Dynamics of biochemical bone and endothelial parameters during the replacement of bone defects in dogs with hydroxyapatite ceramic doped with silicon

Metal structures for osteosynthesis available in veterinary orthopedics are not able to compensate for the lost elements of bone tissue in complex splinter fractures. It is prompt the use of hydroxyappatite materials that replaced bone defects for maintenance of osteoconductive function, and ideally would combine osteointegration and osteoinductive properties. However, their influence on the biological processes of fracture consolidation which go through a number of successive stages and end with the formation of bone tissue in the fracture zone identical to the maternal, is insufficiently substantiated according to the criteria of the molecular biological phase of reparative osteogenesis. The aim of the study was to investigate the dynamics of biochemical osteotropic parameters and the level of NO using silicon-doped ceramics for fractures heeling in dogs. Materials and methods. The animals suffering of fractures that were admitted to the faculty clinic were divided into control (n=7) and experimental (n=7) groups. In both groups, extracortical osteosynthesis was performed with a support plate from an unalloyed titanium alloy. In the control group, bone defects were left to heal under spontaneous blood clot, and in the experimental group, they were replaced with ceramic based on hydroxyapatite with β-tricalciumphosphate doped with silicon (HA/β-TCP/l-Si–3).Blood samples were taken after the injury no later than the 48th day, and on the 3th, 12th, 21th, 42th and 60th days after osteosynthesis. To increase the objectivity of the biochemical analysis, we additionally formed a group of clinically healthy dogs that were admitted to the clinic for routine vaccination (n=10). It included the spectrophotometric determination of the content of NO, BALP, TRACP, Ca, P, Mg, total protein in blood serum, and fibrinogen in blood plasma. Research results. A clinical study showed that in the case of using HA/β-TCP/l-Si–3for splinter fractures, the stages of reparative osteogenesis are more optimized in time, and their consolidation occurs on average 19 days earlier than in the control group. The results of the biochemical study showed that when using HA/β-TCP/l-Si–3, it is accompanied by a peak NO value already on the third day, which is significantly higher than in the control group and indicates early angiogenesis in the research group. In terms of TRACP, the period of osteoresorption in the control group was permanent with little expressed peaks of activity. However, in the research group, the peak of TRACP activity is limited to 12 and 21 days, which is evidence of an optimized inflammatoryresorptive phase. In parallel with this, the activity of BALP increases, which indicates the consistency of the stages of reparative osteogenesis and provides an optimized and accelerated consolidation of fractures in the research group. Conclusion. The dynamics of NO, BALP and TRACP pathochemically substantiates the optimized reparative osteogenesis when using HA/β-TCP/l-Si–3 for bone defects replacement in cases of splinter fractures of tubular bones. Key words: bone markers, bone isoenzyme of alkaline phosphatase, NO, tartrate-resistant acid phosphatase, fibrinogen, calcium, phosphorus.

Influence of Mg Incorporation on Mechanical, Dielectric and Biological Properties of Hydroxyapatite Ceramic

This research focused on the mechanical electrical and biological properties of magnesium doped (Mgx, x = 0.5 - 2.5 mol%) hydroxyapatite(Hap) using chemical method. It was observed that addition of magnesium produced the secondary phase (whitlockite) depended on the concentration of magnesium using the XRD, FTIR and Raman techniques. These two phases forming BCP(Biphasic) are beneficial from the implant point of view. The dielectric properties were measured as a function of frequency for different concentration of Mg. For 1.0 -2.0mol% doped Mg samples showed dielectric constant value within the range required for implant material. The bioactivity and However, beyond 2mol% of Mg third phase of magnesium oxide was also observed which enhanced the micro-hardness and bioactivity of specimen.