PubMed · 12612667
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Robert W Cahn. 2003. Shape-memory alloys: Combinatorial high jinks.. https://doi.org/10.1038/nmat841
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The aim of this study was to assess the osseointegration of copper vapor laser-superfinished titanium alloy (Ti6Al4V) implants with pore sizes of 25, 50, and 200 microm in a rabbit intramedullary model. Control implants were prepared by corundum blasting. Each animal received all four different implants in both femora and humeri. Using static and dynamic histomorphometry, the bone-implant interface and the peri-implant bone tissue were examined 3, 6, and 12 weeks postimplantation. Among the laser-superfinished implants, total bone-implant contact was smallest for the 25-microm pores, and was similar for 50- and 200-microm pore sizes at all time points. However, all laser-superfinished surfaces were inferior to corundum-blasted (CB) control implants in terms of bone-implant contact. Within the 12-week study period, remodeling of woven bone initially formed within pores occurred only in the implants with 200-microm pores. Implants with 25-microm pores showed the highest amount of peri-implant bone volume at all time points, indicating that the amount of peri-implant bone was not correlated with the quality of the bone-implant interface. At 3 and 6 weeks postsurgery, we did not find any differences in mineral apposition rates or bone formation rates between the various implant surfaces. However, the peri-implant bone formation rate at the end of the trial was 70 and 62% higher in implants with 50- and 200-microm pores compared with CB implants, respectively. We conclude that, although laser-superfinished implants were not superior to CB control implants in terms of osseointegration, our study has provided further insights into the mechanisms of bone remodeling within pores of various sizes, and may form a basis for future experiments to design optimal implant surfaces with the help of modern laser technology.
An increase in levels of elemental Ti in the blood and lung of rats with a Ti alloy implant has been demonstrated. However, the pathophysiological role of the elevated elemental Ti level in the circulation remains unclear. Rats were implanted with Ti alloy discs for 4 weeks. The levels of elemental Ti in the blood and lung were especially increased compared with other tissues. The Ti alloy implant enhanced lung injury related to endotoxin from Gram-negative bacteria (lipopolysaccharide, LPS), which was characterized by lung edema and other histological changes such as recruitment of neutrophils, interstitial edema, and alveolar hemorrhage in the lung. In the presence of endotoxin, an increase of nitrite production was shown in the plasma and bronchoalveolar lavage fluid of rats implanted with a Ti alloy. Moreover, the Ti alloy implant further enhanced the induction of inducible nitric oxide (NO) synthase (iNOS) protein expression induced by LPS in the lung. These endotoxin-related responses in the presence or absence of the Ti alloy implant could be inhibited by aminoguanidine (an iNOS inhibitor). These results provide the first experimental evidence that circulating Ti released from Ti alloy implants has an ability to affect pulmonary iNOS protein expression, and enhance the pathogenesis of acute lung injury during endotoxemia.
The crystalline structures of the superionic high-temperature copper selenides Cu(2-x)Se (0 < x < 0.25) produced using mechanical alloying were investigated using X-ray diffraction (XRD). The measured XRD patterns showed the presence of peaks corresponding to the crystalline superionic high-temperature alpha-Cu(2)Se phase in the as-milled sample, and its structural data were determined by means of a Rietveld refinement procedure. After heat treatment in argon at 473 K for 90 h, this phase transforms to the superionic high-temperature alpha-Cu(1.8)Se phase, whose structural data were also determined by Rietveld refinement. In this phase, a very low occupation of the trigonal 32(f) sites ( approximately 3%) by Cu ions is found. In order to explain the evolution of the phases in the samples, two possible mechanisms are suggested: (i). the high mobility of Cu ions in superionic phases and (ii). the important diffusive processes in the interfacial component of samples produced by mechanical alloying.