The Disinfection of Dental Impression Materials

Jennings, Kevin John (1994) The Disinfection of Dental Impression Materials. DDS thesis, University of Glasgow.

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Heightened awareness the importance of cross-infection control in dentistry has resulted in the publication of guide-lines by bodies such as the General Dental Council, the British Dental Association, and the American Dental Association, and, as such advice is regularly upgraded in the light of new information, there is a continuing need for clinical research in this area. Data, in the dental literature, on the contamination of impression materials by oral microorganisms, are limited, and the aim of the first part of this thesis was to assess microbial survival in impression moulds prepared from polysulphide, poly (vinyl siloxane) and alginate materials. The viability of five microbial species was tested over a five hour period. Rapid elimination of microorganisms was evident within moulds made from an alginate impregnated with sodium didecyldimethyl ammonium chloride (Blueprint Asept); a reduction in colonisation with time was less marked with conventional materials. In a further study of the disinfectant-containing alginate, high microbial concentrations were eliminated within 40 minutes, although varying susceptibility of different organisms, to this material, was evident. In a further in-vitro investigation, the persistence of microorganisms following contact with impression surfaces for three minutes, was examined. With Blueprint Asept, there was almost total elimination on initial sampling, and no microbial growth was detectable after five minutes. With the conventional materials, microbial survival varied from 68.5% to 80.5%, five hours after the contaminating inocula were discarded. The retention of microorganisms was dependant upon the material type; initial contamination of the conventional alginate was substantially greater than rubber base materials, and bacteria, which were virtually eliminated from rubber base materials after five hours, survived to varying degrees on conventional alginate (Kromopan). In an investigation of impressions from dentate patients, microbial growth on conventional alginate and rubber base specimens was evident, in some cases, five hours after impressions were recorded. Initial contamination levels of alginate considerably exceeded poly (vinyl siloxane), and there was a rapid reduction in the number of microorganisms on the rubber base materials in comparison with alginate (when considered as a percentage of initial microbial loading). No growth was apparent from Blueprint Asept impressions. With edentulous patients, again no growth was recorded from Blueprint impressions, but five hours after Kromopan impressions were made, substantial contamination was still evident. Comparison of Kromopan impressions from dentate and edentulous patients, showed slightly greater initial contamination from the dentate group. The thesis was developed by examination of the removal of microorganisms from different impression materials, and by comparison of three commonly used disinfectant agents. In order to compare the impression materials, microbial persistence on alginate, polysulphide, and poly (vinyl siloxane) materials, following the application of weak disinfectants, was examined. After removal of the contaminating inocula, impression surfaces were left as non-disinfected control specimens, or were disinfected with dilute aqueous solutions of chlorhexidine gluconate. Initial contamination of poly (vinyl siloxane) was minimal, there was a rapid reduction in the numbers of microorganisms on non-disinfected control specimens of this material, and there was no growth after application of disinfectant. In comparison, there was substantially more loading of polysulphide rubber on initial sampling, and the microorganisms persisted to a greater extent on control samples. Disinfection resulted in substantial reduction, although not total elimination, of contaminants. A heavy initial colonisation of alginate increased with time on control samples, and disinfection was only partially successful. For all three materials. initial colonisation with C albicans was less marked than with Ps aeruginosa. The persistence of microorganisms on alginate (Kromogel), following the application of one of three commercially available disinfectants (2% glutaraldehyde, 0.2% chlorhexidine gluconate, or 0.0125% sodium hypochlorite) was assessed and, while all produced substantial reductions in colonisation, chlorhexidine gluconate was found to be the least effective agent. An alternative method of using chlorhexidine, within impression materials, was then evaluated. Conventional and disinfectant-containing alginates were contaminated, and microbiological testing carried out after various time-intervals. Following inoculation with C albicans, the colonisation of conventional alginate (Kromogel) was greater than colonisation of a chlorhexidine-containing material (Hydrogum); conversely, with Ps aeruginosa, colonisation of Hydrogum was significantly greater than Kromogel. There was no clear distinction between these two materials for the carriage of Staph aureus. In all instances, the contamination of Blueprint (containing didecyldimethyl ammonium chloride) was significantly less than the other two materials.

Item Type: Thesis (DDS)
Qualification Level: Doctoral
Additional Information: Adviser: W H Gilmour
Keywords: Dentistry
Date of Award: 1994
Depositing User: Enlighten Team
Unique ID: glathesis:1994-75805
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 19 Nov 2019 18:09
Last Modified: 19 Nov 2019 18:09

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