Dental implants provide a restorative tool to support crowns, bridge abutments, and removable dentures. Osseointegrated implants are titanium posts that are surgically implanted in alveolar bone. A tight immobile bond (osseointegration) forms between bone and titanium, and prosthetic and restorative fixtures are attached to the implants. Titanium implants differ from natural teeth, which may make them more susceptible to mechanical stress. A small proportion of implants are not successful and may fail due to infection. The microbiota of implants is similar to that of teeth in similar clinical states. Implants that fail because of mechanical stress are colonized by species associated with healthy teeth. Infected implants are colonized by subgingival species, including Porphyromonas gingivalis, Bacteroides forsythus, Fusobacterium nucleatum, Campylobacter gracilis, Streptococcus intermedius, and Peptostreptococcus micros. Different patients may be colonized by different microbial complexes, indicating that optimal treatment should be directed to the specific infection.