Method: Titanium implant abutments were micro textured and acid-etched to facilitate biofilm formation on the surface. The abutments were inoculated in vitro with Aa D7S-1 (WT) and a double knockout mutant (DM) of omp29 and its paralogue. Sham-inoculated abutments served as negative control. Sterile titanium implants were transmucosally inserted into rat maxillary alveolar ridge with the abutments (N=15 for each of WT, DM and sham-inoculated groups). The animals were evaluated clinically up to 6 weeks. Micro-CT imaging was performed at 3 and 6 weeks. The levels of Aa on the abutments were determined by quantitative PCR.
Result: Presurgically, the amount of biofilm was on average 9.9×106 ± 4.9×106 of WT cells/abutment and 2.2×107±8.4×106 DM cells/abutment. After the surgery, bleeding, ulceration, hyperplasia, and necrosis were observed around biofilm-inoculated titanium abutments. By 3 weeks 8/15, 6/15 and 6/15 implants remained stable in WT, DM and sham-inoculated implants, respectively. By 6 weeks 3/15, 5/15 and 5/15 implants remained stable in WT, DM and sham-inoculated implants, respectively. After 6 weeks, the persistence of Aa on the abutment was as followed: 22% of WT and <1% DM. Bone loss was noted in bone surrounding implants inoculated with bacteria but not in shame-inoculated implants.
Conclusion: A novel animal model where Aa biofilm was established in vitro on titanium implant abutments prior to installation in rat oral cavity, leading to an inflammatory response, osteolysis, and tissue destruction. This model could be used to investigate host responses to biofilm and anti-biofilm treatment strategies.