HARD TISSUE-IMPLANT INTERACTIONS-2: BONE-CERAMIC AND BONE-POLYMER INTERACTIONS

Abstract

Ceramics commonly used in orthopedic surgery and traumatology as bone substitutes are of hydroxyapatite (HA), tricalcium phosphate (TCP) and glass origin. The advantage of ceramics over metals is their biological interaction with the implanted host tissue. Ceramics were so far described as biocompatible and biologically active materials. Recent studies, however, indicate that when implanted into the bone marrow, these implants can induce non-specific bone marrow inflammation and cellular depletion. Glass inomers are recently used to improve ceramics mechanical strength. These inomers, on the other hand, may cause adverse effects on neural tissues. Tissue necrosing heat of bone cement without changing its mechanical properties is trying to be reduced in recent years. Adding HA into the bone cement (PMMA) is a method that can be used for this reason. The biocompatibility of bone cement can also be improved by this method. Polymerization heat of bone cement can be decreased from 111°C to 87°C by adding HA into PMMA. This also increased the compressive strength of the bone cement. Injectable calcium phosphate cement is also a novel development in the field of bone ceramics. Polimers are mainly used for fracture fixation, bone replacement, cartilage regeneration, ligament and tendon fixation and controlled release of medicine. Following their clinical application, sterile sinus drainage and osteolysis around the implants are signs of tissue response. As the size of these implants increase the tissue reaction towards the implant is suspectected to increase. Hard tissue engineering will rise on the shoulders of appropriate scaffolds, local mediators and osteogenic cells in the near future. Tissue engineers should seek for scaffolds as close as to the bones elastic and rigid properties. Bioceramics are materials that mimic the mineral phase of the bone being good candidates as appropriate scaffolds.