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Biomedical subjects

D R Radford

Publications and source records attributed to D R Radford.

30 records · Page 2Linked to original sources
PubMed1994

A scanning electronmicroscopy investigation of the structure of colonies of different morphologies produced by phenotypic switching of Candida albicans.

Variant colony formation by Candida albicans has been described and the phenomenon of phenotypic switching has been studied extensively. Whereas the microstructure of non-variant colonies has been investigated by scanning electronmicroscopy (SEM), the relationship between switched variant colonies and microstructure has not been described. The object of this study was to investigate and compared by SEM the microstructure of the normal colony type and five common variant colony types of C. albicans and to determine whether a pattern of dimorphic growth could account for the characteristic colony morphologies. A general relationship between colony type and structure was observed; smooth colonies consisted entirely of blastospores whereas regular, irregular-wrinkled and semi-rough colonies consisted of different proportion of true hyphae and blastospores. Regular extreme-jagged shaped colonies consisted of an almost pure culture of pseudohyphae, and colonies producing aerial hyphae were composed of pseudo- and true hyphae, as well as blastospores. These results show a clear relationship between colony morphology and development of particular cell types.

Candida albicans↗
PubMed1993

A SEM study of denture plaque and oral mucosa of denture-related stomatitis.

The aim of this study was to compare the morphology of denture plaque and adjacent palatal mucosa in five subjects with denture-related stomatitis and a control group of five healthy subjects. Scanning electron microscope examination of copper plate replicas, which preliminary studies established were superior to epoxy resin replicas, showed that there were no consistent differences between the morphology of denture plaque and adjacent mucosa in the denture-related stomatitis group and control group. In each, the surface of the denture plaque was composed predominantly of coccoid- and rod-shaped bacteria with only some yeast cells. The mucosa was largely devoid of microorganisms and individual epithelial cells were shedding from its surface.

Bacteria↗
PubMed1993

Copper plate replica SEM of developing dental plaque in monkeys (Macaca fascicularis).

The aim of the study was to examine the development of dental plaque in macaque monkeys (Macaca fascicularis). Copper plate replicas were constructed from impressions of the labial surface of one of the upper central incisor teeth after tooth cleaning and when plaque had accumulated for 12, 24 and 48 h in each of five animals. Scanning electron microscope examination of the replicas showed that bacteria were present on the tooth surface as scattered individual cells, which after 24 h had formed a continuous layer. Both coccoid and filamentous bacteria were visible in 48-hour-old plaque. Such a rapid accumulation of potentially periodontopathic dental plaque emphasizes the importance of regular and meticulous oral hygiene.

Animals↗
PubMed1991

A two part hinged partial denture design for lower Kennedy Class 4 cases.

It is often difficult to provide patients who have lost lower anterior teeth with a retentive and aesthetic restoration, particularly if the molar and premolar teeth are lingually tilted. A two part hinged denture fully engaging all lingual undercuts for retention provides a useful extension to recognised partial denture design practice.

Denture Design↗
PubMedDate not supplied

The machining of cobalt-chromium alloy in partial denture construction.

PURPOSE: To investigate the performance of different rotary instruments when machining cobalt-chromium alloy. MATERIALS AND METHODS: One tungsten carbide bur, 1 diamond bur, and 2 aluminum oxide abrasive points (pink stones) of different diameter were used to machine cobalt-chromium alloy under standardized conditions. The rate of metal removal was determined and the resulting surfaces and bur wear were investigated using scanning electron microscopy and energy dispersive analysis. RESULTS: Although the larger diameter pink stone was shown to be the most efficient instrument, the tungsten carbide bur produced the smoothest surface. CONCLUSION: Because of its low cost and high cutting efficiency the pink stone is well suited for laboratory use. The tungsten carbide bur is the preferred instrument for clinical use.

Aluminum Oxide↗
PubMedDate not supplied

Effects of electrobrightening on the fit surface of cobalt-chromium RPD frameworks.

PURPOSE: The purpose of this study was to compare 3 different electrobrightening techniques and 3 electrolytic solutions in their effects upon the fit surface of cast cobalt-chromium frameworks. MATERIALS AND METHODS: Fifty cast cobalt-chromium frameworks, which were subsequently divided into batches of 10, were prepared according to a standard protocol. Three electrobrightening techniques were tested initially using a single brand of electrolyte (Croform) and a batch of 10 frameworks per technique. The loss of metal by weight was determined from the fit surface of each casting. The least corrosive technique of these 3 was used again with 2 other brands of electrolyte (Nobilium and E501) in a repetition of the protocol. The fit surfaces of 8 random samples cut from each batch of electrobrightened castings were viewed by scanning electron microscope (SEM). RESULTS: Statistical analysis applying a one-way analysis of variance and Bonferroni's multiple comparison of means test demonstrated that one immersion of the framework for 10 minutes at 1 amp when used in conjunction with Nobilium electrolyte removed the least metal (P = 0.001). The SEM study suggested that the Nobilium electrolyte also produced the smoothest surface. CONCLUSION: Electrobrightening techniques affect the amount of metal removed, and the electrolytic solution used influences the resultant surface.

Analysis of Variance↗
PubMedDate not supplied

A variation in minor connector design for partial dentures.

Whenever possible, the minor connector of a removable partial denture is located in the interdental embrasure. Recent evidence suggests that gingival attachment loss is more probable on the proximal aspect, thus minor connectors located in embrasures cover susceptible sites. A rationale and design are presented for locating the minor connector on the lingual aspect of the abutment tooth rather than in the interproximal area.

Dental Abutments↗
PubMedDate not supplied

The surface of investments poured against different duplicating media.

Two phosphate-bonded investments that were poured into molds of a duplicating gel and a poly(vinyl siloxane) duplicating medium were examined for surface hardness. Untreated surfaces were also examined by the confocal microscope and the scanning electron microscope. The Brinell hardness of samples poured in poly(vinyl siloxane) was greater than that of the same investment poured in duplicating gel. Investments were hardest as set and were significantly softened by drying. Cast hardeners achieved some rehardening of the dried investment samples. Microscopic examination of the investment surfaces revealed greater irregularity of samples poured in duplicating gel than in poly(vinyl siloxane), particularly in one investment.

Agar↗
PubMedDate not supplied

Scanning electron microscopy and energy dispersive analysis of machined denture base surfaces.

To relate the characteristics of rotary instruments to the surfaces they produce, acrylic resin, Molloplast B, and Novus were investigated with energy dispersive analysis and scanning electron microscopy (secondary and backscatter images) before and after machining. The chemical composition of cutting instruments, material surfaces, and residues was identified. Machined debris embedded in Molloplast B after machining with the Molloplast stone was found to contain a mean lead content of 45%. High concentrations of barium sulphate were discovered on the arbor band-machined surface of Novus. These differences were related to clinically appropriate instrumentation, and, therefore, biocompatibility studies that intimately relate to the in vivo situation should be considered for new materials.

Dental Polishing↗
PubMedDate not supplied

Adherence of phenotypically switched Candida albicans to denture base materials.

PURPOSE: The purpose of this study was to investigate in vitro the levels of adhesion of phenotypically switched and nonswitched Candida albicans to the smooth and rough surfaces of heat-cured acrylic resin, Molloplast B, and Novus. MATERIALS AND METHODS: Nonswitched and switched cells of C. albicans 3153A were prepared and adhesion assays were performed. RESULTS: There was no difference in the level of adhesion of blastospores in their nonswitched or switched state. The adherence of hyphae to all three denture base materials was statistically significantly increased when in a switched form. There was greater adhesion to the two soft lining materials than to the acrylic resin. CONCLUSIONS: Rough surfaces promote adhesion. There was no significant difference in the adhesion of switched and nonswitched blastospores, but there was increased adhesion of hyphal cells.

Acrylic Resins↗