Western Society of Periodontics

Clinical Studies

Volume Number 3, 1995

Different types of inflammatory reaction in peri-implant soft tissues

The aim of the present study was to analyze some features of the pert-implant mucosa at sites in the dog model which had been exposed to plaque accumulation for periods up to nine months. After extractions and three months of healing three Branemark titanium fixtures were installed in the edentulous premolar/molar regions. During a preparatory period of three months after abutment connection, the animals were exposed to meticulous cleaning. The main study period constituted nine months. The plaque-control regimen was maintained in some implant segments, while plaque was allowed to accumulate on the others. At the end of the main study period the animals were sacrificed and 10 sections were exposed to histometric and morphometric analysis. The peri-implant mucosa at implant sites exposed to daily and comprehensive plaque control at biopsy was clinically non-inflamed. On the other hand, termination of the plaque-control program resulted in the accumulation of plaque and calculus, and the biopsies demonstrated an inflammatory infiltrate. The histological analysis also revealed that the inflammatory infiltrate was consistently present at the level of borderline between the abutment and the fixture part of the implant. This infiltrate, called abutment ICT, occurred both at sites that had been exposed to plaque control and at sites at which plaque had been accumulated. The histometric determinations disclosed that (1) the bone crest consistently was located about 1-1.5 mm "apical" to the abutment/fixture level, and (2) there was a zone, about 1 mm wide, of a normal noninfiltrated connective tissue that separated the apical portion of the abutment ICT and the bone crest. It is suggested that this infiltrate represents the efforts by the host to close off the internal infection in the implant system and that ICT may explain the 1 mm bone loss observed during the course of the first year after bridge installation. [E.L.H.]