Hard zirconia ceramic in its hot-isostatically pressed constitution can be machined precisely and reproducibly using ultrafast lasers. However, the pulse overlap turns out to be of significant influence on the resulting surface quality.
This can be traced back to particulate process emission from the workpiece surface that influences subsequent pulses in the case of large pulse overlapping and can even agglomerate to debris layers above the processed surface.
Measurements of particle emission indicate that 90% of the ablated particulate material consists of nanoparticles, raising the demands on safe machine housing and suction measures. To produce all-ceramic dental crowns directly from sintered blanks without thermal damage or tool wear, a processing station, including a femtosecond laser system, has been designed based on high necessary processing dynamics and considering safety aspects.
The special demands for manufacturing laser-processed dental crowns led to an unique arrangement of motion axes whose dynamics is considerably increased beyond the state-of-the-art of simultaneous five-axis machining.
Principally accelerations are possible up to 100m/s2 for linear stages and 18000°/s2 for the rotational axes involved. This is realized by light-weight design for all moring parts of the axes and by powerful direct drives. In addition a high-speed CNC with shortest central loop cycles is applied to assure the outstanding dynamical performance of the laser processing system.
Regarding its adhesion to dental cement, Y-TZP has deficits compared to dentin. The fixation between cement and Y-TZP surfaces can be improved by artificial microstructures, added to the inner surface of laser-processed dental crowns in a final step during, ultrafast-laser-based manufacturing. Such microstructures have been evaluated by adhesion measurements between ceramic and cement that were based on shear and tensile strength tests, taking into consideration limit values from numeric simulations...
Reference download: Processing System for All-Ceramic Dental Crowns using Femtosecond Laser Machining by Niko Bärsch, Stephan Barcikowski (LZH) and Klaus Baier (Kugler GmbH).
Project description in German
Project concluded in 2009.
Final Report by Kugler (in German) see Downloads.
Project Partners:
- Polytec GmbH
- Jenoptik L.O.S. GmbH
- Kugler GmbH
- LZH Laserzentrum Hannover e. V.
- FGSW mbH
Project Coordinator:
Dr. Paul Weigl
Poliklinik für Zahnärztliche Prothetik
Uniklinikum ZZMK Haus 29
Theodor-Stern-Kai 7
60590 Frankfurt am Main
Tel:
Fax: 069 6301-3927
weigl@em.uni-frankfurt.de