Modulating the ecology and phenotype of in vitro oral biofilms

Chapter 2 describes the development of a complex healthy biofilm model compared to a cariogenic biofilm model and a biofilm model for periodontal disease. The addition of different nutrients and different incubation times were used to create phenotypically different biofilms. These in vitro models can be used to test novel strategies for maintaining oral health, test new components and identify relevant microbial interactions.
In chapter 3 the effect of the introduction of the eukaryotic micro-organism C. albicans in the biofilm is described. In this chapter, the complex cariogenic model is used to evaluate the effect of C. albicans on the phenotype and ecology of oral biofilms.
Chapter 4 describes the effect of the artificial sweetener erythritol on gingivitis biofilms. Besides the fact that erythritol cannot be converted to acids by oral microbes, it is known to have other caries-preventive properties. It reduces total plaque levels, abundance of mutans streptococci, and organic acid levels in dental plaque. A study using dual-species biofilms shows that erythritol is possibly also effective against gingivitis by reducing the relative abundance of P. gingivalis compared to S. gordonii. In this chapter, the effects of erythritol on a gingivitis biofilm is studied.
To get more insight in microbial interactions in the oral cavity, the effect of several quorum sensing inhibitors on complex oral biofilms is described in chapter 5. A panel of 3 quorum sensing inhibitors, and the precursor for AI-2 (DPD) were tested. Pathology-related phenotypes of the treated and untreated biofilms are compared. One inhibitor significantly reduced lactic acid production of cariogenic biofilms without extensive inhibition of biofilm formation. Therefore, the effect of this quorum sensing inhibitor is described in more detail.