Multispecies biofilms in the oral cavity are shaped by complex interbacterial communication, with quorum sensing potentially playing a central role in maintaining microbial balance or driving dysbiosis. This seminar examines quorum sensing mechanisms in health and periodontitis, focusing on acyl-homoserine lactones (AHLs) and autoinducer-2 (AI-2) signalling molecules. The influence of AI-2 and D-ribose on biofilm formation/inhibition of the key bridging organism Fusobacterium nucleatum will be discussed. Beyond its oral niche, F. nucleatum has been implicated in colorectal cancer, where its ability to adhere to cancer cells may contribute to disease progression. Specific adhesins involved in this interaction and their potential role in mediating host-pathogen dynamics are explored. These insights highlight the broader significance of bacterial communication in both oral and systemic disease contexts.