34 JDMT, Volume 10, Number 1, March 2021 Evaluation of a New Phosphoric Acid Gel Original Article Evaluation and Comparison of Newly Developed Phosphoric Acid Gel (Exir) with Two Different Common Gels in Iran Hamideh sadat Mohammadipour 1 , Majid Akbari 2 , Hossein Bagheri 1 , Mohammadtaghi Malekmohammadi 3 , Elnaz Karimian 4 , Salehe Sekandari 5 1 Assistant Professor, Dental Materials Research Center, Department of Cosmetic and Restorative Dentistry, School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran 2 Professor, Department of Cosmetic and Restorative Dentistry, School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran 3 Dentist, Mashhad, Iran 4 Assistant Professor, Department of Cosmetic and Restorative Dentistry, Dental School, Shahid Sadoughi University of Medical Sciences, Yazd, Iran. 5 Assistant Professor, Dental Research Center, Department of Cosmetic and Restorative Dentistry, School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran Received 15 August 2020 and Accepted December 2020 Abstract Introduction: Different surface treatments were preposed to prepare the tooth structure for resin composite bonding. One of the most common preparation is using of phosphoric acid etching. This study conducted to determine the etching effectiveness of a new formulated acid etchant (Exir) and compared it with two commercial products. Methods: To determine the physical properties, the viscosity and shelf life were evaluated by a viscometer and a centrifuge over the time, respectively. SEM micrographs were uesd to show the geometry of bovine enamel and dentin surfaces which were treated by three etchants. The μSBS of composite to treated dental tissues was also investigated. Data were analyzed by ANOVA and Tukey test (α=0.05). Results: Exir etchant showed the lower viscosity compared with two other gels and two-phase separation did not significantly increase during suggested period. The SEM images of enamel samples treated with Exir etchant showed regular etching patterns and less remnant in comparison with other groups. The SEM mages of dentin samples treated with Exir etchant, unlike others, showed wide open dentin tubules with clear exposed collagen fibers. Enamel and dentin μSBS were 30.08±6.79 and 7.29±1.27 for Exir etchant, 23.31±6.64 and 8.49±3.61 for Morva Etch and 23.22±7.05 and 6.16±1.68 for Ultra- Etch, respectivley. The μSBS values for enamel was significantly higher in Exir treated group (P=0.017), while there was no significant difference in dentin μSBS values among three tested etchants (P=0.07). Conclusion: The results of this study showed Exir etchant can provide acceptable results used on dentin and enamel substrates. Keywords: Phosphoric acid, Acid Etching, Micro-shear bond strength, Etch pattern. -------------------------------------------------------- Mohammadipour H.S., Akbari M, Bagheri H, Malekmohammadi M.T., Karimian E, Sekandari S. Evaluation and comparison of newly developed phosphoric acid gel (Exir) with two different common gels in Iran. J Dent Mater Tech 2021; 10(1): 34-43. Introduction Since teeth and smile are important factors in aesthetics, they more more considered by the patients. Anterior restorations should be mimic shape and color of natural teeth. Currently composites are one of the best materials in terms of esthetic and stability (1). In spite of noticeable achievements in production of composite resins in recent years, polymerization contraction and weak bond are still considered to be the main weaknesses of these tooth- colored restorations (2). In order to create a strong bond between composite resin and tooth surface, it is necessary to prepare tooth surfaces first (3). Acid etching method was first introduced by Buonocore in 1955 as a standard method of preparing enamel surface for micromechanical bond to composite restorations (4). In this method, mineral acids are used to