Amalgam

Silver Amalgam: A heritage material

1. 8-Jun-16 PEOPLE’S COLLEGE OF DENTAL SCIENCE & RESEARCH CENTER DEPT. OF CONSERVATIVE DENTISTRY & ENDODONTICS 1

2. AMALGAM & RECENT ADVANCES Presented By:- Dr Nishant Khurana PG Student Guided By:- Dr M.P. Singh & Dr Hemant Chourasia 8-Jun-16 2

3. CONTENTS INTRODUCTION DEFINITION & TERMINOLOGIES HISTORY CONSTITUENTS IN AMALGAM CLASSIFICATION COMPOSITION LOW COPPER AMALGAM ALLOYS HIGH COPPER AMALGAM ALLOYS PRE AMALGAMATED ALLOY 8-Jun-16 3

4. MANUFACTURE OF ALLOY ARTICLES METALLARGIC PHASES SETTING REACTION PROPERTIES OF AMALGAM FACTORS CONTROLLING QUALITY OF DENTAL AMALGAM INDICATIONS/CONTRAINDICATIONS ADVANTAGES/DISADVANTAGES MANIPULATION AND TECHNICAL CONSIDERATIONS OF DENTAL AMALGAM 8-Jun-16 4

5. CAUSES OF FAILURE OF DENTAL AMALGAM MERCURY TOXICITY RECENT ADVANCES IN DENTAL AMALGAM BONDED AMALGAM RESTORATION GALLIUM ALLOYS LOW MERCURY AMALGAMS INDIUM ALLOYS FLUORIDATED AMALGAM AMALGAM MYTHS AND FACTS CONCLUSION & REFERENCES 8-Jun-16 5

6. INTRODUCTION Dental amalgam is a metal like restorative material composed of a mixture of silver-tin-copper alloy and mercury . Amalgam has been the primary restorative material for around 150 years . ORIGIN OF AMALGAM can be traced back to 659 AD in CHINA. FATHER OF AMALGAM - REGNART 8-Jun-16 6

7. Why Amalgam? Inexpensive Ease of use Proven track record >150 years Familiarity Resin-free less allergies than composite 8-Jun-16 7

8. DEFINITION Amalgam technically means an alloy of mercury with any other metal . Dental amalgam is an alloy made by mixing mercury with a silver-tin dental amalgam alloy. 8-Jun-16 8

9. TERMINOLOGY DEFINITION Amalgam Amalgam is an alloy which has mercury as one of its components – Marzouk (1997) Dental Amalgam An alloy of mercury, silver, copper, tin, which may also contain palladium, zinc, and other elements to improve handling characteristics and clinical performance – Anusavice (2003) Dental Amalgam Alloy / Alloy for Dental Amalgam An alloy of silver, copper, tin, and other elements that is formulated and processed in the form of powder particles or as a compressed pellet – Anusavice (2003) 8-Jun-16 9

10. TERMINOLOGY DEFINITION Amalgamation The process of mixing liquid mercury with one or more metals or alloys to form an amalgam. – Anusavice (2003) Trituration The process of grinding powder, especially within a liquid. In dentistry, the term is used to describe the process of mixing the amalgam alloy particles with mercury in an amalgamator. – Anusavice (2003) 8-Jun-16 10

11. HISTORY 8-Jun-16 11

12. YEAR EVENTS 1819 First dental silver amalgam is supposed to have been introduced into England by Bell – “ Bell’s Putty ” 1833 Introduced to the North American continent by Cawcour brothers termed as “ Royal Mineral Succedaneum ”. 1843 Resolution passed by the American Society of Dental Surgeons (the first organised Dental Society in the U.S.A declaring the use of amalgam a “ Malpractice ”. Thus the Amalgam War began 1845 “ Amalgam Pledge ” was adopted by the society. 8-Jun-16 12

13. YEAR EVENTS 1850 Pledge was rescinded officially ending the amalgam war. 1861 First research programme was conducted by John Tomes ( Trans.Odontol.Soc . G.B., Vol III) Who measured shrinkage of a number of amalgams 1871 Charles Tomes measured shrinkage & expansions by specific gravity tests. 1874 Thomas B.Hitchcock ( Trans.N.Y.Odontol.Soc ) did some important work in measuring more accurately by means of a micrometer changes of amalgam form 8-Jun-16 13

14. True amalgam science began with the investigations by G.V.Black during 1890,s. 1895 G.V. Black developed formula for modern amalgam alloy 67% silver, 27% tin, 5% copper, 1% zinc overcame expansion problems 8-Jun-16 14

15. YEAR EVENTS 1896 Classic work of G.V.Black that a more systematic study was made of the properties & manner of manipulation of silver amalgam and its relation to cavity preparation. Many of G.V.Black’s techniques for amalgam restorations are generally accepted today. New methods are often described as variations or modifications of those used by Black. 8-Jun-16 15

16. YEAR EVENTS 1930 A.D.A research organisation conducted a survey and showed that only a few of the proprietary amalgam alloys on the market & tested by the National Bureau of Standards were reliable. A.D.A specification No. 1 for Alloy. A.D.A specification No. 6 for Mercury. 1934 & 1960 Revision of this specification 8-Jun-16 16

17. YEAR EVENTS 1970 Inclusion of a diametral tensile strength as an indication of the rate of hardening of the amalgam as distinct from a compressive strength test. Adjustments in the setting change & flow requirements that are due to changes in test procedures. Change from hand trituration to mechanical trituration 1957 & 1961 British Standards Institution provided a specification number currently under review 8-Jun-16 17

18. CONSTITUENTS IN AMALGAM Basic Silver Tin Copper Mercury Other Zinc Indium Palladium 8-Jun-16 18

19. Basic Constituents Silver (Ag) increases strength increases expansion Tin (Sn) decreases expansion decreased strength increases setting time Phillip’s Science of Dental Materials 2003 8-Jun-16 19

20. Basic Constituents Copper (Cu) ties up tin reducing gamma-2 formation increases strength reduces tarnish and corrosion reduces creep reduces marginal deterioration Phillip’s Science of Dental Materials 2003 8-Jun-16 20

21. Basic Constituents Mercury (Hg) activates reaction only pure metal that is liquid at room temperature spherical alloys require less mercury smaller surface area easier to wet 40 to 45% Hg admixed alloys require more mercury lathe-cut particles more difficult to wet 45 to 50% Hg Phillip’s Science of Dental Materials 2003 8-Jun-16 21

22. Other Constituents Zinc (Zn) used in manufacturing decreases oxidation of other elements sacrificial anode provides better clinical performance less marginal breakdown causes delayed expansion with low Cu alloys if contaminated with moisture during condensation Phillip’s Science of Dental Materials 2003 H 2 O + Zn ZnO + H 2 Þ 8-Jun-16 22

23. Other Constituents Indium (In) decreases surface tension reduces amount of mercury necessary reduces emitted mercury vapor reduces creep and marginal breakdown increases strength must be used in admixed alloys example Indisperse (Indisperse Distributing Company) 5% indium 8-Jun-16 23

24. Other Constituents Palladium (Pd) reduced corrosion greater luster example Valiant PhD (Ivoclar Vivadent) 0.5% palladium 8-Jun-16 24

25. CLASSIFICATION 8-Jun-16 25

26. ACC. TO STURDEVANT’s BASED ON COPER CONTENT CONVENTIONAL OR LOW COPPER ALLOY HIGH COPPER ALLOY HIGH COPPER ADMIXED ALLOY HIGH COPPER UNICOMPOSITIONAL ALLOY BASED ON AMALGAM ALLOY PARTICLE GEOMETRY & SIZE 1) LATHE CUT ALLOY -REGULAR-CUT -FINE-CUT -MICROFINE-CUT 2) SPHERICAL ALLOY 3)ADMIXED ALLOY 8-Jun-16 26

27. 3) ACCORDING TO ZINC CONTENT 1) ZINC CONTAINING ALLOYS 2) ZINC FREE ALLOYS 4)NEW AMALGAM ALLOYS 8-Jun-16 27

28. CLASSIFICATION (MARZOUK) ACCORDING TO NO. OF ALLOY METALS BINARY ALLOYS(SILVER-TIN) TERNARY ALLOYS(SILVER-TIN-COPPER) QUATERNARY ALLOYS(SILVER-TIN-COPPER-INDIUM) ACCORDING TO THE SHAPE OF POWDER PARTICLES SPHERICAL LATHE CUT ADMIXED 8-Jun-16 28

29. Particle Shape Lathe cut low Cu New True Dentalloy high Cu ANA 2000 Admixture high Cu Dispersalloy, Valiant PhD Spherical low Cu Cavex SF high Cu Tytin, Valiant 8-Jun-16 29

30. 3) ACCORDING TO POWDER PARTICLE SIZE 1) MICROCUT 2)FINE CUT 3)COARSE CUT 4) ACCORDING TO COPPER CONTENT 1) LOW COPPER ALLOYS-Copper content < 6 % 2)HIGH COPPER ALLOYS- Copper content > 6 % 8-Jun-16 30

31. Regular or Coarse cut / Fine cut. /Micro-fine cut. 8-Jun-16 31

32. 5) ACCORDING TO ZINC CONTENT 1) ZINC CONTAINING ALLOYS- Zinc content >0.01% 2)ZINC FREE ALLOYS- Zinc content < 0.01% 6) PRESENCE OF NOBLE METALS 1) NOBLE METAL ALLOYS 2)NON NOBLE METAL ALLOYS 8-Jun-16 32

33. COMPOSITION 8-Jun-16 33

34. Acc. To ADA specification no. 1 requires that the amalgam alloys contain predominantly silver and tin . Unspecified amounts of other elements like copper, zinc, gold and mercury are allowed in concentrations less than the silver or tin content. 8-Jun-16 34

35. LOW COPPER ALLOYS ACCORDING TO STURDEVANT AND ANUSAVICE - SILVER 65 %- 70% TIN 25%-30% COPPER 4%-5% ZINC 1% ACCORDING TO COMBE - SILVER 65-74% TIN 25-27% COPPER 0-6% ZINC 0-2% 8-Jun-16 35

36. HIGH COPPER AMALGAM ALLOY - 1.ADMIXED ALLOY POWDER ACCORDING TO STURDEVANT - SILVER 60% TIN 27% COPPER 13% ZINC 0% ACCORDING TO COMBE - SILVER 69% TIN 17% COPPER 13% ZINC 1% 2. SINGLE COMPOSITION ALLOY- SILVER 60% TIN 25% COPPER 15% 8-Jun-16 36

37. Composition LOW COPPER HIGH COPPER Admixed Unicomposition Particle shape Lathe- Cut / Spherical Lathe-cut (2/3) Spherical (1/3) Spherical Silver 63-70% 40-70 % 40-65 % 40-60 % Tin 26-30 % 26-30 % 0-30 % 22-30 % Copper 2-5 % 2-30 % 20-40 % 13-30 % Zinc 0-2 % 0-2 % 0 % 0-4 % 8-Jun-16 37

38. Method of Adding Copper S ingle C omposition L athe-Cut (SCL) S ingle C omposition S pherical (SCS) A dmixture: L athe-cut + Spherical E utectic (ALE) A dmixture: L athe-cut + S ingle C omposition S pherical (ALSCS) 8-Jun-16 38

39. Also available these days are; PRE AMALGAMATED ALLOYS In this the surface of alloy particles have been introduced to mercury by manufacturer. Contain upto 35% Hg. 8-Jun-16 39

40. MANUFACTURE OF ALLOY POWDER 8-Jun-16 40

41. Manufacturing Process Lathe-cut alloys Ag & Sn melted together alloy cooled phases solidify heat treat 100 ºC for 8 hours grind, then mill to 25 - 50 microns heat treat to release stresses of grinding Phillip’s Science of Dental Materials 2003 8-Jun-16 41

42. Manufacturing Process Spherical alloys melt alloy atomize spheres form as particles cool sizes range from 5 - 40 microns variety improves condensability Phillip’s Science of Dental Materials 2003 8-Jun-16 42

43. METTALURGICAL PHASES 8-Jun-16 43

44. Sn 8 Hg Tin-Mercury phase Ag 2 Hg 3 Silver-Mercury phase Ag 3 Sn Silver-tin phase STOICHIOMETRIC FORMULA  2  1  (gamma) PHASES NUMBER OF ATOMS

45. NUMBER OF ATOMS STOICHIOMETRIC FORMULA PHASES Ag-Cu Silver-Copper Eutectic Cu 6 Sn 5 Copper-Tin phase  (Eta) Cu 3 Sn Copper-Tin phase  (Epsilon) 8-Jun-16 45

46. SCHEMATICs OF SETTING Rx n Before Rxn; Alloy Particles are dispersed in Mercury After Rxn; Residual alloy particles are embeded in a matrix of Crystalline reaction products 8-Jun-16 46

47. Basic Composition A silver-mercury matrix containing filler particles of silver-tin Filler (bricks): Ag 3 Sn called gamma can be in various shapes irregular (lathe-cut), spherical, or a combination Matrix: Ag 2 Hg 3 called gamma 1 cement Sn 8 Hg called gamma 2 voids Phillip’s Science of Dental Materials 2003 8-Jun-16 47

48. AMALGAMATION REACTION 8-Jun-16 48

49. SETTING REACTION Conventional Low Copper Amalgam alloy Ag 3 Sn + Hg ⁼ Ag 2 Hg 3 + Sn 8 Hg + Ag 3 Sn High Copper Admixed Amalgam alloy STEP 1 Ag 3 Sn +Ag-Cu + Hg ⁼ Ag 2 Hg 3 + Sn 8 Hg + Ag 3 Sn + Ag 3 Sn STEP 2 Sn 8 Hg + Ag-Cu= Ag 2 Hg 3 + Cu 6 Sn 5 +Unconsumed Ag-Cu & Ag 2 Hg 3 8-Jun-16 49

50. CONVENTIONAL LOW-COPPER ALLOYS Ag-Sn Alloy Ag-Sn Alloy Ag-Sn Alloy Mercury (Hg) Ag Ag Ag Sn Sn Sn Hg Hg Ag 3 Sn + Hg Þ Ag 3 Sn + Ag 2 Hg 3 + Sn 8 Hg Phillip’s Science of Dental Materials 2003    1  2 8-Jun-16 50

51. ADMIXED HIGH-COPPER ALLOYS Ag-Sn Alloy  1 Ag-Cu Alloy  Ag-Sn Alloy Ag 3 Sn + Ag-Cu + Hg Þ Ag 3 Sn + Ag-Cu + Ag 2 Hg 3 + Cu 6 Sn 5    1  8-Jun-16 51

52. Ag-Sn Alloy Ag-Sn Alloy Ag-Sn Alloy  1  Ag 3 Sn + Cu 3 Sn + Hg Þ Ag 3 Sn + Cu 3 Sn + Ag 2 Hg 3 + Cu 6 Sn 5 Phillip’s Science of Dental Materials 2003    1    SINGLE COMPOSITION HIGH-COPPER ALLOYS 8-Jun-16 52

53. Strength Compresive Strength Tensile Strength Dimensional Changes Flow & Creep Tarnish & Corrosion PHYSICAL PROPERTIES 8-Jun-16 53

54. STRENGTH AMALGAM COMPRESSIVE STENGTH ( MPa ) 1hr 7days CREEP (%) TENSILE STRENGTH 24hrs( MPa ) Low copper 145 343 2 60 Admixed 137 431 0.4 48 Single composition 262 510 0.13 64 8-Jun-16 54

55. Compressive Strength : High Copper amalgam > low copper amalgam Tensile Strength : Its is important for Fracture Resistance ; High Copper amalgam< low copper amalgam FACTORS AFFECTING STRENGTH TRITURATION MERCURY CONTENT EFFECT OF CONDENSATION EFFECT OF POROSITY EFFECT OF AMALGAM HARDENING RATE 8-Jun-16 55

56. DIMENSIONAL CHANGES - When mercury is combined with amalgam it undergoes three distinct dimensional changes STAGE 1- INITIAL CONTRACTION Lasts for about 20 mins Contraction which occurs is not > 4.5µm/cm STAGE 2- EXPANSION STAGE 3- LIMITED DELAYED CONTRACTION EXPANSION IS MORE FOR LOW COPPER THAN HIGH COPPER ALLOYS. 8-Jun-16 56

57. FACTORS THAT AFFECT THE DIMENSIONAL CHANGES - Particle size & shape Mercury Manipulation Moisture contamination- this type of expansion can reach values greater than 400µm. 8-Jun-16 57

58. EXCESSIVE EXPANSION 8-Jun-16 58

59. FLOW AND CREEP WHEN A METAL IS PLACED UNDER STRESS,IT WILL UNDERGO PLASTIC DEFORMATION.THIS CHARACTERISTIC IS REFERRED AS FLOW OR CREEP. FLOW IS MEASURED DURING SETTING OF AMALGAM CREEP IS MEASURED AFTER AMALGAM SETTING. - IT IS DEFINED AS INCREMENTAL DEFORMATION. - VARY FROM 0.1% TO 4% 8-Jun-16 59

60. HIGH COPPER ALLOYS HAVE LOWER CREEP VALUES THAN CONVENTIONAL LOW COPPER ALLOYS. FACTORS INFLUENCING CREEP 1.Phases of amalgam restorations 2.Manipulation 8-Jun-16 60

61. PHYSICAL PROPERTIES Alloy 1hr compressive strength 7 day compressive strength Creep 15 min tensile strength 7 days tensile strength Dimensinal change μm/cm Low copper 45 MPa 302 MPa 6.3% 3.2 MPa 51 MPa -19.7 High Copper admixed 118 MPa 387 MPa 0.45% 3.0MPa 43MPa -1.9 High Copper spherical 252 MPa 455 MPa 0.51% 8.5MPa 556Mpa -8.8

62. TARNISH AND CORROSION- TARNISH: Is a surface discolouration on a metal or even a slight loss or alteration of the surface finish or luster. CORROSION: It is the destructive attack of a metal by chemical or electrochemical reaction with its environment. 8-Jun-16 62

63. TYPES OF CORROSION- Chemical corrosion 2. Electrochemical corrosion Galvanic corrosion Crevice corrosion C) Stress corrosion 8-Jun-16 63

64. Other 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]

65. Chemical Properties ELECTROCHEMICAL CORROSION: Galvanic corrosion Local galvanic corrosion (structure selective) Crevice corrosion (concentration cell) Stress corrosion Sn-O-Cl Sn-O CHEMICAL CORROSION: AgS

66. Biological Properties Mercury Toxicity:Transient : intraoral release (<35 m g/m 3 ) Mercury Hypersensitivity: Low level allergic reaction Estimated to be < 1 / 100,000,000 Amalgam Tatoo : Can occur during amalgam removal if no rubber dam Embedded amalgam particles corrode and locally discolor gum No known adverse reactions

67. FACTORS AFFECTING THE QUALITY OF AMALGAM 1) Factors governed by the dentist: a) Selection of an alloy. b) Mercury alloy ratio. c) Trituration process. d) Condensation technique. e) Marginal integrity . f) Anatomical characteristics . g) Final finish.

68. 2) Factors governed by the manufacturer  : a) Composition of the alloy. b) Heat treatment of the alloy. c) Size, shape and method of production of the alloy particles. d) Surface treatment of the alloy particles. e) The form in which the alloy is supplied.

69. INDICATIONS 1. Moderate to large class I and class II restorations. 2. Temporary caries control restorations for those teeth that are badly broken down and require subsequent evaluation of pulpal health before definitive restoration. 3. Foundations for badly broken down teeth that will require increased retention and resistance form in anticipation of the subsequent placement of a crown or a metallic onlay.

70. CONTRAINDICATIONS 1. Class III and class V restorations in aesthetically critical areas. 2. Small to moderate restorations in posterior teeth. 3. In Patients who are allergic to the alloy components.

71. ADVANTAGES 1. Ease of use. 2. High compressive strength. 3. Excellent wear resistance. 4. Favorable long term clinical results. 5. Low cost than fot composites

72. DISADVANTAGES 1. Non-insulating. 2. Non-esthetic. 3. Weakens tooth structure. 4. More technique sensitive. 5. Less conservative. 6. More difficult tooth preparation. 7. Initial marginal leakage.

73. MANIPULATION AND TECHNICAL CONSIDERATIONS OF DENTAL AMALGAM 8-Jun-16 73

74. Alloy Selection Handling characteristics Mechanical and physical properties Clinical performance

75. Handling Characteristics Spherical advantages easier to condense around pins hardens rapidly smoother polish disadvantages difficult to achieve tight contacts higher tendency for overhangs Phillip’s Science of Dental Materials 2003

76. Handling Characteristics Admixed advantages easy to achieve tight contacts good polish disadvantages hardens slowly lower early strength

77. Overview of Manipulation Selection / Proportioning / Amalgamation / Manipulation / Polishing Placement and Condensation Carving Burnishing Polishing Onset of MIXING Onset of WORKING Onset of SETTING End of SETTING 24 hours TIME

78. ALLOY MANIPULATION Manual Trituration Procedures: Alloy + Hg  mortar + pestle  manual mixing Mechanical Trituration Procedures: Powdered alloy + Hg  capsule + pestle  amalgamator Pelleted alloy + Hg  capsule + pestle  amalgamator Powdered alloy + Hg  pre-capsulated  amalgamator

79. Amalgamators SPEED TIME ENERGY = Speed x Time older amalgamator = Caulk VariMix

80. Trituration Mixing time refer to manufacturer recommendations Overtrituration “hot” mix sticks to capsule decreases working / setting time slight increase in setting contraction Undertrituration grainy, crumbly mix Phillip’s Science of Dental Materials 2003

81. Mulling- It is actually a continuation of trituration . Improves homogenicity of the mass and texture. Done for 2-5 sec. Consistency of mix- Normal mix Undertriturated grainy mix

82. Video On Amalgam Restoration 8-Jun-16 82

83. Condensation Forces lathe-cut alloys small condensers high force spherical alloys large condensers less sensitive to amount of force vertical / lateral with vibratory motion admixture alloys intermediate handling between lathe-cut and spherical

84. CONDENSATION PRESSURE Forces as high as 66.7N are recommended. Average forces exerted by the practitioners range between 13.3 to 17.8N . To ensure maximum density and adaptation to the cavity walls, the condensation forces should be as great as the alloy will allow, consistent with the patient comfort. 8-Jun-16 84

85. Carving- It is the anatomical sculpturing of the amalgam material. A scraping or ringing sound should be heard while carving .

86. Burnishing Pre-carve removes excess mercury improves margin adaptation Post-carve improves smoothness Combined less leakage Ben-Amar Dent Mater 1987

87. Early Finishing After initial set polishing cup with pumice provides initial smoothness to restorations recommended for spherical amalgams

88. Polishing Increased smoothness Decreased plaque retention Decreased corrosion Clinically effective no improvement in marginal integrity Mayhew Oper Dent 1986 Collins J Dent 1992

89. FAILURE OF AMALGAM RESORATIONS SIGNS Of Failure Fracture lines Marginal ditching 3) Proximal overhangs 4 ) poor anatomic contours 5 ) marginal ridge incompatibility

90. 6) Incorrect proximal contacts 7) Recurrent caries 8)Amalgam blues 9 ) Voids 10 ) Poor occlusal contacts 11 ) Bulk fracture of the tooth or amalgam

91. CAUSES OF FAILURE IMPROPER CASE SELECTION IMPROPER CAVITY PREPARATION- Inadequate extensions /Overextended cavity preparation Shallow cavity /Deep cavity preparation Curve pulpal floor Wide isthmus /Narrow isthmus Sharp axiopulpal line angle Lack of butt joint Lack of occlusal convergence Improper convenience form

92. 3) FAULTY SELECTION AND MANIPULATION OF AMALGAM- Selection of the alloy and mercury Improper trituration Improper condensation Contamination Over & under carving Improper finishing 4) ERRORS IN MATRICING PROCEDURES AND RESTORATION- Unstable matrix Poor contour Absence of wedges Premature matrix removal 8-Jun-16 92

93. Mercury the Metal

94. Hg Facts & Uses Quick silver 13.6 times the weight of water Evaporates at room temperature Amalgam Many Industrial uses

95. MERCURY TOXICITY Hg (Vapor)= odorless, colorless gas Hg (Liquid)= penetrating liquid Vapor Limits (TLV) = 0.05 mg/m 3 = 50 m g/m 3 = 5 ppb Vapor Toxicity Calculations : Sensitivity Calculations : ADA  1 / 100,000,000 UNC  1 / 180,000,000 Occupational safety & health administration has set a T hreshold L imit V alue( TLV ) of 0.01mg/cu.mm as maximum amount of mercury in the work place . Lowest level of total blood mercury at which earliest non specific symptoms occur is 35ng/ml

96. SOURCES OF MERCURY EXPOSURE IN DENTAL OFFICE- 1) Amalgam raw materials 2) Mixed but unset amalgam 3) Dental amalgam scrap 4) During finishing and polishing of amalgam. 5) During removal of old amalgam restorations

97. MEASURES TO REDUCE MERCURY EXPOSURE IN THE DENTAL CLINIC- Storage of mercury Care During trituration of amalgam Care During insertion of amalgam Disposal of amalgam scrap During polishing of amalgam During removal of old amalgam restorations Care of contaminated instruments Check mercury vapour levels periodically Awareness of mercury toxicity

98. MERCURY TOXICITY-

99. ALLERGY Allergic responses are marked by itching, rashes, sneezing, difficulty in breathing, swelling or other symptoms like contact dermatitis. These reactions are experienced by less than 1 % of the treated population. When such a reaction has been documented by a dermatologist or an allergist, an alternative material must be used unless the reaction is self limiting.

100. RECENT ADVANCES IN DENTAL AMALGAM 8-Jun-16 100

101. NEWER TRENDS Because of a concern about the possible toxicity of mercury in amalgams, a number of materials have been developed. 1)Mercury-free direct –filling alloy : ADA-NIST (National Institute on Standards and Technology) Patented this alloy Silver coated Silver-Tin particles that can be self-welded by compaction ( hand-consolidated) 2)Transitional approaches/Low M ercury A malgams : Redesigning amalgam to have much less initial mercury Alloy particles pack together well Reduce mercury for mixing to the 15%-25% range

102. PRIMM - Poly Rigid Inorganic Matrix Material - Porous Ceramic fibers. Condensable, curable, carvable , polishable . "White amalgam" . 3) GALLIUM BASED ALLOYS - First suggested by Puttkamer in 1928. Satisfactory gallium restorations were developed by Smith & Others in 1956. Small amounts of indium &/or tin added to gallium produces liquid alloy at room temperature. 8-Jun-16 102

103. Gallium melts at 28 degree Celsius and can be used to produce liquid alloys at room temperature by the addition of small amounts of other elements such as indium. Gallium alloys are made with silver tin particles in gallium- indium. PROPERTIES: Wettability Sets in reasonable time and possesses strength Diametrical stability & corrosion resistance equal to or greater than silver amalgam 8-Jun-16 103 Restoration done with gallium alloys-

104. COMPOSITION: ALLOY LIQUID Silver (Ag) – 60% Gallium (Ga) - 62% Tin (Sn) -25% Iridium (Ir) - 25% Copper (Cu) -13% Tin (Sn) -25% Palladium ( Pd) - 20%

105. Advantages- Compressive strength similar to high copper amalgams. Biocompatibility Good adaptation & reduced marginal leakage . 4 . Low vapour pressure than mercury 5 . Creep values as low as 0.09 % 6 . sets early Disadvantages- Poor corrosion resistance- Corrosion poducts-Ga2O3 & SnO2 Post operative sensitivity Whitening of margins of restoration- Due to crystallization of gallium oxy hydroxide GaO (OH) Stickiness High cost 105

106. ALLOY CREEP % COMPRESSIVE STRENGTH (AFTER 6 HOURS) SETTING (CONTRACTION/EXPANSION %) Silver Alloy (High Copper) 1.04_0.06 370 MPa -0.05 Gallium Alloy 0.09_0.03 350 MPa +0.39 + +

107. Studies of biocompatibility & cytotoxicity by Eakle et al in 1992 & Psarras et al in 1992 have shown it is not significantly different from amalgams and composite resins.

108. 4) INDIUM IN MERCURY- 10-15% Indium in admixed alloys reduces the mercury needed for mixing . Powell et al in 1989 first reported that the addition of pure indium powder to a high copper amalgam alloy decreases mercury vaporization. This type of amalgam is currently marketed by INDISPERSE( Indisperse Inc,Canada ) 8-Jun-16 108

109. 5) BONDED AMALGAM RESTORATIONS: Silver does not adhere properly to cavity walls Adhesive systems designed to bond amalgam to enamel & dentin Improve adhesion, strengthen remaining tooth structure, decreases the need for removal of health tooth structure Pioneers were Sun Medical ( Superbond ), Kurrary ( Panavia ) Superbond was based on 4-META/MMA resins Panavia was based on Bis GMAphosphonated ester

110. Later dentin bonding agents have also been a subject of bonding amalgam to dentin Various Agents are Amalgam Bond with HPA ( Parkell) All Bond 2 (Bisco) Optibond 2 (Kerr) Panavia 21(Kuraray) Clearfil Linear Bond 2 (Kuraray) Scothbond MP (3M)

111. INDICATIONS: Auxillary retention Extensively carious posterior teeth Teeth with low Gingival- Occlusal height Temporary restorations Amalgam Sealants ADVANTAGE: More conservative Reinforces tooth structure Eliminates the use of pins Decreases the incidence of marginal fracture Provides a bond at the tooth restoration interface

112. Biologic sealing of the pulpo -dentinal complex Appointment time Cost effective DISADVANTAGE: Technique sensitive Time to adapt to the new technique Clinical performance are not documented No sustained effects of amalgam bonding when subjected to thermocycling Hydrolytic stability of the bond is questionable

113. Mechanism of bonding- Micromehanical Bond strength is around 10 MPa

114. "...amalgam bonding is an adjunct to and not a substitute for mechanical retentive form. The main advantage of conventional amalgam adhesives seems to be their ability to seal the tooth restorative interface, preventing microleakage into the dental tubules and pulp and reducing post-operative sensitivity. - Cobb, et al, Am J Dent, Oct 1999 8-Jun-16 114

115. 6) FLUORIDATED AMALGAM- Stannous Fluoride is added Exact mechanism of fluoride uptake is not known. In vitro studies have shown reduction in mechanical properties. 8-Jun-16 115

116. AMALGAM MYTHS AND FACTS MYTH #1: Amalgam cannot be bonded to teeth FACT#1 : Amalgam can be bonded to teeth,often yielding higher bond strength than composite resins . MYTH#2: Because of recent advances in material techniques,most studies of amalgam are outdated while of composites are not FACT#2 :Improvements in amalgam restorative material and techniques in recent years have been as dramatic as of composite resins.

117. MYTH#3: Composite resins are superior to amalgam because composites can be repaired. FACT#3 : Like composite resins, amalgam restorations can often be repaired MYTH#4: Amalgam is 100 years old,composites is much newer and therefore better. FACT#4 : Like radiography and gold restorations,amalgam’s longevity is testament of its safety and efficacy.

118. CONCLUSION Amalgam is a very good restorative material. While there are some concerns about its use, it is a safe and effective direct restorative material. A successful amalgam restoration is still relatively easy to accomplish, and adherence to tooth preparation and material handling requirements will still result in a successful restoration.

119. Video On Class II Preparation 8-Jun-16 119

120. REFERECES Sturdevant’s : Art & Science of Operative Dentistry Phillip’s Science of Dental Materials 2003 MARZOUK’S OPERATIVE DENTISTRY COMBE’S NOTES ON DENTAL MATERIALS WEB:- Youtube 8-Jun-16 120

121. ThaNK You 8-Jun-16 121