DISTRIBUTION OF CELLS IN SOFT-TISSUE AND FLUID SPACE AROUND HOLLOW AND SOLID IMPLANTS IN THE RAT

The development of the tissue surrounding an implanted material is ant icipated to be regulated by the biological factors in the interface as well as the physicochemical properties of the implant material. In th e present study light microscopic morphometry and transmission electro n microscopy were used to evaluate the distribution of cells adjacent to the implant surface of different implant designs (hollow and solid implants) and materials (titanium and polytetrafluoroethylene). An inc reased number of leukocytes, predominantly PMN, was retrieved from the exudate inside hollow implants 1 and 9 days after surgery. In contras t, the increased cellularity in the soft tissue around the hollow impl ants was mainly due to an increased number of monocytes/macrophages an d fibroblasts. The presence of a fluid space around both hollow and so lid implants was revealed by the use of an electropolishing technique and ground sections. In the fluid space around solid titanium the conc entration of leukocytes and the proportion of PMN decreased between 1 and 7 days. After 1 day the majority of leukocytes were freely suspend ed in the fluid and were rarely directly apposed to the implant surfac e. A majority of the monocytes/macrophages present in the fluid space after 7 days were attached to the fibrin matrix at the border between the fluid space and the reorganized tissue. Our studies demonstrate th at hollow implants promote the influx and a persistence of PMN in the interior of the implant in comparison with the tissue surrounding the hollow and solid implants. Furthermore, during the first week after im plantation inflammatory cells are not preferentially distributed direc tly on the titanium implant surface.