title: In vitro caries: dental plaque formation and acidogenicity
Creators: name: Owens, Gareth
Publisher: name: University of Liverpool Repository
Year: 2014

description: Dental caries is a significant disease world-wide and although a massive reduction in prevalence has occurred over the past 50 years, incidents of this disease persist (particularly on the occlusal or aproximal surfaces and concerning younger demographics). The main reason for the observed reduction is exposure to fluoride either though water fluoridation and delivery by dentifrice. Environmental exposure reduces incidence by incorporation into the mineral phase of the hard tissue and, as a result, increases the resistance of the enamel mineral to acid-induced demineralisation. Several mechanisms have been proposed in an attempt to explain the caries-inhibiting effects of fluoride however its influence on the balance between de- and re-mineralisation episodes appears to be the principal route by which fluorides exert their effects. Efforts geared towards the continual improvement of fluoride delivery systems have also been successful to some extent and thus further exploration shows promise of improving the anticaries efficacy further. However, a complication is met in that, in vivo, multiple factors interrelated and consequently, differences in the consortia within natural oral biofilms combined with unavoidable inter-individual variations confound clinical investigations and make the distinction between relevant aspects of the process difficult. One possible alternative strategy is the development of in vitro biological models to simulate this process to a point of reflecting the in vivo situation whilst retaining control over the parameters which are known to be crucial to the progression of the disease. To this end, the Constant-Depth Film Fermenter (CDFF) has emerged as powerful tool to potentially meet the needs of current in vitro research. However, due to the lack of an inter-disciplinary approach to multi-faceted disease process, the full potential of the CDFF has not yet been reached. Therefore, the CDFF model was applied to study of anti-caries strategies which aimed to increase the persistence of the fluorides within natural microcosm biofilms. Enamel lesions were successfully produced within this system and, using a combination of both biological and non-biological demineralisations systems, the effects of anticaries agents (calcium and fluoride) were also investigated for their effects on lesion progression or reversal. Sodium fluoride (NaF; 300 ppm F-) exposures exhibited an ambiguous response on the microbial community although definite anticaries activity. Conversely, calcium lactate pre-rinses (Ca-lactate; 100 mM) appears to possess some inhibitory activity on the biofilms produced within the model whereas a less effective anticaries activity was observed in comparison to NaF exposures alone. Thus, further investigation of the effects of Ca-lactate should be pursued. Operation of the CDFF was also further developed to meet the needs of this study and analyses were performed on an integrative basis in order to capture the physiochemical events which take place during caries lesion formation. Microcosm plaques were shown to be highly diverse with respect to their community although homology was found on the bias of their ultimate definition, cariogenicity. The synthesis of inorganic mineral reservoirs within microcosm biofilms holds great potential for augmenting the physiology of the plaque and for increasing the efficacy of fluorides for prevention of enamel demineralisation. Microcosm biofilms may also have an adaptive capacity which could result in predicable response patterns. Ultimately, a holistic approach to the study of caries within a biological context provides greater insight into the caries process than approaches which lack specific interactions for the purposes of assigning direct relationships. With the successful development of a fully functional enamel caries model, the possibilities are endless.