Biomedical subjects

M P Hector

Publications and source records attributed to M P Hector.

26 records · Page 2Linked to original sources

PubMed1996

An immunohistochemical study of the pulpal nerve supply in primary human teeth: evidence for the innervation of deciduous dentine.

The innervation of pulp and dentine was studied in fully formed human deciduous teeth using antibodies to calcitonin gene related peptide (CGRP). Freshly extracted healthy teeth were divided, fixed, demineralised, cryosectioned and treated with antibodies to human CGRP which was then labelled with horseradish peroxidase. Bundles of nerve fibres passed from the apex of the root to the coronal region where a subodontoblast plexus was formed. In the cervical half of the root some nerve fibres branched away from the main bundles to supply both the odontoblast layer and the dentine. Branches from the coronal subodontoblast plexus also reached the odontoblast layer and the dentine. Most of the nerve fibres terminated in the odontoblast layer. In some areas a marginal plexus of nerves was observed between the odontoblasts and the predentine; intratubular nerve fibres arose either from this plexus or directly from the pulp. The dentine of the crown was more densely innervated than that of the root. In the crown the cervical one third had the most densely innervated dentine followed by the pulp horn and the middle third. The most densely innervated areas occurred in regions where the marginal plexus was present. Although many tubules contained a single nerve filament more complex patterns of termination were also observed. The maximum penetration of a nerve fibre into the dentine was 125 microns. The pattern of the deciduous innervation shows some similarities to the permanent dentition but among the differences is the high density of dentinal innervation in the cervical region. The latter point correlates with the clinical impression of greater sensitivity experienced by patients during invasive procedures performed without anaesthetic in the cervical area.

Calcitonin Gene-Related Peptide↗

PubMed1993

Contribution of periodontal receptors and food qualities to masseter muscle inhibition in man.

Previous studies of human muscle inhibition during chewing have shown that many factors contribute to the incidence and intensity of this reflex but few studies have been in a physiological context. During the first crushing cycle of brittle foods ipsilateral masseter muscle EMG, mandibular movement and vibration were recorded simultaneously in four healthy dentate subjects. Experiments were repeated before and during anaesthesia of the cheek teeth on the chewing side. The results suggest that vibration seems to be the most important factor in muscle inhibition during food crushing; conversely periodontal sensation, mandibular closing movement and the preload by the muscle at the onset of food fracture play a minor role.

Adult↗

PubMed1992

Migration of erythrosin-labelled saliva during unilateral chewing in man.

The aim was to monitor the distribution of erythrosin-labelled saliva around the mouth during normal, unilateral chewing on gum. Thirty-one subjects chewed chewing-gum containing erythrosin on the preferred side for 5 min. The mouth was examined and the distribution of the dye recorded on standardized charts. The dye was present mainly ipsilateral to the chewing side. Although the dye did cross the mid-line, it was rarely present in the contralateral premolar and molar regions.

Adult↗

PubMed1991

Parotid protein secretion from the rabbit during feeding.

Rabbits were trained to accept a standardized feeding regime. Under anaesthesia both parotid ducts were cannulated in a retrograde direction and saliva was subsequently collected in feeding sessions involving pellets and carrots before and after the administration of propranolol. Salivary total protein and amylase concentrations were assayed and protein analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Propranolol produced a reduction in protein secretion but not fluid secretion, indicating that protein secretion is partly under beta-adrenergic control. A transient increase in protein secretion was seen 8 h after the administration of propranolol and suggested the existence of different neural mechanisms involved in protein secretion compared to synthesis. Protein output (with high fluid secretion) during feeding on pellets was higher than on carrots (with high protein concentration) and suggested a significant role of the parasympathetic nervous system. The pattern of protein secretion as seen by SDS-PAGE was similar in individual rabbits and remained largely unchanged with the different foods and in the presence of propranolol.

Amylases↗

PubMed1990

The effect of the chewing side on parotid amylase secretion in conscious rabbits.

This study was conducted to investigate whether changes in amylase output accompany changes in salivary flow which occur during feeding. New Zealand White rabbits were trained to eat food offered to them in the laboratory. After chronic parotid duct cannulation, saliva was collected and flow rates recorded bilaterally while the animals fed on fresh carrots or pelleted food. The amylase concentration (U/ml) obtained with carrots was greater than with pellets, but because of the differences in flow rate, the overall amylase output (U/min) for both foods did not differ. There was no difference in the amylase concentration in saliva collected either ipsilateral to or contralateral to the chewing side. However, amylase output was significantly greater ipsilateral than contralateral to chewing with both pellets (p less than 0.01) and carrots (p less than 0.05).

Amylases↗

PubMed1987

The possible role of periodontal mechanoreceptors in the control of parotid secretion in man.

In man, parotid flow has been recorded bilaterally using modified Lashley cups in response to mechanical stimulation of the teeth. The stimulus was defined and controlled by monitoring the rectified and integrated masseter electromyographic activity (e.m.g.) during repeated clenching on closely fitting bite-blocks placed between the molar teeth. Unilateral clenching on a bite-block resulted in a greater flow from the ipsilateral than the contralateral gland, and both exceeded the control values. There was also a positive correlation between the masseter e.m.g. activity and ipsilateral parotid flow. Parotid flow was also recorded before and during local anaesthesia of various intra-oral branches of the trigeminal nerve. Anaesthesia of two to three inputs always produced significant reductions in ipsilateral flow, but anaesthesia of a single input was not always effective. These results provide evidence in support of the hypothesis that intra-oral mechanoreceptors, particularly periodontal mechanoreceptors, are involved in the masticatory-salivary reflex.

Anesthesia, Dental↗

PubMed1987

Periodontal mechanoreceptors and parotid secretion in animals and man.

Parotid flow was determined in rabbits during feeding. The animals produced more saliva when chewing hard laboratory pellets than with carrots, confirming the findings of Gjörstrup (1980a). We showed that one gland always produced more secretion than the other, and that the dominant gland alternated from side to side with changes in the chewing side. Strain-gauge recordings revealed a remarkable similarity in pattern between mandibular strain and ipsilateral parotid flow. Together, these data suggest that chewing movements and chewing force are involved in the control of parotid secretion. In man, flow rates of parotid saliva collected with a Lashley cup and cannula were recorded. During intermittent clenching on a bite block, we found: (1) a positive correlation between rectified integrated masseter EMG and parotid flow; and (2) that anesthesia of various intra-oral nerves could reduce the flow almost to zero. Crushing a particle of breakfast cereal between two teeth resulted in a reproducible parotid flow which was reduced by infiltration anesthesia around one of these teeth. These data point to the involvement of periodontal mechanoreceptors in the control of parotid secretion in rabbits and man.

Animals↗

PubMed1985

The possible relation between mastication and parotid secretion in the rabbit.

Salivary flow has been recorded from conscious rabbits during 1 min periods whilst continuously chewing standard laboratory dry pellets or pieces of carrot and, in some animals, a mash of pellets with water. Flow was measured using contact drop recorders or a continuous flow recorder via Polythene tubes permanently inserted into one or both parotid ducts. Large variations in flow were obtained with unilateral recordings particularly during dry pellet chewing. Bilateral recordings showed that the flow was always greater on one side than on the other and that dominant secretion alternated from side to side in an apparently random manner. Rabbits chew unilaterally. Videotaped recordings of chewing movements showed that the greater secretion was always produced on the chewing side. To test the possibility that drying of the oral mucosa, or the prolonged hardness of the pellets may result in higher flow rates in animals with cannulated ducts than would normally be seen in intact animals, water was injected downstream into the mouth through a third cannula. This was inserted in an anterograde direction in the parotid duct on one side. Significant reductions in flow were recorded during dry pellet eating, but not during carrot eating. When animals were fed a soft pellet mash, salivary flow was significantly lower than with dry pellets. Recordings have been made from strain gauges attached to the ascending ramus of the mandible. Previous findings that dry pellets produce greater strain than carrots have been confirmed. It has also been shown that less strain is produced with soft pellet mash. The strain gauge data suggested that a relation exists between masticatory force and parotid salivary flow. The results are compatible with the hypothesis that intra-oral mechanoreceptors may be involved in a masticatory-salivary reflex.

Animals↗