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S. Baumgartner:
"Development of a 3D-printing process for colored dental ceramics and selective modification of polymers";
Talk: ViCEM - Vienna Center for Engineering in Medicine Biennial Meeting 2019, Wien; 2019-11-14 - 2019-11-15.

This work deals with the development of a hybrid 3D-printing process and the adaption of the
material systems. The stereolithography printers developed at TU Wien have already been used
to produce promising results regarding the production of materials such as alumina, zirconia,
glass ceramic, Bioglas®, bone substitutes and various resins. Limited by the operating principle
those printers do not allow the production of multi-material parts. Different colors or materials
in one single part are therefore not possible.
Parts of this work were performed within the Christian Doppler Laboratory for digital and
restorative dentistry. The goal of the first part of this work was to enable a customized coloring
of dental glass ceramic, especially lithium disilicate, during the stereolithographic process. At
first, this process was optimized, mechanical components implemented and the slurry adapted.
For the lithium disilicate system an outstanding translucency and biaxial bending strength of
over 350 MPa could be reproducibly achieved. Different methods for coloring were shown. For
a selective coloring an inkjet system was integrated into the stereolithographic process. An inkjet
printhead selectively places droplets of a ceramic ink in between the cured layers. Besides the
implementation of the components, a special focus was on the development of a printable
ceramic ink formulation. The limits of this process combination were demonstrated.
The second part of this work deals with another inkjet system and the development of a
polymeric matrix material and a suitable ink formulation. Natural brick-and-mortar structures,
such as nacre, have brittle components with very limited toughness, but outstanding mechanical
properties in combination. Inspired by such materials, the goal was to produce so-called `digital
materials´. For that, an inkjet printhead selectively places droplets of a soft material in between
the hard and brittle stereolithography layers. This leads to a modification of the (thermo-)
mechanical properties of the polymeric part, which was shown for a variety of different material
combinations. An increase of the strain at break as well as the toughness of over 45 % could be
achieved. For the very first time, multi-material polymer parts were produced with such a hybrid
printing process. A toughness modification without negative impact on the creep behavior is
possible.

Stereolithography, Glass Ceramics, Inkjet, Digital Materials