d e n t a l m a t e r i a l s 2 8 ( 2 0 1 2 ) 133–145 Available online at www.sciencedirect.com jo u rn al hom epa ge : www.intl.elsevierhealth.com/journals/dema Nano-porous thermally sintered nano silica as novel fillers for dental composites Mohammad Atai a,∗ , Ayoub Pahlavan b , Niloofar Moin b a Iran Polymer and Petrochemical Institute (IPPI), P.O. Box 14965/115, Tehran, Iran b Dental School, Tehran University of Medical Sciences, Tehran, Iran a r t i c l e i n f o Article history: Received 12 January 2011 Received in revised form 14 July 2011 Accepted 24 October 2011 Keywords: Dental composites Sintered nanofiller Nano-porous filler Mechanical properties Surface topography a b s t r a c t Objectives. The study evaluates properties of an experimental dental composite consisting of a porous thermally sintered nano-silica as filler. The properties are compared with those of an experimental composite containing micro fillers and a commercially available nano- composite, Filtek Supreme ® Translucent. Different models are used to predict the elastic modulus and strength of the composites. Methods. Nano-silica with primary particles of 12 nm was thermally sintered to form nanoporous filer particles. The experimental composites were prepared by incorporating 70 wt.% of the fillers into a mixture of Bis-GMA and TEGDMA as matrix phase. Having added photoinitiator system the composites were inserted into the test molds and light-cured. The microfiller containing composites were also prepared using micron size glass fillers. Degree of conversion (DC%) of the composites was measured using FTIR spectroscopy. Diametral tensile strength (DTS), flexural strength, flexural modulus and fracture toughness were mea- sured. SEM was utilized to study the cross section of the fractured specimens. The surface topography of the specimens was investigated using atomic force microscopy (AFM). The specific surface area of the sintered nano silica was measured using BET method. The data were analyzed and compared by ANOVA and Tukey HSD tests (significance level = 0.05). Results. The results showed improvements in flexural modulus and fracture toughness of the composites containing sintered filler. AFM revealed a lower surface roughness for sintered silica containing composites. No significant difference was observed between DTS, DC%, and flexural strength of the sintered nanofiller composite and the Filtek Supreme ® . The results also showed that the modulus of the composite with sintered filler was higher than the model prediction. Significance. The thermally sintered nano-porous silica fillers significantly enhanced the mechanical properties of dental composites introducing a new approach to develop mate- rials with improved properties. © 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved. 1. Introduction Since the introduction of dental composites to dentistry, their properties have greatly been improved to overcome ∗ Corresponding author. Tel.: +98 21 48662446; fax: +98 21 44580023. E-mail addresses: M.Atai@ippi.ac.ir, moh atai@yahoo.com (M. Atai). the shortcomings of the esthetically interesting materials. The developments in material point of view can be summa- rized in three categories: (i) improvement of filler phase [1–3], (ii) modification of resin monomers and/or introducing new monomer systems [4–8], (iii) improvement of initiator system 0109-5641/$ – see front matter © 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.dental.2011.10.015