Osseointegration of a 3D Printed Stemmed Titanium Dental Implant: A Pilot Study

In this pilot study, a 3D printed Grade V titanium dental implant with a novel dual-stemmed design was investigated for its biocompatibility in vivo. Both dual-stemmed (n = 12) and conventional stainless steel conical (n = 4) implants were inserted into the tibial metaphysis of New Zealand white rabbits for 3 and 12 weeks and then retrieved with the surrounding bone, fixed, dehydrated, and embedded into epoxy resin. The implants were analyzed using correlative histology, microcomputed tomography, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The histological presence of multinucleated osteoclasts and cuboidal osteoblasts revealed active bone remodeling in the stemmed implant starting at 3 weeks and by 12 weeks in the conventional implant. Bone-implant contact values indicated that the stemmed implants supported bone growth along the implant from the coronal crest at both 3- and 12-week time periods and showed bone growth into microporosities of the 3D printed surface after 12 weeks. In some cases, new bone formation was noted in between the stems of the device. Conventional implants showed mechanical interlocking but did have indications of stress cracking and bone debris. This study demonstrates the comparable biocompatibility of these 3D printed stemmed implants in rabbits up to 12 weeks

Multimodal and Multiscale Characterization of the Bone‐Bacteria Interface in a Case of Medication‐Related Osteonecrosis of the Jaw

Medication-related osteonecrosis of the jaw (MRONJ) is a known side effect of bisphosphonates (BPs). Although bacterial infection is usually present, the etiology of MRONJ remains unknown. Here we apply a multimodal and multiscale (micro-to-nano) characterization approach to investigate the interface between necrotic bone and bacteria in MRONJ. A non-necrotic bone sample was used as control. Both necrotic and non-necrotic bone samples were collected from the jaw of a female individual affected by MRONJ after using BPs for 23 years. For the first time, resin cast etching was used to expose bacteria at the necrotic site. The bone–bacteria interface was also resolved at the nanoscale by scanning transmission electron microscopy (STEM). Nanosized particulates, likely corresponding to degraded bone mineral, were often noted in close proximity to or enclosed by the bacteria. STEM also revealed that the bone–bacteria interface is composed of a hypermineralized front fading into a highly disordered region, with decreasing content of calcium and phosphorus, as assessed by electron energy loss spectroscopy (EELS). This, combined with the variation in calcium, phosphorus, and carbon across the necrotic bone–bacteria interface evaluated by scanning electron microscopy (SEM)-energy dispersive X-ray spectroscopy (EDX) and the lower mineral-to-matrix ratio measured by micro-Raman spectroscopy in necrotic bone, indicates the absence of a mineralization front in MRONJ. It appears that the bone–bacteria interface originates not only from uncontrolled mineralization but also from the direct action of bacteria degrading the bone matrix.