Discrimination between random and non-random processes in early bacterial colonization on biomaterial surfaces: application of point pattern analysis

Template assisted surface microstructuring of flowable dental composites and its effect on microbial adhesion properties

OBJECTIVES

Despite their various advantages, such as good esthetic properties, absence of mercury and adhesive bonding to teeth, modern dental composites still have some drawbacks, e.g., a relatively high rate of secondary caries on teeth filled with composite materials. Recent research suggests that microstructured biomaterials surfaces may reduce microbial adhesion to materials due to unfavorable physical material-microbe interactions. The objectives of this study were, therefore, to test the hypotheses that (i) different surface microstructures can be created on composites by a novel straightforward approach potentially suitable for clinical application and (ii) that these surface structures have a statistically significant effect on microbial adhesion properties.

METHODS

Six different dental composites were initially tested for their suitability for microstructuring by polydimethylsiloxane (PDMS) templates. Each composite was light-cured between a glass slide and a microstructured PDMS template. The nano-hybrid composite Grandio Flow was the only tested composite with satisfying structurability, and was therefore used for the bacterial adhesion tests. Composites samples were structured with four different microstructures (flat, cubes, linear trapezoid structures, flat pyramids) and incubated for 4h in centrifuged saliva. The bacterial adherence was then characterized by colony forming units (CFUs) and scanning electron microscopy (SEM).

RESULTS

All four microstructures were successfully transferred from the PDMS templates to the composite Grandio Flow. The CFU-test as well as the quantitative analysis of the SEM images showed the lowest bacterial adhesion on the flat composite samples. The highest bacterial adhesion was observed on the composite samples with linear trapezoid structures, followed by flat pyramids and cubes. The microstructure of dental composite surfaces statistically significantly influenced the adhesion of oral bacteria.

SIGNIFICANCE

Modifying the composite surface structure may be a clinically suitable approach to control the microbial adhesion and thus, to reduce the risk of secondary caries at dental composite restorations. Smaller composite surface structures may be useful for accomplishing this.

Host-pathogen interactions between the human innate immune system and Candida albicans-understanding and modeling defense and evasion strategies

The diploid, polymorphic yeast Candida albicans is one of the most important human pathogenic fungi. C. albicans can grow, proliferate and coexist as a commensal on or within the human host for a long time. However, alterations in the host environment can render C. albicans virulent. In this review, we describe the immunological cross-talk between C. albicans and the human innate immune system. We give an overview in form of pairs of human defense strategies including immunological mechanisms as well as general stressors such as nutrient limitation, pH, fever etc. and the corresponding fungal response and evasion mechanisms. Furthermore, Computational Systems Biology approaches to model and investigate these complex interactions are highlighted with a special focus on game-theoretical methods and agent-based models. An outlook on interesting questions to be tackled by Systems Biology regarding entangled defense and evasion mechanisms is given.