Fracture toughness of yttrium stabilized zirconia sintered in conventional and microwave ovens

Recommended Citation Marinis, Aristotelis. "Fracture toughness of yttrium stabilized zirconia sintered in conventional and microwave ovens. ii To my sister iii When you set out on your journey to Ithaca, pray that the road is long, full of adventure, full of knowledge. iv ACKNOWLEDGMENTS First and foremost I would like to express my sincere gratitude to my thesis supervisor Dr. Steven A. Aquilino for his invaluable guidance, inspiration and willingness to motivate me in this research project. I also would like to thank my graduate committee for their encouragement and constant support. I acknowledge the contribution of Dr. Fang Qian in assisting the statistical analysis. Special thanks to my University of Athens educators who encouraged me to pursue this degree. I am forever grateful to my parents and my sister who supported my graduate studies fully and unconditionally. Without their love, useful advice, endless patience and moral support I would not have been able to achieve my goals. I would like to thank the University of Iowa for providing me the facilities to complete this project. INTRODUCTION Esthetics is a personal preference and is influenced by one's individual personality and cultural factors (Lombardi, 1973). Looking back at history, the perception of what constitutes an ideal smile has changed. Currently a bright, white smile with teeth in perfect alignment is considered an integral part of a beautiful appearance. Nowadays a patient's dental treatment requires materials that will fulfill these expectations. Porcelain fused to metal restorations (PFMs) have been widely used in the last 50 years but with increasing patients' esthetic perceptions, material costs and a shortage in skilled technical support there has been a push towards all-ceramic restorations. Initially the all-ceramic restorations used were predominantly glass materials which could provide high esthetic results. However, due to inferior mechanical properties, these materials remain in use primarily for single anterior restorations (Kelly, 2004). Fillers were dispersed in the glassy material to broaden the clinical use of the all-ceramic restorations. The particle filled glasses provided increased strength. Most recently polycrystalline ceramics have been introduced to provide improved physical properties. Polycrystalline ceramics such as zirconium dioxide (ZrO 2) are tougher and stronger than predominantly glassy materials or particle filled glasses. The utilization of these materials in dentistry provided the ability to construct high strength single unit and multi unit all-ceramic prostheses (Kelly, 2004). The promising development in all-ceramic materials in combination with the high cost …