An objective of the project will be to completely replace existing dental fillers with a high volume fraction of radio-opaque nanoplatelets of very narrow size distribution that will be compatible with a previously synthesized nematic monomer matrix of very low polymerization shrinkage. Of special interest are compositions of high radio-opacity and low cost, such as ZrO2 and barium substituted oxides. Nanoplatelets of narrow size distribution will form workable, nematic and/or columnar phases with liquid crystalline monomers at volume fractions as high as 60% which can be polymerized to radio-opaque resins of high elastic modulus and exceptional toughness. The typical impediments of particle aggregation and mixing inherent in a solution based process will be surmounted and scaled to continuous production at reasonable cost using multiple film coatings by vacuum evaporation or hydrothermal deposition and functionalization by casting on moving plastic substrates. Microprinting-embossing techniques will be used to pattern the substrate and permit the segmentation of the multilayer film into platelets of nanomeric thickness and very well defined micron and submicron lateral dimension. Preparation of ZrO2 nanoplatelets of tetragonal crystal structure is a major objective since the stress induced martensitic transformation to monoclinic form (1) dissipates elastic strain energy by plastic deformation and (2) is volume expansive and thus can further compensate for polymerization shrinkage. We will optimize the particle shape, surface functionalization and composite processing conditions to maximize the particle loading without adversely affecting clinical application. In addition we hypothesize that coating the nanoplatelet, inorganic core with a layer of oligomer that will polymerize to ductile coatings will promulgate conversion to a composite morphology with a nanoplatelet reinforced interpenetrating, ductile phase.
| Furman, Benjamin R; Wellinghoff, Stephen T; Thompson, Paul M et al. (2008) Preparation, characterization, and modeling of alpha-zirconium phosphonates with ether-functional surfaces. Chem Mater 20:5491-5499 |
