Amalgam part 1

Dr.Rachael Gupta
MDS PEDODONTICS STUDENT

1. Amalgam Dr.Rachael Gupta Postgraduate

2. C ontents  Introduction  History of amalgam  Amalgam wars  Classification  Components of amalgam  S etting reaction  Manufacture of alloy powder  Properties of amalgam  Manipulation of amalgam  Recent advances in amalgam  Side effects of mercury  Conclusion

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 before. 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

4. N o adequate economic alternative for dental amalgam. The combination of reliable long-term performance in load bearing situations low cost is unmatched by other dental restorative material . J Conserv Dent. 2010 Oct;13(4):204-8. Dental amalgam: An update

5. Acceptable Biocompatibili t y Less technique sensitive Cost effective and long life AMALGAM POPULARITY J Conserv Dent. 2010 Oct;13(4):204-8. Dental amalgam: An update

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 J Conserv Dent. 2010 Oct;13(4):204-8. Dental amalgam: An update

7. The variables for amalgam’s appearance Amalgam: past,present & future JADA,Vol.86,April 1973

8. What is amalgam???? a.mal.gam : any alloy of mercury with any another metal [silver amalgam is used as a dental filling] W ord amalgam is derived from greek name emolient ’ which means paste. Source: Webster’s New World Dictionary

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 Sturdevant’s Art & Science of Operative dentistry..5 th ed ; 152

10. INDICATIONS OF AMALGAM Moderate to large Class I and Class II restorations. Class V restorations in unaesthetic areas especially when access is limited and moisture control is difficult and for areas that are significantly deep gingivally . Class 3 in unaesthetic areas eg.distal aspect of canine especially if Preparation is extensive with minimal facial involvement

11. CONTRAINDICATIONS OF AMALGAM Anterior teeth where esthetics is a prime concern Esthetically prominent areas of posterior teeth. Small classes I and II restorations that can be well isolated. Small class VI restorations

12. ADVANTAGES OF AMALGAM  Ease of use, Easy to manipulate  Relatively cost effective  ease of placement-excellent wear resistance  prevent marginal leakage after period of time – maintains anatomical forms  Well condensed and triturated amalgam has good compressive strength .  Relatively not technique sensitive .

13. DISADVANTAGES OF AMALGAM  Unnatural appearance (non esthetic )  Tarnish and corrosion  Metallic taste  Discoloration of tooth structure  Lack of chemical or mechanical adhesion to the tooth structure .  Mercury toxicity  Promotes plaque adhesion

14. 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 In Europe, J Stokers, a municipal physician in Germany , recommended amalgam as a filling material in 1528 Later, Li Shihchen (1578) - a dental mixture of 100 parts mercury with 45 parts silver and 900 parts tin In the 18th century, John Hill, an Englishman, described mercury as, “It penetrates the substance of all metals, and dissolves, and makes them brittle .”

15. 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 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.

16. 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

17. 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 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

18. 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 ADA specification No 1 was adapted for amalgam in 1929.

19. Extensive studies of the setting reaction of dental amalgams ( Gayler in 1937) & found that in the coarse filling alloys of that time, copper contents greater than 6% produced excessive expansion Gayler ML. Dental amalgams. J Inst Metals. 1937;60:407–19 This was later challenged by Greener in 1970’s Greener EH. Amalgam-yesterday, today and tomorrow. Oper Dent. 1979;4:24–35 J Conserv Dent. 2010 Oct;13(4):204-8. Dental amalgam: An update

20. 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

21. In 1962, a spherical particle dental alloy was introduced by Innes This was followed in 1963 by a high copper dispersion alloy system that proved to be superior to its low copper 1970’s • first single composition spherical • Tytin (Kerr) • ternary system (silver/tin/copper) 1980’s- mercury free alloys introduced

22. AMALGAM WARS-the controversy In 1841, the American Society of Dental Surgeons declared that “the use of amalgam constitutes malpractice” AMALGAM USE DECLINED The amalgam controversy-an evidence based analysis ; JADA,Vol.132,march 2001

23. 1842-a belief prevailed that amalgam exerted “a influence upon the fluids of the mouth and gives rise to an unhealthy action in the gums .” 1844- 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 The amalgam controversy-an evidence based analysis ; JADA,Vol.132,march 2001

24. 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.

25. 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 miller , - Amalgam is a SAFE, AFFORDABLE, AND DURABLE MATERIAL .”

26. The second amalgam war …. In mid 1920's a German dentist, Professor A. Stock started the so called "second amalgam war". He claimed to have evidence showing that mercury could be absorbed from dental amalgam, which leads to serious health problems . He also expressed concerns over health of dentists, stating that nearly all dentists had excess mercury in their urine

27. 3 rd 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

28. The amalgam controversy-an evidence based analysis ; JADA,Vol.132,march 2001 " Third Amalgam War ' began in 1980 primarily through the seminars and writings of Dr.Huggins , a practicing dentist in Colorado .  He was convinced that mercury released from dental amalgam was responsible for human diseases affecting the cardiovascular system and nervous system  Also stated that patients claimed recoveries from multiple sclerosis , and other diseases as a result of removing their dental amalgam fillings.

29. 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 “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 “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 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

30. Classification of Amalgam A) According to the number of Alloyed Metals N u m b e r of alloyed metal Binary alloy (Ag-Sn) T e r t ia ry alloy (Ag - Sn- Cu) Q u a r t e r na ry alloy (Ag-Sn- Cu ,indium ) Sturdevant’s Art & Science of Operative Dentistry; 5 th ed

31. B) According to shape of powdered particle Lathecut -irregular shapes S pherical -smooth surface spheres Admixed Sturdevant’s Art & Science of Operative Dentistry; 5 th ed

32. C) According to copper content Low copper amal g am(<0-6%) High copper am a l g am(> 6 - 13%) Sturdevant’s Art & Science of Operative Dentistry; 5 th ed

33. D)According to zinc content Zinc containing alloy (>0.01-2%) Non zinc containing alloy (<0-0.01%) Sturdevant’s Art & Science of Operative Dentistry; 5 th ed

34. 1 st generation 2 nd generation 3 rd generation 4 th generation 5 th generation 6 th generation E)Generations based on the improvement in composition was that of G. V Black i.e. 3 parts silver one part tin ( peritectic alloy). 3 parts silver , 1 part tin , 4% copper. 1 % zinc, First generation + Spherical amalgam – copper eutectic alloy Adding copper upto 29% to original silver and tin powder to form ternary alloy. So that tin is bounded to copper. Quatemary alloy i.e. Silver, tin, copper and indium. (consisting eutectic alloy). Marzouk -operative dentistry

35. Composition of amalgam Conventional Amalgam Alloys : (G.V. Black’s: Silver- tin alloy or Low copper alloy). Low copper alloys are available as ( Lathe -cut and Pulverized) and spherical particles. Low copper composition:  Silver : 63-70%  Tin : 26-28%  Copper : 2- 5%  Zinc : 0-2%

36. Components of dental amalgam Other Zinc Indium P alladi u m Silver Tin Copper Me r cu r y Basic Phillip’s Science of Dental Materials;11 th ed

37. Sil v e r ( A g ) Decreases creep & setting time Decreases corrosion Increases hardness & edge strength Increase tarnishing Phillip’s Science of Dental Materials;11 th ed

38. Ti n( S n ) Low strength Larger contraction Decreases expansion Increased corrosion Increased plasticity Increased setting time Phillip’s Science of Dental Materials;11 th ed

39. Copper(Cu) Decreases plasticity Increases hardness strength of alloy Reduce creep Reduce tarnish & corrosion Phillip’s Science of Dental Materials;11 th ed

40. Zinc(Zn) Decreases brittleness Acts as a deoxidizer Less marginal breakdown Phillip’s Science of Dental Materials;11 th ed

41. In d iu m (I n ) 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* operative dentistry journal1992 Sep-Oct;17(5):196-202 Palladium ( Pd ) reduced corrosion greater luster Mahler J Dent Res 1990

42. 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 γ 1 seems to be in the range between 0.50 and 0.75 wt%. Biomaterials , Volume 18, Issue 13 , July 1997 , Pages 939-946

43. Mercury (Hg) - only pure metal that is liquid at room temperature Phillip’s Science of Dental Materials;11 th ed

44. HIGH COPPER AMALGAM ALLOY (COPPER ENRICHED ALLOYS )  To overcome the inferior properties of low copper amalgam alloy -- shorter working time, more dimensional change , difficult to finish, set late, high residual mercury, high creep & lower early strength, low fracture resistant  Innes in 1963 introduced high copper content amalgam alloys. They increased the copper content from earlier used 5% to 12 %.  Copper enriched alloys are of two types: Admixed alloy powder . 2) Single composition alloy powder.

45. Admixed alloy powder : Also called as blended alloys . Contain 2 parts by weight of conventional composition lathe cut particles plus one part by weight of spheres of a silver copper eutectic alloy . Made by mixing particles of silver and tin with particles of silver and copper . Admixed alloy powder : Composition:  Silver-69 %  Copper-13 %  Tin-17 %  Zinc-1 %

46.  Amalgam made from these powders are stronger than amalgam made from lathe cut low copper alloys because of strength of Ag-Cu eutectic alloy particles.  Ag-Cu particles probably act as strong fillers strengthening the amalgam matrix. Total copper content ranges from 9-20 %. Single composition alloy ( Unicomposition ) :  It is so called as it contains particles of same composition.  Usually spherical single composition alloys are used . 1. Ternary alloy in spherical form, silver 60%, tin 25%, copper 15 %. 2.Quaternary alloy in spheroidal form containing Silver: 59%, copper 13%, tin: 24%, indium 4%.

47. AMALGAMATION REACTION/ SETTING REACTION Low copper conventional amalgam alloy  Dissolution and precipitation  Hg dissolves Ag and Sn from alloy  Intermetallic compounds formed Ag 3 Sn + Hg  Ag 3 Sn + Ag 2 Hg 3 + Sn 8 Hg gamma gamma gamma 1 gamma 2

48. 3 Gamma (  ) = Ag Sn unreacted alloy strongest phase and corrodes the least forms 30% of volume of set amalgam Occupy maximum space in volume of restoration 1 Gamma 1 (  ) = Ag Hg 2 3 matrix for unreacted alloy and 2nd strongest phase Most resistant to tarnish and corrosion 60% of volume CRAIG’s Restorative Dental Materials;12 th ed

49. Gamma 2 (  2 ) = Sn 8 Hg weakest and softest phase corrodes fast, voids form 10 % of volume  volume decreases with time due to corrosion

50. High copper admixed alloy 2 . S n8Hg + AgCu  (  2) Cu6Sn5 + Ag2Hg3 + Ag3Sn (  ) (  1 ) (  ) 1. Ag3Sn + AgCu + Hg  Ag2Hg3 + Sn8Hg + Ag3Sn + AgCu (  ) (  1 ) (  2 ) (  ) CRAIG’s Restorative Dental Materials;12 th ed Initial reaction Final reaction

51. Eta (  ) phase Strength the bond betwwen alloy particles and gamma 1 phase Interlocks gamma1 phase thus improving amalgam resistance to deformation Resistance to tarnish and corrosion

52. High copper unicompositional alloy Ag3Sn + Cu3Sn + Hg  Cu6Sn5 + Ag2Hg3 (  ) (  ) (  ) (  1 ) CRAIG’s Restorative Dental Materials;12 th ed Epsilon –reduces creep, and prevent formation of gamma 2 phase

53. 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) Manufacture of alloy powder L l athe cut alloy powder Materials science for dentistry;9 th ed B.W.Darvell

54. 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 Materials science for dentistry;9 th ed B.W.Darvell Spherical alloy powder

55. 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 p a rt i cles

56. Properties of amalgam contains certain requirements :- 1. Maximum creep value of 3% e 2. Minimum Compressive strength of 80 MPa at 1 hr when a cylindrical specimen is compressed at a r o t of 0.25mm/minute ADA specification No.1 for amalgam alloy 3. Dimensional change between 5 min & 24 hrs after trituration, should fall within a range of ±20µm/cm a t 37 ̊ C. CRAIG’s Restorative Dental Materials;12 th ed

57. DIMENSIONAL CHANGES Stage -1: Initial contraction, occurs for about 20 minutes after beginning of trituration. Contraction results as the alloy particles dissolve in mercury. Contraction , which occurs, is no greater than 4.5 μcm . Stage -2: Expansion- this occurs due to formation and growth of the crystal matrix around the unconsumed alloy particles. Stage -3: Limited delayed contraction . Absorption of unreacted mercury Ma rzouk 0operative dentistry Properties When mercury is combined with amalgam it undergoes three distinct dimensional changes Dimensional change between 5 min & 24 hrs after trituration, should fall within a range of ±20µm/cm at 37 ̊C.

58. 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 20µm 20µm 20µm 20µm Materials science for dentistry;9 th ed B.W.Darvell

59. If amalgam expanded during hardening, leakage around the margins of restorations would be eliminated.

60. Factors that affect the dimensional changes : 1) Particle size and shape: More regular the particle shape, more smoother the surface area . Faster and more effectively the mercury can wet the powder particles and faster amalgamation occurs in all stages with no apparent expansion . 2) Mercury: More mercury , more will be the expansion, as more crystals will grow . Low mercury: alloy ratio favors contraction 3) Manipulation :  During trituration, if more energy is used for manipulation , the smaller the particles will become , mercury will be pushed between the particles, discouraging expansion .  More the condensation pressure used during condensation , closer the particles are brought together ; more mercury is expressed out of mix inducing more contraction.

61. Moisture contamination (Delayed Expansion): Certain zinc containing low copper or high copper amalgam alloys which get contaminated by moisture during manipulation results in delayed expansion or secondary expansion This expansion usually starts after 24 hrs, reach at peak within 3-5 days & may continue for months reaching values > 400µm Zinc reacts with water, forming zinc oxide and hydrogen gases. Complications that may result due to delayed expansion are : Protrusion of the entire restoration out of the cavity . Increased micro leakage space around the restoration . Restoration perforations . Increased flow and creep . Pulpal pressure pain . Such pain may be experienced 10-12 days after the insertion of the restoration

62. STRENGTH A) Compressive strength Phillip’s Science of Dental Materials;11 th ed Amalgam is strongest in compression and weaker in tension and shear The prepared cavity design and manipulation should allow for the restoration to receive compression forces and minimum tension and shear forces . The compressive strength of a satisfactory amalgam restoration should be atleast 310 MPa.

63. Compressive Strengths of Low-Copper and High Copper Amalgam Amalgam Compressive Strength (MPa) 1 h 7 day Low copper 145 343 Admix 137 431 Single Composition 262 510

64. B) Tensile strength  Amalgam is much weaker in tension  Tensile strengths of amalgam are only a fraction of their compressive strengths  Cavity design should be constructed to reduce tensile stresses resulting from biting forces  High early tensile strengths are important – resist fracture by prematurely applied biting forces Phillip’s Science of Dental Materials;11 th ed

65. Product Tensile strength ( Mpa ) 15min 7 days LOW COPPER ALLOYS a) Lathe cut b) spherical 3.2 51 4.7 55 HIGH COPPER ALLOYS a) Admixed b) Unicompositional 3.0 43 8.5 56 Tensile strengths of amalgam

66. 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;11 th ed 1) Effect of trituration

67. 2) Effect of mercury content dry granular mix  rough & pitted surface  corrosion high mercury content  more γ2 phase low mercury content  more unreacted AgSn par tic l es  impar t s strength to restoration sufficient mercury should be mixed with the alloy to wet each particle of the alloy Introduction History Amalgam wars Classification

68. -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;11 th ed 3) Effect of condensation

69. -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;11 th ed 4) Effect of porosity

70. - 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;11 th ed 5) Effect of rate of hardening

71. -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;11 th ed

72. 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;11 th ed

73. CREEP Defined as time dependent strain or deformation produced by stress(as in Phillips ) Time dependent plastic deformation When a metal is placed under stress , it will undergo plastic deformation. Phillip’s Science of Dental Materials;11 th ed

74. H i gher the c r eep, the g r e a t er is the deg r ee o f marginal deterioration(ditching) Phillip’s Science of Dental Materials;11 th ed 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%

75. Factors influencing creep : Large  1 volume fraction Larger  1 grain sizes smaller  1 grain sizes 2  associated with high creep rates. Phases of amalgam r e s t o r a t i ons High CREEP Low CREEP  phase which act as barrier to deformation of  1 phase in single compositional Materials science for dentistry;9 th ed B.W.Darvell0

76. 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;11 th ed Effect of manipulative variables

77. Thermal expansion coefficient E 10 -6 / C Thermal conductivity K 10 -6 / C(mm 2 /s) 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 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 CRAIG’s Restorative Dental Materials;12 th ed

78. CHEMICAL PROPERTIES Dental amalgam restorations undergo both chemical and electrochemical corrosion. TARNISH AND CORROSION CRAIG’s Restorative Dental Materials;12 th ed

79. The degree of tarnish depends on : i. The oral environment ii. The type of alloy used CRAIG’s Restorative Dental Materials;12 th ed

80. 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 CRAIG’s Restorative Dental Materials;12 th ed

81. 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 : CRAIG’s Restorative Dental Materials;12 th ed

82. Electrochemical corrosion Chemically different sites act as anode or cathode. Electrolyte (saliva) The anode corrodes, producing soluble and insoluble reaction products. Ag 2 Hg 3 phase has the highest corrosion resistance, followed by Ag 3 Sn, Ag-Cu, Cu 3 Sn, Cu 6 Sn 5 and Sn 7 - 8 Hg. CRAIG’s Restorative Dental Materials;12 th ed

83. The average depth of corrosion for most amalgam alloys is 100-500  m. Most corrodible phase is tin-mercury or  2 phase Even though, a relatively small portion (1- 13%) of the amalgam mass consists of the  2 phase, in an oral environment, the structure of such an amalgam will contain a higher percentage of corroded phase CRAIG’s Restorative Dental Materials;12 th ed

84. The corrosion results in the formation of tin oxychloride, from the tin in  2 and also liberates Hg. Sn 7 - 8 Hg + 1/20 2 + H 2 O + Cl-  Sn 4 (OH) 6 Cl 2 + Tin oxychloride Hg ( Mercuroscopic Expansion ) CRAIG’s Restorative Dental Materials;12 th ed

85. THE HIGH COPPER ADMIXED AND UNICOMPOSITION ALLOY No  2 phase in the final set mass. The η phase formed with high copper alloys is not an interconnected phase such as the  2 phase, and it has better corrosion resistance. η phase is the least corrosion resistant phase in high copper amalgam - corrosion product CuCl 2 .3Cu (OH) 2 Cu 6 Sn 5 + 1/20 2 +H 2 O + Cl-  CuCl 2. 3Cu (OH) 2 + SnO. CRAIG’s Restorative Dental Materials;12 th ed

86. 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;12 th ed

87. 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 : CRAIG’s Restorative Dental Materials;12 th ed

88. Factors related to excess tarnish & corrosion High residual mercury Surface texture- small scratches & exposed voids Contact of dissimilar metals, eg. gold & amalgam Moisture c o n t amin a tion during condensation Type of alloy-low cu alloy>high cu alloy CRAIG’s Restorative Dental Materials;12 th ed

89. Smoothening & polishing the restoration Correct mercury/alloy ratio & proper manipulation Avoid dissimilar metals including mixing of high & low copper amalgams Corrosion of amalgam can be reduced by:-

90. Cavity preparation of amalgam Class 1 cavity preparation of amalgam  Narrow occlusal table – buccolingual dimension of cavity is reduced  0.5mm pulpal to DEJ  Maximum intercuspal width should be minimum  Walls should be parallel or slightly convergent  Outline form should limit to the central pit, its buccal and lingual grooves and triangular fossa  Pulpal floor should be flat or slightly concave  Total depth of the cavity – 1.5  All pits and fissures should be included Intercuspal width Kennedy’s operative pediatric dentistry 4 th edition

91. Steps: External outline form  Start preparation with a no.330 bur, perpendicular to occlusal surface- mesial to distal  Include all deep and defective grooves  Contour the outline parallel to mesial and distal marginal ridges  Width of cavity – 1/3rd intercuspal width Internal outline form  0.50 mm into the dentin – 330 bur  Round line angles – no.330 bur  Converging walls  Sharp cavosurface angle – 169L bur Kennedy’s operative pediatric dentistry 4 th edition

92. Common errors in Class I amalgam restorations 1. Preparing cavity too deep 2 . Carving the anatomy of amalgam too deep 3 . Undercarving that leads to fracture 4 . Not including all susceptible fissures

93. Class II amalgam Depth: This should be 0.5 mm below dentino -enamel junction or 1.5 mm from the cavosurface (i.e.. 'a'.) Isthmus: This should be between 1/4 of the inter cuspal distance (approximately 1.5 mm ) All the internal angles should be rounded Pulpal floor: Pulpal floor should be slightly concave . Buccal and lingual walls: should be converging so making the cavity retentive. Also, the cavosurface angle needs to be a right angle to ensure maximum strength at the enamel-amalgam junction. Gingival floor: should be located just below the contact area with the adjacent tooth. But supragingivally . Kennedy’s operative pediatric dentistry 4 th edition

94. Axial wall: The width of the floor of the box should be approximately 1 mm. follows external contour of tooth . Buccal and lingual walls: These should be convergent, parallel to the appropriate external surface and make a cavo surface angle of 90 degree. Axio -pulpal line angle: This should be rounded which gives the maximum thickness of amalgam with the minimum of stress in this area. Kennedy’s operative pediatric dentistry 4 th edition

95. Sunday, May 06, 2018 PROXIMAL BOX OF DECIDUOUS TEETH Box converges occlusally Minimal flare to prevent weakening of enamel walls Isthmus 1/4 th to 1/5 th inter cuspal width Rounded axio -pulpal angle grooved to increase retention No bevel in gingival seat Depth minimal to prevent pulp exposure at cervial constriction Wide gingival floor

96. Mesiodistal view of correct class 2 preparation Kennedy’s operative pediatric dentistry 4 th edition

97. DIAGRAM ILLUSTRATING THE INCREASED DANGER OF PULP EXPOSURE WHEN THE GINGIVAL WALL IS CARRIED TOO DEEPLY Kennedy’s operative pediatric dentistry 4 th edition

98.  Kennedy (1997) contraindicated the idea of dovetail lock, as in primary teeth occlusal fissures are prepared which produces curved shape that provides retention.  Rodda recommended 1mm depth of cavity because the distance between the mesial surface of mandibular 1st molar and pulp horn is only 1.6 mm.

99.  Messer and Levering reported that SSCs placed in 4 your old and younger children showed a success rate approximately twice that of class II amalgam restoration up to 10 years .  Roberts and Sherriff reported that after 5 year, one third of class II amalgams placed in primary teeth had failed or required replacement, whereas only 8% of SSCs required retreatment. Paul S. Casamassimo , Henry W. Fields Jr ., Dennis J. McTigue , Arthur Nowak. Pediatric Dentistry : Infancy through Adolescence.5 th edition . Saunders: Elsevier ; 2013

100. Class 3 cavity preparation Primary incisor teeth: when contact areas are open Outline form- triangular with base at gingival aspect Buccal and lingual wall parallel to external surface of tooth to meet an apex Pear shaped bur used to prepare cavity Gingival cavity wall –incline slightly occlusally -parallel to enamel rods -undercut for mechanical retention Cavity depth 0.5 pulpal to DEJ Kennedy’s operative pediatric dentistry 4 th edition

101. If contacts are closed For aesthetic access is from palatal surface Dovetail /lock–aid in retention of restoration -dovetail should extend middle of the tooth -resistance to lateral displacement Interproximal areas – c shaped letter when observed Open end of C should meet retentive lock/dovetail Inclination of incisal and gingival towards incisal edge llal to enamel rods Primary canine teeth Palatal lock – maxillary canine Facial lock – mandibular canine (depend on biting forces) Kennedy’s operative pediatric dentistry 4 th edition

102. Class 5 cavity preparation Kidney shaped; gently curved outline form acceptable Sharp outline form at mesial and distal margins No.330 bur used cut cavity Dentinal undercuts are given for mechanical retention Kennedy’s operative pediatric dentistry 4 th edition

103.  Problems with amalgam restorations :  Accounts for anatomic or morphologic structural characteristics .  Fracture of isthmus in Class II amalgam restorations  Marginal failure in the proximal box, due to excessive flare of the cavosurface angle  Failure to remove all caries or to extend the cavity into caries susceptible areas

104. Differences in amalgam cavity preparation in primary and permanent tooth Primary tooth Permanent tooth Intercuspal width should not more than one third One forth or 1.5 mm Cavity depth : 1.5 mm Minimulm : 1.5 to 2 mm Proximal box •No gingival bevel •Gingival floor incline occlussaly •Retentive groove is not indicated Proximal box: •Gingival bevel should be given •Gingival floor is perpendicular to axial wall •Retentive groove for secondary retention form Width of proximal box : 1mm Proximal box should be 0.2- 0.8 mm in dentine

105. Differences in amalgam and composite cavity preparation in primary and permanent tooth Amalgam composite Outline form Include the fault and adjacent suspicious areas Include fault but do not extend to the adjacent suspicious areas Pulpal depth Minimum 1.5 1-2 pulpal floor usually not uniform Axial depth 0.2 to 0.5 mm inside Dej Only extent of the defect, not uniform Cavosurface marginal 90 degree 90 degree Primary retention form Occlusal dovetail and convergence Etching and bonding Secondary resistance Box shape cavity, groove, slots, locks Grooves only large or root surface preparations. Box for large cavity Pulp protection Varnish, base Dentine boding agent

106. REFERENC E S PHILLIPS’ Science of Dental Materials;11 th ed Kenneth J. Anusavice CRAIG’s Restorative Dental Materials;12 th ed John M. Powers, Ronald L. Sakaguchi Materials science for dentistry;9 th ed B.W.Darvell Sturdevant’s Art & Science of Operative Dentistry; ed; Roberson, Heymann, Swift fundamentals of operative dentistry, a contemporary approach; 3 rd ed Summitt, Robbins, Hilton, Schwartz Essentials of operative dentistry; I Anand Sherwood Marzouk operative dentistry Kennedy’s opediatric operative dentistry

107. 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.