The reinforcement effect of nano and microfillers on fracture toughness of two provisional resin materials Caner Yilmaz * , Turan Korkmaz 1 Department of Prosthodontics, Dentistry Faculty of Gazi University, Ankara, Turkey Received 24 November 2005; accepted 25 May 2006 Available online 13 July 2006 Abstract The aim of this study was to survey the fracture toughness values when three different reinforcing particles (Al 2 O 3 whisker, glass fiber and wollastonite) were admixed as reinforcing fillers to pre-polymerized two provisional resin materials. In order to improve the mechan- ical properties, different ratios of nanopowder Al 2 O 3 whisker, floccular E-glass fiber and wollastonite were separately admixed with pre- polimerized acrylic resin beads prior to mixing with the monomer liquid. Polymethylmetacrylate (PMMA) and polyethylmetacrylate (PEMA) were used as resin matrices. All samples were tested for fracture toughness. The results were subjected to ANOVA and Tukey’s test. All test materials showed a statistically significant increase in K Ic after reinforcement with three reinforcement materials when com- pared to the control groups (p < 0.05). The results showed that all of the fillers had effect on increasing fracture toughness (K Ic ). All rein- forced specimens showed better fracture toughness values than unreinforced resins. Specimens reinforced with floccular glass fiber showed the highest K Ic values, followed by wollastonite and Al 2 O 3 whisker. The use of fillers is an effective method to increase the frac- ture toughness of provisional restoration resins. The use of floccular glass fiber and wollastonite is promising for the reinforcement of provisional materials. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Polymer; Alumina; Fracture toughness; Wollastonite 1. Introduction The use of a provisional restoration is an important phase in the treatment of dental prosthetic patients. Pre- pared teeth must be restored temporarily while the final prosthesis is being fabricated. The problems of using resin materials for provisional prostheses have been identified in the literature. Difficulties may be expected with more exten- sive provisional restorations that must be used for longer periods of time. There is a tendency for discoloration, occlusal wear, and fracture that eventually leads to unnec- essary repair [1]. Provisional restorations are a critical com- ponent of fixed prosthodontic treatment, biologically and biomechanically. Authopolymerizing acrylic resin is usu- ally the biomaterial for provisional restorations. Breakage is still a potential problem of provisional resin restorations, especially when long term or long span provisional restora- tions are required. Materials for provisional restoration with improved mechanical properties are important because of the durability of provisional restorations. One of the limitations of provisional restorations is their rela- tively poor strength [2]. Contemporary materials for the fabrication of single and multiple unit provisional restorations are of the most part resin based. They differ with regard to the method of polymerization, filler composition, and monomer type. They include auto-polymerizing and dual curing resins, such as polymethylmethacrylate (PMMA), polyethylmeth- acrylate (PEMA), polyvinyl(ethyl methacrylate), bis-GMA resins, bis-acryl resin composites, and visible light cured (VLC) urethane dimethacrylate resins. Auto polymerizing 0261-3069/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.matdes.2006.05.029 * Corresponding author. Address: 70. sok, 21/7 Emek Mah., 06510 Ankara, Turkey. Tel.: +90 312 212 62 20; fax: +90 312 223 92 26. E-mail address: cyilmaz@gazi.edu.tr (C. Yilmaz). 1 Address: 81. sok, Yildiztepe Blk, 6, blok No. 94, Emek Mahallesi, 06510 Ankara, Turkey. www.elsevier.com/locate/matdes Materials and Design 28 (2007) 2063–2070 Materials & Design