Evaluation of in vivo denture plaque assessment methods.

BACKGROUND: Measurement and assessment of denture plaque can provide valuable information regarding an individual's oral health status and assessment of new treatments or products. Current methods tend to rely on subjective indices or image analysis derived planimetric (area measurement) assessment of stained plaque on dentures. Plaque indices are most commonly used to assess plaque coverage without image capture. This is not ideal because the methods are subjective, examiner bias may occur, there is no reproducibility between studies, the methods have lower accuracy and sensitivity than image analysis, and there is no record. To the authors' knowledge, no standardised published method of denture plaque assessment is currently employed for product development and testing. METHOD: In this study visual and planimetric plaque assessment methods were compared using reference dentures. In addition, an in vivo study compared these methods for evaluating denture cleanser efficacy. RESULTS AND CONCLUSIONS: The results show that blinded image scoring is more representative of the true plaque area coverage than 'live' denture scoring, detecting significant decreases in plaque coverage. Planimetric analysis provides a more sensitive and less subjective technique with greater differentiation between treatments. However, analysis is very time consuming. Thus, a number of recommendations are made regarding quantification of denture plaque for the assessment of cleanser products.

QLF is not readily suitable for in vivo denture plaque assessment.

OBJECTIVES: Current methods available for denture plaque assessment utilise visual and planimetric techniques. This paper evaluates the use of the Quantitative Light-induced Fluorescence system (QLF) in image capture of denture plaque and the suitability of these images for planimetric plaque measurement. It is proposed that fluorescence imaging could provide a valuable and sensitive standardising method for plaque assessment in clinical trials for denture cleansing products and denture hygiene. Indeed, the detection of red fluorescent plaque using the QLF system is indicative of black-pigmented obligate anaerobes and mature plaque. METHODS: The QLF system was evaluated in a clinical study for use in denture plaque assessment in comparison to white light based image capture. RESULTS: Despite appearing as a promising system for denture plaque quantification, this study revealed numerous problems associated with the QLF system including small focal depth, thus large numbers of images and processing time were required. In addition, differential fluorescence of acrylic made images unsuitable for plaque quantification. CONCLUSION: QLF is unsuitable for in vivo denture plaque assessment. However, the visualisation of red autofluorescence, indicating mature plaque, remains an important clinical use of QLF for denture hygiene assessment.

Development of an in vitro denture plaque biofilm to model denture malodour.

This study aimed to develop an in vitro denture plaque biofilm to model denture malodour. No previous studies have attempted to characterize the malodour associated with dentures and the effect of Candida spp. (main aetiological agent of denture-related stomatitis) on malodour. Pooled denture plaque microcosms and 'model' denture plaque biofilms (pooled saliva supplemented with additional microbial species) with and without addition of candida were grown aerobically at 37 °C for up to 13 days in a constant depth film fermenter (CDFF) on denture acrylic discs. Sample discs were removed, rinsed in sterile water and placed in phosphate buffered saline (PBS). The discs were vortex mixed to remove the biofilms, diluted in PBS and plated in duplicate onto general and selective media. The composition and stability of the biofilms over time were assessed. CDFF-grown microcosms and 'model' denture plaque biofilms were relatively stable in composition, with streptococci remaining the dominant microbial group. Model denture plaque biofilms were comparable in composition to denture plaque microcosms. This model system has the potential for evaluation of agents that might affect these parameters such as denture cleansers and other oral hygiene treatments.

Potential pathogenic aspects of denture plaque.

Oral health status declines with age and as a result the need for removable prostheses increases. Oral health is a reflection of one's general health, affecting the ability of an individual to eat and speak, and contributes significantly to a sense of confidence and well-being. Currently, there are 15 million denture wearers in the UK, representing a significant consumer base and a special healthcare consideration. The microbiology of denture plaque has received little attention in comparison with dental plaque, yet it differs in location and composition. Denture plaque and poor denture hygiene is associated with stomatitis (Candida infection), may also serve as a reservoir of potentially infectious pathogens, and may contribute to oral malodour and to caries and periodontitis in people who have remaining natural teeth. Oral bacteria have been implicated in bacterial endocarditis, aspiration pneumonia, gastrointestinal infection and chronic obstructive pulmonary disease, among others, and dentures offer a reservoir for microorganisms associated with these infections. An effective oral hygiene regimen is important to control denture plaque biofilm and contributes to the control of associated oral and systemic diseases.

The microbiological origin of fluorescence observed in plaque on dentures during QLF analysis.

The aim of this study was to determine the microbiological origin of plaque fluorescence observed during quantitative light-induced fluorescence (QLF) analysis. Plaque was sampled from dentures, because of easy accessibility and the homogeneous background provided by the denture tooth during imaging, and the acknowledged comparability to occlusal plaque. Forty removable poly(methyl methacrylate) dentures were screened for the presence of fluorescent plaque deposits during QLF analysis. Dentures were photographed, QLF images were recorded and samples of fluorescent plaque were taken. Plaque samples were cultured on fastidious anaerobe agar, Wilkins Chalgren agar and Sabourauds dextrose agar. Plates were screened under QLF and fluorescent colonies were subcultured and identified. Areas of red, orange and green fluorescence were detected on the fitting and non-fitting surfaces of dentures. The red and orange fluorescing species were Prevotella melaninogenica, Actinomyces israelii and Candida albicans, which are generally acknowledged to be secondary colonisers, present in more mature plaque. Green fluorescence was observed in streptococcal species (early colonisers) and Fusobacterium nucleatum (important organism in plaque development). Non-fluorescent colonies were also cultured. Plaque which accumulates on susceptible surfaces tends to be associated with caries, but it may be its maturity, rather than the presence of cariogenic streptococci, that is more likely to provide a microbiological link between red fluorescence and caries.

Reduced adherence of Candida to silane-treated silicone rubber.

Silicone rubber is widely used in the construction of medical devices that can provide an essential role in the treatment of human illness. However, subsequent microbial colonization of silicone rubber can result in clinical infection or device failure. The objective of this study was to determine the effectiveness of a novel silane-treated silicone rubber in inhibiting microbial adherence and material penetration. Test material was prepared by a combination of argon plasma discharge treatment and fluorinated silane coupling. Chemicophysical changes were then confirmed by X-ray photoelectron spectroscopy, contact-angle measurement, and atomic force microscopy. Two separate adherence assays and a material penetration assay assessed the performance of the new material against four strains of Candida species. Results showed a significant reduction (p < 0.01) of Candida albicans GDH 2346 adherence to silane-treated silicone compared with untreated controls. This reduction was still evident after the incorporation of saliva into the assay. Adherence inhibition also occurred with Candida tropicalis MMU and Candida krusei NCYC, although this was assay dependent. Reduced penetration of silane-treated silicone by Candida was evident when compared to untreated controls, plaster-processed silicone, and acrylic-processed silicone. To summarize, a novel silicone rubber material is described that inhibits both candidal adherence and material penetration. The clinical benefit and performance of this material remains to be determined.