A Model System for Studying Peri-implantitis In Vitro

Dental implants offer a successful treatment for the replacement of missing teeth. In the oral cavity implants can become colonised with bacterial biofilms. The heterogeneous population of microorganisms can in turn initiate immune responses in the surrounding tissue, which if not controlled can result in peri-implantitis. The microbiology of peri-implantitis has been described as broadly similar to that of periodontitis. The aim of this project is to develop an implant biofilm model which can be used to investigate the immune response of epithelial cells exposed to biofilms grown on different surfaces.

Methods:

Mono- and Multi- species biofilms of S. mitis, A. actinomycetemcomitans, F. nucleatum, and P. gingivalis were grown on either thermonox coverslips or sandblasted, large grit, acid etched titanium implant surfaces. Viable bacterial cell counts were obtained after 7 days culture. OKF6 oral epithelial cells were stimulated with the biofilm colonised implant or coverslip for a period of 4 or 24 hours. Cytokine and chemokine mRNA expression was assessed by q-PCR and ELISA.

Results:

A higher level of bacteria was recovered from the mixed- species biofilm, compared with bacterial recovery from the mono- species biofilms grown on coverslips. Mixed- species biofilm grown on implant surfaces yielded similar bacterial recovery results to bacteria recovered from the mixed biofilm grown on coverslips. IL-8 mRNA and protein were increased following stimulation with either biofilm coated implant surfaces or biofilm coated coverslips.

Conclusion:

The results indicate that periodontal bacteria tend to grow better when grown in a mixed species biofilm than as mono- species biofilm on both coverslips and implant. The implant biofilm model will allow further investigation of both the implant surface biofilm and the host immune response.