[Show abstract][Hide abstract] ABSTRACT: Samples of porous Ti metal were subjected to different acid and heat treatments. Ectopic bone formation on specimens embedded in dog muscle was compared with the surface characteristics of the specimen. Treatment of the specimens by H2SO4/HCl and heating at 600°C produced micrometer-scale roughness with surface layers composed of rutile phase of titanium dioxide. The acid- and heat-treated specimens induced ectopic bone formation within 6 months of implantation. A specimen treated using NaOH followed by HCl acid and then heat treatment produced nanometer-scale surface roughness with a surface layer composed of both rutile and anatase phases of titanium dioxide. These specimens also induced bone formation after 6 months of implantation. Both these specimens featured positive surface charge and good apatite-forming abilities in a simulated body fluid. The amount of the bone induced in the porous structure increased with apatite-forming ability and higher positive surface charge. Untreated porous Ti metal samples showed no bone formation even after 12 months. Specimens that were only heat treated featured a smooth surface composed of rutile. A mixed acid treatment produced specimens with micrometer-scale rough surfaces composed of titanium hydride. Both of them also showed no bone formation after 12 months. The specimens that showed no bone formation also featured almost zero surface charge and no apatite-forming ability. These results indicate that osteoinduction of these porous Ti metal samples is directly related to positive surface charge that facilitates formation of apatite on the metal surfaces in vitro.
[Show abstract][Hide abstract] ABSTRACT: Bone ingrowth into porous Ti metal is important for stable fixation of Ti metal implants to surrounding bone. However, without surface treatment this is limited to only a thin region of the outer surface of the Ti metal. In the present study, a porous Ti metal with a porosity of ~60 % and interpore connections of 70-200 micrometers in diameter was investigated in terms of its chemical and heat treatments, by implanting it into rabbit femur for periods varying from 3 to 12 weeks. The porous Ti metal subjected to heat treatment at 600 °C after H2SO4/HCl mixed acid treatment showed the largest bone ingrowth in comparison with those subjected to no treatment, only acid treatment, and only heat treatment even at an early stage after implantation, and remained as such even 12 weeks after implantation. Their bone ingrowths were well interpreted in terms of apatite-forming abilities of the Ti metals in body environment. Their apatite-forming abilities did not depend upon their surface roughness nor type of crystalline phase, but upon the positive surface charge.
Full-text · Article · Mar 2013 · Journal of Materials Science Materials in Medicine
[Show abstract][Hide abstract] ABSTRACT: We previously found that a positively charged Ti metal has a higher apatite forming ability in vitro than a non-charged Ti metal. For in vivo analysis using a rabbit model, two types of Ti metal were examined: porous Ti metals heat-treated subsequent to a mixed acid treatment (MHs) and porous Ti metals not heat-treated subsequent to the same mixed acid treatment (MOs). Although MHs and MOs had the same macro- and micro-structure, they had different surface charges. MHs, considered positively charged, had significantly higher bone ingrowth than MOs, considered charged zero. Similarly, MHs had significantly higher percentages of bone–implant contact than MOs at 3- and 6-week. A simple heat treatment made acid-treated porous titanium implants more osteoconductive. These results suggest that a positive charge obtained by a heat treatment enhances bioactivity of acid-treated titanium implants.
Full-text · Article · Oct 2011 · Key Engineering Materials
[Show abstract][Hide abstract] ABSTRACT: The objective of this study was to establish the efficacy and safety of porous bioactive titanium metal for use in a spinal fusion device, based on a prospective human clinical trial. A high-strength spinal interbody fusion device was manufactured from porous titanium metal. A bioactive surface was produced by simple chemical and thermal treatment. Five patients with unstable lumbar spine disease were treated surgically using this device in a clinical trial approved by our Ethics Review Committee and the University Hospital Medical Information Network. Clinical and radiological results were reported at the minimum follow-up period of 1 year. The optimal mechanical strength and interconnected structure of the porous titanium metal were adjusted for the device. The whole surface of porous titanium metal was treated uniformly and its bioactive ability was confirmed before clinical use. Successful bony union was achieved in all cases within 6 months without the need for autologous iliac crest bone grafting. Two specific findings including an anchoring effect and gap filling were evident radiologically. All clinical parameters improved significantly after the operation and no adverse effects were encountered during the follow-up period. Although a larger and longer-term follow-up clinical study is mandatory to reach any firm conclusions, the study results show that this porous bioactive titanium metal is promising material for a spinal fusion device.
Full-text · Article · Mar 2011 · European Spine Journal
[Show abstract][Hide abstract] ABSTRACT: Porous titanium metal subjected to NaOH and heat treatments is useful as a bone substitute as it shows high mechanical strength as well as osteoconductivity and osteoinductivity. However, the porous metal is liable to be contaminated with oxygen gas during the fabrication process and this incorporated oxygen could lead to adverse effects on the bioactivity and mechanical properties of the prepared porous body. In this study, oxygen contamination during fabrication of bioactive porous bodies was measured. It was found that the oxygen content of the titanium metal was increased from 0.08 to 0.23 mass% when the porous body was prepared from bar stock, and it further increased up to 0.51 mass% when it was subjected to NaOH and heat treatments. Despite this, the porous bodies subjected to NaOH and heat treatments formed apatite on their pore walls within 1 day in a simulated body fluid. This result was consistent with the apatite-forming ability of NaOH- and heat-treated titanium plates with different oxygen contents in the range of 0.05 to 0.30 mass%. The compressive strength of the porous body was increased about 10% by the NaOH and heat treatments.
Full-text · Article · Aug 2009 · Materials Science and Engineering C