Barbara Azzimonti

1. Introduction The intestinal microbiota, i.e., the whole of microorganisms (bacteria, viruses, fungi, and protozoa) that colonize the gastro-enteric tract, has a broad and complex interaction with the immune system through metabolites able to influence the balance between the immune tolerance and the inflammatory state []. Also, it communicates with the skin, as an important regulator of the gastrointestinal–skin axis system (“gut–skin axis”) [].

1. Introduction The incidence of both non-melanoma-skin cancers (NMSCs), and melanoma skin cancers has been increasing over the past years. Globally, in 2020, 1,198,073 new NMSC cases and 63,731 deaths occurred worldwide; of them, 324,635 were new melanoma cases, which caused 57,043 deaths [1]. Recent evidence points out the role of microbiota, the unique combination of micro-organisms residing in a specific environment, in the pathogenesis of several diseases, including skin cancer.

Peri-implantitis is a severe condition affecting the success of transmucosal dental implants: tissue healing is severely limited by the inflammatory processes that come about to control homeostasis in the surrounding tissues. The main cause of peri-implantitis is bacterial biofilm infection; gingival fibroblasts play a pivotal role in regulating the inflammatory cascades.