Oral biofilms and secondary caries formation

The presence of a huge amount of data regarding the onset of a carious lesion in close proximity with a restoration must not make ourselves less aware about the fact that, still, a lot of information is missing about secondary caries formation. Many pieces of information are highly conflicting, such as, for instance, the role that different microbial species have in the onset of the lesion, or the link between the existence – and width – of a gap between hard tissues and restoration, and the development of a secondary lesion, or, again, the clinical decisions regarding the replacement of a restoration due to secondary caries, and, if so, to what point stop excavating? The main difficulty in this field arises from the fact that secondary caries is the result of very complex interactions taking place among already injured human tissues, overlying biofilms that often maintain the dysbiotic conditions that lead to the primitive lesion, and dental materials that may help, or even worsen that situation. Increasing our knowledge about what exactely happens after a material is placed at this three-sided interface may greatly help us in designing new dental materials able to interact in a positive way both with the host and its biofilm, ensuring longevity to restorations and helping in reducing what is nowadays their main cause of failure – secondary caries.