Development and application of models of intra-oral halitosis

Halitosis is a common condition with a multitude of oral and systemic factors implicated in its causality. Although, the pathological factors involved in the systemic causes of halitosis are varied, the oral factors are more consistent and mostly involve the production of malodorous volatiles by the oral microbiota. This phenomenon can therefore be modelled 'in vitro' and two such models, utilising planktonic oral bacteria and tongue-derived biofilms, were used to ascertain the effects of amino acids and foods in the generation of malodour, mainly focusing on the volatile, sulfur-containing compounds. To that end, simple amino acids as well as garlic, onion and coffee were evaluated in both the models. It was found that odorous food components could be retained and released within the biofilm model and that amino acids could be metabolised to a variety of different malodorous compounds. These models were applied in the evaluation of zinc, an active incorporated in oral healthcare products to combat malodour. Further, a thorough evaluation of the role of the bacterium, 'Solobacterium moorei' was undertaken, finding that the organism could generate copious amounts of hydrogen sulfide.