In vitro evaluation of different diameters of quartz fiber posts on root fracture resistance Dr. Jalalian E.,1 Dr. Mirzaei M. 2 1Associate Professor, Department of Prosthodontics, Faculty of Dentistry, Islamic Azad University. Tehran, Iran. 2Dentist. (Received 9 Aug, 2008 Accepted 22 Feb, 2009) Abstract Background and Aim: The fiber diameter of fiber post used in reconstruction of endodontically treated teeth is one of the controversial factors in root fracture resistance. The aim of this study was to evaluate the effect of three different diameters of quartz fiber posts on root fracture resistance. Materials and Method: This in vitro study was conducted on 30 mandibular premolars that were sectioned from CEJ. They were endodontically treated and randomly assigned to 3 groups A, B, C (n=10). Post spaces were prepared and D.T. Light-Post™ with three different diameters (0.8, 1, 1.2 mm) was cemented respectively in each group with dual cure resin bonding and resin cement Panavia F 2.0. Composite resin cores were built up using a preformed polyester matrix. Specimens were embedded in acrylic resin blocks with a layer of elastic polyether Impergum around roots as PDL. A compressive load at a crosshead speed of 1mm/min was applied axially to the central fossa of each specimen using a Universal Testing Machine, until root fracture occurred. Data was analyzed using one-way analysis of variance (ANOVA). Results: Mean fracture load was 1010 (±250.95) N for group A with 0.8 mm post diameter and 934.4 (± 295.18) N for group B with 1 mm post diameter and 1001 (±301.42) N for group C with 1.2 mm post diameter. We could not detect any statistically significant difference in root fracture resistance among the three groups. Conclusions: According to the findings of this study, with larger fiber posts the root fracture resistance is higher and they can provide more stability for core material, although, group differences in fracture resistance were not statistically significant. Key words: Quartz fiber posts - D.T. Light-Post™ - Root fracture resistance – ِDiameter - FRC post. Corresponding Author: Dr. Jalalian E., Associate Professor, Department of Prosthodontics, Faculty of Dentistry, Islamic Azad University. Tehran, Iran. e.mail: Dr_E_Jalalian@yahoo.com | 
