Papers by Author: J. Suzuki

Abstract: The aim of this study was to optimize the surface treatment and to accelerate the osteoinductivity of porous bioactive titanium implant. Previous studies have reported that sodium removal with hot water treatment converts sodium titanate on the surface of an alkali-treated titanium plate into titania with a specific structure, which has better bioactivity than sodium titanate. We developed a dilute hydrochloric acid (HCl) treatment for porous titanium, which removed sodium from the complexly shaped porous structure more effectively than conventional hot water treatment. Three types of surface treatments were applied: (a) alkali and heat treatment, (b) alkali, hot water, and heat treatment (conventional treatment), and (c) alkali, dilute HCl, hot water, and heat treatment (Na-free treatment). The osteoinductivity of the materials implanted in the back muscles of adult beagle dogs was examined at three, six, and twelve months. Na-free porous bioactive titanium exhibited the highest osteoinductivity, and bone formation was observed within three months. This study showed that sodium removal has a significant positive effect on the osteoinductivity of the porous bioactive titanium implant.

Abstract: The nano-composite of a ceria-stabilized tetragonal zirconia polycrystals (Ce-TZP) and alumina (Al2O3) polycrystals (Ce-TZP/Al2O3) is attractive as a load-bearing bone substitute because of its mechanical properties and phase stability. We have developed a new method of hydrofluoric acid and heat treatment (HFT) to give a microporous structure to the surface of this Ce-TZP/Al2O3 nanocomposite ceramic. Bone-bonding ability of a microporous surface and calcium phosphate coating on Ce-TZP/Al2O3 composite has been investigated through in vivo detaching model. Thin calcium phosphate coating layer was added by alternate soaking process, and thick CaP layer was produced by soaking in simulated body fluid for 5 days. HFT treated Ce-TZP/Al2O3 composite showed high bone-bonding ability compared with the control group. Thick and thin CaP coating accelerated bone-bonding ability in early post-implantation period. The submicron microporous surface was beneficial for achieving mechanical interlocking between the ceramic and surrounding bone. These results suggest the possibility of using a Ce-TZP/Al2O3 nanocomposite ceramic with microporous surface and calcium phosphate coating as the bearing material for uncemented total joint replacements.

Abstract: Porous bioactive titanium implant was produced by plasma-spray method and succeeding chemical and thermal treatment. This porous titanium implant possess a porosity of 40% and complex interconnective porous structure. Mechanical property of porous titanium was characterized for compressive and 4-point bending properties, as well as compressive fatigue. Bone tissue response and biocompatibility of porous bioactive titanium implant was evaluated by in vivo osteoconductive model. Ultimate compression strength and bending strength were 280 and 101 MPa. Bone ingrowth showed significant increases in treated implant, while in these untreated porous titanium implant, bone ingrowth seemed to decrease with time. These results suggest that porous bioactive titanium is a candidate for clinical applications under load-bearing conditions.