he regenerative approach is considered a promising direction for the application of biomaterials, where the focus is not on the physical filling of the defect, but on the replacement of the biomaterial with native bone, where the material plays the role of a porous active scaffold necessary for bone tissue ingrowth and mainly performs a guidance function. The regenerative approach also requires an osteostimulating effect of the implant material, while high mechanical stress during treatment can be excluded.

Despite the fact that the principle of complicating the chemical and phase composition of the material to give it qualitatively new properties has been known for a long time, the application of complex high-entropy ceramics for the stabilization of high-temperature resorbable phases releasing specific elements stimulating osteogenesis is offered for the first time.

The complex chemical composition of the scaffold is a key feature that endows the material with a set of biological properties and determines its behavior during the resorption process in the body. Traditional bioceramics with a simple chemical composition based on the main biogenic elements (calcium, phosphorus, oxygen) have limited possibilities to improve their functional properties, unlike, for example, modern structural alloys, which often have a very complex chemical composition and consequently new properties. It seems that the complication of the chemical composition of the inorganic matrix is in line with the development of the regenerative medicine approach - to stimulate the body to produce substances necessary for therapy (the body as a drug factory). Inclusion of microelements in the composition of bioceramics in addition to the main macroelements allows a) stabilization of polymorphic modifications with the required level of resorption (i.e. the rate of entry of biochemically active elements into the organism), b) entry of elements into the organism involved in certain biochemical processes allows targeted activation of these very processes associated with bone tissue regeneration.

Thermodynamic and kinetic stabilization of the high-temperature phase of the complex composition with excess free energy ensures its good resorption (solubility). This is important for the rapid entry of the contained elements into the body with a speed and corresponding effect comparable to the effect of injection or oral administration of a soluble form of a given element.

The architecture with interconnected macropores created by 3D printing will help to increase the resorbability of the composite. However, the main purpose of such architecture is to provide osteoconductive properties of the material, promote de novo bone ingrowth to the material accompanied by blood vessels, provide adhesion and proliferation of bone cells. In addition, the macropores of the scaffold can be filled with active patient cell cultures to stimulate osteogenesis.

Thus, osteoconductive ceramic implants are proposed with a specific macroporous architecture created by stereolithographic 3D printing based on a complex composition of high-entropy phases with controlled yield of osteoinductive elements. Each element of the complex composition of the proposed implant has a well-defined purpose.

This work was supported by the RSF [grant number 22-19-00219].