Alifui-Segbaya, Frank, Cameron, Andrew, Starkey, Shaye, Villamizar Pinilla, Katherynn, Evans, Jane

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1 Are Laser Sintered Alloys Safe in our Mouths? Author Alifui-Segbaya, Frank, Cameron, Andrew, Starkey, Shaye, Villamizar Pinilla, Katherynn, Evans, Jane Published 2013 Conference Title Proceedings of the Gold Coast Health and Medical Research Conference Copyright Statement The Author(s) 2013.The attached file is posted here with permission of the copyright owners for your personal use only. No further distribution permitted. For information about this conference please refer to the publisher's website or contact the authors. Downloaded from Link to published version Griffith Research Online

2 ARE LASER SINTERED ALLOYS SAFE IN OUR MOUTHS? Alifui-Segbaya, F. 1 Cameron, A. 1 Starkey, S. 2 Villamizar Pinilla, K. 2 Evans, J.L. 1 1 Dental Technology Academic 2 Dental Technology Student

3 Content 1. Additive Manufacturing (AM) 2. Applications of Additive manufacturing in Dentistry 3. Current research 4. Corrosion of Dental Alloys 5. Test Design 6. Time dependence corrosion test (ISO 10271) 7. Results 8. Conclusion

4 Traditional Casting Technique Preparing master model, Surveying, Blocking out... Duplicate Additive Manufacturing Technique Wax up Sprue Invest Preheat Digital Surveying and framework design 3D Scanning Additive Manufacture SLM/SLS Casting and Devesting Final Framework Final Framework

5 Additive Manufacturing Metal Additive manufacturing is a digitally driven process that uses focused laser beams or electron beams to fuse metallic powders, in a layer-by-layer fashion into three dimensional (3D) objects. The laser fuses the Co-Cr powder layer by layer at a temperature of 1400 C

6 Additive Manufacturing (AM) in Dentistry Stages of production for a laser sintered removable partial denture. A) Dental prosthesis directly after manufacturing, B) with support structures removed and surface polished, C) after completion (left to right). Source: EOS GmbH Dental prostheses (steps in production from left to right: with support structures, surface ready for veneer, after ceramic veneer) on a dental model. Source: EOS GmbH AM guarantees: Fitting accuracy, Good mechanical properties and Reduced labour time and stock

7 Current Research Research have shown that the different manufacturing techniques could affect the inherent mechanical properties of alloys with a consequent influence on corrosion behaviour. However, there are few published literature on corrosion available for academic reflection. If AM techniques are to be fully adopted in denture framework production, full characterization of material properties is required to ensure compliance with appropriate medical device regulation and specific ISO standards.

8 This project compares the corrosion properties of AM alloy to dental casting alloy for in vitro ion release in accordance with ISO 10271:2009.

9 Corrosion During corrosion, free metals can gain access into the body through swallowing, membrane diffusion and epithelium into the gut, gingiva and other oral tissues and may cause toxic, inflammatory, allergenic or mutagenic reactions in sufficient concentrations. The release of metal ion is said to be continuous in the mouth due to abrasion of alloy restorations from foods, liquids and toothbrushes. Corrosion can lead to poor aesthetics and compromise the strength of alloys.

10 Corrosion Test The most important test that can predict the physical and biocompatibility properties of dental alloys.

11 Test Design Comparative study: Compared AM Co-Cr alloy to a dental casting Co-Cr alloy. International standardized test : ISO 10271:2009 Specimens were prepared to simulate clinical cases. Atomic Absorption Spectroscopy: reliable and widely used measuring technique for clinical, industrial, environmental and pharmaceutical analyses. Long-term corrosion behavior (stringent test - 42 days) > ISO recommend days.

12 Time-dependence corrosion test,iso 10271:2009 The analytes were verified for Cobalt (Co), Chromium (Cr) and Molybdenum (Mo), which form the bulk of both alloys using an atomic absorption spectrometer after 1, 4, 7, 14, 21, 28, 35 and 42 days at a detection limit of one part per million.

13 Total ion release (µg/l) Results Keys: VP = Vitallium Polished VEB = Vitallium Electrobrightened EP = EOS AM Polished EEB = EOS AM Electrobrightened VP VEB EP EEB Test Samples Co Cr Mo Samples Co (µg/l) Cr (µg/l) Mo (µg/l) Total (µg/l)* μg/cm²** VP Mean ±SD ± ± ± ± ±0.147 VEB Mean ±SD ± ± ± ± ±0.067 EP Mean ±SD ± ± ± ± ±0.019 EEB Mean ±SD ± ± ± ± ±0.031

14 Conclusion Overall, the AM Co-Cr alloy shows a higher resistance to corrosion (p<0.01) than the casting alloy, perhaps due to the latter's predictable mechanical properties and superior homogeneity. However, total ion release from both alloys given the two different surface treatments is well within the threshold prescribed by the ISO (200µg/cm² for days).

15 Together with previous research that demonstrates the technical feasibility of designing and producing complex dental framework designs using AM, this research provides further evidence that can support the development of AM techniques as an alternative to casting. Further biocompatibility tests are recommended.

16 Acknowledgements The authors are grateful to Dr. R.J Williams, Dr. Paul Foley, Dr. Dominic Eggbeer, all of Cardiff Metropolitan University (UK) for their support and Renishaw (UK) for supplying the AM test samples.

17 References 1. Agilent technologies - Retrieved 20 September, 2013 from 2. Alifui-Segbaya, F. (2011). In vitro tensile test & corrosion analyses of a rapid manufactureproduced cobalt-chromium alloy compared to cast cobalt-chromium alloys. MPhil. Univ. of Wales, Institute, Cardiff 3. Alifui-Segbaya, F., Foley, P., Williams, R.J. (2013) "The corrosive effects of artificial saliva on cast and rapid manufacture-produced cobalt chromium alloys", Rapid Prototyping Journal, Vol. 19 Iss. 2, Alifui-Segbaya, F., Lewis, J., Eggbeer, D. and Williams, R.J. (In Press). "In vitro corrosion analyses of heat treated cobalt-chromium alloys manufactured by direct metal laser sintering Rapid Prototyping Journal. 5. Brune, D. (1986). Metal release from dental biomaterials. Biomaterials, 7, BS ISO/CD 10271:2009 Dental metallic materials Corrosion test methods. London: British Standards Institute. 7. EOS e-manufacturing solutions - Retrieved 20 September, 2013 from 8. Geis-Gerstorfer, J., Sauer, K. and Passler, K. (1991), Ion release from Ni-Cr-Mo and Co-Cr-Mo casting alloys, The International Journal of Prosthodontics, Vol. 4, pp Wataha, J. C. (2000). Biocompatibility of dental casting alloys: A review. The Journal of Prosthetic Dentistry, 83 (2),

18 Thank you for your Attention