www.elsevier.com/locate/jmbbm Available online at www.sciencedirect.com Research Paper The role of proteoglycans in the nanoindentation creep behavior of human dentin Luiz E. Bertassoni a,b,c,n , Matheus Kury c , Catherine Rathsam d , Christopher B. Little e , Michael V. Swain c,f a Division of Biomaterials and Biomechanics, Department of Restorative Dentistry, School of Dentistry, Oregon Health and Science University, 2730 Moody Avenue, Collaborative Life Sciences Building, Level 6 N6005, Portland, 97201 OR, USA b Center for Regenerative Medicine, Oregon Health and Science University, Portland, OR, USA c Bioengineering Laboratory, Faculty of Dentistry, University of Sydney, Sydney, NSW, Australia d Institute of Dental Research, Westmead Centre for Oral Health, NSW, Australia e Raymond Purves Bone and Joint Research Labs, Kolling Institute of Medical Research, Royal North Shore Hospital, The University of Sydney, NSW, Australia f Bioclinical Sciences Department, Faculty of Dentistry, University of Kuwait, Kuwait article info Article history: Received 6 August 2015 Received in revised form 29 September 2015 Accepted 24 October 2015 Available online 10 November 2015 Keywords: Dentin Proteoglycans Glycosaminoglycans Collagen Nanoindentation Bone abstract Attempts to understand the mechanical behavior of dentin and other mineralized tissues have been primarily focused on the role of their more abundant matrix components, such as collagen and hydroxyapatite. The structural mechanisms endowing these biological materials with outstanding load bearing properties, however, remain elusive to date. Furthermore, while their response to deformation has been extensively studied, mechan- isms contributing to their recovery from induced deformation remain poorly described in the literature. Here, we offer novel insights into the participation of proteoglycans (PG) and glycosaminoglycans (GAG) in regulating the nanoindentation creep deformation and recovery of mineralized and demineralized dentin. Accordingly, after the enzymatic digestion of either PGs and associated GAGs or only GAGs, the nanoindentation creep deformation of dentin increased significantly, while the relative recovery of both the mineralized and demineralized dentin dropped by 40–70%. In summary, our results suggest that PGs and GAGs may participate in a nanoscale mechanism that contributes significantly to the outstanding durability of dentin and possibly other mineralized tissues of similar composition. & 2015 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jmbbm.2015.10.018 1751-6161/& 2015 Elsevier Ltd. All rights reserved. n Corresponding author at: Division of Biomaterials and Biomechanics, Department of Restorative Dentistry, School of Dentistry, Oregon Health and Science University, 2730 Moody Avenue, Collaborative Life Sciences Building, Level 6 N6005, Portland, 97201 OR, USA. E-mail address: bertasso@ohsu.edu (L.E. Bertassoni). journal of the mechanical behavior of biomedical materials55 (2015) 264–270