Papers by Author: Masashi Iwasashi

Abstract: Regenos® is a unidirectional porous hydroxyapatite (UDPHAp) bone substitutes, and the most distinctive feature of UDPHAp is its interconnected porous structure. We used Regenos® for the bone defect while distal radius fracture surgery with metal fixation implant. At six months post-operation, CT scans revealed the Regenos® implant was uniformly composed of cortical bone adjacent to the trabecular bone. At one-year postoperatively, we collected a sample of the implanted Regenos® while metal fixation plate removal surgery for histological evaluation. Regenos® implant sample revealed the presence of ossified bone stained green with Villanueva Goldner stain. Our findings demonstrate that Regenos® is a useful bone substitution material in the clinical setting.

Abstract: Unidirectional porous hydroxyapatite (UDPHAp) was developed which has microstructure in that cross sectionally oval pores 100 ~ 300µm in diameter penetrate through the material, and that is suitable for osteogenesis and angiogenesis.The porosity of the UDPHAp was 75 % and the compression strength was 14 MPa. A cortical bone defect was made at proximal tibia of Japanese white rabbit, and a trapezoidal prisms shaped UDPHAp was implanted. By histlogical evaluation, 2 weeks after implantation, new bone and new capillary was observed inside UDPHAp. Twelve weeks after implantation, new bone formation was observed in 41.6 % of the porous area. The results of this study suggest a great possibility of utilizing it in actual clinical setting as a bone substitution.

Abstract: Porous ceramics of hydroxyapatite was fabricated utilizing the crystal growth of thin ice columns parallel to one another in gelatin gel containing hydroxyapatite nanoparticles. The obtained ceramics possessed unidirectional pore channels with a porosity of around 75% and showed compressive strength of up to 13.1 MPa. As control materials, porous hydroxyapatite ceramics with a directionless pore structure were also fabricated by isotropic freezing and compared with the unidirectional samples regarding compressive strength and tissue reaction in vivo. Although the porosity and pore size distribution were similar, the compressive strength and new bone formation ability of the unidirectional samples were significantly greater than those of the random structured porous ceramics.

Abstract: A biocompatible glue consisting of human serum albumin (HSA) and citric acid derivative (CAD), named CAD-A glue was developed. CAD was successfully synthesized by the reaction between citric acid and N-hydroxysuccinimide in the presence of 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide hydrochloride. When the CAD-A glue was applied to the collagenbased casings, it took 7 min to obtain half of maximum bonding strength (760 g/cm2). The bonding strength of this glue to collagen-based casings increased with increasing of HSA concentration.The bonding strength of CAD-A glue increased with increasing CAD concentration up to 200 mM, and then decreased with increasing CAD concentration under the fixed HSA concentration (50 w/w%). The CAD-A glue showed excellent wound closure ability rather than fibrin glue when applied to the mouse skin. These results suggested that this developed glue had both tissue compatibility and bonding strength for use in clinical field.