Periodontitis and dental caries are two of the most prevalent human diseases, affecting nearly 2 billion worldwide. Persistence is largely attributed to the formation of biofilms (plaque) by oral bacteria, which left undisturbed lead to destruction of surrounding tissues and increase the risk for secondary disease. As current treatments such as mechanical removal and adjunctive therapies can be inadequate, there is a need for new anti-plaque chemical agents. Stabilized hypochlorous acid (sHOCl) has emerged as a potential anti-biofilm agent in areas such as wound therapy but its use in treating oral diseases remains unknown. Therefore, our aim in this thesis was to assess the role of sHOCl as an antimicrobial agent for use in the oral cavity.

We found that at low concentrations, sHOCl was effective in killing bacteria within mixed-species in vitro models resembling periodontitis and dental caries. Moreover,  sHOCl  displayed  higher  antibiofilm  activity  compared  to chlorhexidine, whilst not damaging tested oral surfaces. At sub-lethal levels, sHOCl was observed to target multiple cellular components through oxidative stress in Streptococcus biofilms. Simultaneously, work on our models revealed a possible new application of CFSE-based dyes in microscopy for the live-imaging of biofilms. In particular, multi-dye compatibility opens up the possibilities for future research employing mixed-species biofilms. Finally, our preliminary findings also indicate that sHOCl may permit a selective re-growth of biofilms following exposure.

Taken together, the results of this thesis lay the groundwork for investigations of sHOCl as an antibiofilm agent, and continue to push microbial research towardsmore relevant models.