AVS 56th International Symposium & Exhibition
    Nanometer-scale Science and Technology Monday Sessions
       Session NS+BI-MoM

Paper NS+BI-MoM1
Zirconia Nanoplatelets for use in Dental Restoratives

Monday, November 9, 2009, 8:20 am, Room L

Session: Nanowires and Nanoparticles I
Presenter: K. Coulter, Southwest Research Institute
Authors: K. Coulter, Southwest Research Institute
V.Z. Poenitzsch, Southwest Research Institute
S. Wellinghoff, Southwest Research Institute
B. Furman, Southwest Research Institute
M. Rubal, Southwest Research Institute
D. Nicolella, Southwest Research Institute
K. Chan, Southwest Research Institute
Correspondent: Click to Email
Photopolymerizable composites containing very high volume fractions (>50%) of radio-opaque nanoplatelets in a low polymerization shrinkage, liquid crystalline (LC) monomer mixture are being developed as dental restoratives. The LC monomer promotes the organization of the nanoplatelets into either a smectic or columnar, colloidal liquid crystal structure with significantly enhanced strength. Further, theoretical calculations suggest that the tetragonal form of the yttria-stabilized zirconia nanoplatelets that SwRI is producing by a roll-to-roll, e-beam evaporation process can be induced to transform into a less dense monoclinic form in the presence of the hydrostatic tensile stresses expected at a growing crack tip within the composite resin. This transformational volume expansion coupled with the inherent ductility of the surrounding LC polymer matrix results in substantial improvements in dental composite wear resistance. SwRI has successfully coated onto a 200nm pitch, nanoembossed PET film in single run lengths of hundreds of meters, a 10 nm alkali halide release layer to produce a 50nm thick zirconia film of tetragonal crystal form which is subsequently removed by dissolving the alkali halide layer in water. The nanoembossed pattern transfers to the zirconia layer to produce nanoplatelets. three specific problems have been encountered including: (1) producing tetragonal zirconia of consistent morphology in different ca 100 meter runs, (2) complete fracture along the nanoembossed pattern, (3) color in the zirconia, most probably resulting from oxygen depletion and sub-4+ zirconia oxidation states. In this paper we will present the fabrication process and challenges in producing the nanoplatelets and present some of the preliminary composite data.