Background: Dental implants affected by peri-implantitis, This prospective study investigated the qualitative bacterial etiology of peri-implantitis, a particularly aggressive form of the disease.

Methods: This prospective study included 26 patients (aged 23-45) with healthy, functional implants in service for at least 12 months, presented with acute infection. Patients were divided into two groups based on reverse torque testing values. Group I (n=12) consisted of implants with reverse torque value of less than 15 Ncm, indicating reduced rotational stability and more severe implantitis. Group II (n=12) consisted of implants with reverse torque value of 15 Ncm or greater, indicating adequate rotational stability and less severe implantitis. Group I implants were explanted and cultured. Group II implants underwent supra-structure removal, debridement, laser disinfection, and bacterial swabbing. All patients were examined for primary infection sources (periodontal, endodontic, or other),were managed accordingly. Specimens were cultured.

Results: Seven strains were identified: Porphyromonas gingivalis, methicillin-resistant Staphylococcus aureus (MRSA), Aggregatibacter actinomycetemcomitans, Enterococcus faecalis, Prevotella intermedia, Pseudomonas aeruginosa, and Serratia marcescens. Many specimens exhibited antibiotic resistance, requiring tailored combination therapies. Grade I patients received new implants after 8 weeks; Grade II patients received new abutments/restorations after 6 weeks. Bacterial species from primary infection sources matched those from affected implant sites.

Conclusions: Peri-implantitis is associated with aggressive, often antibiotic-resistant infections, including MRSA. Early diagnosis, pathogen identification, and targeted antimicrobial therapy, along with management of primary infection sources, are essential for preventing rapid osseointegration loss and implant failure. Further studies are needed to quantify the bacterial burden in these infections