Histomorphological evaluation of osteoreplacement with germanium-doped calcium phosphate ceramics for model bone defects in rabbits

To give calcium phosphate ceramics osteoinductive properties, they are doped with silicon, germanium, zinc, and magnesium ions. The aim of this study was to evaluate the effects of doped and undoped calcium phosphate ceramics on reparative osteogenesis in rabbits. Twenty-four California white rabbits, aged 3 months and weighing 2.5 kg each, were used for the study. The rabbits were divided equally into experimental (n=12) and control (n=12) groups. In the experimental group, defects were replaced with granules of germanium -doped hydroxyapatite ceramics (HA/(3-TCP/l-Ge-700), while in the control group, defects were filled with granules of unalloyed ceramics (HA/(3-TCP-700). Subsequently, clinical and histological studies, along with the determination of bone metabolism markers: the activity of total alkaline phosphatase (AP), bone isozyme (BAP), and tartrate -resistant acid phosphatase (TRAcP) were assessed on the 7th, 14th, 30th, and 60th days. Animals were removed from the experiment on the 14th, 30th, and 60th days of the research. A large number of capillaries, vascular channels, and close contact of the regenerate with the implant were detected in the histological samples after HA/(3-TCP/l-Ge-700 osteoreplacement on the 14th day. On the 30th day, formation of lamellar bone tissue well -integrated with the parent bone as well as partial resorption of ceramic granules was noted. When using HA/(3-TCP-700, similar results were observed 2 weeks later. A significant difference was established between the levels of bone biochemical markers in the control and experimental groups. In the experimental group, the activity of AP and BAP reached peak values on the 14th day. In the control group, they increased gradually with a peak on the 60th day. Therefore, osteoreplacement with germanium -doped ceramics was accompanied by an early osteoblastic reaction. TRAcP activity was higher in the experimental group on the 14th day, while in the control group, it was elevated on the 30th and 60th days. This indicates a lower level of osteoresorptive processes in the experimental group. It was concluded that HA/(3-TCP/l-Ge-700 has osteoinductive and osteointegration properties. It also provides early neoangiogenesis and osteoblastic reaction.