Optimisation of the superplastic forming of a dental implant for bone augmentation using finite element simulations Denis Garriga-Majo a, *, Robin J. Paterson a , Richard V. Curtis a , Rajab Said b , Richard D. Wood b , Javier Bonet b a Dental Biomaterials Science, GKT Dental Institute, King’s College, Guy’s Tower, Floor 17, St Thomas Street, London SE1 9RT, UK b Department of Civil Engineering, University of Wales Swansea, UK Received 11 November 2002; accepted 16 July 2003 KEYWORDS Superplastic forming; Finite elements; Bone augmentation membrane; Titanium; Laser scanning Summary Objectives. The phenomenon of superplasticity has made it possible to form complex shapes that require extremely high degrees of ductility in titanium alloy with minimal internal stresses. Combined with the use of an investment casting material as the die material, which makes possible the forming of re-entrant angles, it is possible to produce membranes for ridge augmentation. The aim is to characterise the metal alloy sheet and simulate the superplastic forming process in three dimensions to produce process parameters, namely gas pressure as a function of time, to accurately adapt the titanium sheet to the bone surface. Method. The surface of the die was digitised using a 3D laser scanning system (UBM- Keyence LC2450). Ti-6Al-4V sheet of 140 mm diameter was modelled using a grid of triangular membrane elements. This mesh was automatically refined during the simulations. Finite element simulation was carried out using the Superflag software program (University of Wales Swansea) Three different options for gas pressure control were adopted, namely, target flow stress, target strain rate and target energy dissipation. The pressure cycles produced from the simulation were used to form titanium alloy sheet at 900 8C using argon gas. The deformed regions of the formed sheet were then examined to determine the regions of contact with the die and to characterise surface damage. Results. Comparison of the simulations with experiment showed that there was good agreement between simulated and experimental thickness distributions in most parts of the sheet that were examined. Interrupted tests showed that in the intermediate positions of the forming sheet the simulations were slightly ahead of the experiment. The target stress option was found to produce the best degree of adaptation and the sheet formed using this cycle showed good surface quality, whereas in highly deformed regions using the other target options, the sheet was found to have formed microcracks. The use of a solid lubricant on the surface of the forming sheet was not found to have a significant influence on the adaptation of the titanium alloy sheet except in areas of high deformation where the sheet perforated. 0109-5641/$ - see front matter Q 2003 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.dental.2003.07.001 Dental Materials (2004) 20, 409–418 http://www.intl.elsevierhealth.com/journals/dema * Corresponding author. Tel.: þ44-207-955-4548; fax: þ 44-207-955-2963. E-mail address: richard.curtis@kcl.ac.uk