title: Additive CAD/CAM process for dental prostheses.
abstract: This article describes the evolution of a computer-aided design/computer-aided manufacturing (CAD/CAM) process where ceramic paste is deposited in a layer-by-layer sequence using a computer numerical control machine to build up core and fixed partial denture (FPD) structures (robocasting). Al(2)O(3) (alumina) or ZrO(2) (Y-TZP) are blended into a 0.8% aqueous solution of ammonium polyacrylate in a ratio of approximately 1:1 solid:liquid. A viscosifying agent, hydroxypropyl methylcellulose, is added to a concentration of 1% in the liquid phase, and then a counter polyelectrolyte is added to gel the slurry. There are two methods for robocasting crown structures (cores or FPD framework). One is for the core to be printed using zirconia ink without support materials, in which the stereolithography (STL) file is inverted (occlusal surface resting on a flat substrate) and built. The second method uses a fugitive material composed of carbon black codeposited with the ceramic material. During the sintering process, the carbon black is removed. There are two key challenges to successful printing of ceramic crowns by the robocasting technique. First is the development of suitable materials for printing, and second is the design of printing patterns for assembly of the complex geometry required for a dental restoration. Robocasting has room for improvement. Current development involves enhancing the automation of nozzle alignment for accurate support material deposition and better fidelity of the occlusal surface. An accompanying effort involves calculation of optimal support structures to yield the best geometric results and minimal material usage.
authors.affiliation: Department of Prosthodontics, New York University College of Dentistry, New York, NY 10010, USA. nrd1@nyu.edu
authors.forename: Nelson R F A
authors.initials: NR
authors.lastname: Silva
authors.forename: Lukasz
authors.initials: L
authors.lastname: Witek
authors.forename: Paulo G
authors.initials: PG
authors.lastname: Coelho
authors.forename: Van P
authors.initials: VP
authors.lastname: Thompson
authors.forename: Elizabeth D
authors.initials: ED
authors.lastname: Rekow
authors.forename: Jim
authors.initials: J
authors.lastname: Smay
mesh_terms: D000537:Aluminum Oxide; D017076:Computer-Aided Design; D003442:Crowns; D003776:Dental Porcelain; D017267:Dental Prosthesis Design; D003830:Denture, Partial, Fixed; D007281:Ink; D011327:Printing; D015040:Zirconium
chemical_list: D003776:Dental Porcelain; D015040:Zirconium; D000537:Aluminum Oxide; C028541:zirconium oxide