Amalgam

DEFINITION
HISTORY
MATERIAL ASPECT
COMPOSITION
MANUFACTURING
PHASES OF AMALGAM
AMALGAMATION AND SETTING REACTIONS
PROPERTIES
MANIPULATION
INDICATION
CONTRAINDICATION
ADVANATGES
DISADVANTAGES
HARMFUL EFFECTS OF MERCURY
MERCURY MANAGEMENT
MERCURY CONTROVERSIES
ADVANCES IN AMALGAM
CONCLUSION

1. DENTAL AMALGAM

2. CONTENTS Introduction Definition History Material aspects: - Mercury - Alloy powder Composition Manufacture of alloy powder Phases in the structure of amalgam Amalgamation and microstucture Properties of amalgam Manipulation - Selection of alloy - Proportioning

3. - trituration - Condensation - Burnishing - Carving - Finishing and polishing Indications and contraindications Advantages and disadvantages Harmful effects of mercury Mercury management Controversies Advances in amalgam Conclusion References

4. INTRODUCTION Dental amalgam has served as an excellent & versatile restorative material for many years despite periods of controversy. Acceptance & usage have been based on the biomechanical properties, clinical characteristics, versatility in application & a long experience relating to the serviceability of amalgam in the oral environment. Through the years amalgam has survived despite political discussion such as amalgam war, economic & availability crisis & challenges by comparable alternative restorative materials.

5. DEFINITION The word “Amalgam” is derived from Greek work “emollient ” meaning paste An Amalgam is an alloy that contains mercury as one of it’s constituents - Phillips Dental amalgam is a metal like restorative material composed of a mixture of silver/tin/ copper alloy and mercury - Sturdevants 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

6. HISTORY 659AD First used by Chinese. There is a mention of silver-mercury paste by SuKung in the Chinese materia medica The first book on remedies for holes in the teeth were published. The decayed tooth was cauterized with a gold instrument .Vitriol+ strong acid + mercury were boiled .The mercury will transform itself into an amalgam which was poured into the cavity Li Shitichen used 100parts of Hg, 45parts of Ag & 100 parts of Sn In southern Germany, Johannes recommended amalgam for the purpose of restoration 1528 1578 1601

7. 1800 D ‘ arcets mineral cement –earliest dental amlgam used in France 1818 First dental silver amalgam is supposed to have been introduced into England by Bell – “Bell’s Putty” 1826 Introduction of silver mercury paste by Peter.O.Taveou of Paris ( french silver coin filings & Hg) 1833 Introduced to the North American continent by Cawcour brothers termed as “Royal Mineral Succedaneum”or substitute for gold 1841 Lefoulon introduced amalgam ,but it was rejected because of black discoloration porosity and shrinkage 1843 Resolution passed by the American Society of Dental Surgeons (the first organised Dental Society in the U.S.A declaring the use of amalgam a “Malpractice”). Thus the Amalgam War began (1840-1850)

8. 1845 “Amalgam Pledge” was adopted by the society 1848 Thomas W Evancs in Paris added calcium to Tin-Silver mixture 1861 First research programme was conducted by John Tomes Who measured shrinkage of a number of amalgams 1870 1895 1896 1928 Elish Townsend & J.I Flagg improvised amalgam alloy composition Dr G.V Black gave composition for low copper alloy Formula for “Conventional Amal Circa”. This contains 72.5% silver and 27.5% tin-mercury The use of gallium in direct restorative materials was first suggested by Puttkammer

9. 1930 A.D.A specification No. 1 for amalgam 1951 Markley published a classic article advocating constricted occlusal preparations He designed pear shaped burs (No 330 and 329) 1963 1970 1976 1980 1997 Innes and Youdelis added Spherical particles of silver copper eutectic, 39% copper to silver ,to particles of lathe cut low copper alloy Change from hand trituration to mechanical trituration Introduction of non zinc and zinc free alloys Bonded amalgam restorations was introduced Third amalgam war WHO Consensus Statement on Dental Amalgam considering amalgam to be safe

10. MATERIAL ASPECT Mercury : ADA Specification No.- 6 Silvery white mirror like surface Atomic no. - 80 Specific gravity - 13.55gm/cm 2 Freezing point - -38.8°c Boiling point - 356.9°c Tends to form globules when dropped on a surface due to high surface tension of 465 dynes/cm at 20 deg C.(Water- 72.8 dynes/cm) Being liquid in nature, binds with the alloy particles to form amalgam Almost 50% of amalgam is Elemental Mercury by wt

11. CLASSIFICATION According to Sturdevant Based on particle shape: SPHERICAL LATHE CUT ADMIXED

12. According to Marzouk According to the no. of alloyed metals: Binary alloys (e.g.: silver-tin) Ternary alloys (e.g.: silver-tin-copper) Quaternary alloys ( eg : silver-tin-copper-indium) According to whether the powder consists of unmixed or admixed alloys: Certain amalgam powders are only made of one alloy while others have one or more alloys or metals physically added to the basic alloy

13. According to the shape of the particle : Spherical Irregular Combined According to the size: Micro cut Fine cut Coarse cut According to the copper content: Low copper High copper

14. According to the addition of noble metals: Metals such as pd, Au or pt are alloyed to the powder the resulting amalgams may be classified as “noble metal alloys Can also be classified according to dispensing: As powder and liquid in separate bottles As pre weighed capsules of powder and liquid separated by a thin membrane As pellets,capsules (of the powder) As pre-amalgamated powder(around 2% of Hg is mixed by manufacturer)

15. According to compositional changes of succeeding generations of amalgam 1 st generation – 3 parts silver + 1 part tin peritectic 2 nd generation – copper is added upto 4% 3 rd generation – silver copper eutectic alloy + original alloy 4 th generation – alloying of copper to silver and tin upto 29% 5 th generation – silver, copper, tin, indium 6th generation – alloying palladium 10%, silver 62%, copper 28% - eutectic lathecut blended into 1 st generation in ratio of 1:2

16. COMPOSITION ALLOY PARTICLE SHAPE Ag Sn Cu Zn Low Cu Lathe cut+ Spherical 63-70% 26-28% 2-5% 0-1% High Cu - Admixed Lathe cut + Spherical 60-65% 15-25% 9-13% 0-2% - Single composition Spherical 60-65% 15-25% 13-30% 0-2%

17. Zinc - acts as a deoxidizer - makes alloy particles less brittle and contributes to the workability of the amalgam - Zinc causes delayed expansion, if contaminated. Tin decreases strength & hardness decreases expansion of Amalgam increases flow greater affinity for Hg-helps in amalgamation Copper hardens & strengthens Ag- Sn alloy decreases flow increases setting expansion Silver whitens the alloy increases strength increases expansion decreases flow of amalgam decreases setting time resists tarnish & corrosion

18. Platinum Hardens the alloy Increases resisitance to corrosion Palladium Hardens the alloy Whitens the alloy Indium Increases strength Improved resistance to creep and corrosion Reduces dimensional changes Other constituents include

19. MANUFACTURING Lathe-cut Alloy Powder: (1) Mixing: The ingredient metals are mixed in definite proportion and melted in a graphite crucible.Then poured into a mould to form an ingot(cylinder) of dimension 4cm diameter and 20-25 cm length . (2) Homogenisation : The ingot has cored structure(difference in composition within the alloy) with β and ɣ phases in homogeneously distributed. Then the ingot is heated for various periods of time (usually 6 to 8 hrs ) at 400ºC to produce homogenous distribution of Ag 3 Sn. It is slowly cooled.

20. (3) Lathe milling: The ingot is then reduced to filings by being cut on a lathe & ball milled to form powder. The particles are passed through a fine sieve & then ball milled to form the proper size. The average particle size of modern powders range between 15-35µm.

21. (4) Ageing & Particle treatment: The alloy particles are aged by subjecting them to a controlled temp of 60ºC to 100ºC for 1 to 6 hrs & washed with acid. The aging is related to relief of stress in the particles produced during the cutting of the ingot. Acid washed powders tend to be more reactive than those made from unwashed powders.

22. Spherical alloy powder The spherical particles are prepared by an atomization process. All the desired elements are melted together. The liquid alloy is then sprayed under high pressure of an inert gas, through a fine crack in a crucible into a large chamber. If the droplets solidify before hitting a surface, the spherical shape is attained. They are seperated into different sizes by seiving and then homogenized to remove cored structure.

23. Lathe cut alloys Spherical alloy A lloy particles have irregular shape Alloy particles have spherical shape Alloy particles are manufactured by milling Alloy particles are produced by atomization Requires more mercury for mixing and have poor properties Requires less mercury and have better properties Mix is less plastic and heavy condensation pressure is required Mix is more plastic and it is not sensitive to condensation pressure Cu content is 9-20% Cu content is 13-30% Creep is high due to high mercury content Creep is low due to low mercury content Difficult to finish Easy to finish LATHE CUT VS SPHERICAL ALLOYS

24. Factors governing the quality of a Dental Amalgam Restoration 1) Those that can be controlled by the dentist: - Selection of an alloy - Mercury / Alloy ratio - Trituration procedures - Condensation technique - Marginal integrity - Anatomical characteristics - Final finish

25. 2) Those that are under the control of the manufacturer: - The composition of the alloy - The heat treatment of the alloy - The size, shape and method of production of the alloy particles. - The surface treatment of the particle. - The form in which the alloy is supplied.

26. Symbols & Stoichiometry of phases that are involved in the setting of Dental Amalgam Phases in Ag- Sn alloy system Stoichiometric formula  Ag 3 Sn  1 Ag 2 Hg 3  2 Sn 7-8 Hg Є Cu 3 Sn η Cu 6 Sn 5 Silver-copper eutectic Ag-Cu

27. Amalgamation and resulting microstructures Amalgamation and resulting microstructures Low copper alloys-(setting reaction) Amalgamation occurs when alloy powder and mercury are triturated ,the silver and tin in outer portion of the particles dissolve into mercury . Simultaneously the mercury diffuses into the alloy particles and start reacting with silver and tin within forming crystals of silver –mercury and tin mercury compounds. Silver tin compound (unreacted alloy powder )is known as gamma phase (  )silver mercury compound is known as gamma 1 phase (  1 ) and tin mercury as gamma 2 phase (  2 )

28. Setting Reaction: The alloy particles do not react completely with mercury About 27%of original Ag3Sn remains as unreacted particles - which is called as gamma phase .  1 2

29. Microstructure of set Amalgam: Set mass consists of unreacted particles (  ) surrounded by a matrix of the reaction products (  1 +  2 ). More the unconsumed Ag-Sn phase (  ) present in final structure – more stronger the amalgam will be.  2 is the weakest component & is least stable to corrosion process. The high proportion of the unconsumed  phase will not strengthen the amalgam unless the particles are bound to the matrix.

30. High copper alloys Contain more than 6 wt % copper. High copper alloys have become the materials of choice because of their improved mechanical properties, resistance to corrosion, better marginal integrity and improved performance in clinical trials as compared with low copper alloys. 2 types of high copper alloy powders: - Admixed alloy powder - Single-composition alloy powder.

31. Admixed alloys The admixed alloys was introduced in 1963 and were orignally made by mixing 1 part of silver copper eutectic alloy(high copper spherical particles)with 2 parts of silver tin alloy (low copper lathe cut alloy) An eutectic alloy is one in which the components exhibit complete liquid solubility but limited solid solubility)

32. Admixed alloys are better than lathe cut alloys

33. Setting reaction in admixed alloys When mercury reacts with an admixed powder, silver in Ag-Cu spheres and silver and tin from Ag-Sn particles dissolve into the mercury. Whereas both γ1 and γ2 crystals form, as in lathe-cut alloys, the tin in mercury diffuses to the surfaces of the Ag-Cu alloy particles and reacts with the copper to form a layer of η′ phase crystals on the surface. The η′ layer on the surface of Ag-Cu alloy particles also contains γ1 crystals, since γ1 and η′ phases form simultaneously. As in the low-copper amalgams, γ1 is the matrix phase (i.e., the phase that binds the unconsumed alloy particles together).

34. In this reaction, the γ2 phase does form along with the η′ phase but later reacts with copper from Ag-Cu particles, yielding additional η′ The γ2 phase can be eliminated with at least 11.8% of copper by weight in the alloy powder.

35. Microstructure of set Amalgam: The Cu 6 Sn 5 ( η ) is present as a “halo” surrounding the Ag-Cu particles. The ɳ phase is also found as a mesh of rod crystals binding the matrix of gamma1 crystals together contributing to the strength. Final set material consists of: Core of 1) Ag 3 Sn (  ) 2) Ag-Cu surrounded by a halo of Cu 6 Sn 5 ( η ) Matrix of  1 (Ag 2 Hg 3 )

36. Single-Composition Alloys The major components of single-composition particles are usually silver, copper, and tin. The copper content of various single-composition alloys ranges from 13% to 30% by weight. In addition, small amounts of indium or palladium are included in some of the single-composition alloys. A number of phases are found in each single-composition alloy particle, including the β phase (Ag-Sn), γ phase (Ag3Sn), and ε phase (Cu3Sn). Some of the alloys may also contain some η′ phase

37. Setting reaction When triturated with mercury, silver and tin from the Ag-Sn phases dissolve in mercury. Very little copper dissolves in mercury. The γ1 crystals grow, forming a matrix that binds together the partially dissolved alloy particles. The η′ crystals are found as meshes of rodlike crystals at the surfaces of alloy particles, dispersed in the matrix. In most single-composition amalgams, little or no γ2 forms

38. Microstructure of set amalgam Set material consists of: - a core of Ag 3 Sn & Ag-Cu - a matrix of  1 (Cu 6 Sn 5 is present in the  1 matrix)

39. PROPERTIES Dimensional stability Strength Creep and flow Tarnish and corrosion Thermal properties

40. 1. DIMENSIONAL STABILITY Amalgam can expand or contract, depending on its manipulation. ADA Specification No. 1 requires that the dimensional change of amalgam be in the range of 15 to 20 µm/cm measured at 37 °C between 5 min and 24 h after the beginning of trituration. Severe contraction can lead to microleakage, plaque accumulation, and secondary caries.

41. Excessive expansion can produce pressure on the pulp and postoperative sensitivity Protrusion of a filling can also result from excessive expansion.

42. MECHANISM OF DIMENSIONAL CHANGE Steps Involved:- Initial contraction Expansion Slight contraction Mechanism involved When the alloy and mercury are mixed, contraction results as the particles dissolve (and hence become smaller). Since the final volume of the γ1 phase is less than the sum of the silver and liquid mercury volume needed to produce the γ1 phase, contraction continues as long as the γ1 phase keeps growing. As γ1 crystals grow, they will impinge against one another. When there is sufficient liquid mercury present to provide a plastic matrix, expansion will occur when γ1 crystals impinge on each other

43. After a rigid γ1 matrix has formed, growth of γ1 crystals cannot force the matrix to expand further. The reaction continues with γ1 crystals growing into interstices containing mercury, thereby resulting in slight contraction NET RESULT WITH MODERN AMALGAM IS SMALL AMOUNT OF CONTRACTION of about 0.3 % by volume.

44. More Expansion observed in- High Hg : alloy ratio Less condensation pressure Too little Sn in composition Large particle size of alloy Under trituration Moisture contamination More Contraction Lower mercury/alloy ratios Higher condensation pressures Manipulative procedures that accelerate setting and consumption of mercury also favor contraction, including Longer trituration Smaller particle size M.A. Marzouk et al. Operative dentistry Modern Theory & Practice

45. EFFECT OF MOISTURE CONTAMINATION When a zinc-containing, low-copper or high-copper amalgam is contaminated by moisture during trituration or condensation, a large expansion can take place. This expansion usually starts 3 to 5 days after placement and may continue for months, reaching values greater than 400 µm/cm (4%). This type of expansion is known as delayed expansion or secondary expansion .

46. Mechanism of Delayed Expansion The effect is caused by the hydrogen produced by electrolytic action involving zinc and water. Zn + H 2 O ZnO + H 2 The hydrogen does not combine with the amalgam but, rather, collects within the filling, increasing the internal pressure to levels high enough to cause the amalgam to creep, thus producing the observed expansion.

47. Source of Contaminants Saliva Blood skin Secretions (zinc containing alloys is touched with bare hand ) Other sources -Moisture contamination of the alloy and mercury during storage Moisture contamination of the equipment used for trituration and condensation Moisture contamination of the instruments used for trituration and condensation

48. Complications due to delayed expansion Protrusion of the entire restoration out of the cavity Increased microleakage around the restoration Restoration perforations Increased flow and creep Pulpal pressure pain

49. Mercuroscopic expansion Originally proposed by Jorgensen (1965) Extrusion of the margins is promoted by electrochemical corrosion ,during which the mercury from the Sn-Hg phase reacts with remaining unreacted alloy i.e Ag Sn particles and produce further expansion during the new reaction This mechanism – Mercuroscopic expansion This expansion of the amalgam against the cavity wall results in an unsupported wedge at the margin of the restoration Jorgensen theory of mercuroscopic expansion

50. Relative weakness of this wedge is due to High mercury content Presence of porosities due to corrosion Smaller cavosurface angles This leads to marginal breakdown under the influence of the forces acting in the oral cavity This theory of Jorgensen is one of the arguments to prepare a cavosurface angle of 90° as well as possible

51. 2. STRENGTH Strength of dental amalgam has been measured under the compressive stress. By this manner compressive strength of a satisfactory amalgam should be atleast 310mpa (45,000 psi) or more. When they are manipulated properly, compressive strength ranges from 380 - 550 mpa (55,000 - 80,000 psi ) which is similar to enamel & dentine Amalgam is brittle material i.e. HIGH COMPRESSIVE & LOW TENSILE STRENGTH. Tensile strength of amalgam is 1/5 th —1/8 th of compressive strength.

52. Insufficient mercury between particles yields a dry, granular mix. Such a mix results in a rough, pitted surface that promotes corrosion. Thereby resulting in decreased strength Increasing the final mercury content increases the volume fraction of the matrix phases at the expense of the alloy particles. A higher mercury content promotes the formation of γ2 phase, even in a high-copper amalgam. This in turn decreases the strength of the amalgam 1. Effect of Mercury Content (Marzouk)

53. 2. Effect of Trituration The effect of trituration depends on Type of amalgam alloy The trituration time, and The speed of the triturator More the triturition energy, the more continuous are the interphase between amalgam matrix and alloy particles and more evenly distribution of matrix, thereby providing strength But in case of overtriturition , excess energy will create cracks in the matrix and interphase causing lowering of strength Undertrituration also decrease the strength of both conventional and high-copper amalgams.

54. 3. Effect of Condensation Good condensation techniques will express mercury and result in a smaller volume fraction of matrix phase. Ideal condensation pressure for amalgam with a small head condenser is 13.3-17.8N (3– 4 lb ) Higher condensation pressures are required to minimize porosity and express mercury from lathe-cut amalgams. On the other hand, spherical amalgams condensed with lighter pressures produce adequate strength.

55. 3. Effect of Porosity Porosity & voids reduces strength Porosity is related to plasticity of mix Reduced plasticity More porosity More area for stress concentration Propagation of cracks & corrosion Less strength In lathe cut alloys more condensation pressure required for well adaptation to walls This results in less voids and porosity More strength

56. Porosity can be due to Undertrituration Particle shape Insertion of too large increments into the cavity Delayed insertion after trituration Non plastic mass of amalgam

57. 4. Effect of temperature Amalgam loses 15% of strength when its temperature is elevated from room temperature to mouth temperature Looses 50% of room temperature strength when temperature is elevated to 60°C e.g : hot coffee or soup

58. 3. creep Creep is defined as time dependent plastic deformation Amalgam Creep has been defined as plastic deformation due to slow metallurgic phase transformations that involve diffusion-controlled reactions and produce volume expansion ( Sturdevant ) The associated expansion makes the amalgam protrude from the tooth preparation.

59. According ADA specification creep value – less than 2% Low copper alloy - 0.8 to 8% High copper alloy - 0.4 to 0.1% When an amalgam creeps, it is the γ1 phase that deforms plastically. That is higher creep rates for low copper amalgam with higher γ1 volume fractions and vice versa. Also, the presence of the γ2 phase increases the creep rate. In addition to the absence of the γ2 phase, the very low creep rates in single-composition high-copper amalgams may be associated with η′ phase rods, which act as barriers to deformation of the γ1 phase.

60. The creep of dental amalgam is a continued deformation ,that occurs under constant stress (static creep) or under intermittent masticatory stresses (dynamic creep ) Responsible for the marginal break down Higher the creep, greater is the degree of marginal deterioration

61. Increased creep Decreased creep Effect of microstructure and composition Large gamma 1 volume fractions Presence of gamma2 Excess mercury in the amalgam Larger gamma 1 grains Complete elimination of gamma 2 Presence of eta crystals Effect of manipulative variables Under or over trituration Increased mercury to alloy ratio Increased condensation pressure All manipulative factors that affect maximize the strength also minimizes the creep FACTORS AFFECTING CREEP

62. 5. Tarnish and corrosion TARNISH It is the surface discoloration of a metal or a slight loss or alteration of the surface finish or luster due to formation of thin layer of oxides, chloride or other chemicals CORROSION It is a process in which deterioration of a metal is caused by the reaction of metal with its environment Amalgam restorations often tarnish and corrode in the oral environment. The degree of tarnish depends on: (I) the oral environment (II) the type of alloy used

63. Tarnish of amalgam restorations is due to the formation of black silver sulfide Corrosion products – oxides and chlorides of tin Corrosion products of Cu is also found in the high copper amalgam Corrosion results in the formation of tin oxychloride from the tin in the gamma 2 phase and also liberates mercury Sn 7-8 Hg + H 2 O + Cl Sn 4 (OH ) 6 Cl 2 + Hg The liberated mercury reacts with unreacted gamma can produce additional gamma 1 and gamma 2. the presence of gamma 2 phase is responsible for tarnish and corrosion High copper amalgam is more resistant to tarnish and corrosion due to the absence of gamma 2 phase

64. Types of corrosion Chemical corrosion or Dry corrosion Electrochemical or Wet corrosion Galvanic corrosion Concentration cell corrosion Stress corrosion Chemical Corrosion It is the direct combination of metallic and nonmetallic elements to yield a chemical compound through oxidation reactions. E.g :- discoloration of silver by sulfur, where silver sulfide forms by chemical corrosion. Electrochemical Corrosion

65. Galvanic Corrosion When the two dissimilar metals are brought in contact ,there is sudden short circuit through two alloys ,which may result in the patient experiencing a sharp pain. E.g. An amalgam restoration on the occlusal surface of lower molar opposing a Gold inlay in an upper tooth Concentration cell Corrosion Accumulations of food debris in the inter-proximal Areas produces an electrolyte which is different from the electrolyte produced by normal saliva at the occlusal surface. Electrochemical corrosion of the alloy surface underneath the layer of food debris will take place in this situation.

66. A similar type of attack may occur from differences in the oxygen concentration between parts of the same restoration, with the greatest attack at the areas containing the least oxygen (the anode). Irregularities—such as pits, scratches, and cracks—in restoration surfaces are important examples of this phenomenon. The region at the bottom of such a defect is oxygen-deprived and becomes the anode and thereby undergoes corrosion A pit on a dental alloy as a corrosion cell. The region at the bottom of the pit is an anode, and the surface around the rim of the pit is the cathode

67. Examples of sites susceptible to electrochemical and chemical corrosion on amalgams: galvanic corrosion (a) at interproximal contact with metallic restoration such as gold casti ng alloy; local galvanic (b) corrosion on occlusal surface at grain boundaries between different metallic phases; crevice corrosion (c) at margin due to lower pH and oxygen concentration of saliva; crevice corrosion (d) under retained interproximal plaque due to lower local pH; crevice corrosion (e) within unpolished scratches or detailed secondary anatomy; chemical corrosion (f) of occlusal surface with sulfide ions in saliva, producing surface tarnish.

68. Stress Corrosion Small surface irregularities, such as notches or pits, act as sites of stress concentrations. More deformed areas act as anode and undergo electrochemical corrosion Corrosion can lead to: Reduced strength i.e.. a corroded amalgam restoration is predisposed to fracture; Marginal degradation (“ditching”) which is a stress/corrosion type of degradation Dimensional changes i.e.. a corroding amalgam restoration increases in size Increased internal porosities and surface roughness Discoloration Galvanic effects, rarely including a metallic taste; Biological effects, including allergy to corrosion products and possible toxic reaction in extreme situations.

69. 6. Thermal properties Thermal diffusivity Dental amalgam is a conductor of heat Consequently, large amalgam restorations are usually lined with a thermal insulating cements to protect the pulp from the temperature changes in the mouth caused by hot and cold food and liquids Thermal expansion The coefficient of thermal expansion is about 25 ppm which is almost double of the tooth -results in microleakage Prevented by application of cavity varnish

70. Manipulation of amalgam

71. Selection of alloy Particle size : Micro cut or smaller particles are used because they are: -easy to condense -greater strength -easy to carve -smooth finish -less marginal failure -faster setting time -good adaptation Larger particles lead to porous fillings and decreased strength.

72. 2. Shape of alloy : Spherical alloys are preferred because it: -gives better finish -good marginal adaptation -good strength -requires less condensation forces -carving is easier -requires less mercury (42% conc of Hg ) due to low surface area compared to lathe cut which requires 50% or more Hg. Lathe cut particles gives a rough surface and has poor corrosion resistance.

73. 3. Unicompositional alloys are preferred compared to admixed High early strength(1 st and 7 th hr ) Consumes less mercury and hardens faster Requires less condensation forces Easier to polish However admixed has the advantages of less dimensional changes and longer working time. 4. High Cu is preferred over low Cu Less creep due to absence of gamma2 phase Better corossion resistance. Cheaper

74. Mercury alloy ratio Sufficient mercury must be present in the original mix to provide a coherent and plastic mass after trituration, but it must be low enough that the mercury content of the restoration is at an acceptable level without the need to remove an appreciable amount of mercury during condensation. The mercury content of the lathe-cut alloy is about 50% by weight and that for spherical alloys is 42% by weight.

75. For conventional mercury added systems 2 techniques were used for mercury reduction: By squeezing or wringing the mixed amalgam in a squeeze cloth before insertion into the prepared cavity. Mercury rich amalgam was worked to the top during condensation of each increment, and this excess was removed as the amalgam mix was built up to form a restoration

76. The present day alloys are designated for manipulation with reduced mercury / alloy ratios just enough to get a coherent plastic mass. This method is known as the minimal mercury technique or the Eames technique(1959) It is a technique for mixing dental amalgam in 1:1 ratio of mercury and alloy to minimize free mercury in the unset mass Certain manufacturers use ratios less than 1:1 with the percentage of mercury varying from 43% to 54%

77. proportioning There are different ways of proportioning: Weighing and triturating :this is ideal but time consuming Volume dispensing( Graviometry ): Widely used-however it is difficult to dispense any powder accurately by volume Pre-weighed capsules of alloy powder and Hg seperated by a membrane: Disposable capsules containing pre- proportioned amounts of mercury and alloy are widely used. Just before the mix is triturated the membrane is ruptured by compression of the capsule.

78. Preproportioned capsules The older types of preproportioned capsules require activation before trituration to allow the mercury to enter the compartment with the alloy. Some alloys are now available in self-activating capsules , which bring the alloy and mercury together automatically during the first few oscillations of the triturator . Advantages More convenient Eliminates the chance of mercury spills during proportioning Result in a reliable mercury/alloy ratio Disadvantages Expensive These capsules do not provide an opportunity to make minor adjustments in the mercury/alloy ratio to accommodate personal preferences

79. trituration trituration is the process of mixing alloy particles with mercury Objectives of trituration (Marzouk) To achieve a workable mass of amalgam within a minimum time, leaving sufficient time for its insertion into a cavity preparation and carving the tooth anatomy. To remove oxides from the powder particle surface, facilitating direct contact between the particles and the mercury. To pulverize pellets into particles that can be easily attacked by the mercury. To reduce particle size so as to increase the surface area of the alloy particles per unit volume , leading to a faster and more complete amalgamation.

80. To dissolve the particles or part of the particles of the powder in mercury , which is a prerequisite for the formation of the matrix crystals. To keep the gamma1 matrix crystals as minimal as possible yet evenly distributed throughout the mass for proper binding and consistent adequate strength

81. Hand mixing by the Mortar and Pestle In this a glass mortar and a pestle is used The time of mixing is 30-40sec with a force of 800-900 gm being applied. The mixed mass should be homogeneous,smooth,should not stick to walls of mortar and pestle and should form a lump. Extra mercury can be removed by squeezing the mass with a dental floss. Factors affecting it include: pressure exerted on the mix, no. of revolutions per minute, inclination of the pestle relative to the mortar surface roughness of both mortar and pestle

82. Mechanical trituration A capsule serves as a mortar. A cylindrical metal or plastic piston of smaller diameter than the capsule is inserted into the capsule which serves as the pestle. There are three basic movements of mechanical trituritors : 1.The mixing arm carrying a capsule moves back and forth in a straight line. 2.The mixing arm travels back and forth in a figure of 8 motion. 3.The mixing arm travels in centrifugal fashion. The main mixing mechanism of a mechanical triturator is a reciprocating arm that holds the capsule under a protective hood. The purpose of the hood is to confine mercury that might escape into the room or to prevent a capsule from being accidentally ejected from the triturator during trituration. (Philips)

83. Types of capsules Reusable capsules with pestle. Preproportioned capsule with pestle. Preproportioned capsule without pestle. A reusable capsule should be clean and free of previously mixed, hardened alloy. At the end of each trituration procedure, one should quickly remove the pestle from the capsule, replace the lid, reinsert the capsule in the triturator , turn it on for a second or two, and then remove the amalgam. This mulling process generally causes the mix to cohere so that it can be readily removed from the capsule with minimal residue in the capsule. It minimizes the need of scraping out partially hardened alloy, which usually produces scratches in the capsule.

84. Spherical alloys often do not need a pestle Pestels may be plastic or metal. The diameter and length of the pestle should be considerably less than the capsule. If the pestel is too large,the mix is not homogeneous. Satisfactory size relationship between capsule and pestle Unsatisfactory pestle size a b

85. A commonly used older model is a single-speed device with an automatic timer for controlling the length of the mixing time. Later models have multiple speed settings. A modern triturator is often microprocessor controlled and contains preset trituration programs for a number of materials. It can also be programmed by the operator to include other materials

86. Mechanical Amalgamators are available in the following speeds:- Low speed : 3200-3400 cpm Medium speed : 3700-3800 cpm High speed : 4000-4400 cpm Time of trituration on amalgamator ranges from 3-30 seconds. Variations in 2-3 seconds can also produce a under or overtriturited mass. For a given alloy and mercury, increased trituration time and /or speed shortens the working and setting times.

87. CONSISTENCY OF MIX Normal mix : Has maximum strength. Mix may be warm (not hot),when it is removed from the capsule. The smooth carved surface will retain its luster longer after polishing Under trituration: Rough & grainy mix, difficult to manipulate Rough surface after carving, less resistance to tarnish & corrosion Compressive & tensile strength reduced Mix will harden too rapidly & excess mercury will be left in the restoration

88. Over trituration: Mix will be soupy, too plastic to manipulate Working time decreased Creep is increased Increased contraction of amalgam Compressive & tensile strength increased for lathe cut alloys, reduced for spherical

89. mulling Mulling is actually a continuation of trituration. The step can still be used following mechanical trituration to improve the homogeneity of the mass and to assure a consistent mix. It can be accomplished in two ways: The mix is enveloped in a dry piece of rubber dam and vigorously rubbed between the first finger and thumb; or the thumb of one hand and palm of another hand. The process should not exceed 2 to 5 seconds. After trituration the pestle can be removed from the capsule, and the mix triturated in the pestle-free capsule for additional 2 to 3 seconds. This will also assure cleaning of the capsule walls of remnants of the amalgam mix, thereby delivering the mix in one single, coherent, and consistent mass.

90. condensation Condensation is used to compact the alloy into the prepared cavity so that the greatest possible density is attained with sufficient mercury present to ensure complete continuity of the matrix phase (Ag2Hg3) between the remaining alloy particles. Objectives of condensation: To remove any excess mercury from each increment as it is worked to the top by the condensing procedure. Adapt the amalgam to the margins, walls and line angles of the cavity Minimize voids Acquire maximum physical properties

91. The longer the time that elapses between mixing and condensation, the weaker the amalgam will be Effect of elapsed time between trituration and condensation on the strength of the hardened amalgam. The greater the elapsed time, the lower is the strength Condensation should be as rapid as possible and a fresh mix of amalgam should be made if condensation takes longer than 3-4 minutes.

92. Condensation Procedure (Hand Condensation ) The condenser tip, or face, is forced into the amalgam mass under hand pressure. Condensation is usually started at the center, and then the condenser point is stepped incrementally toward the cavity walls. After condensation of each increment, the surface should be shiny in appearance. This indicates that there is sufficient mercury present at the surface to diffuse into the next increment so that each increment is added, it will bond to the preceding one. The procedure of adding an increment, condensing it, adding another increment, and so forth is continued until the cavity is overfilled. Any mercury-rich material at the surface of the last increment will be removed when the filling is carved.

93. Small increments of amalgam should be used throughout the condensation procedure to reduce void formation and to obtain maximum adaptation to the cavity. After completely filling the cavity, an overdried amalgam mix(made by sqeezing off mercury in a cloth) is condensed heavily over the restoration using the largest condensers possible for the involved tooth. This mix is called the blotting mix . This serves to blot excess mercury from the critical marginal and surface area of the restoration and to adapt amalgam more intimately to the cavosurface anatomy.The mix is excavated and discarded after it achieves these two functions

94. 1. Amalgam carried into the prepared cavity 2. Amalgam condensed 4. Final condensation 3. Blotting mix placed on the restoration

95. The condensation of spherical alloy amalgam differs from the non spherical ones in two ways: It is necessary to use increments large enough to fill the entire cavity or a large part of the cavity.In this situation the condenser acts as a moving roof against the amalgam confined within the cavity with the condenser moving towards the floor. It is necessary to use the largest condenser that will fit the cavity or part of it preventing the lateral escape of the spherical particles during condensation. (Marzouk)

96. Mechanical Condensation: Condensation of the amalgam can be performed by an automatic device. Useful for irregular shaped alloys when high force is used Some provide an impact type of force, whereas others use rapid vibration. Advantages are: a) less energy is needed than for hand condensation. b) the operation may be less fatiguing to the dentist. Ultrasonic condensers are not recommended since they increase the mercury vapour level to above the safety level

97. Condensation Pressure The area of the condenser tip and the force exerted on it by the operator govern the condensation pressure (force per unit area). The smaller the condenser, the greater is the pressure exerted on the amalgam. If the condenser point is too large, the operator cannot generate sufficient pressure to condense the amalgam adequately and force it into retentive areas. A study of 30 practitioners showed that condensation forces average between 13.3 and 17.8 N (3 to 4 lb ) employed. To ensure maximum density and adaptation to the cavity walls, the condensation force should be as great as the alloy will allow, and consistent with patient comfort.

98. Many of the spherical alloys have little “body” and offer only minimal resistance to the condensation force. Therefore, the strength properties of spherical amalgam alloys tend to be less sensitive to condensation pressure. The potential disadvantages of a spherical alloy are the tendency for overhangs in proximal areas and weak proximal contacts. The shape of the condenser tips should conform to the area under condensation. For example, a round condenser tip is ineffective adjacent to a corner or angle of a prepared cavity; a triangular or square tip is indicated in such an area.

99. Precarve burnishing After condensing with amalgam condensers, the amalgam maybe further condensed and shaping of the occlusal anatomy begun with a large burnisher such as an ovoid burnisher. This is done with use of heavy strokes, made in mesiodistal and faciolingual directions. This produces denser amalgam at the margins of the restorations. Mainly useful for high copper amalgams.

100. The objectives of burnishing are : (Marzouk) It is a continuation of condensation, in that it will further reduce the size and number of voids on the critical surface and marginal areas of the amalgam. It brings any excess mercury to the surface, to be discarded during carving. It will adapt the amalgam further to cavosurface anatomy. It conditions the surface amalgam to the carving step.

101. carving After the amalgam has been condensed into the prepared cavity, it is carved to reproduce the proper tooth anatomy. The objective of carving is to simulate the anatomy rather than to reproduce extremely fine details (Philips) Objectives of Carving (Marzouk) To produce a restoration with no underhangs, ie .,all marginal details of the cavity preparation are completely covered with amalgam. To produce a restoration with the proper physiological contours. To produce a restoration with minimal flash (Flash is the thin portion of amalgam extending beyond the margins)

102. To produce a restoration with functional, non interfering occlusal anatomy. To produce a restoration with adequate, compatible marginal ridges. To produce a restoration with the proper size, location, extent and interrelationship of contact areas. To produce a restoration with physiological compatible embrasures. To produce a restoration not interfering in any way with the integrith of the periodontium, enhancing its health and amenable for plaque control.

103. Deep occlusal grooves should not be carved into the restoration because these may thin the amalgam at the margins, invite chipping and weaken the restoration. Undercarving leaves thin portions of amalgam subject to fracture on the tooth surface. Such margins give the appearance that the amalgam has extended beyond the preparation. The mesial and distal fossae should be carved slightly deeper than the proximal marginal ridges. A scraping or ringing sound should be heard when it is carved(amalgam cry). After carving, the outline of the amalgam margin should reflect the contour and location of the prepared cavosurface margin, revealing a regular(not ragged outline) with gentle curves. An amalgam restoration that is more than minimally overcarved ( ie .,a submarginal defect > 0.2mm) should be replaced.

104. Postcarve burnishing After carving is completed, the surface of the restoration should be smoothed. This may be accomplished by judiciously burnishing the surface and margins of the restoration. Burnishing of the occlusal anatomy can be accomplished with a ball burnisher Clinical data on performance of restorations support the desirability of burnishing the fast setting, high-copper systems. Burnishing slow-setting alloys can damage the margins of the restoration. Undue pressure should not be exerted in burnishing, and heat generation should be avoided. Temperatures above 60 °C (140 °F) cause a significant release of mercury

105. Finishing and polishing This step is necessary to Complete the carving Refine the anatomy, contours and marginal integrity. Enhance the surface texture of the restoration. To remove superficial scratches, pits & irregularities which in turn minimizes corrosion & prevents adherence of plaque. The final finishing of the restoration should be delayed until the amalgam develops sufficient strength to resist the pressure of polishing. Generally, the recommendation is to wait for at least 24 h or until the next appointment

106. The area may be further smoothened using light pressure with a suitably shaped round finishing bur. This bur removes the scratches from the green or white stone. Polishing is initiated with coarse abrasive rubber point at slow speed and an air water spray. Diminishing grades (increased fineness) of abrasives are used for polishing. Final polishing may be accomplished by using a rubber cup with a flour of pumice or tin oxide followed by a high lustre agent like precipitated chalk

107. When necessary, a carborundum or fine-grit alumina stone is used to develop continuity of surface from the tooth to the restoration; The restoration is surfaced with a round finishing bur (D) Polishing is initiated with a coarse rubber abrasive point at low speed (F) a high polish is obtained with medium- grit and fine-grit abrasive points and

108. After carving After final finishing

109. Indications and contraindications INDICATIONS: Moderate to large class I & class II restorations(specially those with heavy occlusion,that cannot be isolated well or which extends into the root surface) Class V restorations those that are not esthetically critical. Cuspal restorations (usually amalgam pins) Class III in unesthetic areas ( e.g : distal aspect of canine) especially in extensive preparation with minimal facial involvement Class V lesions in non esthetic areas where access is limited and moisture control is difficult and for areas that are significantly deep gingivally

110. Foundations(including badly broken down teeth that requires increased retention and resistance form in anticipation of the subsequent placement of a crown) As a die material In teeth that act as abutment for removable appliances In combination with composite resins for cavities in posterior teeth (Resin veneer over Amalgam) Restorations that have heavy occlusal contacts Temporary caries control restorations.

111. CONTRAINDICATIONS: Anterior teeth where esthetic is of prime concern Esthetically prominent areas of posterior teeth Small to moderate class I & class II restorations that can be well isolated (a composite may be preferred since tooth preparation will be less) Small class VI restorations. Allergy to any component of amalgam Patients with proven amalgam induced lichenoid reactions Treatment of incipient or early primary fissure caries Remaining tooth structure which requires extensive tooth preparation to accommodate amalgam

112. Advantages and disadvantages ADVANTAGES: Ease of handling Economical High compressive strength Excellent wear resistance Durability : Favourable long term clinical results Restoration is completed within one sitting without requiring much chairside time Not technique sensitive

113. Optimal dimensional changes: ADA specification no. 1 permits + 0.2% expansion/contraction during setting.(amalgam is within that range) Self Sealing ability - Sealing improves with age by formation of corrosion products at tooth amalgam interface Modern alloys used in amalgam undergo less dimensional changes when compared to GIC and Composite Recurrence of caries around amalgam restoration is low. This is proven clinically but poorly understood

114. DISADVANTAGES: Non esthetic Less conservation of tooth structure. Amalgam requires adequate depth and width during cavity preparation for proper retention Weakens tooth structure Technique sensitive More difficult tooth preparation Does not bond to the tooth structure. Lack of chemical or mechanical adhesion to the tooth structure Amalgam is a good thermal conductor-thus base is required. Less tensile strength Galvanic currents produced in certain cases Undergoes tarnish and corrosion

115. Delayed expansion. Restoration may protrude from the tooth structure Occurrence of secondary caries. Postoperative sensitivity. Patients are usually asked to avoid extremely hot or cold food for 24hrs of amalgam placement May cause discoloration of the tooth structure (Amalgam blue) Amalgam tattoo. Mostly due to amalgam scraps left in the open surgical or extraction wounds or into the gingival tissue Not biocompatible. May cause allergic reactions in certain patients. Cause environmental hazards

116. HARMFUL EFFECTS OF MERCURY

117. ALLERGY/ HYPERSENSITIVITY MERCURY TOXICITY Mercury may cause injury to biological tissues in the form cell destruction, organ damage and even death Immediate Hypersensitivity reactions Delayed Hypersensitivity reactions Syed Kashif Abrar SKA et al. Dental amalgam : A controversial filling material. Acta Scientific Dental Sciences, 2019

118. IMMEDIATE HYPERSENSITIVITY REACTION Skin lesion more common than oral lesions Urticarial rash on the face and limbs followed by dermatitis. OTHER SYMPTOMS: Itching Rashes Sneezing Difficulty in breathing Swelling

119. DELAYED HYPERSENSITVITY REACTIONS Contact Dermatitis or Coomb’s Type IV hypersensitivity Erosive lesion on the tongue or buccal mucosa adjacent to amalgam restorations Causes eczematous reaction on skin and mucosa A long term response in the form of erosive lichen planus or lichenoid reaction

120. Mercury toxicity TOXIC EFFECTS OF MERCURY DEPENDS ON Amount of exposure Length of exposure Length of mercury accumulation in body Amount of mercury accumulated Overall health of patient (detoxification)

121. 1. Elemental Mercury vapor (Hg), a stable monoatomic gas Dental amalgams (inhaled and absorbed into lungs) 2. Inorganic Divalent mercury (Hg2+) 2 forms : Mercuric and Mercurous Least Toxic (inhaled into lungs) 3. Organic Methyl mercury (CH3Hg+) Ethyl mercury (CH3CH3Hg+) Most Toxic Fish, sea mammals (absorbed into the gut) CHEMICAL FORMS OF MERCURY

122. CONCENTRATIONS OF MERCURY The Occupational Safety and Health Administration (OSHA) has set a Threshold Limit Value of 0.05 mg/m3 as the maximum amount of mercury vapour allowed in the workplace It has been estimated that a patient with 9 amalgam occlusal surfaces will inhale daily only about 1% of the amount the Occupational Safety and Health Administration (OSHA) allows to be inhaled in the workplace. Lowest dose of mercury that elicits a toxic reaction – 3 to 7 µg/kg body weight Paresthesia – 500 µg/kg body weight Ataxia – 1000 µg/kg body weight Joint pain – 2000 µg/kg body weight Hearing loss and death – 4000 µg/kg body weight

123. AMOUNT OF MERCURY RELEASED DURING MANIPULATION OF AMALGAM

124. 1.PRIOR TO USE: During storage of raw materials of dental amalgam 2.DURING USE: During trituration, insertion, condensation 3.POST USAGE: Amalgam scrap MERCURY EXPOSURE IN DENTAL OFFICE

125. 4.POST RESTORATION: Finishing and polishing, removal of old restoration 5. MERCURY SPILLS: Anytime during usage Jain Rimjhim et al. Mercury toxicity and its management. Int.Res J. Pharm 2016;4(8):38-41.

126. MERCURY HAZARDS IN DENTAL OFFICE

127. RESIDUAL MERCURY CONTENT Residual mercury refers to the amount of mercury present in the fully reacted alloy. Residual mercury levels are highest on the surface and margins of the restoration The ideal range of residual mercury is from 44-48% This concentration should not exceed 55% as this leads to Decrease in strength Decreased resistance to tarnish and corrosion Increased creep as the mercury converts gamma to gamma1 and gamma 2 phases Marginal breakdown Surface roughness

128. Factors that lead to increased residual mercury levels : Alloys that contain high mercury- alloy ratio (lathe cut alloys) Poor condensation Delay between trituration and condensation Effect of residual mercury content on Creep (Rupp - Paffenbarger -Patel: Effect of mercury content on creep in amalgams . JADA;2003) According to a study, silver-tin , spherical-particle alloys with low copper content had relatively low creep values when packed quickly. Creep and residual mercury content, however, increased when compaction was delayed. The effect was comparatively less with the amalgam made from Non-Zinc alloys.

129. Amalgams made with copper-rich alloys, also had relatively low creep values for the early compacted specimens In clinical practice, small amounts of amalgam should be mixed and used immediately after trituration. If the delay between trituration and compaction is longer than three minutes, additional mixes are required. Effect on compressive strength ( SWARTZ AND RALPH W. PHILLIPS. Residual mercury content of amalgam restorations and its influence on compressive strength. Journal of Dental Research) compressive strength of amalgam increased from 53,000 psi to approx 59,000 psi when the residual mercury fell from 48 to 35 per cent. However, they found no correlation between strength and residual mercury within limits of 45-50 per cent. The use of extremely high condensation pressures (256,000 psi) reduced the residual mercury to 28.3 per cent and the compressive strength rose to 73,000 psi

130. Although the average residual mercury content of the entire restoration may be less than 55% it is quite common to find certain areas which may exceed that figure. Certainly those areas of high mercury, and hence low strength, would be more vulnerable to fracture if subjected to stress. Care must be exerted in adhering to the recommended ratio and using adequate condensation pressure(13.3 and 17.8 N) and technic to minimize residual mercury and possible fracture.

131. CARVERS USED IN AMALGAM Discoid and Cleoid : large and small Hollenback carver Proximal carver (CVWI 8) Discoid and Cleoid Initially, Discoid and cleoid (discoid side) is used to remove excess amalgam from the occlusal surface. Use Discoid/ cleoid ( cleoid side) to develop a continuous (smooth) surface from the enamel to the restoration Occlusal carving is done with "pull stroke", however, the "push stroke" can also be suitable in developing occlusal anatomy (grooves) The first decision is to place the central groove. The central groove is found by continuing the central grooves of the teeth mesial and distal to the restoration. This is carved with the discoid end of a discoid- cleoid carving instrument

132. The next steps are to place the marginal grooves and the buccal and lingual grooves. These grooves are placed again with the discoid end of the discoid- cleoid carver in its proper position. Marginal fossae are formed by these grooves Using the cleoid end of the carver, place the tip in the central groove, orient the blade at approximately 45 degrees to the occlusal surface, and develop the shape of the occlusal surface The cleoid is placed in the proximal with the tip forming the marginal groove. The instrument is moved distally, forming a raised, rounded marginal ridge. The occlusal table can be refined and secondary anatomy applied if desired, using the cleoid or the half- Hollenback .

133. Using a half- Hollenback carving instrument , start to define and shape these grooves. Continue to carve the surface until all flash is removed from the cavo -surface margin. Place the Hollenback carver obliquely across the cavity margins with its tip resting against the adjacent tooth (matrix band) and its blade resting on the enamel adjacent to the proximal cavity margins. The proximal contour of the adjacent tooth is used as a guide to develop the restoration’s proximal contour Proximal carver (CVWI 8) is used mainly in difficult access areas

134. Other carvers include: WARDS CARVER : it is used for carving occlusal surfaces and for carving proximal surfaces in class II restoration FRAHMS CARVER : (diamond shaped)used for carving occlusal surfaces

135. FUNCTIONS OF BURNISHING Precarve Burnishing Form of condensation that ensures dense amalgam at the margins It is used to remove excess mercury Done by using heavy strokes with large burnishers moving from centre of restoration outwards beyond the margins Postcarve Burnishing This is done to adapt the material to the walls Promote sealing of amalgam at margins Provide smoothness and produce a shiny appearance Accomplished by light rubbing of carved surface with small ball burnishers

136. DIMENSIONAL CHANGES IN AMALGAM Stage 1 – initial contraction results from absorption of mercury into the interparticular spaces of the alloy powder Stage 2 –expansion due to growth of crystals. This expansion reaches a plateau phase with cessation of crystal formation Stage 3 – limited delayed contraction resulting from absorption of unreacted mercury Net result with modern amalgam is SMALL AMOUNT OF CONTRACTION of about 0.3 % by volume

137. Factors affecting dimensional changes of amalgam: Constituents : greater the gamma phase, greater will be the expansion. Greater traces of tin produces less expansion Mercury content – More mercury in the amalgam produces more prolonged stage of amalgamation. Hence, greater the mercury content, greater is expansion. Therefore, lathe cut alloys exhbit more expansion than spherical alloys Particle size – greater particle size result in marked contraction. Triturition – more the triturition energy, greater distribution of matrix over the mix, preventing outward growth of crystals. Furthermore, faster the amalgamation proceeds, so plateau phase occur before completely filling the cavity. This results in no expansion but limited contraction Condensation – More the energy used for condensing the amalgam, closer the original particles of the powder are brought together. Also, increased condensation squeezes mercury out of the mix. This leads to less formation of matrix crystals, therby contraction Particle shape – more regular the particles, faster and more effectively mercury can wet the alloy particles. This makes amalgamation process faster in all stages. Therefore, maximum expansion occurs before filling the cavity with no apparent expansion. Moisture contamination

138. MERCURY POISONING

139. Inhalation of mercury vapor causes : Chemical pneumonia Pulmonary edema Gingivostomatits Increased salivation CNS symptoms like: Ataxia Restriction of field of vision Delirium Polyneuropathy Bernhoft RA. Mercury toxicity and treatment: a review of the literature. Journal of environmental and public health. 2012

140. Ingestion of mercury causes: Acrid metallic taste in mouth. Feeling of constriction or choking of throat. Hoarseness of voice. Difficulty in breathing Hot burning pain in mouth, stomach and abdomen. Stools are blood stained , urine is suppressed and scanty, contain blood and albumin is accompanied by necrosis of renal tubules and damage to the glomeruli. Pulse is quick small and irregular Thrombocytopenia and bone marrow depression Houston MC. Role of mercury toxicity in hypertension, cardiovascular disease, and stroke. The journal of clinical hypertension. 2011 aug 1;13(8):621-7

141. Other conditions associated with mercury poisoning MINAMATA DISEASE PINK DISEASE HUNTER -RUSSELL SYNDROME ERETHISM

142. Mercury management ADA Council On Scientific Affairs. JADA, Vol. 134, Issue.11November 2003:1498-99. A Review of the ADA Mercury Hygiene Recommendations.Dentistry Today :January 2003. ADA recommendations No. 109 Train all personnel involved in the handling of mercury or dental amalgam regarding the potential hazard of mercury vapor and the necessity of observing good hygiene practices. Work in well-ventilated spaces, with fresh air exchanges and outside exhaust. If the spaces are air-conditioned, air-conditioning filters should be replaced periodically. Periodically check the dental operatory atmosphere for mercury vapour

143. Make personnel aware of the potential sources of mercury vapor in the operatory – that is, spills; open storage of used capsules; trituration of amalgam; placement, polishing or removal of amalgam; heating of amalgam-contaminated instruments; leaky capsules; and leaky bulk amalgam dispensers. Personnel also should be knowledgeable about the proper handling of amalgam waste and be aware of environmental issues. Some state dental societies have published waste management recommendations applicable to their state. Use proper work area design to facilitate spill contamination and cleanup . Flooring covering should be nonabsorbent , seamless and easy to clean Use only precapsulated alloys; discontinue the use of bulk mercury and bulk alloy

144. If possible, recap single-use capsules from precapsulated alloy after use. Properly dispose of them according to applicable waste disposal laws Use high-volume evacuation when finishing or removing amalgam. Evacuation systems should have traps or filters 9. Salvage and store all scrap amalgam (that is, noncontact amalgam remaining after a procedure) in a tightly closed container, either dry or under radiographic fixer solution

145. Use care in handling amalgam. Avoid skin contact with mercury or freshly mixed amalgam Use an amalgamator with a completely enclosed arm Where feasible, recycle amalgam scrap and waste amalgam. Otherwise, dispose of amalgam scrap and waste amalgam in accordance with applicable laws Dispose of mercury-contaminated items in sealed bags according to applicable regulations Clean up spilled mercury properly using trap bottles, tapes or freshly mixed amalgam to pick up droplets, or use commercial cleanup kits. Do not use a household vacuum cleaner. Remove professional clothing before leaving the workplace.

146. MANAGEMENT OF MERCURY SPILLS Never use a vacuum cleaner of any type to clean up the mercury. Never use household cleaning products to clean up the spill, particularly those containing ammonia or chlorine. Never pour mercury, or allow it to go, down the drain. Never use a broom or a paintbrush to clean up the mercury. Never allow people whose shoes may be contaminated with mercury to walk around or leave the spill area until the mercury-contaminated items have been removed.

147. MANAGEMENT OF SMALL MERCURY SPILLS A spill is considered small if there are less than 10 grams of mercury present (a pool no larger than the size of a quarter). Small spills can be cleaned safely using commercially available mercury cleanup kits. ADA Council On Scientific Affairs. JADA, Vol. 134, Issue.11November 2003:1498-99.

148. MANAGEMENT OF LARGE MERCURY SPILLS A mercury spill is considered large if there are more than 10 g of mercury present (a pool larger than the size of a quarter). Cleanup of large mercury spills requires the use of an experienced environmental contractor who specializes in toxic spill cleanup .

149. MANAGEMENT OF MERCURY VAPOUR RELEASE IN DENTAL OFFICE Storage of Mercury • Precapsulated alloys should be preferred for avoiding mercury spill • If bulk mercury is purchased, store it in tight container with tight lid in closed cabinets. • Location of storage should be near the window/exhaust vent.

150. Trituration of Amalgam Use precapsulated alloy in amalgamator Avoid manual mixing High vibrations during mixing can create aerosols of liquid droplets and these vapors may extend up to 6-12 ft from the amalgamator. So, to minimize the risk, small covers are used over the amalgamator to contain the aerosol in that area Air flow should be reasonably high in dental office to minimize air contamination

151. Designing of Office Office should be designed so as to reduce mercury contamination. Following points are to be kept in mind while designing: Proper ventilation of the dental office Avoid carpeting/floor coverings in dental office as there is no way of removing mercury from the carpet. Scrap amalgam on carpeted treatment-room floor (bur shown for scale). Over time, scrap and waste amalgam becomes imbedded in the carpet and breaks into smaller and smaller particles. Carpet scuffed by foot traffic or wheels on an operatory stool releases mercury vapor into the breathing zone of dental personnel. Vacuuming brings mercury vapor into the breathing zone of cleaning staff

152. Insertion and Condensation of Amalgam Use rubberdam to isolate the tooth. Use high volume evacuation system to control the mercury level in air. Polishing of Amalgam The mercury is tightly bound when amalgam is set. Polishing should be done with coolant to decrease heat and vapors present in atmosphere.

153. Disposal of Scrap Amalgam Scrap amalgam during insertion and condensation should be carefully collected and stored under water, glycerin or spent X-ray fixer solution in tightly capped jar Spent X ray fixer is preferred for storage of amalgam scrap because it is a source of both silver and sulfide ions which react with mercury present in scrap amalgam to form solid product and decrease the mercury vapor pressure.

154. Disposal of Mercury Contaminated Waste Disposal of spent capsules, mercury contaminated cotton rolls and paper napkins should be done properly. These items should be disposed in tightly closed plastic container/plastic bag which can be placed into sanitary landfill for disposal. Removal of Old Amalgam Restorations Rubberdam and high volume evacuator should be used to decrease mercury vapor. Watercooling should also be used as high rotary instruments used without water, increase the temperature of filling and increase the mercury vapors in that area.

155. Cleaning of Mercury Contaminated Instruments Clean the mercury contaminated instrument used during insertion, finishing and polishing and during removal of restoration as amalgam material left on the instrument surface, heated during sterilization can release mercury vapor in atmosphere. Isolation of the area along with proper ventilation of sterilization area is preferred.

156. Monitoring of Mercury Vapors The accepted threshold limit for exposure to mercury vapor for a 40-hour work per week is 50 μg /m3 (given by OSHA). Periodical monitoring of mercury vapor in dental office should be done and carefully recorded.

157. Methods to detect mecury vapour release Mercury thermometer Jerome mercury vapours detectives Gold film mercury vapour detectives Twin cell photo acoustic mercury detector Atomic absorption mercury detector Scanning electron microscopy (SEM) and Energy dispensive X-ray analysis (EDXA) of sections teeth with amalgams Perkins Elmer flow infection mercury system

158. GOLD FILM MERCURY VAPOUR DETECTIVES PHOTOACOUSTIC SPECTROSCOPY PHOTOIONIZATION DETECTORS C OLD VAPOUR MERCURY ANALYSIS DOSIMETER

159. SAFE MERCURY AMALGAM REMOVAL TECHNIQUE (SMART) Recommendations given by the International Academy of Oral Medicine and Toxicology (IAOMT): An amalgam separator should be properly installed, utilized and maintained to collect mercury amalgam waste Protective gowns and covers Face shields and hair/head coverings Proper handling, cleaning and/or disposal of mercury contaminated components, equipment, surfaces of the room and flooring in the dental office.

160. controversies AMALGAM WARS First Amalgam War – 1845 – American Society of Dental Surgeons They condemned the use of all filling material other than gold as toxic They further requested members to sign a pledge refusing the use of amalgam Second Amalgam War – 1920 – Dr Alfred Stock He claimed to have evidence showing mercury absorbed from dental amalgam leads to serious health problems He also expressed concerns over health of dentists, stating that nearly all dentists had excess mercury in their urine

161. Third Amalgam War – 1980 – Dr Huggins He convinced that mercury released from dental amalgam was responsible for human diseases affecting cardiovascular and nervous system Also stated that patients claimed recoveries from multiple sclerosis, alzheimers disease and other diseases as a result of removing their dental amalgam fillings But ADA remained adamant that mercury in patients mouth is safe and in 1986 it changed its code of ethics, making it unethical for a dentist to recommend the removal of amalgam filling because of mercury

162. CURRENT STATUS OF AMALGAM WAR Amalgam war continues to rage on today The problem is so serious that American Council of Health and 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 (HR 4163) to ban the continued use of amalgam fillings

163. “ No controlled studies have been published demonstrating systemic adverse effects from amalgam restorations” FDI & WHO 1997 “There is no significant association of Alzheimers disease with the number, surface area or history of having dental amalgam restorations” ADA 1999 “ Based on available scientific information, amalgam continues to be safe and effective restorative material” “There currently appears to be no justification for discontinuing the use of dental amalgam” ADA 1998 STATEMENTS ON DENTAL AMALGAM

164. “The current data are insufficient to support a correlation or causal relationship between exposure to dental amalgam and kidney or cognitive dysfunction, neurodegenerative or adverse pregnancy outcomes.” LSRO (NIH) Report 2004 “No statistical difference in adverse neuropsychological or renal effects in 5 year period in children whose caries were restored with amalgam or composite” JAMA and Environmental Health Perspectives, 2006 “Dental amalgam are effective and safe for both patients and dental personnels and also noted that alternative materials are not without clinical limitations and toxological hazards” Scientific Committee of European Commission, 2008

165. “ Absence of evidence suggesting that exposure of mercury vapour from dental fillings is associated with adverse health effects in population ages six and older” FDA 2009 “ Amalgam is valuable, viable and safe choice for dental patients” ADA 2009 “ Available information does not support the claim that mercury vapour released from dental amalgam is unsafe and results in adverse health effects” 2015 FDA response to citizen petitions

166. MERCURY PHASE OUT There is a global effort spearheaded by the United Nations Environment Programme (UNEP) to reduce mercury usage By the end of 2011 , United Nations Environment Program (UNEP)’s Intergovernmental Negotiating Committee formalized a global, legally-binding treaty named “Minamata Convention on Mercury” to protect human health and environment from the adverse effects of mercury. Thus a proposal for “phase -down” of dental amalgam was supported.

167. The requirements of this Convention includes minimizing the usage of amalgam, promotion of alternatives, and development of mercury free alternatives In 2012 , United Nations adopted a legislation at the Minamata Convention against mercury pollution. The legislation will phase out the use of mercury in dental amalgam by 2030. The Convention now has over 105 parties and 128 signatories ADA, FDI, International Association of Dental Research and WHO as leading authorities on the oral health of public demands reduction of amalgam in order to safeguard public health

168. But at the third meeting of Conference of the parties(COP3) to the Minamata Convention on Mercury in November 2019 held at Geneva, Switzerland, six African countries proposed to amend phase out of Dental amalgam which triggered debate. The proposed amendment sought to phase out amalgam in deciduous teeth, children under 15yrs, pregnant women and breastfeeding women by 2021, and ending all amalgam use by 2024 only when mercury free alternatives are available. COP3 delegates rejected the proposal and agreed to accelerate the phase down of dental amalgam During this conference, delegates representing 113 parties renewed their commitment to “phasing out the use of products containing mercury and promote alternatives”

169. ADVANCES IN AMALGAM RECENT ADVANCES AND MODIFICATIONS OF DENTAL RESTORATIVE MATERIALS - A REVIEW International Journal of Recent Advances in Multidisciplinary Research. 2016 Resin coated amalgam Consolidated silver alloy system Fluoridated amalgam Gallium based alloys Indium based alloy Bonded amalgams Glass cermet

170. 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.

171. Consolidated silver alloy systems 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. Disadvantage:- Difficult to compact it adequately to eliminate internal voids and to achieve good adaptation to the cavity without using excessive force

172. Fluoridated amalgam Fluoride, being cariostatic, has been included in amalgam to deal with the problem of recurrent caries associated with amalgam restorations. Fluoride containing amalgam may release fluoride for several weeks after insertion of the material in mouth. An increase of up to 10-20-fold in the fluoride content of whole saliva could be measured during the first week. 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 plaque and 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"

173. Gallium based alloys Gallium is used as a substitute for mercury in mercury free amalgam Ag3Sn + Ga = Ag3Ga + Sn Advantages: Rapid solidification Adapts well to the cavity walls Good marginal seal by expanding on solidification Heat resistant Strength increases with time Creep value is as low as 0.09% Sets early so polishing can be carried out the same day Toxicity was minimal

174. Disadvantages: Alloy tends to adhere to the walls of capsule. By adding few drops of alcohol, sticking can be minimized Cleaning of instrument tips difficult. Teflon coated instruments can be used. Increased chances of corrosion Increased expansion may cause fracture or postoperative sensitivity Costly Surface roughness, marginal discoloration and fracture reported Could not be used in larger restorations

175. Indium based alloys/ Mercury indium liquid alloy Introduced by POWELL He added pure indium powder with high copper alloy and triturated with mercury A significant decrease in mercury evaporation was seen due to the formation of indium oxide and tin oxide This was marked as Indisperse and Indiloy Youdelis found that less mercury is need for mixing amalgam when 10% indium is added They also exhibited low creep and increase in strength Less cytotoxic than amalgam

176. Bonded Amalgams Introduced by BALWIN The provision for adequate resistance and retention form for amalgams may require removal of healthy tooth structure. Further, 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. After cavity preparation, enamel and dentin etched with a conventional etchant, then a chemically cured bonding agent applied o the walls of the cavity. Amalgam is immediately condensed into the cavity before the resin bond has cured 4-META is used for bonding amalgam to cavity walls

177. Advantages: Treatment option for extensive carious lesions with low cost than either cast metal or metal ceramic crowns It allows use of amalgam in teeth with low gingivo – occlusal height Permits more conservative preparation Reduced marginal leakage Less postoperative sensitivity Reinforces tooth structure weakened by caries and cavity preparation Reduced incidence of marginal fracture Reduced incidence of recurrent caries Allows biological sealing of pulpodentinal complex

178. Disadvantages: Increased time May be technique sensitive Increased cost Requires practitioners to adapt to a new technique

179. Microleakage of bonded amalgam restorations using different adhesive agents with dye under vacuum : an invitro study Indian Journal of Dental Research, 2011 Bonded amalgam with type 1 GIC is a better alternative to amalgam with resin cement and amalgam with varnish for larger restorations. GIC Type 1 under amalgam allows chemical bonding between amalgam and tooth structure Thus reduced microleakage A systematic review of amalgam bonded restorations : Invitro and Clinical findings. The Journal of Contemporary Dental Practice, 2018 Bonded amalgam restorations reduced the need for mechanical retention thus conserving tooth structure and reducing adverse effects of microleakage. Bonded amalgam can be considered as the material of choice for large restorations

180. GLASS CERMET Also called Cermet ionomer cements Introduced by McClean and Gasser It involves fusing the glass powder to silver particles through sintering that can be made to react with polyacid to form the cement Properties: Both tensile and compressive strength is greater than conventional glass ionomer cement Abrasion resistance is greater Radiopacity equal to amalgam Fluoride release is about 3350 µg in 2 weeks and about 4040 µg in 1 month

181. Here, an experimentation was done which involved discarding the mercury content of amalgam and replacing with proprietary antimicrobial silver solution and unsialinized titanium dioxide ceramic nanoparticles for strength, with a favourable easy to manipulate consistency Prepared maxillary premolar controls were filled with Permite amalgam and compared to experimental groups filled with novel material. Both groups were thermocycled , cross sectioned and studied through SEM

182. Results: I t was concluded that addition of 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 alloy

183. 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 Amalgam is safe and can be used if mercury hygiene recommendations are properly followed in order to get minimal mercury vapor exposure. Although small amounts of mercury release from amalgam is known to occur, it does not cause any major health problems. However it might cause allergic reactions in some patients

184. Despite the long history and popularity of dental amalgam as a restorative material, its use has been reducing in clinical practice due to the esthetic requirements of the patients. Although there are other alternatives to amalgam, amalgams cost, durability and ease of manipulation have persuaded many dentist to continue its use as their first choice for restoring posterior teeth. 32%

185. references Kenneth J Anusavice . PHILLIPS’ Science Of Dental Materials, Eleventh Edition Sturdevant’s Art & Science Of Operative Dentistry, Seventh Edition Robert G. Craig & John M. Powers. Science of Dental Materials, Eleventh Edition M.A. Marzouk et al. Operative dentistry Modern Theory & Practice James B. Summitt , Fundamentals Of Operative Dentistry, Second Edition Vimal K Sikri. “Silver Amalgam” Textbook of operative dentistry. CBS Publishers, 1 st edition John F McCabe, Angus W.G Walls. “Dental Amalgam”, Applied Dental materials, 8 th edition, 1998