How Does the Biocompatibility of Molybdenum Compare to the Gold Standard Titanium?—An In Vivo Rat Model

Molybdenum is an essential trace element, considered in recent work to be a promising 3D-printable biodegradable material for medical applications. Specifically, in our recent in vitro work, we were able to show that molybdenum is a material of high biocompatibility, sufficient stability, and uniform degradation. Thus, it seems to fulfill the optimal requirements for a resorbable osteosynthesis material. To confirm these results in a complex organism, we tested molybdenum against the gold standard titanium. For this purpose, we implanted either molybdenum or titanium implants into the nuchal folds of 48 Wistar rats. We examined all animals daily for clinical inflammatory parameters and euthanized one-third of the cohort after 12, 24, and 52 weeks, respectively. Subsequently, the tissues surrounding the samples, as well as the spleens, livers, and kidneys of all animals, were pathologically processed and examined. Subsequently, selected samples were examined metallographically. No significant increased inflammatory reaction of the material molybdenum versus titanium could be detected, either clinically or pathologically. The animals did not show any significant differences regarding their general condition or weight development. However, the introduced molybdenum platelets showed significantly less degradation than previously in the in vitro model. This is most likely due to the capsule formation, which has already been described for other implants.