Mechanical properties, shrinkage stress, cuspal strain and fracture resistance of molars restored with bulk-fill composites and incremental filling technique C.M.P. Rosatto a , A.A. Bicalho a , C. Veríssimo a , G.F. Bragança a , M.P. Rodrigues a , D. Tantbirojn b , A. Versluis c , C.J. Soares a, * a Department of Operative Dentistry and Dental Materials, Dental School, Federal University of Uberlândia, Uberlândia, Minas Gerais, Brazil b Department of Restorative Dentistry, College of Dentistry, University of Tennessee Health Science Center, Memphis, TN, USA c Department of Bioscience Research, College of Dentistry, University of Tennessee Health Science Center, Memphis, TN, USA A R T I C L E I N F O Article history: Received 1 July 2015 Received in revised form 25 September 2015 Accepted 28 September 2015 Available online xxx Keywords: Composite resin Bulk-fill Cuspal strain Shrinkage stress Mechanical properties Finite element analysis A B S T R A C T Objectives: To compare bulk-fill with incremental filling techniques for restoring large mesio-occlusal- distal (MOD) restorations. Methods: Seventy-five molars with MOD preparations were divided into five groups: Z350XT, incrementally filled with Filtek Z350XT and four bulk-fills—FBF/Z350XT, Filtek Bulk Fill/Filtek Z350XT; VBF/CHA, Venus Bulk Fill/Charisma Diamond; SDR/EST-X, SDR/Esthet-X HD; TEC, TetricEvoCeram Bulk Fill. Cuspal strains were measured using strain-gauges (n = 10): CSt-Re, during restorative procedure; CSt- 100N, during 100N occlusal loading; CSt-Fr, at fracture load. Before fracture load, teeth were load-cycled. Fracture resistance, fracture mode, and enamel cracks were recorded. The other five teeth were used for Elastic modulus (E) and Vickers hardness (VH). Post-gel shrinkage (Shr), diametral tensile strength (DTS) and compressive strength (CS) were determined (n = 10). Shrinkage stresses were analyzed using finite element analysis. Results: SDR had similar CS values as TEC, lower than all other composites. CHA had similar DTS values as Z350XT, higher than all other composites. Z350XT had the highest mean Shr and SDR the lowest Shr. New enamel cracks and propagation was observed after the restoration, regardless of filling technique. Z350XT had lower fracture resistance than bulk-fill composite techniques. No significant differences in failure modes were found. E and VH were constant through the depth for all techniques. Bulk-filling techniques had lower stresses compared to Z350XT. Conclusions: Flowable bulk-fill composites had lower mechanical properties than paste bulk-fill and conventional composites. All bulk-fill composites had lower post-gel shrinkage than conventional composite. Bulk-fill filling techniques resulted in lower cusp strain, shrinkage stress and higher fracture resistance. Clinical significance: Using bulk-fill composites cause lower CSt wich indicates lower stress in restored tooth. Furthermore, bulk-fill composites have a higher fracture resistance. Therefore, clinicians may choose the bulk-fill composite to decrease undesirable effects of restoration while simplifying filling procedure. ã 2015 Elsevier Ltd. All rights reserved. 1. Introduction Resin composites have been extensively employed in restor- ative dentistry for several decades [1]. More than five hundred millions direct dental restorations are placed every year around the world which represents one of the most prevalent medical interventions in the human body [2]. Incremental filling technique has been used for placement of resin composite restoration [3–5]. However, the post-operative sensivity is frenquently observed, which is commonly associated with polymerization shrinkage stresses [5]. Different filling techniques and composite resins have been developed in order to minimize polymerization shrinkage and their clinical effects [6]. The latest trend in composite technology * Corresponding author at: Av. Pará, 1720, Bloco 4L, Anexo A, Campos Umuarama, 38400-902 Uberlândia, Minas Gerais, Brazil. E-mail address: carlosjsoares@umuarama.ufu.br (C.J. Soares). http://dx.doi.org/10.1016/j.jdent.2015.09.007 0300-5712/ ã 2015 Elsevier Ltd. All rights reserved. Journal of Dentistry xxx (2015) xxx–xxx G Model JJOD 2527 No. of Pages 10 Please cite this article in press as: C.M.P. Rosatto, et al., Mechanical properties, shrinkage stress, cuspal strain and fracture resistance of molars restored with bulk-fill composites and incremental filling technique, Journal of Dentistry (2015), http://dx.doi.org/10.1016/j.jdent.2015.09.007 Contents lists available at ScienceDirect Journal of Dentistry journal homepage: www.intl.elsevierhea lt h.com/journa ls/jde n