Papers by Author: Sergej M. Barinov

Abstract: A novel hydroxyapatite (HA-A) was developed and we evaluated the slow release of antibiotic in vitro as well as osteoconduction of the material in vivo. HA-A (4 x 4 mm) was synthesized by mixing HA powder, gelatin, and vegetable oil. The material had a bi-modal pore size distribution, with intragranular (10 nm to 10 µm) and intergranular (100 µm) pores, and porosity of 40 vol%, while a control HA had pore sizes ranging from 50 to 300 µm and identical porosity. In vitro drug release was tested using antibiotics soaked on the HA cylinders using a vacuum system. The mean adsorption efficiency was higher for HA-A than for control and higher levels of antibiotic were released from HA-A. Bone ingrowth into the pores was observed for both materials. Since the novel HA showed both the slower release of antibiotic (nanosize pores) and supported excellent osteoconduction (microsize pores), it could be useful for the treatment of osteomyelitis.

Abstract: Ultrafine hydroxyapatite (HA) and fluorhydroxyapatite (FHA) powders were synthesized and dense bioceramic samples were fabricated thereof. The samples were treepoint bend tested in different environments, i.e. in ambient air, distilled water and simulated human saliva, in the wide deformation rate range. Weibull’ statistics test was performed under standard testing conditions but in different media. The stress velocity exponent was evaluated from the dynamic fatigue testing data. The mean strength is shown to decrease when both ceramics are exposed to water or to simulated saliva. HA ceramics is more susceptible to the environment compared to FHA ceramics, due to the later is less subjected to the stress corrosion. Fracture surface observations revealed the crack propagation is of mixed trans- and intergranular mode. Strength distribution changes from uni-modal in air environment to bimodal in harsh conditions of water and saliva, indicating slow increment of flaw size in ceramics. Crack velocity exponent values correspond to transient region from dissociative chemisorption to ion solvation mechanisms of stress corrosion in both HA and FHA ceramics. Generally, FHA ceramics is considered to be much more reliable for application in bone defects replacement or dental reconstruction.