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Lasers in medicine and biophotonics: Parry and Jones

Laser Machining of Zirconia Ceramic for Manufacture of Dental Restorations

J. Parry¹ and N. Jones<sup>2

1</sup>Heriot-Watt University, Riccarton, Edinburgh, UK and ²Renishaw PLC, New Mills, Wotton-under-Edge, Gloucestershire, UK

Yittria-stabilized Tetragonal-Zirconia-Polycrystal (Y-TZP) is a high toughness and bio-inert engineering ceramic used in a number of medical applications including dentistry. Dental restorations manufactured from Y-TZP at Renishaw are machined from billets of Y-TZP in its final state using diamond grinding tools. Final state machining is necessary as every restoration is unique yet must be made to high precision. Unfortunately, due to the same properties that make Y-TZP desirable for this application, the machining time is slow and tool intensive.

Recent work conducted at Heriot Watt University has focused on laser machining of Y-TZP as an alternative or complimentary process to diamond grinding with the goal of significantly reducing machining times and therefore cost. Due to the thermal characteristics of the material laser machining is not trivial. High (relatively) material removal rates may be achieved by operating at ms pulse durations. In this regime it is possible to produce cuts of up to 13mm depth suitable for outline cutting. The surface finish is however poor with a significant heat affected zone (HAZ) and limited minimum feature size.

Improvements in surface finish and fine features (smaller than for diamond-grinding) can be achieved by moving to shorter pulse durations (ns or shorter) but at the expense of processing time. Using a ns-pulse duration system it is possible to remove the HAZ from a ms-laser-machined part and impart fine scale features. In this way a combined laser process is possible utilising the benefits of the ms and ns regimes while avoiding the disadvantages of each.

 

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AILU one-day technology workshop as part of the Industry and Technology Programme at Photon08.

Photonics is an enabling technology for many products in different sectors. Increasingly important in all areas this seminar is designed to highlight developments in laser technology as applied to medical and biophotonics areas. The burgeoning specialism of photonics in the medical sector is addressed in this one-day meeting as part of Photon 08.

Duncan Hand of Heriot-Watt University will be chairing the event.

This is a Medical Group event - for more information about the Medical Special Interest Group or to join contact the AILU Office.