Papers by Author: Jiro Tamura

Abstract: We had investigated the biocompatibility, osteoconductivity, and biodegradability of a porous composite of hydroxyapatite (HA) and poly-DL-lactide (PDLLA) implanted into rabbit femoral condyles. It showed excellent osteoconductivity and biodegradability as a bone substitute. Newly formed bones were remodeled, and materials were resorbed almost completely at 78weeks after implantation. In consideration of its biocompatibility and degradability, we investigated its potential for use as a cellular scaffold and evaluated its osteoinductive property. On implantation to the rat dorsal subcutaneous tissue loaded with syngeneic bone marrow cells, osteogenesis with enchondral ossification was seen both on and in the material at 3 weeks after implantation. This osteogenesis in the HA/PDLLA tended to get mature and newly formed bone tissues were found in the material by 6weeks. To investigate the osteoinductive property material itself has, we attempted to implant this porous composite material to extra-osseous canine dorsal muscle. At 2months, osteogenesis was seen in the pores of the material. It indicated the material induced osteogenesis with intramembranous ossification process. Therefore, HA/PDLLA might be a desirable material for bone substitutes and cellar scaffolds with osteoconductive and osteoinductive property.

Abstract: A new composite bone cement designated ‘G2B1’ was developed for percutaneous transpedicular vertebroplasty. G2B1 contains beta tricalcium phosphate particles and methylmethacrylate –methylacrylate copolymer as the powder components, and methylmethacrylate, urethane dimethacrylate, and tetrahydrofurfuryl methacrylate as the liquid components. Osteoconductivity and histological changes with time were evaluated using scanning electron microscopy, contact microradiography, and Giemsa surface staining 4, 8, 12, 26, and 52 weeks after implantation into rat tibiae. To evaluate osteoconductivity, affinity indices (%) were calculated. Scanning electron microscopy and contact microradiography revealed that bone contact with G2B1 was attained within 4 weeks (affinity index: 50.2 ± 11.8 at 4 weeks) and at most of the margin within 26 weeks (affinity index: 87.4 ± 7.2 at 26 weeks). Giemsa surface staining showed that there was almost no inflammatory reaction around the G2B1. These results indicate that G2B1 is a biocompatible and highly osteoconductive bone cement.

Abstract: Three types of polymethylmethacrylate (PMMA)-based composite cements containing 40− 56 wt% micron-sized titania (titanium oxide) particles, designated ST2-40c, ST2-50c, and ST2-56c, were developed as bone substitutes for vertebroplasty, and evaluated for their mechanical, setting, and biological properties. In animal experiments, ST2-50c and ST2-56c were implanted into rat tibiae and solidified in situ. Their biological properties were evaluated at 6 and 12 weeks after implantation. Compressive strength, bending strength, and bending modulus increased with increasing titania content. Peak temperature during the setting reaction decreased as the filler content increased. ST2-56c had direct contact with bone over larger areas than ST2-50c at 6 and 12 weeks. Data from the present study indicated that ST2-56c is a good candidate as a bone substitute for vertebroplasty.

Abstract: We investigated the biocompatibility, osteoconductivity, and biodegradability of porous composite of Hydroxyapatite (HA) and Poly D/L-lactide (PDLLA). At 6weeks afterimplantation to rabbit femoral condyle, HA/PDLLA was covered with bone and contacted with bone directly. The amounts of newly formed bone in the pores had increased during the examined period. By 26weeks, bone remodeling of formed bone in the pores was seen and bone marrow tissue formation was seen in the pores of HA/PDLLA. Porous HA/PDLLA was resorbed much faster than porous HA as a control. Porous HA/PDLLA was resorbed constantly through the bone formation and bone remodeling but porous HA was hardly resorbed during the period. It might be one of the desirable materials for bone substitute. To evaluate for a scaffold, disc shaped blocks loaded with rat bone marrow cell were implanted in the subcutaneous pouch of the back of syngeneic rat. At 3weeks afterimplantation, newly bone formation in the pores was observed at ectopic site. It also suggested the availability of this material as cell scaffolds.