Detection of T. forsythia and other important bacteria in crestal and subcrestal implants with ligature-induced peri-implant infection in dogs.

Background: The study was designed to compare peri-implant microbial colonization of inflamed implants placed at different levels in dogs.

Methods: Two screwed-in (SI) and two tapped-in (TI) conical connection implants were placed on each side of mandibles in six dogs respectively. Four experimental groups were constituted according to implant types and placement depth in one side: SI crestally (SIC), SI 1.5 mm subcrestally (SIS), TI crestally (TIC), and TI 1.5 mm subcrestally (TIS). Plaque accumulation of implants was promoted by cotton ligatures at either side randomly selected in each dog four weeks after abutment connection. Peri-implant sulcular fluid (PISF) samples were collected at 4 weeks, 10 weeks, and 16 weeks after abutment connection. Common periodontal pathogens in PISF were analyzed by PCR and realtime-PCR to investigate the influence of placement depth on microbial accumulation. The microbial results were further correlated with clinical parameters.

Results: At ligatured sides, detection rates of T. forsythia and P. gingivalis increased significantly in four groups. T. forsythia levels increased significantly from baseline in four groups at ligatured sides at 16 weeks (p < 0.05). TIS group harbored significantly more T. forsythia than TIC at ligatured sides at 16 weeks (p < 0.05). At ligatured sides, probing depth was correlated to T. forsythia level in four groups as well as in total.

Conclusions: Subcrestal placement could increase the peri-implant T. forsythia level at the early stage of peri-implantitis. The T. forsythia level in the peri-implant sulcus is associated with probing depth.