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Biomedical subjects

R Orchardson

Publications and source records attributed to R Orchardson.

At least 37 records · Page 2Linked to original sources
PubMed1993

Pilot clinical study of a fluoride resin and conditioning paste for desensitising dentine.

The clinical trial was carried out on 34 'hypersensitive' teeth in 10 subjects. Dentine sensitivity was measured as the pain perception thresholds to controlled air and probe stimuli. In each subject, pairs of teeth of comparable initial sensitivity were randomly assigned to a test (T) or control (C) treatment. All teeth were cleaned and a conditioning paste applied. Group T was treated with a topically-applied light-cured resin; Group C received a placebo, sham light-cured. Air sensitivity was remeasured after treatment, and the procedures were repeated after 1, 2, and 3 weeks. When comparing air thresholds before and after treatment at each visit, the test agent caused significantly greater reduction in sensitivity than the control. The median increase in air threshold in the test group was 2.5 s at visit no. 1, 1.3 s at visit no. 2 and 0.8 s at visit no. 3. Comparisons of the initial thresholds at each visit showed no significant long-term changes in sensitivity in either group.

Administration, Topical↗
PubMed1993

The effect of an electronic analgesia device on dental pain thresholds.

The effect of UltraCalm, an electronic dental analgesia (EDA) device, on dental pain thresholds was studied in 32 volunteers. For each subject, two initial baseline measurements of dental pain thresholds were made using an electric pulp tester. Pain thresholds were then measured during EDA with either UltraCalm or an inactive (placebo) device. No significant differences were found between the first and second baseline threshold measurements nor between the pain thresholds measured during the application of the UltraCalm and placebo devices. The mean baseline pain threshold was significantly lower than the threshold measured during application of the placebo device, but was not significantly different from the threshold during application of UltraCalm. it is concluded that UltraCalm has no consistent effect in altering dental pain thresholds.

Anesthesia, Dental↗
PubMed1988

Comparison of the human perception of hole size by the tongue and the fingers.

Thirty blindfolded subjects assessed the size of holes (2.4-19.1 mm dia) that were presented to the tongue by using their fingers to select a matching hole from a comparator series of 38 holes (1.6-25.4 mm dia). Subjects consistently overestimated the size of holes less than 10 mm, but there was little disparity for holes greater 14 mm in diameter. The relationship between the size of hole presented to the tongue and that judged by the fingers to be of equal size was not linear across the range tested. The illusion, expressed as the ratio of apparent size to real size, could be described as an hyperbolic function of stimulus size.

Adolescent↗
PubMed1987

Thresholds of hypersensitive teeth to 2 forms of controlled stimulation.

2 new methods are described for measuring the sensitivity of dentine to mechanical (probe) and cold-air stimulation. The methods are suitable for clinical use and could be used in the evaluation of desensitising treatments. In addition to qualitative differences in the pattern of sensitivity of teeth to these stimuli, considerable variation was observed in the distribution of pain thresholds to probe and air stimulation. Thresholds were not significantly affected by the age or sex of the subjects, but mean thresholds of teeth sensitive to only one stimulus were significantly greater than thresholds of teeth sensitive to both stimuli; these differences were most marked in female subjects. Factors such as the qualitative differences in sensitivity to various stimuli and quantitative differences in the degree of sensitivity to the stimuli require to be considered in clinical evaluation of desensitizing treatments.

Adolescent↗
PubMed1986

Relationship between mouth-opening force and facial skeletal dimensions in human females.

Maximum (MOF) and average (AOF) isometric mouth-opening forces were measured with an extra-oral gnathodynamometer in 34 females. Mean MOF and AOF with the teeth in centric relation were respectively 99.6 +/- 22.2 and 89.0 +/- 19.4 N with significant relationships between both MOF and AOF and body mass. Analysis of cephalometric measurements from 22 of the subjects revealed significant relationships between opening force (OF) and certain facial dimensions. In particular, larger OF were associated with features characteristic of an angular facial profile, viz long mandibular base, short mandibular body, large gonial angle and large angle NS-ML.

Adolescent↗
PubMed1978

The generation of nerve impulses in mammalian axons by changing the concentrations of the normal constituents of extracellular fluid.

1. Experiments have been performed to determine what changes in normal constituents of extracellular fluid are necessary to generate action potentials in mammalian axons. 2. Single and multifibre preparations of rat spinal roots were tested with Krebs solutions in which Na+, K+, Ca2+, Mg2+, pH, PCO2 or osmotic pressure were varied. 3. [Ca2+] below 1.0 mM produced impulses in all preparations. Lowering [Mg2+] did not generate any impulses but did enhance the response to low [Ca2+]. 4. Increasing [Na+] or [K+] caused excitation in some of the multifibres; increased [Na+] evoked 'off' responses in two single fibre preparations. The response to low [Ca2+] was enhanced by increasing [Na+] and depressed by increasing [K+]. 5. Increasing the osmotic pressure (with glucose) did not generate impulses and depressed the response to low [Ca2+]. 6. Changing the pH of Krebs solution did not generate impulses, but modified the response to other stimuli. The response to low [Ca2+] was increased as pH increased from pH 7.4 to 8.2, and decreased with pH in the range pH 7.4--6.2. 7. Altering pCO2 did not have any effect on the responses to low [Ca2+] unless pH also changed.

Action Potentials↗
PubMedDate not supplied

Effects of pulsed Nd:YAG laser radiation on action potential conduction in nerve fibres inside teeth in vitro.

OBJECTIVE: This study aimed to simulate the effects of lasing dentine on pulpal nerve function. METHODS: Rat spinal nerve roots were threaded through the prepared pulp canal of a 10 mm long tooth root segment which was mounted in a perspex bath. The protruding ends of the nerve were placed on platinum wire electrodes used to elicit and to record compound nerve action potentials (CAPs). Laser energy (average power = 0.3-3.0 W) was applied to the surface of the root segment using a pulsed Nd:YAG dental laser (dLase 300). RESULTS: With the laser probe tip placed in static contact with the tooth surface, the nerve CAP was irreversibly abolished within 60 s of lasing at 1.0-3.0 W power. When the laser tip was moved to and fro over the root surface in a scanning mode, similar levels of radiation produced less marked effects. In the latter mode, CAP attenuation increased with increasing power and duration of lasing. After 60 s lasing at 0.3 W, the CAP size was 95% (+/- 5, S.D.) of the prelasing controls value; with 2.0 W the CAP was reduced to 54% (+/- 33). The CAP recovered to 90% of control levels after lasing at powers up to 1.5 W, but reached only 72% of control values after lasing at 2.0 W power. CONCLUSIONS: Laser radiation applied to dentine caused a dose-dependent block of action potential conduction in nerve fibres in the underlying pulp chamber.

Action Potentials↗