d e n t a l m a t e r i a l s 2 8 ( 2 0 1 2 ) e27–e34 Available online at www.sciencedirect.com jo u rn al hom epa ge : www.intl.elsevierhealth.com/journals/dema A method to investigate the shrinkage stress developed by resin-composites bonded to a single flat surface Lucas V.S. Pabis a , Tathy A. Xavier a , Ecinele F. Rosa a , Flávia P. Rodrigues b , Josete B.C. Meira a , Raul G. Lima c , Leonardo E. Rodrigues Filho a , Rafael Y. Ballester a,∗ a Department of Dental Materials, School of Dentistry, University of São Paulo, São Paulo, Brazil b Biomaterials Research Group, School of Dentistry, Anhanguera-Bandeirante University of São Paulo-UNIBAN, São Paulo, Brazil c Department of Mechanical Engineering, Polytechnic School, University of São Paulo, São Paulo, Brazil a r t i c l e i n f o Article history: Received 14 June 2011 Received in revised form 24 November 2011 Accepted 11 January 2012 Keywords: Resin-composite Finite element analysis Mechanical stress Dental stress analysis Dental bonding Materials testing biomechanics a b s t r a c t Objectives. To purpose a method for predicting the shrinkage stress development in the adhesive layer of resin-composite cylinders that shrink bonded to a single flat surface, by measuring the deflection of a glass coverslip caused by the shrinkage of the bonded cylinders. The correlation between the volume of the bonded resin-composite and the stress-peak was also investigated. Methods. A glass coverslip deflection caused by the shrinkage of a bonded resin-composite cylinder (diameter: d = 8 mm, 4 mm, or 2 mm, height: h = 4 mm, 2 mm, 1 mm, or 0.5 mm) was measured, and the same set-up was simulated by finite element analysis (3D-FEA). Stresses generated in the adhesive layer were plotted versus two geometric variables of the resin- composite cylinder (C-Factor and volume) to verify the existence of correlations between them and stresses. Results. The FEA models were validated. A significant correlation (p < 0.01, Pearson’s test) between the stress-peak and the coverslip deflection when the resin-composites were grouped by diameter was found for diameters of 2 and 4 mm. The stress-peak of the whole set of data showed a logarithmic correlation with the bonded resin-composite volume (p < 0.001, Pearson’s test), but did not correlate with the C-Factor. Significance. The described method should be considered for standardizing the stress gener- ated by the shrinkage of resin-composite blocks bonded to a single flat surface. © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved. 1. Introduction A significant factor in the adhesion quality of a resin- composite to the tooth is the polymerization shrinkage. When a resin-composite shrinks bonded to rigid surfaces that can- not passively follow the deformation, stresses in the bonding interface and into these two materials are generated. If the ∗ Corresponding author at: Dental Materials Department, School of Dentistry, University of São Paulo Av. Prof. Lineu Prestes, 2227 05508-000, São Paulo, SP, Brazil. Tel.: +55 11 30917840/30917842; fax: +55 11 30917840/30917842. E-mail address: ryb@usp.br (R.Y. Ballester). shrinkage stress exceeds the tooth/restoration bond strength, debonding may occur [1–4], which will result in microleak- age and subsequent caries and marginal discoloration. Thus, sealing the interface between the tooth and the restorative material influences the restoration longevity. The quality of the tooth/restoration interface is often verified by microtensile bond strength testing [5–8]. To obtain micro-specimens, the tooth is flattened, and a 0109-5641/$ – see front matter © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.dental.2012.01.004