Results of thermal osteonecrosis for implant removal on electron microscopy, implant stability, and radiographic parameters – a rat study

Background: The aim of this rat study was to evaluate the feasibility of temperature thresholds that affect peri-implant bone cells and morphology and the potential usefulness of thermal necrosis for inducing implant removal for a subsequent in vivo pig study. Methods On one side, rat tibiae were thermally treated before implant insertion. The contralateral side was used as the control group without tempering. Temperatures of 4°C, 3°C, 2°C, 48°C, 49°C, and 50°C were evaluated with a tempering time of 1 min. Energy-dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM) analyses were performed. Results The EDX analysis revealed significant increases in element weights at 50°C (e.g., calcium, phosphate, sodium, and sulfur; p  < 0.01). The results of the TEM analysis showed that at all the applied cold and warm temperatures, signs of cell damage were observed, including vacuolization, shrinkage, and detachment from the surrounding bone matrix. Some cells became necrotic, leaving the lacunae empty. Conclusions Although this was a preliminary study, from the results, we identified that a temperature of 50°C at a time interval of 60 min can lower the number of samples in a further study of thermo-explantation. Thus, the subsequent planned in vivo study in pigs, which will consider osseointegrated implants, is feasible.