3dentalamalgam-materialaspects-190624144416.pptx

dental amalgam

1. Dr. SANDEEP M 1 st YEAR MDS Department of Conservative Dentistry and Endodontics GDCH,CUDDALORE. DENTAL AMALGAM MATERIAL ASPECTS

2. CONTENTS INTRODUCTION HISTORY AMALGAM WARS ADA SPECIFICATION CLASSIFICATION INDICATIONS AND CONTRAINDICATIONS ADVANTAGES AND DISADVANTAGES COMPOSITION MANUFACTURING PROCESS PHASES METALLURGIC PROCESSES PROPERTIES NEWER ADVANCES CONTROVERSIES CONCLUSION REFERENCES

3. AMALGAM POPULARITY

4. over the last few years, improvements in composition have led to: REDUCED MARGINAL CORROSION DUE TO DECREASED CREEP AND CORROSION EARLY SEAL BETWEEN TOOTH AND RESTORATION But development of alternatives based on ceramics and composites , and questions on its safety have led to its decline.

5. AMALGAM Amalgam -An alloy containing mercury Dental Amalgam – An alloy of mercury silver copper and tin, which may also contain palladium, zinc and other elements to improve handling characteristics and clinical performance Dental amalgam Alloy – An alloy of silver copper and tin that is formulated and processed in the form of powder particles or compressed pellets. Phillips’ Science of dental materials, 11/e Anusavice .

6. Amalgam -- First used by Chinese. There is a mention of silver mercury paste by Sukung (659AD) in the Chinese medicine and later by Li schichan First use of room temp mixed amalgam- Bell in England 1819 (Bell’s putty) Traveau in France ( 1826 ) – advocated a mixture of silver and mercury as a filling material – produced amalgam by grinding silver coins with mercury. 1833 – Introduction of Royal Mineral Succedaneum to USA as substitute for gold – Crawcour Brothers - “ Royal mineral succedaneum ”

7. 1840s – AMALGAM WAR 1859 - ADA was formed 1860’S -1870’S – Elisa townsend and Flagg did a lot of work to improve Dental Amalgam 1895 - To overcome expansion problems G.V. Black developed a formula for modern amalgam alloy -67% silver, 27% tin, 5% copper, 1% zinc 1920 – Dr Grey – Delayed expansion 1926 - Second amalgam war – Europe – as a result of the writings of Alfred Stock, a professor of Chemistry published papers on the dangers of mercury vapor

8. 1937- Gaylerin 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 1946 - Skinner, added copper to the amalgam alloy composition in a small amount. This served to increase strength and decrease flow 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. 1962- spherical particle dental alloy was introduced by Innes & Youdelis

9. 1963 – Innes and Youdelis – High Cu admixed alloy 1970 - Change from hand trituration to mechanical trituration 1973 - Current controversy – termed Third amalgam war – due to writings of Dr HA Higgins 1973 - First single composition spherical alloy named Tytin (Kerr) a ternary system (silver/tin/copper) was discovered by Kamal Asgar of the University of Michigan 1979 – Gay and workers found mercury vapor in breath of patients with amalgam fillings following chewing.

10. 1984- human autopsy demonstrated the mercury found in brain and kidneys were related to the amalgam fillings in the teeth. 1990 - media was involved when the TV show “is there a poison in your mouth?” came out. 1991 - Dental amalgam mercury syndrome groups started being active. May 1991- Illinois house of representatives concluded amalgam was safe. August 1991- national institute of health technology concluded amalgam was safe.

11. AMALGAM WARS

12. WHAT ENDED THE 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.

13. SECOND AMALGAM WAR

14. During this Second Amalgam War, the American Dental Association vigorously defended silver amalgam and its widespread use was continued. 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

15. THIRD AMALGAM WAR But it began primarily through seminars ,writings,& videotapes of Dr HA Higgins, a dentist from Colorado Springs

16. 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. 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

17. CURRENT STATUS ON AMALGAM WAR The amalgam war continues to rage on today. 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 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.

18. Norway banned dental amalgam in 2008 Sweden banned the use of dental amalgam for almost all purposes in 2009 and Denmark, Estonia, Finland, and Italy use it for less than 5% of tooth restorations. Japan and Switzerland have also restricted or almost banned dental amalgam. France has recommended that alternative mercury-free dental materials be used for pregnant women.

19. In December of 2016, three EU institutions (the European Parliament, the European Commission and the Council of the European Union) reached a provisional agreement to ban dental amalgam fillings for children under 15 and pregnant and breastfeeding women as of July 1, 2018, and to consider banning dental amalgam completely by 2030. Safe Mercury Amalgam Removal Technique (SMART) should be used when amalgam fillings are removed. SMART was developed by IAOMT to mitigate mercury exposures that can occur when the fillings are taken out of people’s mouths, which often occurs due to hypersensitivity, and/or patient preference.

20. ADA SPECIFICATION SPECIFICATION NO. 1 ANSI/ADA STANDARD NO. 6—DENTAL MERCURY: 1987 (REAFFIRMED 2005)

21. Classification by marzouk According to number of alloy metals : 1. Binary alloys (Silver-Tin) 2. Ternary alloys (Silver-Tin-Copper) 3. Quaternary alloys (Silver-Tin-Copper-Indium).

22. According to the shape of the powdered particles . 1. Spherical shape (smooth surfaced spheres). 2. Lathe cut (Irregular ranging from spindles to shavings). 3. Combination of spherical and lathe cut (admixed).

23. According to Powder particle size. Micro cut Fine cut Coarse cut According to copper content of powder Low copper content alloy - Less than 4% High copper content alloy - more than 10%

24. Based on zinc content- Zn containing (>0.01%) Zn free (<0.01%) According to addition of Noble metals Platinum Gold Pallidum

25. According to compositional changes of succeeding generations of amalgam First generation amalgam was that of G. V Black i.e. 3 parts silver one part tin ( peritectic alloy). Second generation amalgam alloys - 3 parts silver, 1 part tin, 4% copper to decrease the plasticity and to increase the hardness and strength. 1 % zinc, acts as a oxygen scavenger and to decrease the brittleness. Third generation: First generation + Spherical amalgam – copper eutectic alloy. Fourth generation: Adding copper upto 29% to original silver and tin powder to form ternary alloy. So that tin is bounded to copper. Fifth generation: Quatenary alloy i.e. Silver, tin, copper and indium. Sixth generation: consisting eutectic alloy which includes palladium, silver and copper.

26. Class I and class II cavities-moderate to large restorations. As a core build up material. Can be used for cuspal restorations (with pins usually) In combination with composite resins for cavities in posterior teeth. As a die material Restorations that have heavy occlusal contacts. INDICATIONS

27. Class 3 in unaesthetic areas eg.distal aspect of canine. especially if preparation is extensive with minimal facial involvement Class 5 lesions in non-esthetic areas especially when access is limited and moisture control is difficult and for areas that are significantly deep gingivally . Restorations that cannot be well isolated. In teeth that act as an abutment for removable appliances.

28. contraindications Anterior teeth where esthetics is a prime concern Esthetically prominent areas of posterior teeth. Small –to-moderate classes I and II restorations that can be well isolated. Small class VI restorations

29. ADVANTAGES Ease of use, Easy to manipulate Relatively inexpensive Excellent wear resistance Restoration is completed within one sitting without requiring much chair side time. Well condensed and triturated amalgam has good compressive strength.

30. Sealing ability improves with age by formation of corrosion products at tooth amalgam interface. Relatively not technique sensitive. Bonded amalgams have “bonding benefits”. Less microleakage Slightly increased strength of remaining tooth structure. Minimal postoperative sensitivity.

31. DISADVANTAGES Unnatural appearance (non esthetic ) Tarnish and corrosion Metallic taste and galvanic shock Discoloration of tooth structure Lack of chemical or mechanical adhesion to the tooth structure. Mercury toxicity Promotes plaque adhesion Delayed expansion Weakens tooth structure (unless bonded).

32. COMPOSITION

33. Silver (Ag) increases strength increases expansion Decreases creep & setting time Decreases corrosion Increases hardness Increases tarnishing Tin (Sn) decreases expansion decreased strength increases setting time Increases corrosion Increases plasticity

34. Copper (Cu) ties up tin thereby reducing gamma-2 formation increases strength Increases setting expansion reduces tarnish and corrosion reduces creep, flow. reduces marginal deterioration, increases edge strength.

35. Zinc (Zn) provides better clinical performance less marginal breakdown decreases oxidation of other elements Give plasticity, hastens setting , improves color of mass. causes delayed expansion - both high & low Cu alloys if contaminated with moisture.

36. Indium (In) decreases surface tension reduces amount of mercury necessary reduces emitted mercury vapor reduces creep and marginal breakdown increases strength must be used in admixed alloys

37. Palladium ( Pd ) reduces corrosion greater luster

38. Mercury (Hg) activates reaction only pure metal that is liquid at room temperature Spherical alloys require less mercury smaller surface area easier to wet Admixed alloys require more mercury lathe-cut particles more difficult to wet

39. Manufacturing process- lathe cut

40. PARTICLE TREATMENT Acid washed – Preferential dissolution of specific components – acid washed powders more reactive than unwashed powders Aging is basically a stress relief process. It makes the alloy stable in its reactivity and property for indefinite period of time – improves shelf life. Generally done by heating them 60 to 100 ̊c for 1 to 6 hours

41. Manufacturing process- spherical

42. Phases in amalgam alloys

43. Metallurgical processes in amalgamation- low copper alloys Amalgamation occurs when mercury contacts the surface of the silver-tin alloy particles. The silver and tin dissolve into the mercury. During the reaction, the formation of body centered cubic form of Ag2Hg3 and hexagonal Sn7-8Hg occurs. Gamma 1 and 2 crystals grow as the remaining mercury dissolves the alloy particles. As the mercury disappears, amalgam hardens.

44. Alloy is mixed with mercury in the ratio of 1:1 γ + Hg γ1 + γ2 + Unreacted alloy particles γ1 - Dominant phase – 54-56% Unreacted γ - 27- 35% γ2- 11-13%

45. High copper alloys- admixed 1963 innes and youdelis added silver copper eutectic alloy particles ( 71.9% of Ag and 28.1% Cu) to lathe cut low copper alloys. 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. The silver tin particle is usually formed by the lathe cut method, whereas the silver copper particle is usually spherical in shape The AgCu particles acts as strong fillers in strengthening the amalgam matrix. copper content - 9 to 20%.

46. The mercury dissolved in the Ag-Sn particles forms gamma 1 and 2 phases leaving some unreacted Ag-Sn particles. The newly formed gamma 2 around the Ag-Sn particles reacts with AgCu eutectic alloy particles and forms the η phase (Cu6Sn5) along with some gamma 1 phase around Ag-Cu particles. Ag3Sn + Ag-Cu + Hg Ag3Sn + Ag2Hg3 + Sn8Hg + Ag-Cu Sn8Hg + Ag-Cu Cu6Sn5 + Ag2Hg3 + Ag-Cu

47. Unicompositional alloy It is so called as it contains particles of same composition ( Asgar – 1974) Usually Spherical in nature Cu Content 13 – 30 %. The particles of unicompositional alloys in very early stages of setting are surrounded by gamma 1 and 2 phases and the periphery becomes an alloy of Ag and Cu. Gamma 2 reacts with Ag-Cu phase and forms η and more gamma 1.

48. The unicompositional alloy reaction with Hg is

49. properties ADA specification No.1 for amalgam lists following physical properties as a measure of quality of the amalgam. Creep Strength Dimensional changes Modulus of elasticity

50. 1) strength A) COMPRESSIVE STRENGTH Amalgam is strongest in compression & much weaker in tension & shear. 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 functions as a brittle material 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(145 Mpa )

51. 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. Tooth preparation should be done in such a way that they are subjected to more of compressive stresses and less of tensile stresses. The compressive strength of a satisfactory amalgam restoration should be atleast 310 MPa

52. Compressive Strengths of Low-Copper and High Copper Amalgam

53. 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 Both low & high copper amalgams have tensile strength that range between 48-70 MPa

54. Tensile strengths of amalgam

55. FACTORS AFFECTING STRENGTH A) Effect of Trituration: Effect of trituration on strength depends on the type of amalgam alloy, the trituration time and the speed of the amalgamator. Under trituration or over-trituration decreases the strength for both traditional and high copper amalgams. More the trituration energy used, more evenly distributed are the matrix crystals over the amalgam mix and consequently more the strength pattern in the restoration. Excess trituration after formation of matrix crystals will create cracks in the crystals, and lead to drop in strength of set amalgam

56. B) Effect of Mercury Sufficient mercury should be there to coat the particles. Low mercury alloy content, contain stronger alloy particles and less of the weaker matrix phase, therefore there is more strength. If mercury is too less it leads to a dry, granular mix, which results in a rough, pitted surface that invites corrosion. If the mercury content increases beyond 54% the strength reduces markedly

57. C) Effect of condensation For lathe cut amalgam, greater the condensation pressure higher the compressive strength. Higher condensation pressure is required to minimize porosity and to express mercury. Spherical amalgam - light condensation pressure produces adequate strength.

58. D) Effect of porosity Voids & porosities reduces strength Porosity is caused by: a. Decreased plasticity of the mix (due to low Hg/alloy ratio, delayed condensation, under-trituration) b. Inadequate condensation pressure (results in inappropriate adaptation at the margins & increase number of voids) c. Irregularly shaped particles of alloy powder d. Insertion of too large increments

59. E) Temperature: Amalgam looses 15% of its strength when its temperature is elevated from room temperature to mouth temperature It looses 50% of room temperature strength when temperature is elevated to 60 deg C e.g. hot coffee or soup .

60. 2) Creep and flow Creep is 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) Creep is related to marginal breakdown of low copper amalgams Higher the creep, the greater is the degree of marginal deterioration (ditching) It is measured after the amalgam has set.

61. 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% Creep rate has been found to correlate with marginal breakdown of conventional low-copper amalgams. High-copper amalgams have creep resistance because of lack of gamma-2 phase. FLOW: Flow refers to the deformation that occurs during the setting of amalgam. Greater the flow, greater are chances for restoration failure.

62. Factors influencing creep Phases of amalgam restorations Creep rate decreases with larger gamma1 grain sizes. Gamma 2 is associated with high creep rates. In absence of gamma 2, low creep rates in single composition alloy may be due to eta phase which act as barrier to deformation of gamma1 phase.

63. B) Manipulations: Greater compressive strength will minimize creep rates. Low mercury: alloy ratio, greater the condensation pressure and time of trituration, will decrease the creep rate.

64. 3) Dimensional change Severe contraction leads to plaque accumulation & secondary caries Expansion leads to postoperative pain & splitting of tooth If amalgam expanded during hardening, leakage around the margins of restorations would be eliminated. Largest dimensional change -19.7µg/cm- low cu lathe cut alloy. Lowest -1.9µm/cm – high cu admixed alloy.

65. Evidently the detrimental effect of shrinkage occurs only when the amalgam mass shrinks > 50 µm. According to ADA/ANSA SPECIFICATION NO-1. +-20µm/Cm is allowed.

66. When mercury is combined with amalgam it undergoes three distinct 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.

67. Factors that affect the dimensional changes: 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.

68. 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.

69. contraction Alloys dissolve in mercury and becomes smaller in size. FACTORS FAVOURING CONTRACTION Less mercury content Higher condensation pressure Over trituration Smaller particle size Spherical alloys have more contraction Low Hg - higher contraction.

70. EXPANSION: 16.6% of restorations fail- 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 According U.S Bureau of standards a dimensional change on setting, value of 5 - 10µm allowable.

71. Delayed expansion Dr Grey - 1920 Takes place after 24 hours. Zinc containing amalgam when contaminated with moisture during trituration or condensation can result in delayed expansion. This expansion can be for 3-5 days to months reaching values greater than 400µm • Also called as secondary expansion. Hydrogen is produced by the electrolytic action involving zinc and water which does not combine in amalgam but rather collects within the restoration increasing the internal pressure causing amalgam to expand. Zn + H2O  ZnO + H2

72. 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

73. 4) TARNISH AND CORROSSION Tarnish – surface discolouration on a metallic surface without the loss of structure. ( sulphide layer) It depends on oral environment and type of alloy. In case of low copper alloys, gamma phase is responsible. For high copper alloys, eta and Ag-Cu eutectic are responsible. Does not cause any detrimental effect on the amalgam

74. corrosion Corrosion – actual deterioration of metal by reaction with its environment. • Porosity, • Reduced marginal integrity and • Loss of strength Tin oxychloride is the corrosion product formed. (low copper) Sn7-8Hg + 1/202 + H2O + Cl- -> Sn4 (OH)6 Cl2 + Hg Corrosion product CuCl2.3Cu(OH)2 (high copper) Cu6Sn5 + 1/202 +H2O + Cl- -> CuCl2.3Cu (OH)2 + SnO.

75. GALVANIC CORROSION: If dental amalgam is in direct contact with an adjacent metallic restoration such as gold crown galvanic corrosion takes place. The dental amalgam is the anode in the circuit. Saliva being the electrolyte. STRESS 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: 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.

76. Electro chemical studies show γ1 phase has the highest corrosive resistance followed by γ, AgCu , ε and η Least resistant to corrosion is the γ2 phase. γ2 phase crystals are long and blade like, penetrating throughout the matrix. They form a penetrating matrix because of the intercrystalline contact between the blades. Hence this phase is more prone for corrosion producing penetrating corrosion. γ2 is more electronegative than γ and γ1 phases. So this induces galvanic corrosion.

77. Corrosion products from the tin in gamma 2 phase include tin oxychloride. Due to corrosion, mercury gets released. This mercury then reacts with unreacted gamma particles and produces additional gamma 1 and 2 phases which results in some expansion called as MERCUROSCOPIC EXPANSION . This results in porosity and reduction in strength. Corrosion on surface of amalgam restorations usually occurs to a depth of about 100 – 500 micrometers . Phosphate buffering ability of saliva is known to inhibit this process and provide protection against corrosion.

78. Factors related to excess tarnish & corrosion

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

80. Self sealing ability of amalgam Though corrosion and corrosion products are detrimental to a restoration, it is advantageous in amalgam restorations. Since amalgam doesn’t bond to the tooth, the corrosion products seal the amalgam and tooth interference. This is seen more in low copper amalgam than high copper amalgam.

81. RECENT ADVANCES

82. RESIN COATED AMALGAM To overcome the limitation of microleakage with amalgams, a coating of unfilled resin over the restoration margins and the adjacent enamel, after etching the enamel, has been tried. Although the resin may eventually wear away, it delays microleakage until corrosion products begin to fill the tooth restoration interface.

83. FLUORIDATED AMALGAM Fluoride, being cariostatic , has been included in amalgam to deal with the problem of recurrent caries associated with amalgam restorations. It was proposed by Innes and Youdelis in 1966, Serman in 1970 and Stone in 1971 Several studies concluded that a fluoride containing amalgam may release fluoride for several weeks after insertion of the material in mouth. the fluoride release from this amalgam seems to be considerable during the first week .

84. An anticariogenic action of fluoride amalgam could be explained by its ability to deposit fluoride in the hard tissues around the fillings and to increase the fluoride content of saliva, subsequently affecting remineralization. In this way, fluoride from amalgam could have a favorable effect not only on caries around the filling but on any initial enamel demineralization. The fluoride amalgam thus serves as a “slow release device” Example: Fluoralloy The problem with this method is that the fluoride is not delivered long enough to provide maximum benefit. Fluoride release from a fluoride-containing amalgam in vivo. Skartveit L, Tveit AB, Ekstrand J Scand J Dent Res. 1985 Oct; 93(5):448-52.

85. BONDED AMALGAM Since amalgam does not bond to tooth structure, microleakage immediately after insertion is inevitable. So, to overcome these disadvantages of amalgam, adhesive systems that reliably bond to enamel and dentin have been introduced. Amalgam bond is based on a dentinal bonding system developed in Japan by Nakabayashi and co-workers . 4META has been used to bond amalgam to cavity walls. The bond strength in admixed alloys was lower than those achieved with spherical alloys.

86. One study compared post-insertion sensitivity of teeth with bonded amalgams to that of teeth with pin-retained amalgams. After 6 months, teeth with bonded amalgams were less sensitive than teeth with pin-retained amalgams. This difference in sensitivity was not present 1 year after insertion. This is possibly because of corrosion products in nonbonded amalgam restorations filling the interface, and thus, decreasing microleakage and sensitivity. Summitt JB, Burgess JO, Osborne JW, Berry TG, Robbins JW. Two year evaluation of amalgambond plus and pin-retained amalgam restorations (abstract 1529) J Dent Res. 1998;77:297 .

87. Glass Cermet It is also called as cermet ionomer cements. McLen and Gasser in 1985 first developed this material. Fusing the glass powder to silver particles through sintering that can be made to react with polyacid to form the cement. The properties include strength which is both tensile and compressive strength is greater than conventional glass ionomer cement. The abrasion resistance is greater than conventional GIC due to silver particle incorporation. The silver cement radiopacity is equal to that of dental amalgam. The fluoride release for cermet is about 3350 ug in 2 weeks and about 4040 ug in 1 month.

88. GALLIUM – AN ALTERNATIVE TO AMALGAM As early as 1956, Smith and Caul and Smith and co-workers claimed that a gallium based alloy could serve as a possible alternative to dental amalgam. They found that mixing gallium with either nickel or copper and tin produced a pliable mass that could be condensed into a prepared cavity, which, after setting, had physical properties suitable for a restorative material. Commercial brands are: Galloy , Bayswater , Gallium GF, Gallium GF II

89. However…

90. Indium containing alloy powder and mercury-indium liquid alloy Powell et al in 1989 added pure indium powder with high copper alloy and triturated it with mercury. A significant decrease in mercury evaporation was seen. This was marked as : Indisperse and Indiloy Youdelis found that less mercury is required for mixing amalgam when 10% Indium is present. Johnson GH et al : indium containing high copper alloy exhibited low creep and increase in strength.

91. CONSOLIDATED SILVER ALLOY SYSTEM One amalgam substitute being tested is a consolidated silver alloy system developed at the National Institute of Standards and Technology. It uses a fluoroboric acid solution to keep the surface of the silver alloy particles clean. The alloy, in a spherical form, is condensed into a prepared cavity in a manner similar to that for placing compacted gold. One problem associated with the insertion of this material is that the alloy strain hardens, so it is difficult to compact it adequately to eliminate internal voids and to achieve good adaptation to the cavity without using excessive force. Bharti R, Wadhwani KK, Tikku AP, Chandra A. Dental amalgam: An update. Journal of conservative dentistry: JCD. 2010 Oct;13(4):204.

92. Mercury free amalgam Here, an experimentation was done which involved discarding the mercury content of amalgam and replacing it with a proprietary antimicrobial silver solution and unsialinized titanium dioxide ceramic nanoparticles for strength, with a favorable , easy to manipulate consistency. Prepared maxillary premolar controls were filled with Permite amalgam and compared to an experimental group filled with the novel material.

93. Both groups were then thermocycled , cross-sectioned, and studied through scanning electron microscopy (SEM). It was concluded that the addition of the silver solution and ceramic nanoparticles to mercury-free regular-set Permite alloy yielded a product that exhibits improved marginal adaptation with less application of condensation pressure, when compared to regular-set Permite amalgam.

94. CONTROVERSIES IN AMALGAM Basun et al. (1991) and Hock et al. (1998) demonstrated a significant nearly twofold increase in plasma and blood Hg levels in AD patients when compared to the respective values from age matched controls. Ehmann et al. (1986) found higher levels of Hg in the brain of autopsied AD patients than the control subjects without AD.

95. CONTROVERSIES IN AMALGAM Mackert and Berglund concluded that the extremely low dosage of mercury attributable to amalgam restorations was insufficient to produce any detectable negative effect on general health. Data strongly suggest that mercury levels many times higher than those associated with a mouth full of amalgam pose no risk of adverse health effects. Ekstrand and colleagues found no effects on various parameters of kidney function in humans

96. Conclusion: Dental amalgam has served as an excellent and versatile restorative material for many years, despite periods of controversy. It has served as a dental restoration for more than 165 years. There is still no adequate economic alternative for dental amalgam. Although there is evidence of a decrease in its use in the world, amalgam’s cost, durability and ease of manipulation have persuaded many dentists to continue to use it as their first choice for restoring posterior teeth.

97. Also, in regards to dental allergies, Dr. Stejskal introduced the MELISA test in 1994. This is a modified version of the Lymphocyte Transformation Test designed to test for metal sensitivity type IV delayed hypersensitivity to metals, including sensitivity to mercury. Amalgam will probably disappear eventually, but its disappearance will be brought about by a better and more esthetic material, rather than by concerns over health hazards. When it does disappear, it will have served dentistry and patients well for more than 200 years.

98. REFERENCES J Conserv Dent. 2010 Oct;13(4):204-8. Dental amalgam: An update The amalgam controversy-an evidence based analysis ; JADA,Vol.132,march 2001 Mertz- Fairhurst EJ, Curtis JW, Jr, Ergle JW, Rueggeberg RA, Adair SM. Ultraconservative and cariostatic sealed restorations: Results at year 10. J Am Dent Assoc. 1998;129:55–66. Summitt JB, Burgess JO, Osborne JW, Berry TG, Robbins JW. Two year evaluation of amalgambond plus and pin-retained amalgam restorations (abstract 1529) J Dent Res. 1998;77:297. Bharti R, Wadhwani KK, Tikku AP, Chandra A. Dental amalgam: An update. Journal of conservative dentistry: JCD. 2010 Oct;13(4):204. DODES, J. E. (2001). The amalgam controversy. The Journal of the American Dental Association, 132(3), 348–356. doi:10.14219/jada.archive.2001.0178 PHILLIPS’ Science of Dental Materials;11th ed Kenneth J. Anusavice CRAIG’s Restorative Dental Materials;12th ed John M. Powers, Ronald L. Sakaguchi

99. THANK YOU