Histological evaluation of peri-implant bone in RBM Implant retrieved 6 weeks after insertion

Objective: A variety of implant designs as well as surgical and prosthetic protocols have been proposed in order to achieve optimal osseointegration and prosthetic loading in the shortest time. Still, data provided on this issue by research-base evidence are quite controversial and understanding of bone response around implants in early stages presents great interest. The objective of this study was to evaluate histologically the characteristics of tissues growing on the surface of a RBM (Resorbable Blast Media) titanium submerged implant removed 6 weeks after insertion in an edentulous posterior mandibular area. Case Presentation: Implant placed in a 45-years-old patient was removed six weeks after insertion, due to prosthetic-related incorrect positioning. Implant and surrounding tissues were washed in saline solution and fixed in 4% paraformaldehyde and 0.01 M phosphate-buffered saline solution (PBS pH 7.2) for 24h at 4°C, to be processed for histology. The specimens were processed, dehydrated and polymerised. Cross sections of 35 µm were obtained by means of a circular diamond-bladed saw (SP1600 Leica Mcr), polished and air dried in incubator at 37°C for 24 hours. Five sections corresponding to different levels of the fixture were chosen and microradiographed (XRG-3000 - IST). Contact high resolution microradiographies were developed (Kodak HC-110), fixed (IHRF), washed, dried and observed at light microscope (Nikon E400). Images acquired by means of a digital camera (DS-5M - Nikon Corporation) were saved in a computer. Results: Histological analyses highlight the presence of an adequate mature bone deposition and absence of connective tissue or immature bone in four out of five levels evaluated. In particular, the section number 3, corresponding to the middle level of the implant, appears more involved by bone deposition processes than the other ones. Moving to bottom, the first and second levels exhibit an adequate mature bone deposition but the amount of bone on the surface of the implant appears to be slightly reduced when compared to previous section. Conversely, moving to apex, the fourth level shows a moderate bone deposition, although the presence of bone tissue appears continued and confined in two diametrically opposite parts of the fixture surface. Finally the apical level shows a quite absent osseointegration and a negligible amount of mineralized tissues around the implant. Conclusions: On the periimplant surface of a RBM Implant retrieved 6 weeks after insertion it was observed a high quantity of mature bone, indicating a good osseointegration of the implant.