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Biomedical subjects

R M Davies

Publications and source records attributed to R M Davies.

At least 19 recordsLinked to original sources
PubMed1992

Rinses to control plaque and gingivitis.

The dental profession and the public have two different perceptions when it comes to oral hygiene. The profession has oral health as its main objective whereas the public is more concerned with personal cleanliness and social acceptability. Nevertheless the desired outcome is the same, namely to remove supragingival plaque. The concept of using a mouthrinse as an adjunct to brushing with a dentifrice is a sound one. In recent years there has been a rapid increase in the use of mouthrinses and this review considers the relative merits of those currently on the market. It is evident that some progress has been made in satisfying the priorities of the consumer and clinician.

Dental Plaque↗
PubMed1991

Students of midwifery: 'doing the obs' and other coping strategies.

The paper is based on qualitative research on the early experiences of student midwives in one school of midwifery. During their initial encounters the students go through a status passage from experienced nurse to novice midwife. Student diaries and ethnographic data were used to explore how students manage the transition and to document their coping strategies. In particular it is shown how, in response to the uncertainties of their new status, student midwives may revert to routinised nursing activities.

Adaptation, Psychological↗
PubMed1986

Specific absorption rate and tissue temperature in local hyperthermia.

Specific absorption rate (SAR) and tissue temperature were measured for a total of 83 treatments in 33 patients who received local hyperthermia treatment for cancer. The patients were grouped into three categories according to tumor size. Hyperthermia was induced by 13.56 MHz electromagnetic energy applied using capacitive coupling. A method is described for evaluating SAR from the tissue temperature traces at any time in the treatment when a step change is made in applied power. The method is possible only if the temperature traces are free from interference and the total power delivered to the patient is monitored. Mean values of SAR ranged from 4.6 to 89 W kg-1 depending on the treatment site. Satisfactory heating was achieved for superficial tumors, with temperatures greater than 42 degrees C being recorded in 69% of treatments. For axillary nodes only 4% of treatments exceeded 42 degrees C. For cervix tumors an idealized tumor model was used to estimate tumor temperature from the temperature and SAR measured in the adjacent normal tissue. From the model it appears necessary either to raise the systemic temperature to 40 degrees C or to increase the SAR by at least a factor of 4 to obtain a temperature of 42 degrees C in a typical tumor. Measurements of SAR and temperature are essential for feedback control of computer models which, in principle, could provide a complete distribution of temperature during a hyperthermia treatment. Furthermore, measured SAR provides a direct comparison of the power deposition from different treatment machines in a clinical environment. The data presented form a basis for comparison with the clinical use of other heating systems.

Absorption↗
PubMed1986

Association between HLA-A9 and rapidly progressive periodontitis.

HLA-A, B, C, DR antigen frequencies and Properdin factor B (Bf) allotypes were studied in a group of 44 patients with rapidly progressive periodontitis. HLA-A9 (A24) was the only antigen with a frequency statistically significantly different from the control population. An increased frequency of HLA-A9 was previously reported in periodontal diseases. Our results in a well characterised group of patients adds to the evidence that HLA-A9 plays a role in the susceptibility to severe periodontitis.

Complement Factor B↗
PubMed1986

Use of panoramic radiographs in general dental practice in England.

The rapid growth in the use of panoramic radiographs provoked this survey of the reasons why general dental practitioners in Avon take such views. Of the 193 dentists who responded, 42 (22%) took one or more panoramic radiographs during a specified week. A total of 195 patients, 8% of those x-rayed, had a panoramic radiograph taken either alone or in combination with other views. Panoramic radiographs were stated to have been taken primarily for the diagnosis of caries (48%) and surgical (24%), periodontal (20%), orthodontic (20%) and endodontic/apical assessment. These findings are discussed with respect to published guidelines on the use of panoramic radiographs and the teaching of radiology in dental schools.

Adolescent↗
PubMed1986

Reasons for taking radiographs in general dental practice.

This survey investigated the reasons why general dental practitioners take radiographs. 179 (54%) dentists responded and provided information for 2359 patients who were radiographed during a specified week. Of those patients aged less than 15 yr, 62% were radiographed primarily for orthodontic purposes and 22% for caries. In older age groups, caries was the predominant reason for taking radiographs but endodontic assessment assumed increasing importance with age and accounted for 37% of radiographs in patients aged more than 45 yr. Only 8% of patients were radiographed for periodontal reasons. These findings are discussed with respect to the changing pattern of disease and treatment provided in general dental practice.

Adolescent↗
PubMed1985

Jealousy: loss of relationship rewards, loss of self-esteem, depression, anxiety, and anger.

White's (1981) theory of romantic jealousy states that the loss (or anticipated loss) of a romantic partner to a rival causes two kinds of suffering: loss (or anticipated loss) of relationship rewards and loss (or anticipated loss) of self-esteem. Elaborating this theory, we proposed that loss of relationship rewards causes depression, whereas loss of self-esteem causes anxiety and anger. General support was found for White's theory and the elaborations, but not for the hypothesis that the loss of self-esteem causes anxiety. Anxiety may be a product of both loss of self-esteem and loss of relationship rewards.

Adaptation, Psychological↗
PubMed1985

Resistance in oral streptococci after repeated three-dose erythromycin prophylaxis.

Ten healthy volunteers, from whom no erythromycin-resistant oral streptococci could be isolated initially, received three doses of erythromycin stearate (1.0, 0.5 and 0.5 g) on two separate occasions with a one-week interval between them. After the second administration all volunteers yielded moderately resistant strains (MIC 1-4 mg/l) and four harboured highly resistant streptococci (MIC 16- greater than 256 mg; MBC 128- greater than 256 mg/l). Erythromycin-resistant strains persisted in eight of the volunteers at 23 weeks and in five of eight volunteers at 43 weeks. Species included Streptococcus sanguis, Str. mitior and unclassified streptococci, and dextran-positive strains were encountered. Erythromycin-resistant streptococci are thus readily selected by two administrations of the three-dose regimen. Until the time of emergence of the resistant strains is further clarified a full assessment of the antibiotic sensitivity of the flora of the gingival sulcus is advisable before erythromycin prophylaxis is repeated.

Drug Resistance, Microbial↗
PubMed1985

Resistance in oral streptococci after repetition of a single-dose amoxycillin prophylactic regimen.

Ten healthy volunteers received 3 g amoxycillin each week for up to four weeks. One volunteer carried streptococci resistant to amoxycillin in small numbers before the first dose was administered. After one administration of amoxycillin, this volunteer and one other yielded streptococci resistant to 1 mg/l amoxycillin on direct culture of dental plaque; after two administrations, resistant streptococci were detected in one further volunteer; and a total of six volunteers yielded resistant streptococci after the fourth week of amoxycillin administration. Repeated use of the single-dose prophylactic regimen encourages the emergence of streptococci considerably more resistant to amoxycillin than those generally encountered in the oral cavity, but the clinical significance of these results is uncertain as the peak serum concentrations of amoxycillin achieved after a 3 g oral dose for prophylaxis exceed the minimum bactericidal concentrations of amoxycillin for these strains.

Amoxicillin↗
PubMed1985

The removal of root surface deposits.

The importance of adequate root surface instrumentation has received increasing emphasis. The purpose of this study was to determine the extent to which root planning could produce surfaces free of stainable deposits. Initial laboratory investigations on extracted, periodontally involved roots demonstrated that after meticulous root preparation, totally non-stainable surfaces could be obtained. These surfaces were shown to consist of either thin cementum or dentine. The efficacy of instrumenting periodontally involved buccal root surfaces on the anterior teeth of 33 patients, undergoing routine periodontal flap surgery was then evaluated. Root surfaces were instrumented either before or after the reflection of surgical flaps. Remaining bacterial deposits were disclosed with a gentian violet solution and the root surfaces then photographed. Further root planing, disclosure and photography were then carried out. These photographic slides were analysed for stainable deposits on the root surfaces using an image analysis system, based on densitometric principles, to measure the areas of stainable root surface deposits. The findings revealed that root planning under direct vision at the time of surgery was more effective than blind instrumentation. However, in no instance was any root surface found to be completely free of stainable deposits.

Adolescent↗
PubMed1985

Radiographs taken for orthodontic purposes in general practice.

This paper deals with the orthodontic aspects of a wider survey undertaken to determine the use of radiographs in general dental practice in the county of Avon. During the sample week 218 patients had radiography for orthodontic purposes of whom 184 were below the age of 15 years. There were marked differences in the radiographs used by general practitioners and specialist orthodontists and the possible reasons for these differences are discussed.

Adolescent↗
PubMed1985

The use of bicomponent fabrics for bonding polypropylene sockets in prostheses.

A technique has been established for bonding polypropylene sockets to the structural components of prostheses based on the use of bicomponent knitted fabrics which adhere to the surface of polypropylene sockets during thermoforming. The strength of adhesion of fabric bonded polypropylene with polyester resin based microballoon for instance is increased by more than 10 times relative to uncoated polypropylene. This procedure has been approved by the United Kingdom Department of Health for incorporating polypropylene sockets in conventional, laminated plastic patellar tendon bearing (PTB) prostheses. The bonding technique described should find general application for bonding polypropylene during the manufacture of both prosthetic and orthotic devices.

Artificial Limbs↗
PubMed1985

The Rapidform process for automated thermoplastic socket production.

This paper describes the genesis of the Rapidform process and its pioneering place in the new developments leading to complete control of the processes of manufacture of prostheses. The materials and geometric considerations involved in the development of a double deformation process under microprocessor control are described. Stages in the development of the system show the advance from the initial application to modular below-knee prostheses through extensions to special suspension systems (supracondylar and suprapatellar) to Syme's and above-knee sockets. The clinical and laboratory results are summarized along with an account of the current aspects of the project, ie advanced clinical trials, testing and analysis. Setting the scene historically for the other computer based modules in this high technology approach to prosthetics, Rapidform has proven to be swift, accurate and economical in its operation. Also, in common with the rest of the suite of equipment, this socket production facility, despite its flexibility and technical sophistication, requires no special services beyond standard single phase mains electricity supply.

Amputation Stumps↗
PubMed1985

Rotational moulding in the production of prostheses.

This paper discusses the place of rotational moulding in the provision of prosthetic shanks and shank sections. It covers the selection of thermoplastic material, the moulding conditions and their automation in a machine process, and the development of a suitable range of moulds. Also covered is the question of interfacing between the moulded shank sections and other limb components, fatigue strength as tested to date and early results of patient field trials. The most developed of the possible prosthetic options available consists of a hollow tapered column having inserts at each end by which it is clamped through alignment couplings to the socket and foot respectively. For a below-knee application, the complete tapered column prosthesis weighs typically 1 kg. Static and fatigue testing of representative samples by the simultaneous application of compressive and bending loads to the maximum values specified by international standards exposed no failures by the time a million cycles had been reached. This method of fabrication has the merit of being capable of implementation locally on an "as required" basis. Additional advantages include the low cost of the mould tooling and the flexibility to mould a variety of shapes. Prosthetic feet are a possibility as are special shoes and orthotic parts. These may require other materials and experimentation is proceeding using structural and resilient foams.

Biomedical Engineering↗
PubMed1985

Thermoplastic alignment couplings for prostheses.

In the context of modern engineering practice, this paper describes the exploitation of thermoplastic materials for the provision of lightweight, low cost, corrosion free, alignment devices for lower limb prostheses. After setting out design requirements, four newly developed devices are described and discussed. These are respectively a four jack system, a serrated wedge system, a spherical alignment system and a serrated slider. The level of laboratory fatigue testing and experimental field performance is reported and examples are shown of the application of these systems to tapered column thermoplastic below-knee prostheses.

Biomedical Engineering↗
PubMed1979

Gingival bleeding in an experimental clinical trial design.

An experimental clinical trial design is described in which the onset of gingival bleeding was used as an indicator of early gingivitis. Twenty-nine dental students participated in a double-blind crossover trial utilising chlorhexidine as a known plaque inhibitor. The onset of gingival bleeding was assessed in three ways, one of which yielded a statistically significant difference in favour of the active mouthrinse (P = 0.02). The method has a role in screening agents believed to be active against gingivitis.

Adult↗