Surface Modification of Silicone and its Effect on Yeast Colonisation

Objective: The purpose of this study was to investigate the retention and penetration of Candida species to an experimental silicone surface-modified with silane and to maxillofacial silicone processed against dental stone or polymethylmethacrylate (PMMA) to produce rough and smooth surfaces respectively. Methods: Standardised washed cell suspensions of C.tropicalis, C.krusei and two strains of C.albicans were incubated with test materials for one hour at 37°C, after which retained cells were measured as percentage area coverage using an image analysis system. Colonisation of silicone by Candida species was assessed after six weeks incubation in inoculated artificial saliva. Materials were manually sectioned and hyphal and yeast penetration estimated qualitatively and quantitatively for three levels in each section. Results: There was a significant decrease in yeast retention to the silane treated silicone (P<0.01) with the exception of C.tropicalis, which showed no significant difference in retention to silane treated or PMMA processed silicone. The dental stone processed silicone showed greater retention of yeast cells, particularly in surface defects. The incidence of hyphae and yeast cells was higher for all three levels of penetration in stone processed silicone. Least colonisation was observed within sections of silane treated silicone by all Candida isolates. Conclusion: All materials studied showed some degree of penetration by Candida species. However modification of the silicone surface by topographical or chemical means has the potential to influence the rate of material deterioration by fungi.