Characterisation of Implant Supported Soft Tissue Prostheses Produced with 3D Colour Printing Technology School of Clinical Dentistry The University of Sheffield A PhD thesis submitted by Faraedon M. M. Zardawi November 2012 i Dedication I lovingly dedicate this thesis to my wife Wasnaa, who has supported me each step of the way. To my parents, who always stood by me, gone now, but never forgotten. I will miss them always and love them forever. To my lovely daughter Farah, my sons Ahmed and Ali, their wives Marwa and Israa and my sweet grand kids Lavin, Lana and Meran; that is my lovely family. ii Acknowledgments I would like to convey my gratitude to my supervisors, Professor Julian Yates and Professor Richard van Noort for providing me with the inspiration and support during my PhD work. Their kind but rigorous oversight of this project constantly gave me the motivation to perform to my maximum ability. I was very fortunate to have been able to work with them; their detailed and constructive comments were vital to the development of this thesis. I would also like to extend my gratitude to Mr. David Wildgoose for his advice and support I am most grateful to the other members of the project team at Sheffield based Industrial Design Company, Fripp Design and Research: Mrs Sue Roberts, Tom Fripp, Neil Frewer and Steve Roberts for their time and expertise throughout this project. Very special thanks to Neil Frewer for his great help in designing the alignment process and producing the magnet boss designs for the prostheses. Without Dr. Nishant Yadev the biocompatibility tests would not have taken place; he promised to help till the end and he did. So thank you so much Nish. I am grateful to my friend and colleague Dr. Kaida Xiao; we worked side by side on this project for 3 years, it was more than nice to work with him and I really appreciate his support and the great work we have done in colour reproduction and colour measurements. My thanks must go also to Mrs L. Gill, a senior lecturer in maxillofacial technology at Manchester University for being very kind and helpful to me in designating the skin colour shade guide used for colour reproduction. Many thanks to Mr. Frank Johnson, a maxillofacial technician at the Northern General Hospital in Sheffield for his kind help and being generous in answering all my questions about handmade facial prostheses. I must say thank you to Dr. Duncan Wood for his help with the spectrophotometer. My special thanks to Dr. Rob Moorehead for being always nearby to help. iii I must acknowledge as well the many friends and colleagues who have supported me in one way or another during my studies, Haitham Almansour, Salam Al Zahawi, Raad Al Marza, Ahmed Abusarwel, Omar Alsadon, Shreen shahrabaf, Neda akaisy, Hawa Fathi. and Dalal Alotaibi. I would like to thank the staff in the Academic Unit of Restorative Dentistry for being so friendly and helpful. Finally I wish to express my most sincere gratitude and appreciation to the Iraqi Ministry of Higher Education and Scientific Researches for their sponsorship of this Doctoral Scholarship with a very special thanks to the staff of the Iraqi Cultural Attaché in London for their kind help and support during the period of my PhD study. iv Summary The numbers of patients needing facial prostheses has increased in the last few decades due to improving cancer survival rates. The many limitations of the handmade prostheses together with rapid expansion of prototyping in all directions, particularly in producing human anatomically accurate parts, have raised the question of how to employ this technology for rapid manufacturing of facial soft tissue prostheses. The idea started to grow and the project was implemented based on CAD/CAM principles – additive manufacturing technology, by employing layered fabrication of facial prostheses from starch powder and a water based binder and infiltrated with a silicone polymer (SPIS). The project aimed to produce a facial prosthesis by using 3D colour printing, which would match the patient’s skin shade and have the desirable mechanical properties, through a relatively low cost process that would be accessible to the global patient community. This was achieved by providing a simple system for data capture, design and reproducible method of manufacture with a clinically acceptable material. The prosthesis produced has several advantages and few limitations when compared to existing products/prostheses made from silicone polymer (SP). The mechanical properties and durability were not as good as those of the SP made prosthesis but they were acceptable, although the ideal properties have yet to be identified. Colour reproduction and colour matching were more than acceptable, although the colour of the SPIS parts was less stable than the SP colour under natural and accelerated weathering conditions. However, it is acknowledged that neither of the two methods used represent the natural life use on patients and the deficiencies demonstrated in terms of mechanical properties and colour instability were partially inherent in the methodology used, as the project was still at the developmental stage and it was not possible to apply real v life tests on patients. Moreover, deficiencies in mechanical and optical properties were probably caused by the starch present, which was used as a scaffold for the SP. Furthermore, a suitable retention system utilising existing components was designed and added to the prosthesis. This enabled the prosthesis to be retained by implants with no need for the addition of adhesive. This would also help to prolong the durability and life span of the prosthesis. The capability of the printer to produce skin shades was determined and it was found that all the skin colours measured fall within the range of the 3D colour printer and thereby the printer was able to produce all the colours required. Biocompatibility was also acceptable, with a very low rate of toxicity. However, no material is 100% safe and each material has a certain range of toxicity at certain concentrations. At this stage of the project, it can be confirmed that facial prostheses were successfully manufactured by using 3D colour printing to match the patient’s skin shade, using biocompatible materials and having the desirable mechanical properties. Furthermore, the technology used enabled prostheses to be produced in a shorter time frame and at a lower cost than conventional SP prostheses. They are also very lightweight, easier to use and possibly more comfortable for the patients. Moreover, this technology has the capability of producing multiple prostheses at the time of manufacture at reduced extra cost, whilst the data can be saved and can be utilised/modified for producing further copies in the future without having to going through all the steps involved with handmade prostheses. Based on the mechanical properties and colour measurements the prostheses will have a finite service life and the recommendation is that these prostheses will need replacing every 6 to 12 months, depending on how the patient handles and maintains the prostheses and whether the prosthesis is being used as an interim or definitive prosthesis. This was largely comparable to existing prostheses but without the time and cost implications for replacement. vi However, it is acknowledged that further investigations and clinical case studies are required to investigate the “real life” effect on the prostheses and to get feedback from the patients in order to make appropriate improvements to the mechanical properties and the durability of the prosthesis. vii Table of Contents DEDICATION .................................................................................. II ACKNOWLEDGMENTS ................................................................ III LIST OF ABBREVIATIONS .......................................................... XII LIST OF FIGURES ....................................................................... XIV LIST OF TABLES ........................................................................ XIX 1 INTRODUCTION ...................................................................... 1 2 LITERATURE REVIEW ............................................................ 5 2.1 Maxillofacial Prostheses – Past and Present Trends ..................... 6 2.2 Current Facial Prostheses .............................................................. 13 2.2.1 Materials Available ........................................................................ 13 2.2.2 Fabrication ..................................................................................... 19 2.2.3 Requirements: ............................................................................... 21 2.2.4 Limitations of Current Prostheses .................................................. 25 2.3 Material Properties .......................................................................... 25 2.3.1 The Mechanical Properties ............................................................ 26 2.3.2 Optical Properties .......................................................................... 28 2.4 Durability .......................................................................................... 28 2.4.1 Changes in the Mechanical Properties .......................................... 29 2.4.2 Changes in the Optical Properties: ................................................ 30 2.4.3 Aging Mechanism and Effect of Accelerated Weathering Conditions on Maxillofacial Silicone Polymers ...........................................................