Which bacteria are PRIMARILY associated with peri-implantitis?

Peri-implantitis is associated with a polymicrobial biofilm dominated by gram-negative anaerobic bacteria — similar to the microbiota of periodontitis. Key pathogens include: Tannerella forsythia, Porphyromonas gingivalis, Treponema denticola (the 'red complex'), and Fusobacterium, Prevotella, Aggregatibacter actinomycetemcomitans. This is clinically relevant because the treatment of peri-implantitis mirrors periodontal therapy and may include adjunctive antibiotics effective against gram-negative anaerobes.