis and masseter muscles during isometric bites were recorded on all subjects over time. Data obtained before and after completion of presurgical orthodontics were statistically compared. RESULTS: Presurgical orthodontics reduced mandibular mobility somewhat, but the amount was not significant. Statistically significant reductions in bite force were noted after orthodontics for incisor, canine, premolar, and molar bite positions. No significant difference in the EMG/bite force slopes was obtained, nor was there any difference in the moment arms of the bite points or the muscles of mastication from orthodontics. CONCLUSIONS: This study showed significant changes in measures of oral motor function resulting from orthodontic treatment. A larger study is needed to confirm that these results will be similar in all orthodontic patients. There is no indication that these changes are the result of physiologic alterations of the muscles of mastication. The best current explanation is that these changes result from the pain and discomfort of the orthodontic appliances and the induced malocclusion.

Adolescent↗
PubMed1993

An immunocytochemical and autoradiographic investigation of the serotoninergic innervation of trigeminal mesencephalic and motor nuclei in the rabbit.

The results of a previous experiment suggest that the cell bodies of many jaw closing muscle spindle afferents in the trigeminal mesencephalic nucleus of the rabbit are phasically inhibited during fictive mastication. The aim of this study was to investigate one possible neurotransmitter system that could be involved in this modulation, serotonin, by use of receptor autoradiography techniques and immunofluorescence combined with retrograde labelling of masseteric spindle afferents and motoneurons. A second objective was to compare the serotonin innervation of neurons in the trigeminal mesencephalic nucleus with that of masseteric motoneurons. Serotoninergic fibres were seen surrounding labelled masseteric spindle afferents, as well as unlabelled neurons, in the trigeminal mesencephalic nucleus. These fibres were close to the cell bodies and sometimes to the axon hillocks of the neurons. Although it has been reported that many neurons of the trigeminal nucleus are multipolar in some species, none of the labelled spindle afferent in this study had more than one process. Throughout the motor trigeminal nucleus, serotonin fibres were found in close proximity with cell bodies and with the proximal portions of axons and dendrites of labelled and unlabelled motoneurons. Serotonin fibres were also seen adjacent to cell bodies and processes of efferent neurons in cell group k. Autoradiography with several tritiated ligands was used to reveal the presence of receptors for serotonin as well as its uptake sites. Only serotonin2 receptors were found to be abundant in the trigeminal mesencephalic nucleus. The motor nucleus and cell group k contained serotonin2 and serotonin3 receptors, as well as serotonin uptake sites. Serotonin1A receptors appear to be absent from both nuclei. The findings suggest that release of serotonin from fibres in close proximity to trigeminal primary afferent somata could modify the transmission of action potentials from muscle spindle receptors during mastication through an action on serotonin2 receptors. In the motor nucleus and cell group k, serotonin may alter neuronal properties through actions on at least two receptor subtypes (serotonin2 and serotonin3).

Action Potentials↗
PubMed1995

Operculum syndrome: unusual feature of herpes simplex encephalitis.

Herpes simplex encephalitis in adults and young patients carries a high mortality and morbidity. Its presentation may be nonspecific, sometimes hampering early diagnosis. Two young children are reported with herpes simplex encephalitis in whom the operculum syndrome was an outstanding feature. This syndrome is caused by focal, bilateral cortical damage to the anterior opercular regions resulting in anarthria and impairment of mastication and swallowing. After initiation of treatment with acyclovir in the early stage of the disease, the outcomes in both patients were characterized by good general recovery with persistence of deficits of speech, mastication, and swallowing, more pronounced in the patient who was comatose during the illness. Early recognition of the operculum syndrome as a presenting feature of herpes simplex encephalitis may expedite the diagnosis and thereby improve the prognosis.

Acyclovir↗
PubMed2006

The influence of pain on masseter spindle afferent discharge.

Muscle spindles provide proprioceptive feedback supporting normal patterns of motor activity and kinesthetic sensibility. During mastication, jaw muscle spindles play an important role in monitoring and regulating the chewing cycle and the bite forces generated during mastication. Both acute and chronic orofacial pain disorders are associated with changes in proprioceptive feedback and motor function. Experimental jaw muscle pain also alters the normal response of masseter spindle afferents to ramp and hold jaw movements. It has been proposed that altered motor function and proprioceptive input results from group III muscle afferent modulation of the fusimotor system which alters spindle afferent sensitivity in limb muscles. The response to nociceptive stimuli may enhance or reduce the response of spindle afferents to proprioceptive stimuli. Several experimental observations suggesting the possibility that a similar mechanism also functions in jaw muscles are presented in this report. First, evidence is provided to show that nociceptive stimulation of the masseter muscle primarily influences the amplitude sensitivity of spindle afferents with relatively little effect on the dynamic sensitivity. Second, reversible inactivation of the caudal trigeminal nuclei attenuates the nociceptive modulation of spindle afferents. Finally, functionally identified gamma-motoneurons in the trigeminal motor nucleus are modulated by intramuscular injection with algesic substances. Taken together, these results suggest that pain-induced modulation of spindle afferent responses are mediated by small diameter muscle afferents and that this modulation is dependent, in part, on the relay of muscle nociceptive information from trigeminal subnucleus caudalis onto trigeminal gamma-motoneurons. The implication of these results will be considered in light of current theories on the relationship between jaw muscle pain and oral motor function.

Afferent Pathways↗
PubMed2005

Preparation and evaluation of release characteristics of 3TabGum, a novel chewing device.

A new chewing gum device in the form of a three layers tablet (3TabGum) has been developed. The new drug delivery system is obtained, at room temperature, by direct compression using conventional pharmaceutical equipment. Basically, the resulting chewing gum tablets comprise a gum core combined with two protective antiadherent external layers, which prevent gum adhesion to the punches of the tableting machine. Drug release from a dosage form is the critical step in drug absorption and bioavailability, thus an experimental protocol has been designed to evaluate the efficiency of this kind of therapeutic system by verifying its capability to release the drug dose and by assessing the delivery rate. Simple diffusion into the medium causes the release of only a small percentage of the drug contained in the medicated chewing gum, while the delivery of the major part of the dose occurs during mastication. The results obtained in this study suggest that water soluble drugs are freely and easily released by chewing gums, while for actives characterized by reduced water solubility the release rate depends on the chewing time although all the drugs tested are completely released after a reasonable mastication time.

Chewing Gum↗
PubMed2006

Functional significance of the microstructural detail of the primate dentino-enamel junction: a possible example of exaptation.

In primate teeth, the dentino-enamel junction (DEJ) exhibits a scalloped appearance, the functional importance of which has been the subject of various suggestions and speculations. Simplified finite-element (FE) models of DEJ microanatomy were created, both in 2D and 3D, and their biomechanical behavior was tested and compared. Consistently, the models with the scalloped DEJ, although having higher maximum tensile stresses than the straight DEJ models, showed discontinuous concentrations of stress. In straight DEJ models, tensile stresses act at the DEJ over continuous areas in a direction, which would push the two tissues apart, thus leading to delamination of the DEJ. Perhaps even more important, in the scallop model, the net-compression towards the DEJ was consistently higher than net-tension away from it. As a consequence, dentine and enamel would be pushed towards each other during loading (i.e., during mastication). These findings suggest that the scalloped nature of the DEJ confers a biomechanical advantage to the integrity of the tooth during mastication. Furthermore, there exists a correlation between pronounced prism decussation and scallop magnitude, suggesting that scallops may have been selected for in response to high bite forces. However, given the equivocal relationship between scallops and presumed bite force across mammalian taxa, we propose that scallops could in fact be exaptations.

Animals↗
PubMed2006

Severe odontogenic infections, part 1: prospective report.

PURPOSE: The purpose of this study was to prospectively evaluate a series of patients with severe odontogenic infections (OI). PATIENTS AND METHODS: In this study, 37 consecutive hospitalized patients with odontogenic infection were treated with intravenous penicillin (PCN) (unless allergic), and prompt incision and drainage. Standardized data collection included demographic, preadmission, time-related, preoperative, anatomic, treatment, microbiologic, and complications information. Appropriate descriptive statistics were computed. RESULTS: The sample consisted of 37 subjects (38% female) with a mean age of 34.9 years. Three subjects (8%) had immunocompromising diseases. Caries was the most frequent dental disease (65%) and the lower third molar was the most frequently involved tooth (68%). Trismus and dysphagia were present on admission in over 70% of cases. The masticator, perimandibular (submandibular, submental, and/or sublingual), and peripharyngeal (lateral pharyngeal, retropharyngeal, and/or pretracheal) spaces were infected in 78%, 60%, and 43% of cases, respectively. Abscess was found in 76% of cases. PCN-resistant organisms were identified in 19% of all strains isolated and in 54% of patients with sensitivity data. PCN therapeutic failure occurred in 21% of cases and reoperation was required in 8%. Length of hospital stay was 5.1 +/- 3.0 days. No deaths occurred. CONCLUSIONS: This study indicated that PCN resistance, resulting in PCN therapeutic failure, was unacceptably high in this sample. Alternative antibiotics, such as clindamycin, should be considered in hospitalized patients with OI. Masticator space infection occurred much more frequently than previously reported. Trismus and dysphagia should be appreciated as significant indicators of severe OI.

Abscess↗
PubMed1988

Enhancement of rehabilitation by use of implantable adjuncts with vascularized bone grafts for mandible reconstruction.

Restoration of mandibular continuity after trauma or cancer by means of vascularized bone grafts, as described by Taylor and coworkers in 1979, has become an established method of oral rehabilitation. Still considered by some an endpoint in reconstruction, we have found that the judicious application of newly described dental prosthetic materials can provide the patient with improved appearance and function associated with a fully restored mandible. Twelve patients who underwent vascularized bone grafting for mandibular reconstruction had adjunctive implantation to improve either dentition or to reconstruct the temporomandibular joint. Nine patients had dental implants to restore permanent stable dentition either by placement of the mandibular bone staple plate or osseointegrated implants. Three additional patients underwent placement of metallic condylar head prostheses placed on the vascularized bone graft at the time of transfer. These patients demonstrated good mastication and an excellent incisal opening which was maintained in the late postoperative period. Vascularized bone transfer for restoration of continuity of the mandible should not be considered an endpoint in and of itself. By using implantable dental devices to restore dentition and condylar head prostheses to improve both the aesthetic result and function of the mandible to complement the vascularized osteocutaneous flap, we can bring our patients closer to the goal of total rehabilitation. The majority of these patients would otherwise never have been offered a chance at restoration of dentition. All had beneficial effects with regard to mastication and the majority also had improved speech.

Biomechanical Phenomena↗
PubMed2002

The effect of dietary consistency and water content on the parotid glands of submandibular and sublingual duct-ligated rats.

The aim here was to estimate the significance of oral sensation and mastication on functional changes in the parotid glands of partially desalivated rats. Submandibular and sublingual duct-ligated and sham-operated control rats were fed three diets of similar chemical composition but different physical presentations. Two were solid, either pellets or powder, and one was liquid. Water and food intakes were similar for both the duct-ligated rats and sham-operated control rats when they ate the pelleted or powdered-diet, though more food was wasted by the duct-ligated rats in the powdered-diet group than in the pelleted-diet group. No food was wasted in the rats fed the liquid-diet. Parotid gland weight and amylase activity were greatest with the submandibular and sublingual duct-ligated rats fed the powdered-diet and smallest with the duct-ligated and sham-operated control rats fed the liquid-diet. The amount of food wasted correlated positively with the parotid gland weight and parotid amylase activity of the rats. These findings support the view that it is the contact of dry food with the oral mucosa rather than the jaw movements involved in mastication that increases parotid gland weight and amylase activity in partial desalivated rats.

Amylases↗
PubMed2003

Percutaneous trigeminal ganglion balloon compression for treatment of trigeminal neuralgia, part II: results related to compression duration.

OBJECTIVE: The purpose of this study is to find out how different compression time affects the results of percutaneous trigeminal ganglion compression for treatment of trigeminal neuralgia. METHODS: This study includes 80 patients with intractable third-branch trigeminal (V3) neuralgia who had received percutanious trigeminal ganglion balloon compression. All the patients received some treatment protocol except for the duration of compression. Group 1 patients received 60-second and group 2 patients received 180-second compression. A computerized pressure recording system was used for pressure monitoring and analysis. RESULTS: Both groups had 100% immediate pain relief and all patients experienced mastication weakness immediately after the procedure. The facial numbness was severe in group 2 in the first trigeminal (V1) distribution (p<0.05) but not in the second or third trigeminal (V2,3) distribution (p>0.05) in the immediate period after the operation. The recurrence rate in the first year follow-up was higher in group 1 (5%) than in group 2 (2.5%) but did not reach the statistical difference (p>0.05). At 1 year follow-up after the procedure, group 1 and lower incidence of facial numbness over all trigeminal distribution (V1,2,3) than group 2 (p<0.05) mastication weakness all recovered during the first-year follow up. CONCLUSIONS: With accurate monitoring of the balloon pressure during the percutaneous trigeminal ganglion compression, it was found that the shorter duration of compression had less side effect. At one year follow-up, the incidence of recurrrence rate was slightly higher in the patients who received 60-second compressions than in those who received 180-second compressions, but there was no significant statistical difference. Whether patients with first or second branch of trigeminal neuralgia require longer compression duration needs further study.

Aged↗
PubMed2002

Studies on the development of a microencapsulated delivery system for norbormide, a species-specific acute rodenticide.

Norbormide, a selective rat toxicant, was microencapsulated to both mask the flavour and delay the release until after a lethal dose has been ingested by the rat. To this end, gelatine microspheres containing norbormide were made and over coated with either shellac resin or an equal mixture of shellac and Eudragit RS in a fluid-bed coating machine. The microcapsules absorb water, swell and burst to release their contents. In rats an 8 h window is available to delay the release of encapsulated material. In initial experiments, a shellac coating of 20% w/w was established as suitable for delaying the release. A capsule size range of 200-400 microm was selected, from capsule mastication experiment, for oral gavaging and feeding studies in rat. Oral gavage study has demonstrated for the first time that a substantial delay in release of a lethal dose of an acute poison has been achieved by microencapsulation. Feeding test has demonstrated that there is a fine balance between the size and density of the capsules in the bait to overcome mastication of the capsules by rats. A combination of shellac and Eudragit RS resins is a viable polymeric wall material to control the rate of penetration of water in to microcapsules.

Animals↗