logging in or signing up Dr. Gehan eloleimy-Amalgam-Structure-and-Properties-PPT gae2002 Download Post to : URL : Related Presentations : Let's Connect Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Copy embed code: Embed: Flash iPad Dynamic Copy Does not support media & animations Automatically changes to Flash or non-Flash embed WordPress Embed Customize Embed URL: Copy Thumbnail: Copy The presentation is successfully added In Your Favorites. Views: 817 Category: Entertainment License: All Rights Reserved Like it (0) Dislike it (0) Added: November 25, 2010 This Presentation is Public Favorites: 0 Presentation Description No description available. Comments Posting comment... Premium member Presentation Transcript Slide 1: DENTAL AMALGAM Stephen C. Bayne Department of Operative Dentistry School of Dentistry University of North Carolina Chapel Hill, NC 27599-7450 2006, Bayne and Thompson Slide 2: DENTAL AMALGAM Where is it? Slide 3: AMALGAM TERMINOLOGY AMALGAM = an alloy containing Hg as the major ingredient. DENTAL AMALGAM = an alloy of Hg with Ag-Sn. DENTAL AMALGAM ALLOY = a Ag-Sn alloy (to be mixed with Hg). Slide 4: ALLOY PRODUCTION Melting / Casting / Comminution IRREGULAR Particles “Cast ingots --> filed into powder” Irregular particles = lathe cut = filings Hot alloy sprayed into cold air Particles spherodize and solidify Polycrystalline particles Homogenized by HT to remove coring Annealing HT to relieve cold work in filings Spheres are acid-washed Generally spheres are HT Slide 5: Hg / Alloy RATIOS Slide 6: ALLOY MANIPULATION Slide 7: CLASSIFICATION Copper content = low copper, high copper Particle size (and shape) = irregular, spherical Number of particle types = 1 or 2 Zinc content = Zn-containing, Zn-free Slide 8: Rx and MICROSTRUCTURE Ag Primary reactant Sn Creates solubility, fluidity Cu Reacts with Sn Zn Alloy processing aid Hg Reactant with Ag (and Sn) Slide 9: SETTING REACTIONS Low-Copper Dental Amalgam: S-Alloy + Hg Residual Alloy + Matrix-1 + Matrix-2 Ag3Sn/Cu+ Hg Ag3Sn/Cu + Ag2Hg3 + CuSn + Cu3Sn g + Hg g + g 1 + e + h I-Alloy + Hg Residual Alloy + Matrix-1 + Matrix-2 g + Hg g (Ag3Sn) + g 1 + (g 2) S-Alloy + Hg Residual Alloy + Matrix-1 + Matrix-2 Alloy + Hg Alloy (Ag-Cu) + g 1 + e + h I/S-Alloy + Hg Residual Alloy + Matrix-1 + Matrix-2 Ag-Sn + Hg Ag-Sn + Ag-Hg + Sn-Hg Ag3Sn + Hg Ag3Sn + Ag2Hg3 + Sn7-8Hg g + Hg g + g 1 + g 2 Slide 10: Rx and MICROSTRUCTURE Slide 11: Rx and MICROSTRUCTURE Slide 12: PHASE DIAGRAMS Ag3Sn + Hg >>> Ag2Hg3 = g1 (26Ag-74Hg) Slide 13: Overview of Manipulation Selection / Proportioning / Amalgamation / Manipulation / Polishing Slide 14: Amalgamators ENERGY = Speed x Time Slide 15: Unset amalgam A Slide 16: DIMENSIONAL CHANGES Dimensional changes on setting: CONTRACTION during alloy dissolution EXPANSION during impingement of reaction product crystals (EXPANSION if side reactions due to H2O contamination) Dimensional changes on depend on reaction variables: Particle size, Hg/alloy ratio, trituration time, condensation, ... Slide 17: AMALGAM PROPERTIES 2. Clinical Performance a. Longevity = 20-25 yrs ideally, 8-12 yrs practically b. Modes of failure = caries, marginal fracture, bulk B. Properties: 1. Physical 2. Mechanical 3. Chemical 4. Biological A. Introduction: 1. Specifications for Amalgam Properties a. ADA / ANSI and ISO b. Determination of “safety and efficacy” Slide 18: Physical Properties 1. Thermal conductivity = 2. Electrical conductivity = 3. Coefficient of thermal expansion = 4. Radiopacity = 5. Color = [>2 mm Aluminum] [Lustrous, shiny, white] 25 ppm/ºC [High] [High] Slide 19: Mechanical Properties Slide 20: Mechanical Properties TYTIN (Kerr Dental Mfg) = “tie up the tin” High-Copper, Spherical, 1 Particle, Zn-free 42% Hg mixed with alloy Fast-setting High early strength Slide 21: Chemical Properties Slide 22: Biological Properties Mercury Toxicity: OSHA maximum TLV = 50 mg/m3 (vapor) per 40 hr work week. Transient intraoral release (<35 mg/m3). Mercury Hypersensitivity: Low level allergic reaction. Estimated to be < 1 / 100,000,000 Slide 23: Clinical Performance Reasons for Failure: Low-copper amalgam – marginal fracture and secondary caries. High-copper amalgam – marginal fracture and bulk fracture. Slide 24: Clinical Evaluation Slide 25: THANK YOU You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.