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Biomedical subjects

J E Dyson

Publications and source records attributed to J E Dyson.

At least 19 recordsLinked to original sources
PubMed2006

ART and conventional root restorations in elders after 12 months.

Successful use of atraumatic restorative treatment (ART) in children has been reported, but little information is available regarding its use in older adults. The hypothesis of this study was that survival rates of root restorations placed by both ART and the conventional technique were similar. Root-surface caries lesions in 103 institutionalized elders in Hong Kong were treated randomly by either: (1) the conventional approach-caries removed by dental burs, and the cavity filled with light-cured resin-modified glass ionomer; or (2) the ART approach-caries removed by hand instruments, and the cavity filled with chemically cured high-strength glass ionomer. In total, 84 conventional and 78 ART restorations were placed. After 12 months, 63 conventional and 59 ART restorations were reviewed, and the respective 12-month survival rates were 91.7% and 87.0% (p > 0.05). It is concluded that the survival rates of both types of root restorations were high and similar.

Age Factors↗
PubMed2005

Discharge of lubricant from air turbine handpieces.

OBJECTIVE: To demonstrate and quantify the discharge of lubricating oil from high-speed air turbine handpieces whilst running. MATERIALS AND METHODS: Dye-marked oil (Kavospray, KaVo) was used to lubricate four handpieces (Quiet-Air, Midwest) and the air discharged from around the lower bearing was directed at the moving chart paper on a recorder whilst running for 40 minutes. Secondly, seven new handpieces (Quiet-Air, 300SE, Midwest; Topair 796, Topair 795, W+H; VIP-Sigma, Pana-air, NSK; Lares, Lares Research) were cleaned, weighed and then lubricated with unmarked oil (Kavospray, KaVo). Oil discharge was determined gravimetrically over runs of 240 minutes. Data were fitted to the logistic dose response function. RESULT: The dye-marked oil tests showed that oil was discharged for at least 40 minutes in the direction of the bur. The gravimetric tests showed that oil continued to be discharged up to at least 240 minutes, and that the usual practice of removing excess lubricant by running for 1-2 minutes was ineffective in preventing cut-surface contamination. SIGNIFICANCE: Bonding procedures in dentistry may be jeopardised by oil contamination from handpiece lubricants. Decontamination with a detergent is suggested as a means of ensuring effective adhesive dentistry.

Air Pollution, Indoor↗
PubMed2002

Bacterial and yeast flora of root surface caries in elderly, ethnic Chinese.

OBJECTIVES: Root caries is emerging as a significant problem in the middle aged and elderly. As little data is available on the microbiology of root caries in Chinese cohorts, we evaluated 30 such lesions in elderly, institutionalized, ethnic Chinese. METHODS: Samples of carious dentine were aseptically taken from root caries lesions of 18 subjects (five males and 13 females, mean age 79.67 +/- 8.57). The cultivable bacteria, both aerobic and anaerobic, were isolated and identified using standard methods and commercial identification kits. The yeasts were isolated on Sabouraud's agar and identified using the API system. RESULTS: The main findings were: (1) of the total isolates, 91.09% were Gram-positive and 8.91% were Gram-negative microorganisms; (2) the proportions of cocci and rods were 36.68 and 63.31%, respectively; (3) the predominant groups of organisms isolated were Streptococcus spp., Lactobacillus spp., Staphylococcus spp. and Actinomyces spp. with isolation frequencies of 100, 90.00, 73.33 and 63.33%, respectively; (4) the isolation frequency of yeasts belonging to Candida spp. (63.33%) was notably high although the proportion of yeasts within each sample was low (0.01%). Candida dubliniensis, a newly identified yeast species particularly prevalent in HIV infection, comprised 14.29% of yeasts. CONCLUSIONS: This study provides baseline information on the microbiologic features of root caries in the elderly, ethnic Chinese. Whilst our data on the most predominant bacteria isolated in root caries concur with those from other regions of the world the isolation of C. dubliniensis from these lesions has not been documented before.

Actinomyces↗
PubMed1999

Flow and free running speed characterization of dental air turbine handpieces.

OBJECTIVES: Dental air turbine handpieces have been widely used in clinical dentistry for over 30 years, yet little work has been reported on their performance. A few studies have been concerned with measurement of speed (i.e. rotation rate), torque and power performance of these devices, but neither investigations of functional relationships between controlling variables nor theory dealing specifically with this class of turbine have been reported. This has hindered the development of satisfactory methods of handpiece specification and of testing dental rotary cutting tools. It was the intention of the present work to remedy that deficiency. METHODS: Measurements of pressure, temperature, gas flow rate and rotation rate were made with improved accuracy and precision for 14 ball bearing turbine handpieces on several gases. Functional relationships between gas properties, supply pressure, flow rate, turbine design factors and free running speed were identified and equations describing these aspects of behaviour of this class of turbine developed. RESULTS: The rotor radius, through peripheral Mach number, was found to be a major determinant of speed performance. In addition, gas flow was found to be an important limiting factor through the effect of choke. CONCLUSIONS: Each dental handpiece can be treated as a simple orifice of a characteristic cross-sectional area. Free running speed can be explained in terms of gas properties and pressure, with allowance for a design-specific performance coefficient.

Air↗
PubMed1999

Torque, power and efficiency characterization of dental air turbine handpieces.

OBJECTIVES: In a previous paper the flow and free running speed characteristics of dental air turbine handpieces were discussed. The present work was to continue the analysis and characterization of these handpieces by addressing the issues of torque, power generation, efficiency and the specification of figures of merit to aid comparative testing and selection. METHODS: Using the principle of the rope brake, torque was determined from stall to free running at a variety of supply pressures for fourteen models of handpiece. Using previous results for air flow rate and free running speed, power and efficiency were calculated. RESULTS: Stall torque was demonstrated to depend on rotor position. Dynamic torque was found to closely approach the expected linear relationship over the range from stall to free running. Several figures of merit (performance indices) were identified which might be used for routine rating and specification of handpieces. CONCLUSIONS: Standardized testing can now be performed and effective figures of merit derived to characterize the behaviour of dental air turbine handpieces.

Algorithms↗
PubMed1997

A laboratory evaluation of two brands of disposable air turbine handpiece.

OBJECTIVE: To report on the essential performance characteristics of two brands of disposable air turbine handpiece and on aspects of their safety and convenience for clinical use. MATERIALS AND METHODS: Oralsafe and Feathertouch disposable handpieces were characterised using a variety of techniques in respect of the following: turbine rotor radius, equivalent orifice radius, stall torque coefficient, pressure effectiveness, power index, efficiency index, sound level and instrument retention force. RESULTS: Free-running speed versus pressure curves for many of the disposable handpieces showed marked deviations from the expected smooth form. Considerable variation between examples of each type was found in most measured values. Evidence of eccentric rotors and high bearing friction was not found. CONCLUSIONS: Both brands of disposable handpiece had a number of problems: poor performance, vibration, excessive noise, variability of behaviour, poor bearings. Use of these devices is difficult to recommend. Improvement in design seems necessary.

Air Pressure↗
PubMed1995

Dental air turbine handpiece performance testing.

Air turbine handpieces are expected to continue to be widely used as the main means of carrying out dental cutting work and scope exists for further design improvements. An understanding of the theoretical principles governing the performance of these devices seems essential for the systematic development of better handpiece designs and methods of specification. Furthermore, for experimental work on cutting behaviour with air turbine equipment, this knowledge is required for appropriate characterization of the performance of the particular handpiece used with respect to actual rates of energy disposition. The literature relating to air turbine handpiece performance is critically reviewed to assess currently available methods of measuring important variables such as speed, torque, and power. In this, consideration is given to the current state of knowledge of the influence on these variables of air pressure, flow and turbine design features. It is apparent that, although various measurement methods have been described and data for individual handpieces published, no attempt has yet been made to explore the functional relationships that exist between the variables. It is concluded that there is a need to identify the factors influencing turbine performance, to develop measurement systems which would provide adequate accuracy and precision and then to investigate the functional relationships between these relevant variables.

Air↗
PubMed1995

The present status of dental rotary cutting performance tests.

Appropriate methods of assessing the cutting ability of handpiece and rotary cutting instrument combinations are needed for research into the processes involved in dental cutting. They are also required for the development of improved devices and recommendations on operation as well as for equipment specification and standards testing. In reviewing the literature on dental rotary cutting performance testing to evaluate available methods, the factors which may influence clinical cutting behaviour are identified as those related to characteristics of the operator, handpiece, rotary cutting instrument, coolant/lubricant used and workpiece material. Existing industrial cutting theory is of limited help in understanding dental cutting in view of the differences between the control of relevant variables in the two cases. Consideration is given to the ways in which the important variables have (or have not) been controlled in past studies of dental cutting and thus the clinical relevance of available methods evaluated. Serious problems such as the lack of suitable test workpiece materials, as well as deficiencies in current knowledge of operator behaviour, handpiece characteristics and effects of coolant/lubricant application are noted. It is concluded that before improved, clinically relevant tests can be developed, further fundamental research in these areas is essential and that until this is done, further work under arbitrary experimental conditions would be of little value.

Animals↗
PubMed1993

Aspects of the design of modern dental air turbine handpieces.

Air turbine handpieces are manufactured with a wide range of alternative design features which may influence their suitability for particular clinical procedures. In this article a general account of these features is presented and their advantages and disadvantages are discussed. Some deficiencies in current methods of stating equipment specifications are reported and suggested improvements are given. Where appropriate, general recommendations are made regarding handpiece selection for clinical practice.

Air Pressure↗
PubMed1993

The development of the dental high-speed air turbine handpiece. Part 1.

The high-speed air turbine handpiece is currently used for most dental cutting procedures and has been in widespread use for more than thirty years. Although reports of its historical background have been previously published these have not dealt with all relevant developments and some inconsistencies exist. The history of the development of turbines and their application in dental cutting systems from the late 19th century to the present day is now reviewed. An historical account of the recognition of benefits that may accrue from rotary cutting at increased speeds is given and the various attempts that have been made to design equipment capable of high speeds are discussed. Consideration is given to the development of non-rotary cutting devices, as is the failure of these adequately to replace the air turbine handpiece for routine work. It is concluded that the air turbine handpiece will continue to hold a leading position in the field for some years to come but that future improvements would be facilitated by the development of an understanding of the theoretical aspects of its behaviour.

Dental High-Speed Equipment↗
PubMed1992

The effect of sodium butyrate on the growth characteristics of human cervix tumour cells.

Sodium butyrate has been shown to affect cell proliferation, and, at concentrations above approximately 0.5 mM, to cause cell death in some tumour cell lines. When combined with cytotoxic drugs increase in chemosensitivity has been observed. We are presently carrying out a study of the combined effects of sodium butyrate and cytotoxic drugs on cultured cervix tumour cells. To provide a baseline for this study we have carried out a systematic investigation of the effects of sodium butyrate alone on the growth characteristics of cervix tumour cells cultured as multicell spheroids. This has shown that concentrations of n-butyrate of 0.005 mM to 0.50 mM decrease cell proliferation without inducing cell death, the effect increasing with increasing concentration. Butyrate concentrations greater than 0.50 mM cause cell death after a period of 5 to 15 days exposure, dependent on concentration. Concentrations of 0.010 mM and above cause fragmentation of, and increased cell shedding from, multicell spheroids, suggesting an effect on the cell surface. Concentrations of butyrate greater than 0.10 mM cause a considerable increase in the synthesis of cytokeratin, as shown by reaction with cytokeratin antibody. Correlated with this is a marked increase in cell size, concentrations of butyrate of 2.0 or 3.0 mM leading to an approximate doubling of cell diameter, followed by cell disintegration. The effects of butyrate less than 0.25 mM are readily reversible. At concentrations greater than 0.25 mM the effects are reversible up to a limit of about 7 to 20 days depending on concentration, even when cytokeratin synthesis has been induced.

Butyrates↗
PubMed1990

Characterization of six textile dyes as fluorescent stains for flow cytometry.

Few fluorescent stains specific for cell constituents other than DNA are available. To assess their potential use as fluorescent stains for flow cytometry, the cell staining specificity of 55 compounds, originally synthesized for use as textile dyes and fluorescent brighteners, was explored and their excitation and emission wavebands determined. From these, six dyes were chosen for more detailed analysis. All six are vital stains, with excitation wavelengths allowing their use with an argon ion laser, and specific for a range of cell structures including mitochondria, Golgi bodies, lipid droplets, nuclear membrane, and endoplasmic reticulum. Concentrations as low as 0.01-0.25 microM were found to be adequate for most purposes, and high background fluorescence was not a problem. Their specificity allows differentiation between non-cycling and cycling cells. The properties of two of the stains allows their combination with propidium iodide or ethidium bromide for simultaneous determination of DNA content profiles. Being vital stains, usable at very low concentrations, and specific for a range of cell organelles, these six stains may be of considerable utility in flow cytofluorometry. We suggest that other textile dyes may be of use in flow cytofluorometry, or that their structures may form a starting point for the synthesis of further fluorescent stains of enhanced specificity.

Animals↗
PubMed1989

Fluorescein isothiocyanate staining intensity as a probe of hyperthermia-induced changes in chromatin conformation.

In a previous report we presented evidence for large increases in fluorescein isothiocyanate (FITC) fluorescent intensity caused by hyperthermia which were not associated with synthesis of heat-shock proteins. We have now refined and considerably extended the measurements of increases in FITC fluorescent intensity caused by hyperthermia within the range 41.0 degrees C to 50.0 degrees C, and associated these with the extent of cell death caused by the hyperthermia. It appears that cell death ensues when the FITC fluorescent intensity has not returned to its baseline value within the time of one cell cycle. If thermotolerance is induced, there is a concomitant reduction in the increase in FITC staining intensity and the extent of cell death. When hyperthermia is followed by acid extraction, an additional increase in FITC staining intensity (above that due to hyperthermia alone) is observed, indicating separate sites of action on basic nuclear proteins. Hyperthermia and acid extraction have related effects on the relationship between FITC and propidium iodide staining. Hyperthermia-induced increases in FITC staining intensity are almost completely reversed by 6.7 mM formaldehyde with a marginal effect on the control FITC staining at this formaldehyde concentration. We suggest that hyperthermia causes extensive dissociation of basic protein-protein binding within nuclear chromatin, and that this may be a contributory cause of hyperthermia-induced cell death.

Cell Line↗
PubMed1989

Use of a laser diffraction particle sizer for the measurement of mean diameter of multicellular tumor spheroids.

Increasing use is being made of tumor cell lines cultured as cell aggregates (generally referred to as multicellular spheroids) in in vitro radiosensitivity and/or chemosensitivity tests. Conventional procedures for the determination of mean spheroid diameters for the construction of growth delay curves employ a microscope-image analyzer. However, this approach can prove excessively time consuming when large numbers of samples have to be measured. We have, therefore, been exploring the use of a Laser Diffraction Particle Sizer, the Malvern 2600 long bench model, for the measurement of mean spheroid diameter and size distribution. We report here a direct comparison between measurements carried out by the instrument and under the microscope. Also a comparison of growth curves for six cell lines constructed from measurements by the microscope and by the instrument. A number of factors that might affect the accuracy of spheroid diameter measurement by the instrument have been investigated: The effect of stirring to maintain the spheroids in suspension during measurement. Sampling error due to removal of a series of spheroid samples from culture flasks for measurement. Optimum numbers of scans to be carried out by the instrument to reach a constant value for mean diameter, and minimum SE of the mean.

Animals↗
PubMed1988

Primary malignant melanoma of the uterine cervix.

A case of primary malignant melanoma of the uterine cervix is presented. It demonstrates the histological findings at both light and electron microscopy, the unusual flow cytofluorometric analysis, the clinical response to irradiation and the rapid dissemination of the tumour.

Female↗
PubMed1988

Calibration of a flow cytometer against a microphotometer for morphologic cell identification.

The calibration of a flow cytometer against a microphotometer, to allow the correlation of cell morphology with fluorescence intensity, is described. Using three human lymphoblastoid cell lines, the photomultiplier amplification of the microphotometer and the flow cytometer that gave optimum linearity between fluorescence intensity and DNA content for the two instruments was established. Thereafter, at these settings, there was satisfactory linear agreement between the fluorescence intensity profiles, as measured by the flow cytometer and the microphotometer, of stained cell populations. Day-to-day variation was also minimal, and it was demonstrated that the application of this procedure can provide an alternative to the employment of the sorting facility of a flow cytometer for the morphologic identification of cell subpopulations during flow cytometric analysis.

Cell Separation↗