EVALUATING THE EFFECT OF SOFT LINING MATERIALS ON THE GROWTH OF YEAST

Statement of problem. Soft lining materials continue to have a place i n clinical removable prosthodontics. However, there is an increased pr obability of yeast colonization on soft lining materials. Purpose. Thi s study (1) assessed a method of evaluating the effect of long-term so ft lining materials on the growth of yeast and (2) investigated the ef fect five soft lining materials had on the growth of three species ofy east. Material and methods. Coe Supersoft, Novus, and three experiment al soft lining materials were investigated together with Candida albic ans, Candida tropicalis, and Issatchenkia oreintalis (formerly Candida krusei) yeasts. Strips of soft lining material incubated on blood aga r plates were examined for inhibition of the growth of yeast. Soft lin ing materials soaked in sterile trypticase soya broth or water were in oculated with yeast and incubated. The change in colony forming units per milliliter from the initial load of yeast at 3 days was measured. Statistical analysis was performed with an independent paired Student t test. Results. Inhibition of yeast growth occurred for two soft lini ng materials. Despite the presence of sufficient viable organisms, dif ferences between the initial load of yeast and the 3-day results were mostly small, both for the test and control groups, suggesting that th e material does not support the growth of the tested yeast during this period. Conclusions. The often described increased prevalence of yeas t associated with soft lining materials in the oral environment is lik ely related to readily available nutrients in the mouth and the diffic ulty in maintaining and cleaning these materials.