| 概要 |
βTCP foam is thought to be an ideal bone replacement because (1) it would be replaced to new bone due to balanced bioresorbability and bone formation and (2) it has fully interconnected porous structu...re that allows tissue ingrowth and nourishment supply to bone cells. However, βTCP foam has not been fabricated using the polyurethane foam replica method up to date due to insufficient sintering reaction when sintered below α-β transition temperature. In this study, new methods was proposed to fabricated βTCP foam. One is the use of β phase stabilizer and the other is the phase transformation from αTCP to βTCP based on heat treatment. In Chapter 2, βTCP foam was found to be fabricated by employing MgO as βTCP stabilizer. 3 mol% or larger amount of Mg was the key to stabilize βTCP phase when sintered at 1,500°C. The compressive strength of the βTCP foam fabricated using MgO stabilizer was similar regardless of the amount of added Mg. In Chapter 3, pure βTCP foam was prepared based on phase transformation of sintered αTCP foam by heat treatment below α-β transition temperature. The heat treatment at 800°C to 1,000°C resulted in complete phase transformation from αTCP to βTCP. Heat treatment at 1,000ºC for 300 hours resulted in highest compressive strength or the same compressive strength with that of αTCP foam. In Chapter 4, osteoconductivity and bioresorbability was evaluated using experimental animals, rabbits. Micro-CT scan analysis and histological analysis demonstrated that dissolution and replacement to newly formed bone occurred simultaneously in rabbit bone for both Mg-βTCP foam and βTCP foam fabricated by heat treatment (HT-βTCP foam). Especially, HT-βTCP foam showed proper osteoconductivity and bioresorbability in the condition employed in this animal study. HT-βTCP foam replaced to new bone after 20 weeks of implantation. Mg-βTCP foam also showed bioresorbability and thus, the bone defect was healed after 20 weeks implantation. However some Mg-βTCP foam still remained even at 20 weeks. In other words, Mg stabilizer is also useful for the regulation of bioresorbability. In conclusion, the results of the present study demonstrated that βTCP foam with fully interconnected porous structure can be fabricated in two methods. One is using Mg as β phase stabilizer, and the other is heat treatment of the αTCP foam. The βTCP foams thus prepared could be ideal bone replacements which can be replaced to new bone.続きを見る
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