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Influence of Cement on Survival of All-Ceramic Restorations

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INFLUENCE OF CEMENT ON SURVIVAL OF ALL-CERAMIC RESTORATIONS THESIS Presented in Partial Fulfillment of the Requirements for The Degree of Master of Science in the Graduate School of The Ohio State University By Enas Elbahie Alakhras, B.D.S Graduate Program in Dentistry The Ohio State University 2011 Thesis Committee: Dr. Robert Seghi, DDS, MS (Advisor) Dr. William A. Brantley, PhD Dr. Noriko Katsube, PhD Copyright by Enas Mohamed Elbahie Alakhras 2011 ABSTRACT Previous research has shown that new technology in adhesive dentistry improves the performance of all-ceramic restorations. However, the major reason for failure of these restorations remains the occurrence of fractures. The overall objective of this research project was to investigate the influence of cement on the survival of all-ceramic restorations. A preliminary study was performed to evaluate the influence of the cement as a supporting structure on the survival of a simulated all-ceramic restoration. A trilayer simulation of a model restoration subjected to a clinically relevant condition of functional mastication was used. The results from the preliminary study showed that adhesively bonded specimens had higher survival rates than those conventionally cemented and that one of the adhesive cements had a significant higher survival rate than the other. Based on results from the preliminary study, three other studies were performed to investigate why adhesive cementation improves the performance of all-ceramic restorations. Results from these studies showed: (1) Resin cements had fewer defects or were void-free at the ceramic-cement interface of our ceramic model, while conventional cements showed areas of voids at the this interface. (2) The resin cement had no influence on ceramic sensitivity to slow crack growth (SCG). (3) While the actual mechanism for ii resin strengthening could not be determined, it may involve the formation of a more durable bond at the ceramic/cement interface. iii Dedicated to My Mother, Father and Husband iv ACKNOWLEDGEMENTS I would like to thank my thesis advisor; Dr. Robert Seghi for taking me under his wing and teaching me everything I know about research. You have an enormously generous heart. I am always inspired by you and I thank you for standing by me and helping me constructs and executes this study. Thank you so much for giving me an opportunity to work with you and for you always support, encouraging and helping me see the true value in research and inspiring me to be a better researcher. I would like to also thank Dr. William Brantley whose knowledge and guidance contributed tremendously to this project. It is an honor to me to be Dr. Brantley‟s student and learning from him does not only contribute to my academic performance but also influenced my personal life. To my parents, Sana and Mohammed, I would like to first and foremost thank you both for the amazing love and support you have given me throughout the years. Thank you for encouraging me endlessly to pursue higher education and explaining to me how through education and knowledge comes enlightenment and humility. Both of you have inspired me to always do my best and to constantly challenge and better myself. As well, in my difficult moments you were both endlessly comforting and even more supporting. You have done your best to give me the opportunities and the means to pursue my dreams that were not available to either one of you growing up, and for that I am v eternally grateful. I love you both very much and I dedicate everything to my loving parents. I am nothing without you and I am everything with you. To my wonderful beloved husband Mohamed, whose love, patient and support brighten my life and enabled me to finish my masters program. Thanks you for being always by my side, inspite of being busy, but you were always there when it most needed. To my mother in law Safiya, for her love, encouragement and patient. To my wonderful sisters, Amira, Eman, Sara and Dalia, even though we have been far apart for a long time, I still feel the love and care every time we meet. I wish you the very best in everything you pursue in life. I would like to also thank all my faculty members at The Ohio State University for educating me and being great mentors. vi VITA December 09, 1983…………………………………………Sharkiya, EGYPT 2005…………………………………………………………B.D.S ………………………………………………………………Suez Canal University ………………………………………………………………Ismailia, EGYPT 2007……………………………………………………...….Instructor ………………………………………………………………Dental Materials Department ………………………………………………………………School of Dentistry ………………………………………………………………Suez Canal University ………………………………………………………………Ismailia, EGYPT 2008-09……………………………………………………...Research Assistant ………………………………………………………………School of Dentistry ………………………………………………………………The Ohio State University ………………………………………………………………Columbus, Ohio 2009 to present………………………………………………MS, Dental Material Program ………………………………………………………………The Ohio State University ………………………………………………………………Columbus, Ohio 2010 to present……………………………………………...Bench Instructor ………………………………………………………………School of Dentistry ………………………………………………………………The Ohio State University ………………………………………………………………Columbus, Ohio vii FIELDS OF STUDY Major Field: Dentistry Specialty: Dental Materials viii TABLE OF CONTENTS Page Abstract................................................................................................................................ii Dedication...........................................................................................................................iv Acknowledgements .............................................................................................................v Vita....................................................................................................................................vii Chapter 1 Introduction ........................................................................................................................1 Chapter2 Influence of cement on the interface initiated fracture rate of all ceramic restorations under cyclic loading...........................................................................................................14 Chapter 3 Nondestructive acoustic microscopic Evaluation of the cement / glass-ceramic interface..............................................................................................................................36 ix Chapter 4 Influence of resin cement on slow crack growth parameter of two glass-ceramic…........51 Chapter 5 Effect of short and long terms aging conditions on the micro-tensile bond strength of resin cement to glass-ceramic…………………………….………………………….......78 Chapter 6 summary and conclusion………………………………………………………………...93 References………………………….………………………………….……………...…94 x Chapter 1 Introduction Over the past decade the high demand for esthetically pleasing restorations has driven the development of all-ceramic systems for use in dental restorations (inlays, onlays, crowns, fixed partial dentures (FPD‟s), and implant-supported restorations). The absence of a metallic substructure in all-ceramic restorations allows them to have improved esthetics, as the underlying tooth structure can potentially influence the final shade of the restoration and more closely imitate the optical effects of the natural teeth and result in a more “life-like” or natural appearance. These restorations are nonmetallic and biocompatible, which provide an advantage to soft tissue health since lesser amounts of plaque and adherence molecules are recovered from ceramic surfaces 1. It is often acceptable in all-ceramic restorations to leave the margin of the prosthesis supragingival or at the gingival margin, which adds the benefit of more predictable and less traumatic impression making. Improved clinical performance, especially with the use of higher strength ceramics and adhesives for bonding the ceramic restoration to tooth structure, have led to a resurgence of interest in all-ceramic restorations and make these restorations a more favorable choice by patients and dentists. 1 Dental ceramics can be considered as “composites” because they have two or more distinct entities in their compositions. Dental ceramic materials can be classified according to their crystalline content into three main divisions: (1) predominantly glassy materials, (2) particle-filled glasses, and (3) polycrystalline ceramics. Defining characteristics are provided for each of these ceramic types 2, 3. High-esthetic dental ceramic restorations consist predominantly of glass, while high-strength ceramics are generally polycrystalline. Predominantly glassy ceramics are the best at mimicking the optical properties of enamel and dentin. Glasses in dental ceramics are derived from a group of mined minerals called feldspars, and are based on silicon and aluminum oxides. Hence, the dental feldspathic porcelains belong to a family called aluminosilicate glasses 3. Feldspar glass-ceramics are resistant to crystallization (devitrification) during firing and have long firing temperature ranges. They resist slumping if firing temperatures rise above optimal. There is a wide range of materials used for all-ceramic restorations, and they contain a variety of crystalline phases. Theses crystalline phases act primarily as reinforcements to the ceramic matrix and improve the material properties. The physical and mechanical properties of ceramics are very sensitive to the nature, amount, and particle size distribution of the crystalline phases 4. Filler particles are usually added to
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