DENTAL AMALGAM Dr.linda Maher
WHAT IS AMALGAM?? Amalgam is a special type of alloy in which mercury is one of the components. used in dentistry as a restorative material
MERCURY MERCURY: it is a chemical heavy, silvery element with the symbol (Hg) It is the only metal that is liquid at standard conditions for temperature and pressure
ADVANTAGES OF AMALGAM • 1\ease of use • 2\high compressive strength • 3\excellent wear resistant • 4\favorable long term clinical results • 5\economic
DISADVANTAGES OF AMALGAM • 1\lack of esthetic • 2\less conservative to tooth structure • 3\corrosion
COMPOSITION A\THE ALLOY POWDER: 1\silver(60-69%) 2\tin(27%) 3\copper(13%) 4\zinc(0-2%) B\LIQUID MERCURY
TYPES OF AMALGAM ACCORDING TO COMPOSITION: 1\conventional amalgam(low copper-4%) 2\high copper amalgam(13%) ACCORDING TO PARTICLE SHAPE: 1\lathe-cut(irregular) 2\spherical 3\admixed(containing both types)
AMALGAM PARTICLES 1\LATHE-CUT: Irregularly shaped particles 2\SPHERICAL: Particles produced as small spheres 3\ADMIXED: Mixture of spherical and lathe-cut
REACTION 1\LOW COPPER AMALGAM Ag3Sn() + Hg Ag2Hg3(1) + Sn7-8Hg(2) + Ag3Sn() This reaction with mercury produces a corrosion prone phase= Sn7-8Hg(2) Called gamma2 phase (weak phase)
. 2\HIGH COPPER AMALGAM Ag3Sn() + Ag-Cu + Hg Ag2Hg3(1) + Sn7-8Hg(2) + Ag3Sn() + Ag-Cu and Sn7-8Hg(2) + Ag-Cu Cu6Sn5() + Ag2Hg3(1) Copper reacts with the week gamma 2 phase
AMALGAM CAPSULES • Contain (in separate compartments): • 1\powdered amalgam alloy • 2\liquid mercury
AMALGAMATOR • Speeds vary upward from 3000 rpm • Times vary from 5–20 seconds • Mix powder and liquid components to achieve a pliable mass • Reaction begins after components are mixed
MANIPULATION 1\MIXING OR TRITURATION: • powder and mercury are mixed together mechanically by the amalgamator • the duration of trituration varies from 5 to 20 seconds • over triturated alloy and under triturated alloys results in weaker restorations
. 2\PLACEMENT AND CONDENSATION • Carry out incrementally by amalgam carrier and placed into the cavity preparation. • Condensers are used to carefully work the amalgam into all of the corners of the preparation • Slightly over fill the cavity to allow enough material for carving • Should be done within 3-4 minutes(mixed amalgam hardens fast)
. 3\BURNISHING AND CARVING • To restore tooth contour .
. 4\FINISHING AND POLISHING • Best done after 24 hours to allow completion of crystallization
PROPERTIES 1\Good compressive strength: giving amalgam the ability to withstand the forces of biting. 2\Corrosion is reduced due to the addition of copper.
MERCURY TOXICITY • Person with average number of fillings (7) would absorb ~1.6 µg/day of mercury • Person with a moderately high number of fillings (13) would absorb ~3 µg/day • According to EPA, absorbed dose of mercury from food, water, and air is 5.7 µg/day • SO, the amount of mercury(Hg) that is released from amalgam is very small and has not shown to be dangerous to patient.
. • The greatest risk appear to be related to the inhalation of (Hg) vapor during placing or removing amalgam restoration from patients mouth. To minimize the risk of inhalation 1)to the patient: use of rubber dam and high-volume evacuation
. 2)to dental staff: 1-instruments contaminated by the amalgam should never be heated above 800 degree C to avoid release of mercury vapor 2-sterilization rooms must have adequate ventilation to disperse any mercury vapor that may com from the sterilizer 3-floors of dental clinic should be nonporous and easy to clean
. 4-operator should wear gloves , masks ,and eye protection glass when working with amalgam 5-dispose used amalgam capsules and amalgam remnants in sealed containers
JEROME MERCURY DOSE ANALYSER Used by many dentists to measure intra-oral mercury vapor