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Biomedical subjects

A R Loescher

Publications and source records attributed to A R Loescher.

18 recordsLinked to original sources
PubMed2006

Effects of capsaicin and menthol on oral thermal sensory thresholds.

OBJECTIVE: To determine the long-term effect of capsaicin and short-term effect of menthol on oral thermal thresholds. DESIGN: The thresholds for cold detection (CDT), warm detection (WDT), cold pain (CPT) and warm pain (WPT) were determined in 11 regular chilli-eaters (capsaicin group) and 11 control subjects that were closely matched for age, gender and ethnicity. The effect of menthol was determined by asking all 22 participants to suck a lozenge containing 0.52% menthol for 5min. RESULTS: An ANOVA revealed a significant difference between the capsaicin and control groups (P=0.014), with the greatest difference in the WDT (capsaicin group 4.7+/-2.7[S.D.] degrees C; control group 2.3+/-2.2 degrees C). Immediately after sucking a menthol lozenge there was a significant rise in the CDT (2.2+/-1.1 degrees C to 5.9+/-6.2 degrees C; P<0.01) and WDT (3.6+/-2.7 degrees C to 7.6+/-4.4 degrees C; P<0.001). CONCLUSIONS: The consumption of foods containing capsaicin and menthol significantly alters thermal sensory thresholds in the oral cavity. Dietary habits should therefore be taken into account when intra-oral thermal thresholds are determined.

Adult↗
PubMed2003

Nerve damage and third molar removal.

The surgical removal of lower third molars endangers both the lingual and inferior alveolar nerves. Patients sustaining an injury to either of these nerves must be managed correctly, and this requires a diagnosis of the injury type and regular monitoring of the recovery of sensation. Surgical intervention for a damaged inferior alveolar nerve is not usually indicated but may be undertaken: if the nerve is completely divided and the severed ends are misaligned; if a bony fragment has compressed the mandibular canal; or if the patient suffers from persistent neuropathic pain. In contrast, after injury to the lingual nerve, if sensory testing demonstrates no neural recovery within 3-4 months, exploration of the injury site and microsurgical repair of the damaged nerve is indicated.

Cranial Nerve Injuries↗
PubMed2001

Calcitonin gene-related peptide modifies the ectopic discharge from damaged nerve fibres in the ferret.

Previous studies in our laboratory have shown that the neuropeptide, calcitonin gene-related peptide (CGRP) accumulates at a site of inferior alveolar nerve injury at the time when high levels of spontaneous activity and mechanical sensitivity are recorded electrophysiologically. The present study was undertaken to determine whether or not the CGRP could be playing a role in initiating or modulating the neuronal activity. In 18 anaesthetised adult ferrets the left inferior alveolar nerve was sectioned and ligated and recovery permitted for 3 days. Under a second anaesthetic recordings were made from a fine nerve filament, containing up to four active or silent units, dissected from the nerve proximal to the injury. After recording activity for a 30 min control period, CGRP and then the CGRP antagonist (CGRP 8-37) were applied either by close-arterial injection or topically (10(-4) M, 0.2 ml). After each application activity was recorded for a 30 min period. Recordings were made from 52 units, of which 26 (50%) were spontaneously active and 30 (58%) were mechanically sensitive. The spontaneous activity in five units was increased by the application of CGRP, and the CGRP antagonist subsequently reduced the activity in two of these units. Activity was induced by CGRP in three previously silent units. Overall, activity was affected in 19% of the units studied. We conclude that CGRP present within a neuroma may initiate or modulate the level of ectopic discharge from some damaged nerve fibres and therefore may contribute to the sensory disturbances which follow nerve injury.

Action Potentials↗
PubMed2000

A prospective, quantitative study on the clinical outcome of lingual nerve repair.

We previously showed in laboratory studies that the most effective method for repair of damaged lingual nerves was by excision of the neuroma, mobilization of the stumps, and direct reapposition with epineurial sutures. We have now undertaken a prospective study in a series of 53 patients treated by this method and have evaluated the outcome by quantifying and comparing the results of tests of sensation before and after operation. The outcome in individual patients was variable. However, pooled data from all patients showed a highly significant improvement in sensation at the final assessment 12 months or more after the repair. The proportion of patients who responded to most or all light touch stimuli increased from 0% to 51% after repair, and the proportion who responded to pin-prick stimuli increased from 34% to 77%. There was no correlation between the final results of any of the tests and the delay before repair. None of the patients regained completely normal sensation and there was no reduction in the number with spontaneous paraesthesia or pain. However, fewer patients tended to bite the tongue by accident and most of them considered the operation worthwhile. These data show that lingual nerve repair is effective in most patients and we suggest that it should be offered to all those who show few signs of spontaneous recovery after injury.

Adolescent↗
PubMed1999

The effect of surgical technique on lingual nerve damage during lower 3rd molar removal by dental students.

We have previously shown that avoidance of lingual flap retraction with a Howarth periosteal elevator during lower 3rd molar removal, reduces the incidence of lingual nerve damage. In that study, the surgery was undertaken by qualified staff and we have now assessed the effect of revising the method taught to our junior undergraduate dental students. We evaluated the outcome of surgery undertaken by 2 consecutive years of students, each group being taught 1 of the 2 methods. A total of 200 patients requiring lower 3rd molar removal under local anaesthesia were included in the study. In year 1, the surgery included elevation of a lingual flap and insertion of a Howarth elevator adjacent to the lingual plate; in year 2 this part of the procedure was avoided by using a purely buccal approach. There were no significant differences between the levels of tooth eruption and types of impaction of the teeth removed in each year. Lingual sensory disturbance occurred in 3 patients in the 'flap' group (3.3%) and in 1 patient (0.9%) in the 'no flap' group. As this incidence is not significantly different in the 2 groups (P < 0.4), we conclude that avoidance of lingual retraction by students undertaking lower 3rd molar removal does not appear to place the lingual nerve at greater risk. In view of the results of our previous study, we therefore advocate this method for use in undergraduate dental education.

Clinical Competence↗
PubMed1998

Immunocytochemical and electron-microscopic features of tooth pulp innervation in hereditary sensory and autonomic neuropathy.

Characteristics of the pulpal innervation in teeth obtained from a 4-year-old Asian boy with hereditary sensory and autonomic neuropathy, type II (HSAN) were investigated. Four minimally carious primary teeth were split longitudinally and prepared for either fluorescent immunocytochemistry or electron microscopy. The occurrence and distribution of specific neuropeptides were determined by the use of antisera to calcitonin gene-related peptide (CGRP), substance P (SP), neuropeptide Y (NPY), and vasoactive intestinal polypeptide (VIP). The overall innervation of the pulps was visualized using antiserum to protein gene product 9.5; an antiserum to dopamine beta-hydroxylase was used to identify postganglionic sympathetic fibres. Pulpal innervation in HSAN was notably different from that of normal teeth: in comparison with the controls, HSAN teeth had an overall marked reduction in pulpal innervation with an absence of large nerve bundles and the subodontoblastic plexus. CGRP- and SP-immunoreactivity was absent in HSAN specimens and VIP-immunoreactivity was reduced. However, NPY-immunoreactivity appeared to be increased within certain regions of the pulp/dentine complex. In addition, there was evidence of NPY-immunoreactive fibres extending into dentine, a feature not seen in the controls. Electron microscopy revealed an absence of myelinated nerve fibres and a paucity of unmyelinated fibres. CGRP and SP have a well-established role in nociceptive processing and their absence in the HSAN teeth would seem to correspond with the clinical presentation of marked peripheral sensory deficit, characteristic of this condition. An up-regulation of NPY-immunoreactivity has previously been reported in animal teeth following nerve injury and a similar mechanism may have stimulated increased NPY expression in HSAN teeth, but the functional significance of its presence within dentinal nerves is not known.

Calcitonin Gene-Related Peptide↗
PubMed1998

The effect of surgical medicaments on peripheral nerve function.

Surgical medicaments are often placed in close proximity to peripheral nerves and may be responsible for some postoperative sensory disturbances. In this study we investigated the effect of four medicaments -- BIPP, (bismuth iodoform paraffin paste), Whitehead's varnish (compound iodoform paint), Surgicel (oxidized regenerated cellulose) and Carnoy's solution (ethanol, chloroform and acetic acid) -- on peripheral nerve function. The experiments were carried out on the saphenous nerve in anaesthetized adult rats. Electrical stimuli (30 V, 0.1 ms duration) were applied to the saphenous nerve through electrodes placed distally (at the ankle) to evoke a compound action potential (CAP) which was recorded proximally (in the thigh). The CAP was recorded before, and for 2 h after, the application of the medicament to a 1 cm length of nerve between the electrodes. In other animals (n = 4 in each group) recordings were made after the medicament had been placed in a connective tissue pocket immediately overlying the nerve for a 2-week period. BIPP (n = 4) had no immediate or delayed effect on neural function, whereas Whitehead's varnish (n = 4) and Carnoy's (n = 4) solution both blocked neural conduction within 2 min of being placed adjacent to the nerve. The effect of Surgicel (n = 8) was more variable; axonal conduction was blocked within 2 h in five of the eight experiments undertaken. After the application of Whitehead's varnish or Surgicel for 2 weeks, the CAPs had regained characteristics which were similar to those of the controls, but after the application of Carnoy's solution they remained significantly diminished (P < 0.004). These results suggest that, with the exception of BIPP, the medicaments tested could be responsible for some postoperative sensory disturbances, and the effects of Carnoy's solution on neural function may be persistent.

Acetic Acid↗
PubMed1995

A quantitative study on the myelinated fiber innervation of the periodontal ligament of cat canine teeth.

The periodontal ligament is richly innervated with mechanosensitive afferent nerve fibers, and the location of the mechanoreceptive terminals within the ligament is of functional significance. In this study, we have obtained quantitative information on mechanoreceptor distribution in the lower canine teeth of the cat. Using light microscopy, we quantified the number of myelinated axons in the periodontal ligament at 1 mm, 3 mm, and 5 mm from the tooth root apex. Grouped axons and axons which were isolated in the cemental half of the ligament (and therefore putative mechanoreceptors) were identified. The mean total number of axons was 1290 (n = 20) at 1 mm from the apex, 1290 at 3 mm, and 814 at 5 mm. The distribution of axons around the tooth root circumference was found to be non-uniform. Near the root apex, the highest numbers of grouped axons were located distally and mesially, and in the middle region of the root, the highest numbers were found mesially. The highest numbers of isolated axons at the apical levels were located distally, and in the mid-root region, mesially. At all levels, the lingual region was the most sparsely innervated by both groups. There was a positive correlation between the number of grouped axons and the width of the ligament in the same region, but this correlation was much weaker for isolated axons, suggesting that their distribution does not result only from the volume of tissue. Variations in the number of axons and, to a lesser extent, the dimensions of the periodontal ligament were considerable.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1993

Characteristics of periodontal mechanoreceptors supplying cat canine teeth which have sustained orthodontic forces.

The characteristics of these mechanoreceptors were investigated after orthodontic forces had been applied for either 3 days or 12 weeks, and also 8 weeks after the tooth had been moved into a new position and the tissues allowed to recover. Electrophysiological recordings were made from single mechanosensitive units dissected from the inferior alveolar nerve and each was characterized by applying forces to the tooth crown. The characteristics were compared with those of receptors innervating normal teeth. Three days after the onset of tooth movement, the periodontal mechanoreceptors had higher thresholds to forces applied at slow rates and lower discharge frequencies. Twelve weeks after the onset of tooth movement, the mechanoreceptors again had higher force thresholds and lower discharge frequencies but also responded to applied forces over a narrower range of directions and adapted more rapidly than the controls. After the tooth had been moved into a new position and the tissues allowed to recover, the mechanoreceptor characteristics were nearer to normal but they still had raised thresholds to forces applied at slow rates, lower discharge frequencies, and responded to applied forces over a narrower range of directions. It seems likely that the altered receptor characteristics would have resulted from a combination of disorganization of the collagen matrix and direct injury to the nerve terminals.

Action Potentials↗
PubMed1993

The distribution and morphological characteristics of axons innervating the periodontal ligament of reimplanted teeth in cats.

Twelve weeks after reimplanting lower canines the distribution and characteristics of myelinated and non-myelinated axons within the periodontal ligament were investigated by light and electron microscopy. The ligament was examined at 2-mm intervals along the length of the root of four reimplanted teeth and of the contralateral canines, which served as controls. In each case the periodontal ligament was reinnervated. In two of the teeth, which showed extensive apical resorption, the innervation was much less than in control teeth. In two teeth showing minimal or no apical resorption the degree of innervation at the most apical level did not differ significantly from controls.

Animals↗
PubMed1991

Distribution and morphological characteristics of axons in the periodontal ligament of cat canine teeth and the changes observed after reinnervation.

The distribution and morphological characteristics of myelinated and non-myelinated axons innervating the lower canine periodontal ligament (PDL) in adult cats have been analysed. After perfusion fixation and decalcification, the teeth were slit transversely, divided into segments, and embedded in plastic. Ultrathin sections of each segment were examined in the electron microscope and used to reconstruct the whole PDL at 1, 4, 7, and 9 mm from the tooth apex. One millimeter from the tooth apex there were a mean of 920 myelinated axons and 1,415 non-myelinated axons. The numbers of axons declined toward the tooth crown. Bundles of myelinated and small non-myelinated axons lay adjacent to the blood vessels midway between the bone and cementum. Isolated myelinated axons appeared to have split away from these main nerve bundles and entered the avascular zone of the ligament, where they lost their myelin sheaths to become large non-myelinated axons rich in mitochondria. These non-myelinated axons sometimes appeared to be linked to collagen fibres and were thought to be the mechanoreceptor terminals. Twelve weeks after sectioning and inferior alveolar nerve, the total number of axons innervating the periodontal ligament was 50% of that found in the contralateral controls. The large non-myelinated axons had smaller mean diameters and contained fewer mitochondria, a change which may be consistent with a reduction in mechanoreceptor excitability.

Animals↗
PubMed1991

Characteristics of periodontal mechanoreceptors supplying reimplanted canine teeth in cats.

These characteristics were investigated 12 weeks and one year after tooth reimplantation. Electrophysiological recordings were made from single mechanosensitive units dissected from the inferior alveolar nerve and each unit was characterized by applying forces to the crown of the tooth. The characteristics were compared with those of receptors innervating normal teeth. The periodontal mechanoreceptors supplying teeth reimplanted 12 weeks earlier responded to applied forces over a narrower range of directions, had higher force thresholds, lower discharge frequencies and adapted more rapidly than controls. One year after reimplantation their characteristics were nearer to normal but they remained significantly different from those of control units. It seems likely that the altered receptor characteristics could have resulted from a combination of changes in tooth mobility, disorganisation of the collagen matrix and direct injury to the nerve terminals.

Action Potentials↗
PubMed1991

Properties of periodontal mechanoreceptors supplying the cat's lower canine at short and long periods after reinnervation.

1. The properties of periodontal mechanoreceptors innervating the lower canine teeth of cats have been determined 6 weeks and 1 year after sectioning the inferior alveolar nerve. Recordings were made from single fibres dissected from the nerve central to the injury site, whilst forces were applied at right angles to the long axis of the tooth. 2. The range of directions over which each mechanosensitive unit responded (are of sensitivity) was established. Forces were then applied in the direction of maximum sensitivity and the maximum discharge frequency, dynamic index, adaptation rate, and the force threshold at three rates of force application (0.25, 2 and 20 N s-1) were determined. 3. Data from 115 units characterized 6 weeks after nerve section revealed a significantly reduced mean dynamic index and raised mean force threshold to forces applied at 2 and 0.25 N s-1, when compared with the controls. These units were, however, more sensitive than those examined 12 weeks after nerve section in a previous study (Loescher & Robinson, 1989b). 4. Data from 158 units characterized 1 year after nerve section revealed a significantly narrower mean are of sensitivity, reduced mean maximum discharge frequency, lower mean dynamic index and raised mean threshold to forces applied at 0.25 N s-1, when compared with the controls. 5. Bone overlying the roots of the reinnervated teeth was removed in order to localize receptors in the underlying periodontal ligament. Forty-six units were localized 6 weeks after nerve section and thirty-eight 1 year after nerve section. The mean conduction velocity of these units was significantly reduced both 6 weeks and 1 year after nerve section compared to the controls. One unit was found which branched to innervate receptors at two locations within the ligament, and one unit was found which branched to innervate a receptor in the ligament and another in the overlying skin. 6. The higher level of sensitivity of receptors when first reinnervated than at later stages is attributed to their immaturity. This immaturity may also contribute to the paraesthesia which is experienced by patients at a corresponding stage in recovery from nerve injury. The persistent reduction in sensitivity of units 1 year after nerve injury suggests that changes occur which have a permanent effect on their properties.

Animals↗
PubMed1990

Characteristics of periodontal mechanoreceptors reinnervated after freezing the inferior alveolar nerve.

Previous electrophysiological investigations have shown that reinnervated periodontal mechanoreceptors, 12 weeks after crushing or sectioning the inferior alveolar nerve, have altered discharge properties. These alterations may have resulted from the regeneration of axons along inappropriate endoneurial sheaths distal to the injury site and this possibility was investigated by comparing the properties of reinnervated mechanoreceptors after nerve crush with those after nerve freeze (after which endoneurial sheath guidance is not lost). In 4 cats, 67 periodontal mechanosensitive units supplying the lower canine were examined 12 weeks after freezing the inferior alveolar nerve. When compared with controls, they were found to have significantly smaller arcs of sensitivity, raised force thresholds, lower discharge frequencies and reduced dynamic indices. These characteristics were, however, similar to those of units examined after nerve crush. These results suggest that the alterations in receptor properties after nerve injury cannot be attributed to a mismatch between the regenerating axons and their receptors.

Animals↗
PubMed1989

Receptor characteristics of periodontal mechanosensitive units supplying the cat's lower canine.

1. Forces have been applied to the lower canine teeth of cats, and the range of directions over which single periodontal mechanoreceptors are sensitive (arc of sensitivity) has been determined. We have further studied the response of each unit to forces applied in the direction of maximum sensitivity and investigated whether there is any relationship between the properties of the unit and its location within the periodontal ligament. 2. Recordings were made from 91 single units dissected from the inferior alveolar nerve in six cats. The mean arc of sensitivity to a 0.5 N force applied at right angles to the long axis of the tooth was 312 degrees. The arc of sensitivity was dependent on the force applied and the threshold of the receptor. 3. More units responded maximally to forces applied in a distolingual direction than would have been expected had the responses been evenly distributed around the tooth. Thirty-four of the units were bidirectionally sensitive, 28 became active when the force was removed, and 20 were spontaneously active. 4. The force threshold decreased with increasing rates of force application. 5. The majority of the units (81%) were slowly adapting. The rapidly adapting units had significantly higher force thresholds. 6. Twenty-eight of the receptors could be localized in the periodontal ligament after removing bone overlying the tooth root. There was no apparent relationship between the distance of the receptor from the fulcrum and its arc of sensitivity, threshold, maximum frequency of discharge, or adaptation properties.

Animals↗
PubMed1989

Properties of reinnervated periodontal mechanoreceptors after inferior alveolar nerve injuries in cats.

1. The properties of periodontal mechanoreceptors supplying lower canine teeth in cats have been investigated 12 wk after the crushing or sectioning of the inferior alveolar nerve. Forces were applied at right angles to the crown of the tooth and recordings made from filaments dissected from the nerve central to the injury site. Data obtained from 41 units after nerve crush and 65 units after nerve section were compared with those from a series of control animals. 2. The range of directions to which each receptor was sensitive was significantly smaller after both nerve crush and nerve section. There were significantly more rapidly adapting units after both nerve crush (37%) and nerve section (34%) than in the controls (19%). 3. Force thresholds measured at three rates of application (20 N/s, 2 N/s, and 0.25 N/s) were significantly higher after nerve section but not after nerve crush. The maximum frequency of discharge was significantly reduced after both nerve crush and nerve section. 4. Bone was removed from over the roots of the teeth to localize receptors in the underlying periodontal ligament. Seventeen receptors were localized in the nerve crush group and 23 in the nerve section group, and their distribution appeared similar to that found in controls. The conduction velocities of these units were significantly reduced after nerve section but not after nerve crush. One unit in the nerve section group appeared to have branched and innervated receptors in two locations.

Animals↗
PubMedDate not supplied

A histological study on the effect of different periods of orthodontic force on the innervation and dimensions of the cat periodontal ligament.

Using light microscopy, the numbers of myelinated axons in the periodontal ligament of the cat mandibular canine were counted after orthodontic forces had been applied for either 3 days or 12 weeks, and also 8 weeks after removal of a force that had been applied for the previous 12 weeks. After 3 days no significant changes in axon number were recorded, but after 12 weeks there were significantly fewer myelinated axons in the periodontal ligament of the experimental teeth than in the control teeth. This reduction was not reversed after an 8 week recovery period. The width of the ligament was measured in an attempt to correlate regions of nerve fibre degeneration with areas of compression or tension, and the tooth root circumference was measured to assess the extent of any root resorption. It appeared that axon degeneration occurred both in areas of compression and tension. Root resorption had occurred after 12 weeks of applied force and there was no significant change after the 8 week recovery period. These findings support the view that nerve injury occurs as a result of orthodontic force and may possibly be permanent.

Animals↗