Amalgam past,present& future-I

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PAST, PRESENT & FUTURE

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Amalgam past,present& future-I

  1. 1. POSTGRADUATE DEPARTMENT OF CONSERVATIVE DENTISTRY AND ENDODONTICS SEMINAR TOPIC:- DENTAL AMALGAM- PAST, PRESENT & FUTURE-I (EVOLUTION & PROPERTIES) Presented by-Ashish Choudhary Pg student UNDER GUIDANCE OF :- Prof. Dr Riyaz Farooq (HOD) Dr Aamir Rashid (lecturer) Dr Fayaz Ahmed (lecturer)
  2. 2. Contents  Introduction  History of amalgam  Amalgam wars  Classification  Components of amalgam  Basic setting reaction  Manufacture of alloy powder  Properties of amalgam  Manipulation of amalgam  Recent advances in amalgam  Side effects of mercury  Durability of amalgam  Future of amalgam  Conclusion
  3. 3. INTRODUCTION Dental amalgam is one of the most versatile restorative materials used in dentistry. It constitutes approximately 75% of all restorative materials used by dentists. It has served as a dental restoration for more than 165 years. J Conserv Dent. 2010 Oct;13(4):204-8. Dental amalgam: An update Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  4. 4. • There is still no adequate economic alternative for dental amalgam. The combination of reliable long-term performance in load bearing situations and low cost is unmatched by other dental restorative material. It has a myriad of uses: rather low technique sensitivity, self-sealing property and its longevity Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion J Conserv Dent. 2010 Oct;13(4):204-8. Dental amalgam: An update
  5. 5. AMALGAM POPULARITY Cost effective and long life Acceptable biocompatibility Less technique sensitive Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion J Conserv Dent. 2010 Oct;13(4):204-8. Dental amalgam: An update
  6. 6. Over the last few years improvements in composition have led to - Reduced marginal failure due to decreased creep and corrosion Early seal between the tooth and restoration But development of alternatives based on ceramics and composites , and questions on its safety have led to its decline. Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion J Conserv Dent. 2010 Oct;13(4):204-8. Dental amalgam: An update
  7. 7. Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion Cavity design & prepation Selection of alloy & its manipulation with mercury Contouring & finishing procedures Age of the restoration & its environment The variables for amalgam’s appearance Amalgam: past,present & future JADA,Vol.86,April 1973
  8. 8. What is amalgam???? a·mal·gam: any alloy of mercury with any another metal [silver amalgam is used as a dental filling] word amalgam is derived from greek name ‘emolient’ which means paste. Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion Source: Webster’s New World Dictionary of the American Language, Guralnik DB, Ed., New York: World Publishing Co., 1972
  9. 9. Dental amalgam is an alloy made by mixing mercury with a silver tin amalgam alloy (Ag-Sn) Amalgam alloy is a silver tin alloy to which varying amounts of copper(Cu) and small amounts of zinc(Zn) have been added Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion Sturdevant’s Art & Science of Operative dentistry..5th ed; 152
  10. 10. INDICATIONS OF AMALGAM Moderate to large Class I and Class II restorations Class V restorations in unaesthetic areas Foundations Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  11. 11. Esthetics Small (even moderate) defects in posterior teeth Requirement for reinforcement of tooth CONTRAINDICATIONS OF AMALGAM Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  12. 12. ADVANTAGES OF AMALGAM • Cost effective • Time effective • Ease of placement • Wear resistance • Prevent marginal leakage after a period of time • Adequate resistance to fracture • Maintains anatomical form • Not overly technique sensitive • Favourable long term clinical research results Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  13. 13. • Aesthetics • Toxicity • Corrosion and galvanic action • Difficult tooth preparation • Initial marginal leakage • Technique sensitive if bonded • Brittle • Marginal breakdown • Do not help retain weakened tooth structure Disadvantages Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  14. 14. • Less microleakage, interfacial staining. • Slightly increase strength of remaining tooth structure. • Minimal postoperative sensitivity. • Some retention benefit. • Esthetic benefit of sealing by not permitting the Amalgam to discolor the adjacent tooth structure. Bonded Amalgams have “Bonding benefits” : Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  15. 15. HISTORY OF AMALGAM A Chinese medical text(Material medica) mentions using a “silver paste”, a type of amalgam, to fill teeth in the 7th century -by Su Kung in 659 AD Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion J Conserv Dent. 2010 Oct;13(4):204-8. Dental amalgam: An update
  16. 16. In Europe, Johannes Stokers, a municipal physician in Ulm, Germany, recommended amalgam as a filling material in 1528. Later, Li Shihchen (1578) chronicled a dental mixture of 100 parts mercury with 45 parts silver and 900 parts tin J Conserv Dent. 2010 Oct;13(4):204-8. Dental amalgam: An update Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  17. 17. In the 18th century, John Hill, an Englishman, described mercury as, “It penetrates the substance of all metals, and dissolves, and makes them brittle.” Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion • In 1818, Louis Nicolas Regnart, a Parisian physician invented amalgam by the addition of one-tenth by weight of mercury to another metal or metals. Dental silver amalgam was probably introduced in England by Joseph Bell, a British chemist, in 1819, and was known as ‘Bell’s putty’. J Conserv Dent. 2010 Oct;13(4):204-8. Dental amalgam: An update
  18. 18. • Traveau described a “silver paste” filing material in 1826. He produced amalgam by mixing the silver coins with mercury. Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  19. 19. 1833 -- Crawcours brothers introduced their “Royal Mineral Succedaneum” to America --mixed shaved French silver coins and mercury. J Conserv Dent. 2010 Oct;13(4):204-8. Dental amalgam: An update Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  20. 20. In 1877, Foster Flagg published the results of his laboratory tests and 5-year clinical observation of new alloys with 60% of silver and 40% of tin as major constituents in 1881 and thus predated by some 15 years the work of G.V. Black J Conserv Dent. 2010 Oct;13(4):204-8. Dental amalgam: An update Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  21. 21. The universal acceptance of amalgam as a restorative material resulted from investigations of G V Black in 1895, 1896, 1908 By combining the principles of cavity design, extension of the cavity into “immune” areas and the development of an alloy with the composition of 68.5% silver, 25.5% tin, 5% gold, 1% zinc, Black advanced amalgams into modern times J Conserv Dent. 2010 Oct;13(4):204-8. Dental amalgam: An update Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  22. 22. Traditional or conventional amalgam alloys were produced by early dental manufactures (S S White) & predominated from 1900 untill 1970.the basic composition was 65%Ag, 30%Sn, 5%Cu,& less than 1%zinc J Conserv Dent. 2010 Oct;13(4):204-8. Dental amalgam: An update Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion ADA specification No 1 was adapted for amalgam in 1929.
  23. 23. Extensive studies of the setting reaction of dental amalgams was performed by Gayler in 1937 & found that in the coarse filling alloys of that time, copper contents greater than 6% produced excessive expansion This was later challenged by Greener in 1970’s J Conserv Dent. 2010 Oct;13(4):204-8. Dental amalgam: An update Gayler ML. Dental amalgams. J Inst Metals. 1937;60:407–19 Greener EH. Amalgam-yesterday, today and tomorrow. Oper Dent. 1979;4:24–35. Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  24. 24. • In 1959, Dr. Wilmer Eames recommended a 1:1 ratio of mercury to alloy, thus lowering the 8:5 ratio of mercury to alloy that others had recommended. Eames WB. Preparation and condensation of amalgam with low mercury alloy ratio. J Am Dent Assoc. 1959;58:78–83 J Conserv Dent. 2010 Oct;13(4):204-8. Dental amalgam: An update Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  25. 25. In 1962, a spherical particle dental alloy was introduced by Innes & Youdelis This was followed in 1963 by a high copper dispersion alloy system that proved to be superior to its low copper predecessors Example; Dispersalloy (Caulk) J Conserv Dent. 2010 Oct;13(4):204-8. Dental amalgam: An update Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  26. 26. 1970’s • first single composition spherical • Tytin (Kerr) • ternary system (silver/tin/copper) 1980’s- mercury free alloys introduced Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  27. 27. AMALGAMWARS-thecontroversy Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion • In 1841, the American Society of Dental Surgeons declared that “the use of amalgam constitutes malpractice” AMALGAM USE DECLINED Dr. Christopher S. Brewster (1846) - condemned the use of amalgam in all cases merely because its use was abused by some “unprincipled quacks” was unwise. The amalgam controversy-an evidence based analysis ; JADA,Vol.132,march 2001
  28. 28. a belief prevailed that amalgam exerted “a vitiating influence upon the fluids of the mouth and gives rise to an unhealthy action in the gums.” - the society’s members were warned that they were to sign a pledge “NEVER TO USE amalgam” or they would risk being expelled from the membership. Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion The amalgam controversy-an evidence based analysis ; JADA,Vol.132,march 2001
  29. 29. Townsend - gave his personal directions for preparing the amalgam, known as “Townsend’s Amalgam”. In 1858, Townsend reversed his stance on amalgam and recommended removal of teeth that could not be saved by gold. In 1867, the St. Louis Odontological Society unanimously adopted a resolution to the effect that amalgam was “injurious and detrimental to health” AMALGAM Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  30. 30. Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion The amalgam controversy-an evidence based analysis ; JADA,Vol.132,march 2001
  31. 31. 1924 - Alfred Stock became poisoned with mercury & published papers on the dangers of mercury in dentistry 1934 - German physicians - no health risk from amalgams In December 2003, Dr. Frederick Eichmiller, - Amalgam is a SAFE, AFFORDABLE, AND DURABLE MATERIAL.” Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion The amalgam controversy-an evidence based analysis ; JADA,Vol.132,march 2001
  32. 32. the first one…… • In 1845, American Society of Dental Surgeons condemned the use of all filling material other than gold as toxic, thereby igniting "first amalgam war'. Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion The amalgam controversy-an evidence based analysis ; JADA,Vol.132,march 2001
  33. 33. What ended the amalgam war?? • Professional and consumer demand. • In 1859, the leaders of the profession regrouped to form the American Dental Association. • Between 1860 and 1890, many experiments were done to improve amalgam filling materials. • it was the classical work of GV Black in 1895 that a systemic study was done on properties & appropriate manipulation of amalgam. The amalgam controversy-an evidence based analysis ; JADA,Vol.132,march 2001 Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  34. 34. Then came the second amalgam war…. • Controversy over amalgam use surfaced again in 1926 and into the 1930's when a German physician, Dr. Alfred Stock, showed that mercury escaped from fillings in the form of a dangerous vapor that could cause significant medical damage. The amalgam controversy-an evidence based analysis ; JADA,Vol.132,march 2001 Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  35. 35. • During this Second Amalgam War, the American Dental Association vigorously defended silver amalgam and its widespread use was continued The amalgam controversy-an evidence based analysis ; JADA,Vol.132,march 2001 Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  36. 36. Remarkably, the Food and Drug Administration (FDA) has separately approved the mercury and the alloy powder for dental use; but the amalgam mixture has never been approved as a dental device Unfortunately now came the second world war over Europe &" the second amalgam war" fell in forgetfulness The amalgam controversy-an evidence based analysis ; JADA,Vol.132,march 2001 Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  37. 37. 3rd amalgam war in 1980s It was the Neurobiologist Mats Hanson, Assosiate professor in physiology at Lund University in Sweden, who in 1981 started the fight against the authorities The amalgam controversy-an evidence based analysis ; JADA,Vol.132,march 2001 Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  38. 38. 3rd amalgam war in 1980s but began primarily through seminars ,writings,& videotapes of Dr HA Higgins, a dentist from Colarado Springs in the same year Pressure from mounting clinical evidence forced the ADA to finally publicly concede that mercury vapor does escape from the amalgam filling into the patients mouth. The amalgam controversy-an evidence based analysis ; JADA,Vol.132,march 2001 Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  39. 39. 3rd amalgam war in 1980s But the ADA remained adamant that mercury in patients' mouths is safe, and in 1986 it changed its code of ethics, making it unethical for a dentist to recommend the removal of amalgam because of mercury but problem flared in 1990’s by the telecast of television program ‘60 minutes’ in CBC television The amalgam controversy-an evidence based analysis ; JADA,Vol.132,march 2001 Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  40. 40. Current status on the amalgam war The amalgam war continues to rage on today. some states have already appointed holistic/biological dentists to dental boards, effectively ending the ADA monopoly on state dental boards. The amalgam controversy-an evidence based analysis ; JADA,Vol.132,march 2001 Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  41. 41. Current status on the amalgam war • The problem is so serious that American Council on Health & Science, has determined that allegations against amalgam constitute one of the greatest “unfounded health scares of recent times” The amalgam controversy-an evidence based analysis ; JADA,Vol.132,march 2001 Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  42. 42. • There is presently a congressional bill in The United States House of Representatives (H.R. 4163) introduced by Rep. Diane Watson (D-CA) and Rep. Dan Burton (R-IN) to ban the continued use dental amalgam fillings. The amalgam controversy-an evidence based analysis ; JADA,Vol.132,march 2001 Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  43. 43. STATEMENT ON AMALGAM-ADA "No controlled studies have been published demonstrating systemic adverse effects from amalgam restorations-FDI & WHO;1997 “based on available scientific information, amalgam continues to be a safe and effective restorative material.“-ADA;1998 "There currently appears to be no justification for discontinuing the use of dental amalgam.“-ADA;1998 Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion American Dental Association (ADA) Council on Scientific Affairs, “Statement on dental amalgam,” 2011, http://www .ada.org/1741.aspx
  44. 44. “The current data are insufficient to support an association between mercury release from dental amalgam and the various complaints that have been attributed to this restoration material”-LSRO &FDA;2004 Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion American Dental Association (ADA) Council on Scientific Affairs, “Statement on dental amalgam,” 2011, http://www .ada.org/1741.aspx
  45. 45. “there were no statistically significant differences in adverse neuropsychological or renal effects observed over the 5-year period in children whose caries are restored using dental amalgam or composite materials- Journal of the American Medical Association (JAMA) and Environmental Health Perspectives;2006 Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion American Dental Association (ADA) Council on Scientific Affairs, “Statement on dental amalgam,” 2011, http://www .ada.org/1741.aspx
  46. 46. amalgam is a valuable, viable and safe choice for dental patients-ADA;2009 material is a safe and effective restorative option for patients-FDA;2009 Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion American Dental Association (ADA) Council on Scientific Affairs, “Statement on dental amalgam,” 2011, http://www .ada.org/1741.aspx
  47. 47. Classification of Amalgam A) According to Alloyed Metals Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion Sturdevant’s Art & Science of Operative Dentistry; 5th ed Number of alloyed metal Binary alloy (Ag-Sn) Tertiary alloy (Ag-Sn- Cu) Quarternary alloy (Ag-Sn- Cu-Zn)
  48. 48. B) According to shape of powdered particle Sturdevant’s Art & Science of Operative Dentistry; 5th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion Lathecut spherical Admixed
  49. 49. C) According to copper content Sturdevant’s Art & Science of Operative Dentistry; 5th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion Low copper amalgam(<0-6%) High copper amalgam(>6- 13%)
  50. 50. D)According to zinc content Sturdevant’s Art & Science of Operative Dentistry; 5th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion Zinc containing alloy (>0.01-2%) Non zinc containing alloy (<0-0.01%)
  51. 51. 1st generation 2nd generation 3rd generation Cu Zn Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion Ag3Cu 4th generation Ag Sn Cu upto 29% 5th generation Ag Sn Cu In 6th generation E)Generations based on the improvement in composition Ag Cu Pd Ternary alloy Quaternary alloy Eutectic alloy 1st, 2nd, 3rd generation+
  52. 52. Components of dental amalgam Other Zinc Indium Palladium Silver Tin Copper Mercury Basic Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion Phillip’s Science of Dental Materials;11th ed
  53. 53. Silver(Ag) Decreases creep & setting time Decreases corrosion Increases hardness & edge strength Increase tarnishing Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion Phillip’s Science of Dental Materials;11th ed
  54. 54. Tin(Sn) Low strength Larger contraction Decreases expansion Increased corrosion Increased plasticity Increased setting time Phillip’s Science of Dental Materials;11th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  55. 55. Copper(Cu) Decreases plasticity Increases hardness strength of alloy Reduce creep Reduce tarnish & corrosion Phillip’s Science of Dental Materials;11th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  56. 56. Zinc(Zn) Decreases brittleness Acts as a deoxidizer Less marginal breakdown Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion Phillip’s Science of Dental Materials;11th ed
  57. 57. Indium(In) decreases surface tension • reduces amount of mercury necessary • reduces emitted mercury vapor reduces creep and marginal breakdown increases strength example • Indisperse (Indisperse Distributing Company) • 5% indium* Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion operative dentistry journal1992 Sep-Oct;17(5):196-202
  58. 58. ` • Palladium (Pd) – reduced corrosion – greater luster – example • Valiant PhD (Ivoclar Vivadent) – 0.5% palladium Mahler J Dent Res 1990 Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  59. 59. Palladium pellets placed in an amalgam restoration were effective in reducing the amount of mercury vapor released in the 7 days following placement. Dental Materials Volume 15, Issue 6, November 1999, Pages 382-389 The optimal palladium content in γ1 seems to be in the range between 0.50 and 0.75 wt%. Biomaterials, Volume 18, Issue 13, July 1997, Pages 939-946 Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  60. 60. Mercury (Hg) - only pure metal that is liquid at room temperature Phillip’s Science of Dental Materials;11th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  61. 61. Alloy Powder Composition Type Ag Sn Cu Zn Other Low copper 63-72 26-28 2-7 0-2 — High-Cu admixed lathe- cut 40-70 26-30 12-30 0-2 — High-Cu admixed spherical 40-65 0-30 20-40 0 0-1 Pd High-Cu single spherical 40-60 22-30 13-30 0 0-5 In, 0-1 Pd compositions in weight percent Sturdevant’s Art & Science of Operative Dentistry;5th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  62. 62. Alloy Powder: Dispersalloy® Silver 69% Tin 18% Copper 12% Zinc 1% Mixing proportions: 50% alloy, 50% mercury Sturdevant’s Art & Science of Operative Dentistry;5th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  63. 63. Alloy Powder: Tytin® Mixing proportions: 57.5% alloy, 42.5% mercury Silver 59% Tin 13% Copper 28% Zinc 0% Sturdevant’s Art & Science of Operative Dentistry;5th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  64. 64. Phases in Amalgam Alloys and Set Dental Amalgams Formula g Ag3Sn g1 Ag2Hg3 g2 Sn7-8Hg b Ag4Sn (silver-rich) e Cu3Sn h Cu6Sn5 Silver-copper eutectic Ag-Cu Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion Phillip’s Science of Dental Materials;11th ed
  65. 65. BASIC COMPOSITION Matrix Ag2Hg3 called gamma 1 - cement Sn7Hg called gamma 2 - voids Filler (bricks) Ag3Sn called gamma can be in various shapes irregular (lathe-cut), spherical or a combination of both. A silver-mercury matrix containing filler particles of silver-tin. Ag3Sn Ag2Hg3 Sn7Hg8 Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  66. 66. Basic setting reactions Ag-Hg Ag Hg Ag4Hg5 (ƴ1 phase) Initial product Ag Hg Ag5Hg4 (β1 phase) In p/o excess Ag Introduction History Amalgam wars Classification Components Setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion Materials science for dentistry;9th ed B.W.Darvell
  67. 67. Silver-Tin (Ag - Sn) System  Most commercial alloys fall within the limited composition range of B to C i.e (β + γ) and γ  If Sn > 26.8 wt%  γ + Sn-rich phase is formed. Introduction History Amalgam wars Classification Components Setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  68. 68. • Dissolution and precipitation • Hg dissolves Ag and Sn from alloy • Intermetallic compounds formed Ag Sn Conventional Low-Copper Alloys Hg Ag3Sn + Hg  Ag3Sn + Ag2Hg3 + Sn8Hg g g g1 g2 CRAIG’s Restorative Dental Materials;12th ed Introduction History Amalgam wars Classification Components Setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  69. 69. • Gamma (g) = Ag3Sn – unreacted alloy – strongest phase and corrodes the least – forms 30% of volume of set amalgam • Gamma 1 (g1) = Ag2Hg3 – matrix for unreacted alloy and 2nd strongest phase – 60% of volume CRAIG’s Restorative Dental Materials;12th ed Introduction History Amalgam wars Classification Components Setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  70. 70. IMPORTANCE OF γ2 PHASE:- • Sn8Hg in a set amalgam may be reduced in quantity or even eliminated by the presence of ε–phase (Cu3Sn) • Potentially valuable rxn for several reasons:-  tin act as a most electropositive element present in absence of Zn, so with high activity in the γ2 phase, it makes the most electropositive phase, hence the most easily corroded Materials science for dentistry;9th ed B.W.Darvell Introduction History Amalgam wars Classification Components Setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  71. 71.  γ2 phase is extremely weak & soft, deforming readily & the strength of amalgam is limited by its presence Contributes to static creep of amalgam Materials science for dentistry;9th ed B.W.Darvell Introduction History Amalgam wars Classification Components Setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  72. 72. Scanning electron microscopic view of SnHg (γ2) crystals, that occurs in the matrix of set low copper amalgam Sturdevant’s Art & Science of Operative Dentistry;5th ed Introduction History Amalgam wars Classification Components Setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  73. 73. Improves strength of the resulting amalgam But if in excess, leads to expansion on setting Materials science for dentistry;9th ed B.W.Darvell Introduction History Amalgam wars Classification Components Setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion COPPER
  74. 74. Depending on its quantity & amt of Sn in the alloy, it may present as:- 1.Cu3Sn (ε-phase) 2.Cu6Sn (ή-phase) As solubility of Cu in γ and γ1 phase is low, thus Cu-Sn phase formed during setting process will probably be ή phase Materials science for dentistry;9th ed B.W.Darvell Introduction History Amalgam wars Classification Components Setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  75. 75. The reaction rate of β or γ phase Ag-Sn with Hg is sufficiently fast that the γ2 phase is always formed initially, but Cu3Sn (ε phase) & γ2 phase cannot exist together for long & relatively slow reaction must occur. ε + γ2 → ή + (Hg) Materials science for dentistry;9th ed B.W.Darvell Introduction History Amalgam wars Classification Components Setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion SLOW REACTIONS
  76. 76.  This is at relatively low rate because it is a solid state reaction  Also the 2 phases will be distributed as small grains throughout the amalgam without necessarily touching , & all diffusion of metal atoms must be through other phases or grain boundaries Materials science for dentistry;9th ed B.W.Darvell Introduction History Amalgam wars Classification Components Setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  77. 77. In the long term the conversion of γ1 to β1 may occur in the presence of unreacted γ phase alloy… γ + γ1 → β1 Materials science for dentistry;9th ed B.W.Darvell Introduction History Amalgam wars Classification Components Setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  78. 78. In the presence of excess Hg ( in terms of reaction with Ag-Sn phases),namely the decomposition of Cu-Sn phases to give the phase Cu7Hg6 (β2 phase) occurs…. ε , ή (IN P/O EXCESS Hg) → β2 + γ2 Materials science for dentistry;9th ed B.W.Darvell Introduction History Amalgam wars Classification Components Setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  79. 79. Added Cu As >6% Cu may not be included in the ‘conventionally’ formulated alloy because of excessive expansion However, if the extra Cu in incorporated in the form of second alloy powder, mixed with the first(admixed alloy),the difficulty may be avoided Materials science for dentistry;9th ed B.W.Darvell Introduction History Amalgam wars Classification Components Setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  80. 80. One such second alloy is eutectic of Ag-Cu system;this corresponds to composition 3Ag.2Cu α + α1 + γ2  ή + γ1 The elimination of γ2 phase results in improved properties, particularly in the compressive strength. Materials science for dentistry;9th ed B.W.Darvell Introduction History Amalgam wars Classification Components Setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  81. 81. High copper admixed alloy 2. Sn8Hg + AgCu  Cu6Sn5 + Ag2Hg3 + Ag3Sn (g2) (h ) (g1 ) (g ) 1. Ag3Sn + AgCu + Hg  Ag2Hg3 + Sn8Hg + Ag3Sn + AgCu (g ) (g1 ) (g2 ) (g ) CRAIG’s Restorative Dental Materials;12th ed Introduction History Amalgam wars Classification Components Setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  82. 82. High copper unicompositional alloy Ag3Sn + Cu3Sn + Hg  Cu6Sn5 + Ag2Hg3 (g ) ( e ) ( h ) (g1 ) CRAIG’s Restorative Dental Materials;12th ed Introduction History Amalgam wars Classification Components Setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  83. 83. Microstructure of Set Low Copper Amalgam. g(Ag3Sn) g2(Sn8Hg) Voids g1(Ag2Hg3) Introduction History Amalgam wars Classification Components Setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  84. 84. Microstructure of Set High-Copper Admixed Amalgam. g1(Ag2Hg3) g(Ag3Sn) Eutectic(Ag3Cu2) h(Cu6Sn5) Introduction History Amalgam wars Classification Components Setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  85. 85. Produced by cooling molten 72% Ag and 28% Sn and forming an ingot (The ingot may be 3-4 cm in diameter and 20 -30 cm in length) Alloy is heated for 8 hours at 400°C for homogeneous distribution of silver and tin Ingot is lathe-cut to produce the particles, ball- milled to reduce their size The particles are 60-120µm in length, 10-70µm in width & 10-35µm in thickness(Irregular in shape) Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion Manufacture of alloy powder Lathe cut alloy powder Materials science for dentistry;9th ed B.W.Darvell
  86. 86. Produced by atomizing the molten alloy in a chamber filled with an inert gas- argon Molten metal falls through a distance of approximately 30 feet and cools Results in characteristic spherical particle shapes. If particles are allowed to cool before they contact the surface of chamber, they are spherical in shape. If they are allowed to cool on contact with the surface they are flake shaped. Particle size ranges form 5 to 40 microns Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion Spherical alloy powder Materials science for dentistry;9th ed B.W.Darvell
  87. 87. A. Lathecut alloy B. Spherical alloy C. Admixed alloy Phillip’s Science of Dental Materials;11th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  88. 88. Homogenizing anneal 1. to overcome the coring & segregation in the solid ingot 2. to reestablish the equilibrium phase relationship the ingot is placed in an oven & heated at temp. below solidus for a sufficient time to allow diffusion of the atoms to occur. Phillip’s Science of Dental Materials;11th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  89. 89. Temperature for Ag-Sn: 480 degree Celsius if Cu present: 465 degree celsius if Zn present: lower it further The time of heat treatment may vary depending on the temp. used & size of ingot, but 24 hr at the selected temp.(350 to 450 ͦC) is usual. Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion Phillip’s Science of Dental Materials;11th ed
  90. 90. • At the end of heat treatment:- If rapid quenching done • The phase distribution remains unchanged • e.g. in an Ag-Sn alloy results in the formation of βphase in max. amount If allowed to cool slowly • The proportion of phases continue to adjust towards room temperature equilibrium ratio • e.g. formation of γ phase Phillip’s Science of Dental Materials;11th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  91. 91. Particle(surface) treatment Freshly cut alloys amalgamate & set more promptly than aged particles, but some aging of alloy is desirable to improve the shelf life of product Amalgams made from acid washed powders tends to be more reactive than those ,made from unwashed powders Phillip’s Science of Dental Materials;11th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  92. 92. • The aging is related to relief of stress in the particles during the cutting of the ingot (Phillip’s Science of Dental Materials;11th ed ) • The alloy particles are aged by subjecting them to a controlled temperature of 60-100 degree celsius for 1-6 hrs (Craig’s restorative dental materials,12th ed) Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  93. 93. PARTICLE SIZE • Greater amount of mercury to form an acceptable amalgam Tiny particles • More rapid hardening and a greater early strength Small-to- average particle size • A rough surface • Corrosion Larger particles Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  94. 94. Properties of amalgam • ANSI/ADA specification No.1 for amalgam alloy contains certain requirements:- 1. Maximum creep value of 3% 2. Minimum Compressive strength of 80 MPa at 1 hr when a cylindrical specimen is compressed at a rate of 0.25mm/minute 3. Dimensional change between 5 min & 24 hrs after trituration, should fall within a range of ±20µm/cm at 37̊ ̊C. Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion CRAIG’s Restorative Dental Materials;12th ed
  95. 95. DIMENSIONAL CHANGES Amalgam can expand or contract depending on manipulation Severe contraction leads to plaque accumulation & secondary caries Expansion leads to postoperative pain & splitting of tooth Materials science for dentistry;9th ed B.W.Darvell Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  96. 96. Immediately after packing a rapid contraction may be observed, followed by a slower expansion, and then a slight & slower contraction(amalgam setting dimensional change curve) Materials science for dentistry;9th ed B.W.Darvell Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion 20µm 20µm 20µm 20µm
  97. 97. Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion High-Cu, admixed High-Cu, single comp. Low-Cu
  98. 98. If amalgam expanded during hardening, leakage around the margins of restorations would be eliminated. Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  99. 99.  Shrinkage • when alloy & mercury are mixed ,contraction results as particles begin to dissolve & ƴ1 crystals grow • 8Ag3Sn + 31Hg (823.5ml/mol)=6Ag4Hg5 + Sn8Hg (774.9ml/mol) • Thereby a decrease of 5.9% by volume, or 2.0% by length (effect of solidification of mercury) Materials science for dentistry;9th ed B.W.Darvell Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  100. 100. Evidently the detrimental effect of shrinkage occurs only when the amalgam mass shrinks > 50 µm. Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  101. 101.  LOSS OF GLOSS • Shrinkage due to reaction will initially cause a decrease in the bulk volume, but once contacts between alloy particles or new crystals interfere with this, there is no choice but for the Hg to be withdrawn into the mass, leaving behind outline of the alloy particles. Materials science for dentistry;9th ed B.W.Darvell Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  102. 102. The failure of any amalgam to provide a marginal seal is due to the shrinkage of the liquid mercury on reaction & surface tension(a,b) Materials science for dentistry;9th ed B.W.Darvell Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  103. 103. • The crinkly surface thus produced clearly cannot be in direct contact with the cavity wall & a leakage path exists which survives even if there is subsequent expansion Materials science for dentistry;9th ed B.W.Darvell Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  104. 104. • The effect infact lead to loss of gloss, a freshly mixed pellet of amalgam is very smooth & shiny-metallically wet looking, but as setting proceeds it acquires a frosted or sand blasted appearance. • Leakage path can also occur because of the surface tension of mercury Materials science for dentistry;9th ed B.W.Darvell Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  105. 105.  EXPANSION • The impingement of growing crystals one on another will cause outward forces which will result in some expansion (crystal growth pressure) • If sufficient Hg is present to produce a plastic matrix, expansion occurs as a result of growth of ƴ1 crystals & viceversa Materials science for dentistry;9th ed B.W.Darvell Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  106. 106.  DELAYED EXPANSION Zinc containing low/high copper amalgam is contaminated by moisture during trituration or condensation, a large expansion can take place This expansion usually starts after 24 hrs, reach at peak within 3-5 days & may continue for months reaching values >400µm. Materials science for dentistry;9th ed B.W.Darvell Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  107. 107. • Hydrogen is produced by electrolytic action involving zinc & water • H2 doesnt combine with the amalgam rather it collects within amalgam, increasing internal pressure of amalgam leading to expansion Materials science for dentistry;9th ed B.W.Darvell Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  108. 108. Delayed expansion Materials science for dentistry;9th ed B.W.Darvell Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  109. 109. STRENGTH A) Compressive strength  Because amalgam is strongest in compression & much weaker in tension & shear, the prepared cavity design should take benefit of that  When subject to a rapid application of stress either in tension or compression a dental amalgam does not exhibit significant deformation or elongation & as a result function as a brittle material Phillip’s Science of Dental Materials;11th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  110. 110. • High copper single composition materials have the highest early compressive strength of more than 250 Mpa at 1 hr • While it is lowest for the low copper lathe cut alloy(45 Mpa) Phillip’s Science of Dental Materials;11th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  111. 111. • High values for early compressive strength are advantage for an amalgam, because they reduce the possibility of fracture by application of prematurely high occlusal forces by the patient before the final strength is reached • The compressive strength at 7 days is again highest for the high copper single composition alloys, with only modest differences in the other alloys Phillip’s Science of Dental Materials;11th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  112. 112. B) Tensile strength • Amalgam cannot withstand high tensile or bending stresses • The design of the restoration should include supporting structures whenever there is danger that it will be bent or pulled in tension • Both low & high copper amalgams have tensile strength that range between 48-70 MPa Phillip’s Science of Dental Materials;11th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  113. 113. Factors affecting strength -depends on the type of amalgam alloy, the trituration time & the speed of amalgamator -either under or overtrituration decreases the strength in both traditional & high copper amalgams Phillip’s Science of Dental Materials;11th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion 1) Effect of trituration
  114. 114. 2) Effect of mercury content dry granular mixrough & pitted surfacecorrosion high mercury contentmore γ2 phase low mercury contentmore unreacted AgSn particlesimparts strength to restoration sufficient mercury should be mixed with the alloy to wet each particle of the alloy Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  115. 115. -good condensation techniques express mercury & results in smaller volume fraction of matrix phases -in lathe cut alloys, higher condensation pressure results in higher compressive strength, particularly the early strength(at 1 hr) -on the other hand spherical amalgams condensed with lighter pressures produce adequate strength Phillip’s Science of Dental Materials;11th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion 3) Effect of condensation
  116. 116. -voids & porosities reduces strength -porosity is caused by:- a. decreased plasticity of the mix (due to low Hg/alloy ratio, delayed condensation, undertrituration) b. inadequate condensation pressure(results in inappropriate adaptation at the margins & increase number of voids) Phillip’s Science of Dental Materials;11th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion 4) Effect of porosity
  117. 117. c. irregularly shaped particles of alloy powder d. insertion of too large increments -fortunately, voids are not the problem with spherical alloys Phillip’s Science of Dental Materials;11th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  118. 118. -amalgams do not gain strength as rapidly as might be desired -at the end of 20min,compressive strength may be only 6% of 1 wk strength -ADA stipulates a min of 80MPa at 1 hr Phillip’s Science of Dental Materials;11th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion 5) Effect of rate of hardening
  119. 119. -the 1 hr compressive strength of high Cu single composition amalgams is relatively high compared with admixed high Cu amalgams -patients should be cautioned not to subject the restoration to high bitting stresses for atleast 8 hrs after placement ,by that time a typical amalgam has reached at least 70% of its strength Phillip’s Science of Dental Materials;11th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  120. 120. even after 6 months ,some amalgams may still be increasing in strength, suggesting that the reactions between matrix phases & the alloy particles may continue indefinitely Phillip’s Science of Dental Materials;11th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  121. 121. Strength of various phases • By studying the initiation & propagation of crack in a set amalgam, the strength of various phases can be observed • Possible to view under a conventional metallographical microscope • The propagation of the crack can be halted & the specimen etched to identify the various phases CRAIG’s Restorative Dental Materials;12th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  122. 122. • Results of such studies have led to the following ranking of different phases of a set low copper amalgam from strongest to weaker: Ag3Sn(γ),silver-Hg phase(γ1),tin-Hg phase(γ2) and the voids • In high copper amalgams, there is preferential crack propagation through the γ1 phase & copper containing particle CRAIG’s Restorative Dental Materials;12th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  123. 123. CREEP • Defined as time dependent strain or deformation produced by stress(as in Phillips) • Creep of dental amalgam is a slow progressive permanent deformation of set amalgam which occurs under constant stress(static creep) or intermittent stress(dynamic creep) Phillip’s Science of Dental Materials;11th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  124. 124. • Creep is related to marginal breakdown of low copper amalgams • Higher the creep, the greater is the degree of marginal deterioration(ditching) Phillip’s Science of Dental Materials;11th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  125. 125. • According to ADA sp. No.1 creep should be below 3% • creep values:- -low copper amalgam:0.8-8% -high copper amalgam:0.1-1% Phillip’s Science of Dental Materials;11th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  126. 126. Creep rate has been found to correlate with marginal breakdown of conventional low-copper amalgams. ADA spec. #1: creep rate < 3% Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  127. 127. Microstructure Vs. Creep Low-Cu Larger g1 volume fraction Presence of g2 Larger g1 grain sizes Single composition spherical h(Cu6Sn5) around Ag-Cu particles improves bonding to g 1 h (Cu6Sn5) embedded in g1 grains and interlock High-copper amalgams have creep resistance:- lack of gamma-2 phase. Admixture Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  128. 128. Factors influencing creep: Large g1 volume fraction Larger g1 grain sizes smaller g1 grain sizes g2 associated with high creep rates. h phase which act as barrier to deformation of g1 phase. Phases of amalgam restorations High CREEP Low CREEP Materials science for dentistry;9th ed B.W.Darvell0
  129. 129. For increased strength & low creep values:- Mercury alloy ratio should be minimum Condensation pressure should be maximum for lathe cut or admixed alloys Careful attention should be given towards timing of trituration & condensation Phillip’s Science of Dental Materials;11th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion Effect of manipulative variables
  130. 130. Compressive Strength (MPa) % Creep Tensile Strength (24 hrs) (MPa) Amalgam Type 1 hr 7 days Low Copper1 145 343 2.0 60 Admixture2 137 431 0.4 48 Single Composition3 262 510 0.13 64 Phillip’s Science of Dental Materials 2003 1Fine Cut, Caulk 2 Dispersalloy, Caulk 3Tytin, Kerr
  131. 131. MICROLEAKAGE OF AMALGAM The 2 to 20micron-wide gap Poor condensation techniques - marginal voids Lack of corrosion by-products Coefficient of thermal expansion Single-composition-spherical alloys which leak more - do not adapt as well to the margins Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  132. 132. • Penetration of fluids & debris around the margins may cause secondary caries • If the amalgam restoration is inserted properly, leakage decreases as the restoration ages in mouth due to the corrosion products that forms in the tooth-restoration interface • Thus amalgam is the self sealing restoration Phillip’s Science of Dental Materials;11th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  133. 133. • Both low & high copper amalgams are capable of sealing against microleakage but the accumulation of corrosion products is slower with the high copper alloys* *Corrosion sealing of amalgam restorations -in vitro study Oper Dent. 2009 May-Jun;34(3):312-20. Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  134. 134. • The sealing ability of different types of dental amalgams when used as retrograde fillings with and without a cavity varnish was studied. • Of the materials tested, a copper-containing spherical amalgam gave the best results. • Regardless of material used, the apical seal was significantly improved when a varnish was applied to the cavity prior to the placement of the retrograde amalgam filling Journal of Endodontics Volume 9, Issue 12 , Pages 551-553, December 1983 Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  135. 135. THERMAL EXPANSION AND CONDUCTIVITY Amalgam 22-28 9.4 Composite resin 20-60 0.25 GIC 10-11 0.15-0.35 Tooth 11.4 0.18-0.47 Thermal expansion coefficient E 10-6 / C Thermal conductivity K 10-6 / C(mm2/s) E = volume expansion for unit rise in temperature K = quantity of heat passing per s through a block of unit thickness and cross sectional area for a temp. difference of 1C Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion CRAIG’s Restorative Dental Materials;12th ed
  136. 136. CHEMICAL PROPERTIES Dental amalgam restorations undergo both chemical and electrochemical corrosion. TARNISH AND CORROSION Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion CRAIG’s Restorative Dental Materials;12th ed
  137. 137. The degree of tarnish depends on : i. The oral environment ii. The type of alloy used Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion CRAIG’s Restorative Dental Materials;12th ed
  138. 138. In dental practice , a limited amount of corrosion around the margins of amalgam restorations may be beneficial, since the corrosion products tends to seal the marginal gap & inhibit the ingress of fluids & bacteria But excessive corrosion can lead to increased porosity, reduced marginal integrity, loss of strength & the release of metallic products into the oral environment Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion CRAIG’s Restorative Dental Materials;12th ed
  139. 139. GAP Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion CRAIG’s Restorative Dental Materials;12th ed Liberation of corrosion products
  140. 140. Electrochemical measurements on pure phases Ag2Hg3(γ1) (highest corrosion resistance) Ag3Sn(γ) Ag3Cu2 Cu3Sn(ε),Cu6Sn5(ή) Sn7-8Hg(γ2) (least corrosion resistance) CRAIG’s Restorative Dental Materials;12th ed
  141. 141. • The p/o small amounts of tin, silver & copper that may dissolve in various amalgam phases has a great influence on their corrosion resistance CRAIG’s Restorative Dental Materials;12th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  142. 142. •The higher content of tin , less the corrosion resistance • The tin content of the γ1 phase is higher for low copper alloys than for high copper alloys CRAIG’s Restorative Dental Materials;12th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  143. 143. • The p/o a relatively high %age of tin in low copper alloys reduces the corrosion resistance of their γ1 phase so its lower than their γ phase • This is not true for high copper alloys CRAIG’s Restorative Dental Materials;12th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  144. 144. • Occurs most notably on the occlusal surface and produces a black amalgam silver tarnish film • Corrosion products are mainly oxides and chlorides of tin. Chemical Corrosion : Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion CRAIG’s Restorative Dental Materials;12th ed
  145. 145. Electrochemical corrosion Chemically different sites act as anode or cathode. Electrolyte (saliva) The anode corrodes, producing soluble and insoluble reaction products. Ag2Hg3 phase has the highest corrosion resistance, followed by Ag3Sn, Ag-Cu, Cu3Sn, Cu6Sn5 and Sn7-8Hg. Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion CRAIG’s Restorative Dental Materials;12th ed
  146. 146. LOW COPPER ALLOYS – low corrosion resistance The average depth of corrosion for most amalgam alloys is 100-500 m. Most corrodible phase is tin-mercury or g2 phase Even though, a relatively small portion (1- 13%) of the amalgam mass consists of the g2 phase, in an oral environment, the structure of such an amalgam will contain a higher percentage of corroded phase Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion CRAIG’s Restorative Dental Materials;12th ed
  147. 147. The corrosion results in the formation of tin oxychloride, from the tin in g2 and also liberates Hg. Sn7-8Hg + 1/202 + H2O + Cl-  Sn4 (OH) 6 Cl2 + Tin oxychloride Additional gl and g2 result in porosity and lower strength. Unreacted g Hg g 1 and g 2 ( Mercuroscopic Expansion ) CRAIG’s Restorative Dental Materials;12th ed
  148. 148. THE HIGH COPPER ADMIXED AND UNICOMPOSITION ALLOY • No g2 phase in the final set mass. • The η phase formed with high copper alloys is not an interconnected phase such as the g2 phase, and it has better corrosion resistance. • η phase is the least corrosion resistant phase in high copper amalgam - corrosion product CuCl2.3Cu (OH)2 Cu6Sn5 + 1/202 +H2O + Cl-  CuCl2.3Cu (OH)2 + SnO. Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion CRAIG’s Restorative Dental Materials;12th ed
  149. 149. • Surface tarnish of low copper amalgams is more associated with γ than γ1 phase, whereas in high copper amalgams surface tarnish is related to the copper rich phases,ή & silver-copper eutectic CRAIG’s Restorative Dental Materials;12th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  150. 150. Galvanic corrosion If dental amalgam is in direct contact with an adjacent metallic restoration such as gold crown, the dental amalgam is the anode in the circuit. Between titanium and direct filling alloys • Small galvanic interaction High copper dental amalgams when in contact with Ti • little galvanic corrosion Gallium direct filling alloys • galvanic interaction more detrimental Dental Materials, Volume 15, Issue 5, September 1999, Pages 318-322 Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  151. 151. Local electrochemical cells may arise whenever a portion of amalgam is covered by plaque on soft tissue. It behaves anodically and corrodes. If these occur in cracks or crevice, it is called crevice corrosion. • Regions that are under stress display a greater probability for corrosion, thus resulting in stress corrosion. • For occlusal dental amalgam greatest combination of stress and corrosion occurs along the margins. Crevice Corrosion: Stress Corrosion: Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion CRAIG’s Restorative Dental Materials;12th ed
  152. 152. Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion Sturdevant’s Art & Science of Operative Dentistry;5th ed
  153. 153. Factors related to excess tarnish & corrosion High residual mercury Surface texture- small scratches & exposed voids Contact of dissimilar metals, eg. gold & amalgam Moisture contamination during condensation Type of alloy-low cu alloy>high cu alloy CRAIG’s Restorative Dental Materials;12th ed Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion
  154. 154. • Smoothening & polishing the restoration • Correct mercury/alloy ratio & proper manipulation • Avoid dissimilar metals including mixing of high & low copper amalgams Introduction History Amalgam wars Classification Components setting reaction Manufacture Properties Manipulation Recent advances Sideeffects of mercury Durability Future Conclusion Corrosion of amalgam can be reduced by:-
  155. 155. REFERENCES • PHILLIPS’ Science of Dental Materials;11th ed Kenneth J. Anusavice • CRAIG’s Restorative Dental Materials;12th ed John M. Powers, Ronald L. Sakaguchi • Materials science for dentistry;9th ed B.W.Darvell • Sturdevant’s Art & Science of Operative Dentistry; 5th ed; Roberson, Heymann, Swift • fundamentals of operative dentistry, a contemporary approach; 3rd ed Summitt, Robbins, Hilton, Schwartz • Essentials of operative dentistry; I Anand Sherwood
  156. 156. • Dental amalgam: An update J Conserv Dent. 2010 Oct-Dec; 13(4): 204–208 • The amalgam controversy-an evidence based analysis ; JADA,Vol.132,march 2001 • Effect of admixed indium on the clinical success of amalgam restorations . operative dentistry journal1992 Sep-Oct;17(5):196-202 • American Dental Association (ADA) Council on Scientific Affairs, “Statement on dental amalgam,” 2011, • Dental Materials Volume 15, Issue 6, November 1999, Pages 382-389 • Biomaterials, Volume 18, Issue 13, July 1997, Pages 939-946 • Journal of Endodontics Volume 9, Issue 12 , Pages 551-553, December 1983 • Corrosion sealing of amalgam restorations -in vitro study Oper Dent. 2009 May-Jun;34(3):312-20.

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