The patientís satisfaction with esthetics is an important clinical objective. Knowledge within dental technology, dental science, and dental practice has dramatically expanded, leading to better quality, artistry, and more standards-based clinical applications. Ceramics are the most consistently predictable esthetic dental material. All-ceramic materials were developed to improve ceramic color and marginal fit. Despite substantial improvements in ceramic material strength and toughness, all-ceramic crowns may fail, particularly on molars. Ultimately, crown performance is a complex set of interactions between crown material and geometry, the characteristics of the support structure of the cement and crown, and the clinical loading history. This presentation will provide a comprehensive look at failure modes and effects in bilayer all-ceramic crown-cement-tooth systems, tying together the influences on resistance to fracture initiation and propagation of ceramic material properties and thickness; crown and tooth geometry; cement modulus and layer thickness; damage induced by shaping, fabrication, clinical adjustments, and sandblasting; and fatigue in the wet intraoral environment. Some counter-intuitive findings will be addressed, including changes in fracture behavior with different geometry and the influence of the compliant cement layer beneath stiff cores. Physical factors that may impact long-term restoration survival as well as original research demonstrating the effect of different core materials on the survival of various all-ceramic materials also will be discussed.
Kenneth A. Malament, DDS, MScD, is an examining director and a diplomate of the American Board of Prosthodontics and maintains a full-time practice in Boston that includes a dental laboratory with master dental technicians. He is also a clinical professor in postgraduate prosthodontics at Tufts University. Dr Malament is secretary of the American College of Prosthodontics and president-elect of the Greater New York Academy of Prosthodontics. He has also served as president of the Northeastern Gnathological Society and the Northeastern Prosthodontic Society and as secretary-treasurer of the International College of Prosthodontics. Dr Malament has been a consultant to three journals and has published in the dental literature in the areas of all-ceramic survival statistics, fixed and implant prosthodontics, risk analysis, occlusion, material science, and periodontics.