All-Ceramic Crowns Over Single Implant Zircon Abutment. Influence of Young’s Modulus on Mechanics Amilcar Chagas Freitas Ju ´ nior, DDS, MS,* Eduardo Passos Rocha, DDS, MS, PhD,† Paulo Henrique dos Santos, DDS, MS, PhD,‡ Erika Oliveira de Almeida, DDS, MS,* and Rodolfo Bruniera Anchieta, DDS* T he demand for more esthetic prosthetic treatments have led manufacturers, researchers, and dental professionals to search for tech- nological improvements of restorative materials. Accordingly, all-ceramic crowns are in the process of replacing traditional metal-based crowns on the market. 1,2 Besides their excellent es- thetics, ceramics have continuously been modified for the improvement of its mechanical resistance, eliminating the need for the use of metal as a reinforcement structure. 2–5 Dental ce- ramics also satisfy biocompatibility, color stability, marginal accuracy, and low thermal conductivity require- ments, which contribute to clinical success. 1,2,6 Despite of some esthetic advan- tages, mechanical failure as regards ceramics continues to occur because of an inability to absorb stress forces by plastic deformation. 5 Although the literature shows the use of ceramics for veneering or supporting implant crowns, 7–9 data on mechanical behav- ior of ceramics in such a condition are not completely clear. For instance, the use of ceramics with a lower Young’s modulus (E) such as IPS e.max Press over high E abutments, such as zircon abutments, might represent a failure scenario with crown fracture. Never- theless, the use of high E ceramic crowns could be appropriate for keep- ing ceramic integrity, but their influ- ence on the mechanical behavior of resin cement layer is not completely understood. Although there are studies on the mechanical properties of dental ce- ramics, 6,8 –14 few are the studies in lit- erature evaluating the mechanical behavior of the resin’s adhesive inter- face in implant-supported crowns. 15–20 Studies are important in this sense: once it is a determinant factor for the *PhD student, Department of Dental Materials and Prosthodontics, Arac ¸ atuba School of Dentistry, Sa ˜ o Paulo State University, Sa ˜ o Paulo, Brazil. †Professor, Department of Dental Materials and Prosthodontics, Arac ¸ atuba School of Dentistry, Sa ˜ o Paulo State University, Sa ˜ o Paulo, Brazil. ‡Professor, Department of Dental Materials and Prosthodontics, Arac ¸ atuba School of Dentistry, Sa ˜ o Paulo State University, Sa ˜ o Paulo, Brazil. Editor’s Note: The authors state that this was a Master thesis that involved the collaboration of all the authors: the 2 professors were the advisor and co-advisor, respectively; and the 2 other postgraduate students helped in the numerical analysis. Reprint requests and correspondence to: Amilcar Chagas Freitas Ju ´ nior, DDS, MS, 1193 Jose Bonifacio, Vila Mendonc ¸a, Arac ¸atuba, Sa ˜o Paulo 16015-050, Brazil, Phone: 55 18 36363246, E-mail: dr.amilcar.jr@hotmail.com ISSN 1056-6163/10/01906-539 Implant Dentistry Volume 19 • Number 6 Copyright © 2010 by Lippincott Williams & Wilkins DOI: 10.1097/ID.0b013e31820030ca Purpose: The aim of this study was to evaluate the influence of dif- ferent Young moduli of the ceramic crown on the distribution of tensions in the region of the abutment-crown interface by making use of 2D finite element analysis. Materials: Two representative models of a sagittally sectioned max- illa were built through AutoCad program showing an implant in the region of the upper central incisor and were restored by means of IPS e.max Press or Procera AllCeram on zircon abutment. Numerical analysis (Ansys 10.0) was performed under 2 loading conditions (50 N): on the lingual face, at 45 degrees with the implant’s long axis (L1) and perpendicular to the incisal edge (L2). The von Mises equivalent stress ( vM ) and maximum principal stress ( max ) were obtained. Results: It was noticed that, inde- pendent of the restoring system, the maximum  vM values were in the in- cisal region of the cementation inter- face for both loading conditions. The IPS e.max Press system showed higher  vM on the adhesive interface with higher L1 influence. The same behavior was also observed as re- gards the  max variation. Conclusions: It was concluded that a restoring system with a lower Young modulus shows higher stress concentration on the abutment-crown interface when cemented on an abut- ment with a high Young modulus. Thus, IPS e.max Press system pro- vides higher stress concentration in the resin cement layer than Procera AllCeram system, suggesting that the resin cement layer shows lower failure risk when the Procera crown is used. (Implant Dent 2010;19:539 –548) Key Words: dental implants, fixed partial denture, biomechanics, finite element analysis IMPLANT DENTISTRY /VOLUME 19, NUMBER 6 2010 539