Histologic analysis of a screw implant retrieved from man: influence of early loading and primary stability

This paper presents a histologic analysis of a one-piece screw implant put into immediate function and retrieved from man after 7 years of clinical function. Compact lamellar bone with many Haversian canals and osteons was found very near the metal surface, and the morphometric analysis of the perimeter of the implant showed a percentage of bone contact of 86.69% (SD = 5.43). The compact bone was particularly thickened around the top of the spires. At high-power magnification, it was possible to observe optically a small empty gap between bone and titanium, and the use of a histochemical stain (von Kossa) showed that mineralized bone was separated from the metal surface by a very thin layer of unmineralized red-stained material; this layer had the same staining features as the osteoid and the osteocyte lamina limitans.