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Biomedical subjects

B C Webb

Publications and source records attributed to B C Webb.

12 recordsLinked to original sources
PubMed1998

Effectiveness of two methods of denture sterilization.

Species of Candida and in particular Candida albicans may be involved in the aetiology of denture stomatitis. Studies have shown that Candida and other oral micro-organisms including Streptococcus gordonii are associated with denture plaque; hence denture hygiene is an important factor in the prevention and treatment of the disease. The aim of this investigation was to test in vitro the efficacy of two methods of denture sterilization: (1) microwave irradiation and (2) sodium hypochlorite soak. Twenty upper acrylic dentures were prepared for microbiological assay; 10 were inoculated with C. albicans H1 and 10 with S. gordonii LGR2. Within each group, five dentures were tested in a domestic microwave oven for optimal exposure time and temperature to ensure sterilization; the five control dentures were not microwaved. Microbiological analyses showed that the inoculated dentures became sterile after six min of irradiation at medium setting (2450 MHz, 350 W). Damage to the microorganisms after microwave irradiation was clearly visible by scanning electron microscopy (SEM). Following the same protocol as above, experimental dentures were soaked for 8 h in either 0.02%, or 0.0125% sodium hypochlorite solution and control dentures soaked in distilled water. Microbiological analyses showed that the experimental dentures inoculated with C. albicans H1 became sterile. By contrast, those inoculated with S. gordonii LGR2 did not become sterile, and the SEM procedures confirmed these findings. The results of this study indicate that microwaving may be a more effective method of denture sterilization than denture soaking in sodium hypochlorite. However, compared with microwaving, hypochlorite reduces the levels of residual non-viable micro-organisms attached to the denture surface.

Acrylic Resins↗
PubMed1998

Interactions between Candida species and platelets.

Candida spp. are able to cause disseminated disease in immunocompromised patients. This study examined the interactions of Candida spp. with platelets, complement and polymorphonuclear leucocytes (PMNLs). With the exception of C. albicans, all other Candida spp., including a C. albicans strain previously classified as C. stellatoidia, aggregated human platelets at a ratio of yeast cells: platelets of 1:80. Usually, those species and strains that aggregated platelets were either killed or prevented from growing in platelet-rich plasma indicating that the aggregation released microbicidal or microbistatic substances that were active against Candida spp. All Candida spp. were resistant to attack by complement in 50% serum. However, all species activated complement as determined by the presence of C3 fragments on their surface, in particular a 195-kDa fragment corresponding to C3c, two fragments at 67 and 40 kDa corresponding to iC3b, and a 33-kDa fragment corresponding to C3d. When strains were tested for their ability to stimulate the release of pro-inflammatory substances from platelets and PMNLs, it was found that most strains stimulated PMNLs to release interleukin(IL)-8 but not IL-1beta or leucotriene B4. The ability of C. albicans to evade complement-mediated killing and not to aggregate platelets may contribute to the survival of this species in the blood during vascular infections.

Anticoagulants↗
PubMed1998

Candida-associated denture stomatitis. Aetiology and management: a review. Part 1. Factors influencing distribution of Candida species in the oral cavity.

Candida species are yeasts and within the oral cavity, Candida albicans is the most frequently isolated. There is clear evidence that C. albicans adheres to oral surfaces including acrylic dentures and mucosa. The mechanisms of attachment differ, with candidal adhesion to inert surfaces under the control of hydrophobic and electrostatic forces and adhesion to mucosa dependent on a number of complex ligand-recognition systems. Other factors within the oral environment such as saliva, pH, bacteria and hyphal formation have been shown to influence adhesion of candida species to surfaces in the mouth.

Acrylic Resins↗
PubMed1998

Candida-associated denture stomatitis. Aetiology and management: a review. Part 2. Oral diseases caused by Candida species.

Certain systemic conditions and/or defects in the immune system may predispose the host to oral candidal infection and the commonest form of oral candidosis is candida-associated denture stomatitis. Until recently there has been controversy concerning the aetiology of the disease. Although some earlier investigators linked denture stomatitis with trauma or bacterial infection, others had isolated Candida albicans from the mouths of patients with the condition. Current studies indicate that denture stomatitis lesions are associated with the detection of candida species while other factors such as denture hygiene, trauma, systemic diseases and deficiencies of the immune system may be involved.

Bacterial Infections↗
PubMed1998

Candida-associated denture stomatitis. Aetiology and management: a review. Part 3. Treatment of oral candidosis.

Treatment of oral candidosis with topical antifungal agents such as nystatin and amphotericin B is effective initially. However, medication can produce side effects in some patients and when therapy is stopped the condition can recur. Alternative treatment involving the use of antiseptics and disinfecting agents has been shown to play an important role in the control of dental plaque. The use of sodium hypochlorite as an overnight denture soak has been shown to eliminate denture plaque and recent investigations have demonstrated that microwave irradiation of dentures at a specified setting and exposure time is bactericidal and candidacidal.

Anti-Infective Agents, Local↗
PubMed1995

The effect of sodium hypochlorite on potential pathogenic traits of Candida albicans and other Candida species.

Strains of Candida albicans, Candida krusei, Candida kefyr, Candida tropicalis, Candida parapsilosis and Candida guilliermondii were grown in the presence or absence of concentrations of sodium hypochlorite below the minimal inhibitory concentration and tested for a range of characteristics that may be associated with pathogenicity. Sodium hypochlorite is used routinely in hospitals in Australia for disinfection procedures, and these experiments were designed to assess the efficacy of hypochlorite as a sterilizing agent for acrylic dentures. Candida showed varying abilities to adhere to surfaces that may be present in the oral cavity. Sodium hypochlorite reduced the adhesion of all C. albicans strains and most other Candida species to both polystyrene and buccal epithelial cells. A biofilm of Streptococcus gordonii reduced the adhesion of most C. albicans strains and most other Candida species to polystyrene. However, Candida species were able to coaggregate with S. gordonii in suspension, with one strain of C. albicans, GDH 2346, showing greater coaggregating ability than the other strains or species. Sodium hypochlorite increased coaggregation of all C. albicans strains and most other Candida species. Examination of cell wall proteins from strains of C. albicans and a strain of C. parapsilosis showed that growth in hypochlorite increased the amount of protein in some existing bands and, in one strain of C. albicans, increased the number of detectable protein bands ranging from 56 to 26 kDa. Only 4 strains of C. albicans were able to produce hyphae, and 3 of these same strains and C. parapsilosis were able to produce proteinase. Hypochlorite increased the rate of blastospore to hyphal transition but had no effect on proteinase production or activity. It is concluded that hypochlorite at a concentration below the minimal inhibitory concentration may function as an anti-adhesin for Candida species but may not affect their more pathogenic characteristics.

Acrylic Resins↗
PubMed1995

Microwaving of acrylic resin dentures.

Denture hygiene is an important factor in the treatment of denture stomatitis. Sterilization of dentures by microwaves has been recommended, but using specialized equipment not available to the average person. This study tests the effect of microwaving on the dimensional stability of dentures (in an unmodified domestic microwave oven). After microwaving (10 mins at 604 W) some measurements showed significant contraction or expansion but reduced exposure (6 mins at 331 W) caused much smaller changes. The dimensional changes are inexplicable but at lower radiation are considered to be harmless.

Absorption↗
PubMedDate not supplied

A validated calibration method for hydrogen peroxide vapour sensors.

A method of calibrating hydrogen peroxide vapour sensors is described which is based on the well-defined saturated vapour pressures of hydrogen peroxide over its aqueous solutions at fixed temperatures. The calibration technique was developed for use with amperometric gas sensors but could be applied to other sensor types. The method can be used over the entire range of vapour pressures that are likely to be of practical interest in the context of isolator sterilisation and has been reliably validated by quantitative volumetric analysis. The method depends not only on the well understood underlying principles but also on the solution of practical problems associated with ensuring full saturation of the carrier gas stream and, simultaneously, the elimination of aerosol droplets which might otherwise interfere with the calibration.

Algorithms↗