Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 12 1 2015 02 15 Effect of chloroform, eucalyptol and orange oil solvents on the microhardness of human root dentin. 25 30 Sedigheh Khedmat Dental Research Center, Dentistry Research Institute, Department of Endodontics, School of Dentistry, Tehran University of Medical Sciences, and Iranian Center for Endodontic Research, Tehran, Iran. Alaleh Hashemi Undergraduate student, School of Dentistry, International Campus of Tehran University of Medical Sciences. Tehran, Iran. Fatemeh Dibaji Department of Endodontics, School of Dentistry, International Campus of Tehran University of Medical Sciences. Tehran, Iran. Mohammad Javad Kharrazifard Statistical Advisor, Dental Research center, Tehran University of Medical Sciences, Tehran, Iran. 2015 10 16 This study aimed to assess the effect of chloroform, eucalyptol and orange oil solvents on the microhardness of human root dentin.Sixty-eight single-rooted single-canal extracted human premolar teeth were used. Tooth crowns were separated from the roots at the cementoenamel junction (CEJ). Roots were buccolingually sectioned into mesial and distal halves. Specimens were randomly divided into 5 groups, with 20 teeth in each solvent group and 4 teeth in each control group. Primary microhardness of specimens was measured using Vickers microhardness tester. Specimens were exposed to solvents for 15 minutes and were subjected to microhardness testing again. Data were recorded and analyzed using repeated measure ANOVA.No significant difference was found in dentin microhardness before and after exposure to solvents in any of the orange oil, eucalyptol, chloroform or saline groups (P=0.727). None of the experimental groups showed any significant difference in terms of dentin microhardness reduction (P=0.99) and had no significant difference with the negative control group.This study showed that chloroform, eucalyptol and orange oil as gutta percha solvents did not decrease the microhardness of root dentin. Thus, none of the mentioned solvents has any superiority over the others in terms of affecting dentin properties. https://fid.tums.ac.ir/index.php/fid/article/view/373 https://fid.tums.ac.ir/index.php/fid/article/download/373/349