Effects of cellulose fibers on the physical and chemical properties of glass ionomer dental restorative materials R.M. Silva a,b, *, P.H.N. Santos a , L.B. Souza a , V.C. Dumont a,b , J.A. Soares a , M.H. Santos a,b a Department of Dentistry, Federal University of Vales do Jequitinhonha e Mucuri – UFVJM, Diamantina/MG, CEP 39100-000, Brazil b Center for Assessment and Development of Biomaterials – BioMat, UFVJM, Diamantina/MG, CEP 39100-000, Brazil 1. Introduction The widespread use of polyalcenoate glass cements called glass ionomer cements as restorative dental material is related to its bond to tooth structure, coefficient of linear thermal expansion similar to dentin, biocompatibility and storage and fluoride releasing capacity [1–4]. Due to their chemical characteristics and biocompatibility, indications for their use have been extended to other fields as well. For example, glass-ionomer cements are widely used in medicine, primarily in otology, reconstructive surgery, orthopedics [5] and also as a structural material (scaffold) for bone formation [6,7]. Nevertheless, glass-ionomer cements also have some mechan- ical and clinical limitations as dental restorative materials. In addition to having a poor esthetic appearance due to their limited translucency, and technique sensitivity, they have a short working time and prolonged setting period, in which first 24 h are critical, making this material susceptible to hygroscopic change in the medium and solubility [8]. Thus, immediate surface protection of the glass ionomer cement restoration with a waterproofing material is indicated [9–11]. The chemical bonding capacity of glass ionomer cement to dental structures is highlighted. There is a chemical interaction between the carboxylic groups of polyacids, which are chelating agents within the cement, and calcium ions in the tooth enamel and dentin [12]. Although this is a positive feature of the material, it is known that its bond strength is still considered low [13]. Another feature of these cements is the deficiency of their mechanical integrity and their ability to withstand fracture loads [8]. Many studies have reported the degree of deformation of glass ionomer cements, by testing the compressive, diametral tensile, bond strength and wear strength [14–17]. Successive changes have been made in the conventional glass ionomer cement, in order to increase its mechanical strength. Thus, several materials have emerged with different compositions such as glass ionomer cements reinforced with metal, modified with resin, and finally the high-viscosity ionomer cements and those with incorporation of nanoparticles, all to meet individual clinical needs and improve their physicochemical properties [8,18–20]. For many years there have been attempts to incorporate fibers into the composition of these materials as agents to reinforce their physical structure [21,22]. In recent decades there has been rapid development of natural fiber-reinforced composites, giving them better mechanical strength and an increase in elasticity modulus [22–24]. The use of these fibers in composites requires compatibility between the fibers and matrix, the incorporation of a relatively large amount of fibers and wettability capacity, factors that increase the load transfer to them [23]. Cellulosic fibers meet these needs, because although they have interesting features for use, such as low cost, low density, specific strength and high elasticity modulus, they have a high number of fibers per gram, which provide resistance to flatness and rigidity [22,24]. Moreover, they Materials Research Bulletin 48 (2013) 118–126 A R T I C L E I N F O Article history: Received 18 April 2012 Received in revised form 5 October 2012 Accepted 9 October 2012 Available online 17 October 2012 Keywords: A. Composites C. Electron microscopy D. Mechanical properties A B S T R A C T A dental glass ionomer cement (GIC) was modified with cellulosic fibers. The microstructural analysis and physicochemical properties were evaluated in four groups: GIC (control) and GIC modified with different concentrations of fibers, GICMF1, GICMF2 and GICMF3. Within clinically acceptable limits, composites showed capacity of water absorption and solubility in water similar to GIC and no signs of disintegration were observed. GICMF2 provided greater resistance to compression, wear and adhesion, however it had no effect on the diametral tensile strength. Morphological and chemical element analyses of GICMF2 showed the formation of a new and stable composite with interaction between fiber/ionomer matrix/load particles. ß 2012 Elsevier Ltd. All rights reserved. * Corresponding author at: Center for Assessment and Development of Biomaterials – BioMat, Federal University of Vales do Jequitinhonha e Mucuri – UFVJM, Rua da Glo ´ ria, 187, Diamantina/MG, CEP 39100-000, Brazil. Tel.: +55 38 35326066; fax: +55 38 35326077. E-mail address: rafa18ms@hotmail.com (R.M. Silva). Contents lists available at SciVerse ScienceDirect Materials Research Bulletin jo u rn al h om ep age: ww w.els evier.c o m/lo c ate/mat res b u 0025-5408/$ – see front matter ß 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.materresbull.2012.10.016