Experimental studies on the mechanical property and biocompatibility of zirconia dispersed hydroxyapatite ceramic.
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The mechanical properties and biocompatibility of zirconia dispersed hydroxyapatite ceramic (HAP-ZrO<SUB>2</SUB>) were examined. The composition of HAP-ZrO<SUB>2</SUB> was 50 Vol% hydroxyapatite and 50 Vol% zirconia.<BR>1. Mechanical properties.<BR>Bending strength, Young's modulus and fracture toughness of HAP-ZrO<SUB>2</SUB> were 270 MPa, 60 GPa, 4.5 MPa·m<SUP>1/2</SUP> respectively.<BR>Compared with other bioactive ceramics, such as tricalcium phosphate (TCP), hydroxyapatite ceramic (HAP) and apatite-wollastonite-whitlokite glass ceramic (A-NV-CP GC), these values showed the HAP-ZrO<SUB>2</SUB>, had high mechanical strength and low Young's modulus which was close to those of human cortical bone and tooth.<BR>2. Biocompatibility <I>in vitro</I>.<BR>By using L-929 cells, the HAP-ZrO<SUB>2</SUB> and HAP cell adhesiveness experiements and cell growth were evaluated.<BR>HAP-ZrO<SUB>2</SUB> and HAP showed no cytotoxity to L-929 cells. There were no significant differences between both ceramics concerning initial cell attachment and cell growth rate. Morphological changes of the cells on both materials observed by scanning electron microscopy also showed excellent biocompatibility of HAP-ZrO<SUB>2</SUB> and HAP.<BR>3. The biocompatibility in vivo.<BR>HAP-ZrO<SUB>2</SUB> and HAP were implanted into femurs of 10 week old male rats of an inbred Wistar strain. These rats were killed 1, 2, 4, 8, 12 weeks after implantation. Undecalcified ground sections were examined by light microscopy, contact microradiography and scanning electron microscopy.<BR>Both ceramics were in direct contact with newly formed bone and there was no fibrous connective tissue at the interface. Mode and rate of bone formation were quite similar in both ceramics.<BR>Because of its high bending strength and fracture toughness low Young's modulus and excellent biocompatibility, HAP-ZrO<SUB>2</SUB> seems to be one of the most useful substitute materials for bone and tooth.