Metal Alloys Used in Dental Prosthetics and Their Impact on the Oral Microbiome: Narrative Review

Introduction: One of the fundamental principles of modern medicine, including dentistry, is prevention. However, if treatment is not initiated, tooth loss can occur, necessitating the use of dental prostheses to restore the function and aesthetics of the stomatognathic system. The oral microbiome is a complex ecosystem that is sensitive to external factors, including the biomaterials used to manufacture dental prostheses. Objectives: This narrative literature review aims to identify and compare the effects of various metal alloys used in dentistry, specifically high-precious (gold), precious (silver–palladium) and base (cobalt–chromium and nickel–chromium) alloys, as well as titanium, on the balance of the oral microbiome and biofilm formation. Results: The analysis indicates that gold, silver and palladium alloys demonstrate the most favourable biocompatibility and antibacterial properties, significantly reducing biofilm accumulation. Titanium and titanium-based alloys generally exhibit neutral properties under healthy conditions, although their biocorrosion products can alter the microbial environment in pathological states such as peri-implantitis. In contrast, base metal alloys (cobalt–chromium and nickel–chromium) are highly susceptible to biocorrosion in acidic environments, which can encourage the growth of bacteria that cause tooth decay and inflammation, potentially exacerbating oral dysbiosis. Conclusions: The selection of materials plays a critical role in maintaining oral microbial homeostasis and preventing plaque-related diseases. High-noble alloys and titanium are more biocompatible than base metal alloys. However, further long-term clinical trials and multi-species biofilm models are needed to fully understand these interactions between materials and microbes.