Nanophase ceramics

Thomas J. Webster, Nanophase Ceramics The Future Orthopedic and Dental Implant Material Yu-Ming Lin, Mildred S. Dresselhaus, and Jackie Y. Ying, Fabrication, Structure, and Transport Properties if Nanowires... 

Burggraaf, A. J., K. Keizer and B. A. van Hassel. 1989a. Nanophase ceramics, membranes and ion implanted layers. Paper read at S.I.C. Mat. 88-Nato ASl, Surfaces and interfaces of ceramic materials, 4-16 September 1988, lie d 01eron. 

The application of ceramics has infiltrated almost all fields in the last 20 years, because of their advantages over metals due to their strong ionic or covalent bonding. But it is just this bonding nature of ceramics that directly results in their inherent brittleness and difficulty in machining. In other words, ceramics show hardly any macroscopic plasticity at room temperature or at low temperatures like metals. Hence, superplasticity at room temperature is a research objective for structural ceramics. In recent years, many researches have been carried out to investigate nanophase ceramic composites. 

NANOPHASE CERAMICS THE FUTURE ORTHOPEDIC AND DENTAL IMPLANT MATERIAL... 

This chapter will discuss, in detail, properties of bone and of nanophase ceramics that promise increased orthopedic and dental implant efficacy. 

Limited reports in the literature that discuss the design, synthesis, and evaluation of nanophase ceramics for orthopedic and dental implants will also be discussed. 

VI. Next Generation of Orthopedic and Dental Implants Nanophase Ceramics... 

A. Surface Properties of Nanophase Ceramics for Enhanced Orthopedic and Dental Implant Efficacy... 

Enhanced osteoblast and osteoclast functions on nanophase ceramics due to increased surface wettability. Compared to conventional ceramics, nanophase ceramics exhibit enhanced surface wettability [evidenced, for example, by aqueous contact angles three times smaller... 

Fig. 11. Unfolding of vitronectin exposes epitopes for osteoblast adhesion on nanophase ceramics. Schematic representation (not in scale) of a possible mechanism for enhanced osteoblast adhesion on (a) nanophase, compared to (b) conventional, ceramics, which involves unfolding of the vitronectin macromolecule to expose select cell-adhesive epitopes (such as arginine-glycine-aspartic acid) for osteoblast adhesion. Increased exposure of cell-adhesive epitopes of vitronectin for enhanced osteoblast adhesion on nanophase ceramics may be due to nanometer surface topography and/or increased wettability due to the greater number of grain boundaries at the surface.

Due to their ability to selectively promote both osteoblast and osteoclast function, nanophase ceramics provide a preferable alternative to conventional orthopedic and dental implants that fail to integrate with surrounding bone it is undoubtedly highly desirable to minimize, if not avoid, clinical complications that necessitate removal of failed implants as a result of poor surface properties that lead to insufficient osseointegration. These results provide evidence that nanoceramics may be synthesized to match surface properties of bone and, thus, demonstrate strong promise and potential for their use in orthopedic and dental applications. 

Fig. 12. Schematic deformation properties of nanophase ceramics. For ceramics, decreasing the grain size into the nanometer regime corresponds to an increase in grain boundary sliding, resulting in increased ductility of these materials. (Adapted and redrawn from Siegel, 1994.)...

To date, few research groups have incorporated the enhanced mechanical properties of nanophase ceramics into orthopedic and dental applications. 

Undoubtedly, changes in porosity (such as bulk and surface porosity and diameter of individual pores) of nanophase ceramic formulated by Webster et al. (1999) provide an explanation for the observed differences in mechanical properties of respective nanophase and conventional ceramic formulations for example, individual surface pores four times smaller were achieved in nanophase (67-nm grain size) compared to conventional (179-nm grain size) HA formulations (Webster et al., 2000a). Compared to conventional formulations, therefore, the bending modulus of nanophase ceramics... 

Nanostructured ceramics provide alternatives not yet fully explored for orthopedic and dental implant applications the improved mechanical properties of these novel ceramic formulations, in addition to their established exceptional biocompatibility, constitute characteristics that promise improved orthopedic and dental efficacy. Requirements applicable for the design of nanophase ceramics for orthopedic and dental applications include the following ... 

As the disciplines of cell-tissue engineering and nanophase material science develop and mature, the preceding design criteria will be expanded and refined. Undoubtedly, nanophase ceramics have great potential to become the next generation of choice proactive biomaterials for innovative biotechnology and biomedical applications that could have profound clinical impact. 

Webster, T. J., Siegel, R. W., and Bizios, R., Osteoblast adhesion on nanophase ceramics. Biomaterials 20,1221-1227 (1999b). 

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