Bacterial viability on surface-modified resin-based dental restorative materials.

UNLABELLED: The purpose of the present investigation was to investigate the viability of early colonizers on the surfaces of resin-based dental restorative materials modified with low-surface tension active agents in comparison with the unmodified material. A novel polymeric sorption material, loaded with two low-surface tension γ(L) active agents (hydroxyfunctional polydimethylsiloxane and polydimethylsiloxane) or a polymerizable active agent (silicone polyether acrylate), was used to modify commonly formulated experimental dental resin composites. The non-modified resin was used as the standard (ST). The viability of Actinomyces naeslundii, Actinomyces viscosus, Streptococcus mitis, Streptococcus oralis, and Streptococcus sanguinis on water-stored, polished, and human saliva pellicle-coated specimens was determined using a fluorescence microscope after 8 and 24h. Total, vital, and non-vital cells were calculated from the microscopic images by counting pixels per colour. Means, standard deviations, univariate ANOVA and multiple comparisons with post hoc Scheffé's tests were calculated. t-Test was done to compare 8-h and 24-h bacteria counts. For all tests p<0.05 was chosen. NULL HYPOTHESIS: the test materials and the standard did not differ either in the total bacterial counts or in the respective bacterium's viability after 8 or 24h. The test materials modified with the silicone polyether acrylate showed lower total bacteria count after 8 or 24h than ST. But all test materials had significantly fewer vital cells after 8 or 24h compared to ST. The contact angle did not influence bacterial adhesion, but low total SFE and a low polar term of SFE resulted in fewer bacteria. The material's chemistry also affected the total and vital cell counts. Different bacteria viabilities needed to be explored to obtain relevant information regarding bacterial adhesion on dental composite resins. The novel sorption material loaded with low γ(L) active agents or with a low γ(L) polymerizable silicone polyether acrylate used to modify the chemistry of the test materials was appropriate to reduce bacterial adhesion or cell viability, respectively.