A COMPARISON OF THE MECHANICAL PROPERTIES OF PIGMENTED SILICONE ELASTOMERS USED IN MAXILLOFACIAL PROSTHESES by Nora El-Mowafy BDS, Future University in Egypt, 2012 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES (CRANIOFACIAL SCIENCE) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) August 2018 © Nora El-Mowafy, 2018 The following individuals certify that they have read, and recommend to the Faculty of Graduate and Postdoctoral Studies for acceptance, a thesis/dissertation entitled: A comparison of the mechanical properties of pigmented silicone elastomers used in maxillofacial prostheses submitted by Nora El-Mowafy in partial fulfillment of the requirements for the degree of Master of Science in Craniofacial Science Examining Committee: Dr. Caroline Nguyen Supervisor Dr. Rick Carvalho Supervisory Committee Member Dr. Adriana Manso Supervisory Committee Member Dr. Sudarat Kiat-Amnuay Additional Examiner ii Abstract Purpose: To evaluate and compare the mechanical properties of various commercially available pigmented polydimethylsiloxane elastomers (silicone elastomers) utilized in the fabrication of maxillofacial prostheses. Materials & Methods: Three commonly used silicone elastomers were evaluated: A-2000 (Factor II), A-2186 (Factor II), A-103 (Factor II). The silicones was combined with opacifier: Titanium White (Factor II), and pigment: Intrinsic Pigment in Naturelle (Factor II). Specimens were fabricated through the use of aluminum and stone moulds to form trouser- and dumbbell- shaped specimens. From each material 20 specimens were prepared, 10 dumbbell-shaped and 10 trouser-shaped (n=10) for a total of 60 specimens. Mechanical properties evaluated included: Shore-A hardness, tear strength, tensile strength, and percent elongation. These properties were tested according to ASTM protocols. Data was statistically-analyzed with one-way ANOVA of each property at the 95% level of confidence as well as Tukey’s post-hoc tests for specific identification of significant differences between materials. Results: ANOVA indicated statistically-significant differences among the three materials for each of the four outcomes tested. Further statistical analysis with Tukey’s post-hoc tests showed significantly lower tensile strength and tear strength and higher % elongation for A-103 when compared to both A-2000 and A-2186. No statistically significant differences were found between A-2000 and A-2186 with respect to tensile strength, percent elongation or tear strength. All three groups were found to be significantly different from each other in terms of Shore-A hardness. A-103 exhibited the lowest hardness values, whereas A-2186 was found to have the highest hardness. iii Conclusions: Material A-103 exhibited the lowest tensile and tear strengths as well as hardness, however, it displayed the greatest percent elongation. Material A-2000 and A-2186 displayed similar characteristics with regard to tensile and tear strengths, but differed in terms of Shore-A hardness with A-2186 exhibiting the greatest hardness. iv Lay Summary Maxillofacial prostheses are of great value for the restoration of head and neck defects in affected patients. Various commercially available silicone materials are used for the fabrication of these prostheses, however no one material possesses all the necessary characteristics of the ideal material for this application. Pigments and opacifiers are added to these materials in an effort to reproduce a natural likeness and esthetic result. The literature examining the effects of these additives on the mechanical properties of silicones is limited. The aim of this project was to evaluate and compare the mechanical properties of various commercially available pigmented silicones that are used in the fabrication of maxillofacial prostheses. In addition, the mechanical properties of a silicone material that has yet to be reported on in the literature were evaluated. v Preface This thesis is an original intellectual product of the author, Nora El-Mowafy. This project was conducted under the direct supervision of Dr. Caroline Nguyen. The other members of the research committee were Dr. Rick Carvalho and Dr. Adriana Manso. The custom-made aluminum molds were fabricated by Dr. Caroline Nguyen at the UT MD Anderson Cancer Center in Houston, Texas. The fabrication of the resin molds was carried out at Frontier Dental Laboratories (325 W 6th Ave, Vancouver, British Columbia) by David Bird and his team of lab technicians. Shore- A Hardness testing was conducted by Jeffrey Mount at UTHealth, School of Dentistry (7500 Cambridge St, Houston, Texas). Statistical analyses were conducted with the help of Anton Svendrovski. With the exception of the above mentioned, the lead investigator, Nora El-Mowafy, completed all components of this project independently including: research, specimen preparation and testing, data analysis and dissertation writing. Ethical approval from the UBC Ethics Board was not required, as this study did not involve the of use human or animal subjects and bio-hazardous materials. vi Table of Contents Abstract ......................................................................................................................................... iii Lay Summary .................................................................................................................................v Preface ........................................................................................................................................... vi Table of Contents ........................................................................................................................ vii List of Tables ................................................................................................................................ ix List of Figures .................................................................................................................................x List of Abbreviations ................................................................................................................. xiii Acknowledgements .................................................................................................................... xiv Dedication ................................................................................................................................... xvi Chapter 1: Introduction ................................................................................................................1 0.1 Introduction ........................................................................................................................ 1 0.1.1 History of Materials Used for Maxillofacial Prostheses ............................................. 1 0.2 The Ideal Material .............................................................................................................. 2 0.2.1 Silicone Elastomers ..................................................................................................... 4 Chapter 1: Review of Literature ..................................................................................................6 1.1 Review of Literature .......................................................................................................... 6 1.2 Aims ................................................................................................................................. 15 Chapter 2: Materials and Methods ............................................................................................16 2.1 Material Selection ............................................................................................................ 16 2.2 Mold Fabrication .............................................................................................................. 19 2.3 Specimen Fabrication ....................................................................................................... 21 vii 2.4 Specimen Identification ................................................................................................... 23 2.5 Mechanical Testing .......................................................................................................... 25 2.5.1 Tensile Strength ........................................................................................................ 25 2.5.2 Percent Elongation .................................................................................................... 25 2.5.3 Tear Strength ............................................................................................................. 26 2.5.4 Shore-A Hardness ..................................................................................................... 27 2.6 Statistical Analysis ........................................................................................................... 28 Chapter 3: Results ........................................................................................................................29 3.1 Tensile Strength ............................................................................................................... 29 3.2 Percent Elongation ........................................................................................................... 31 3.3 Tear Strength .................................................................................................................... 37 3.4 Hardness ..........................................................................................................................