Please cite this article in press as: Spazzin AO, et al. Ceramic strengthening by tuning the elastic moduli of resin-based luting agents. Dent Mater (2017), http://dx.doi.org/10.1016/j.dental.2017.01.002 ARTICLE IN PRESS DENTAL-2897; No. of Pages 9 d e n t a l m a t e r i a l s x x x ( 2 0 1 7 ) xxx–xxx Available online at www.sciencedirect.com ScienceDirect jo ur nal home p ag e: www.intl.elsevierhealth.com/journals/dema Ceramic strengthening by tuning the elastic moduli of resin-based luting agents Aloísio O. Spazzin a,c , Ataís Bacchi a , Rodrigo Alessandretti b , Mateus B. Santos c , Gabriela R. Basso c , Jason Griggs d , Rafael R. Moraes c,∗ a School of Dentistry, Meridional Faculty – IMED, Brazil b Graduate Program in Dentistry, University of Passo Fundo, Brazil c Graduate Program in Dentistry, Federal University of Pelotas, Brazil d Department of Biomedical Materials Science, University of Mississippi Medical Center, USA a r t i c l e i n f o Article history: Received 28 November 2016 Received in revised form 17 January 2017 Accepted 18 January 2017 Available online xxx Keywords: 3D finite element analysis Acid-sensitive ceramics Fractography Mechanical strength Weibull analysis a b s t r a c t Objective. Resin-based luting agents (RBLAs) with tuned elastic moduli (E) were prepared and their influence on the strengthening, reliability, and mode of failure of luted feldspar ceramic was investigated. Methods. RBLAs with low E (2.6 GPa), intermediate E (6.6 GPa), and high E (13.3 GPa) were pre- pared and used to coat acid-etched ceramic disks. Positive (untreated ceramic) and negative (acid-etched ceramic) control groups were tested. The response variables (n = 30) were biax- ial flexural strength ( bf , MPa), characteristic strength ( 0 , MPa), and Weibull modulus at the ceramic surface (z = 0) and luting agent surface (z = −t 2 ). A 3D finite element analysis simulated the biaxial flexural test. Fractographic analysis and morphology of the bonded interfaces were analyzed using scanning electron microscopy. Results. The RBLAs improved  bf and  0 at z = 0, particularly those with intermediate and high E, whereas the mechanical reliability was only affected in the negative control. At z = −t 2 , differences between all RBLAs were observed but the structural reliability was inde- pendent of the RBLA tested. Increasing E of the RBLA was associated with increased stress concentration at the RBLA and reduced stresses reaching the ceramic. Failures originated on the ceramic surface at the ceramic-cement interface. In the high E group, failure sometimes originated from the RBLA free surface. All RBLAs completely filled the ceramic irregularities. Significance. Increased E of the RBLA reduced the variability of strength, the stress reaching the ceramic structure, and sometimes altered the origin of failure. The use of high E RBLAs seems beneficial for luting feldspar ceramics. © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved. 1. Introduction Bonding intrinsically fragile feldspar ceramics to dental struc- tures using resin-based luting agents strengthens the ceramic ∗ Corresponding author at: Graduate Program in Dentistry, Federal University of Pelotas, Rua Gonc ¸ alves Chaves 457, Pelotas, RS 96015-560, Brazil. Fax: +55 53 3225 6741. E-mail address: moraesrr@gmail.com (R.R. Moraes). restorations [1–3]. The strengthening effect is explained by mechanisms such as ceramic crack healing by polymer infil- tration [4] and induction of crack closure stress by polymer shrinkage upon curing [5]. The extent of strengthening is dependent on the formation of a proper interpenetrated http://dx.doi.org/10.1016/j.dental.2017.01.002 0109-5641/© 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.