Characteristics of Reactogenicity in Distant Time Periods After Implantation of Bone Tissue Substituting Biomaterials. Summary of the Doctoral Thesis

Abstract

Prevention of functional and esthetic oral defects as a result of pathologies and trauma is still a topical practice in stomatology in Latvia, as well as in other countries of the world. Various type of implants are used, being the basic means in solution of this problem, but mostly these are calcium phosphate-containing materials. Alongside with it, research work is going on too, mainly for the improvement of implants’ qualitative properties. Despite it, research in investigating the use of bone tissue substituting biomaterials in stomatology and orthopaedics is a topical issue in the world and also in Latvia. The aim of the study was to analyze morphological factors of local reactions in experimental animals’ tissues at different periods of time after the implantation of bone tissue substituting biomaterials. 19 animals were included into the study, altogether 33 experimental samples were obtained from biomaterials implantation zone, and 12 control samples. Animals were implanted noncommercial – Riga Tehnical university Rudolfs Cimdins Riga Biomaterials Innovation and Development Centre developed biomaterials implants and commercial material, and in 3, 4.5, 6 and 8 months there was done the animal euthanasia and removal of bone tissue samples. In morphological routine examination of tissue samples there was found the formation of a new bone three months after the implantation of uncoated hydroxyapatite (HAP) tablet, with polycaprolactone coated HAP tablet (HAP/PCL), polymethylmethacrylate (PMMA) cement and unsintered HAP granule implantation without extensive resorbtion zones which indicate to the more expressed osteoinductivity of the materials mentioned in comparison to different tricalcium phophate cements. In bone tissue samples there were determined antimicrobial protein β-Defensin-2 (βDef-2), proinflammatory cytokins – interleukin (IL)-1, IL-6, IL-8, antiinflammatory cytokin IL-10, bone matrix protein osteopontin (OP) and osteocalcin (OC), bone morphogenetic factor (BMP-2/4) and cell functional activity parameter osteoprotegerin (OPG) expressing osteocytes, as well as apoptotic osteocytes, their amount in 3, 4.5, 6 and 8 months being variable. Data analysis showed statistically significant BMP-2/4 expression for three months after implantation of HAP and their containing materials, indicating to the selectivity of expression, depending on the type of biomaterial. Apoptosis is more active within 3 months after implantation, during which one can find a statistically significantly greater number of apoptotic osteocytes and proinflammatory cytokin IL-1 containing osteocytes and selectivity being prevalent, which is characteristic for HAP biomaterial.