Amalgam

Dental Amalgam

1. DENTAL AMALGAM Guided by – Dr. Vivek Hegde Presented by – Hussain Mookhtiar 1 st year Post-graduate

2. Contents Introduction History Definitions Classifications Indication and contraindication Alloy composition Amalgamation Reactions Technical consideration

3. Clinical consideration Advantages & disadvantages. Limitations Failure Mercury toxicity Alternatives to amalgam Conclusion.

4. Introduction Ag Sn Cu Zn The word AMALGAM is of Greek origin Derived from MALAGMA , which means an emollient or poultice. ADA specification no of AMALGAM ALLOY is 1 which includes the requirement of its composition.

5. HISTORY Su Kung (659 AD) mentioned silver-mercury paste in the Chinese materia medica . 1578-Li Shitichen used 100parts of Hg, 45parts of Ag & 100 parts of Sn 1819 - Charles Bell a chemist (England) produced silver amalgam ( spanish & mexican coin filings + mercury) & distributed as Bell’s cement & later known as “ mineral succedaneum ”(replacement mineral).

6. The 1 st “Amalgam War”: 1833 – Frenchmen known as the Crawcour brothers came to USA. They advertised silver amalgam as ‘ Royal Mineral Succedaneum ’ hoping to add a greater esteem to the material by adding the prefix ‘royal’. However they did not make any attempt to remove the caries from the teeth they were filling. They advertised in the newspapers that they could fill teeth in about two minutes without the slightest pain inconvenience or pressure. They made a fortune with their new amalgam.

7. The Organisation of that time, represented by the newly formed American Society of Dental Surgeons began a campaign against the use of amalgam and this drive soon assumed the tone of a religious crusade. Members of the ASDS were required to sign a pledge. Those who refused to sign were summararily expelled. However, soon a number of highly reputed dentists, found in amalgam the answer to many of the problems faced with gold. Thus they used it to treat the poor who could not afford gold and also to compete with the quacks who were using amalgam widely. As a consequence, so many dentists refused to sign the pledge that by 1850 ,the ASDS was forced to remove it.

8. 1895 – Chicago’s prominent teacher of dentistry, the great G.V Black, using instruments of his own design to measure hardness and flow, hit upon a mixture of metals which has remained essentially unchanged Ag-68.5% Sn-25.5% Cu-5% Zn-1%.

9. The 2 nd Amalgam War: 1920 - second amalgam war by Alfred Stock of Germany who published “The Dangers of Mercury Fumes”. 1928 - Putt Kamer suggested Gallium alloy as substitute for Hg 1930 - ADA specification no.1 for amalgam alloy

10. The 3 rd Amalgam War 1980 - Hal Huggins publically condemned use of amalgam as he promoted the theory that amalgam restoration cause wide variety of diseases like multiple sclerosis, depression, high low blood pressure, tachycardia, arthritis, lupus, scleroderma, leukemia, Crohns disease, ulcers and other digestive problems Thus the third amalgam war.

11. Definition An amalgam is an alloy that contains mercury as one of it’s constituents (Phillips’ science of dental materials- 11 th edition) Dental amalgam is a metal like restorative material composed of a mixture of silver-tin-copper alloy & mercury ( Sturdevant-5 th Edition)

12. Classification Sturdevant Acc. to particle shape A) Spherical B) Irregular C) Combined Acc. to particle size A) Micro cut B) Fine cut C) Coarse cut Acc. to copper content A) Low copper alloy B) High copper alloy Acc. to zinc content A) Zinc alloys B) Non-zinc alloys

13. Marzouk Acc. to the no. of alloyed metals A) Binary alloys (eg: silver-tin) B) Ternary alloys (eg: silver-tin-copper) C) Quaternary alloys (eg: silver-tin-copper-indium) Acc. to whether the powder consists of unmixed or admixed alloys A) Made of one alloy B) One or more alloys

14. Clinical indications Moderate to large class I & class II restorations Class V restorations -non esthetic non isolated on the root surface Temporary caries control restorations Retrograde root canal filling

15. Contraindications In more prominent esthetic areas of the mouth Small to moderate class I & class II restorations ( well isolated ) Small class VI restorations

16. Alloy composition - ADA specification no.1 requires that amalgam alloy predominantly contain Ag & Sn.

17. ALLOY PARTICLE SHAPE Ag Sn Cu Zn 1)Low Cu lathe cut 63-70% 26-28% 2-5% 0-1% 2)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%

18. Constituents of amalgam alloy & functions of each ingredient Silver:- - Increases strength, expansion -Decreases flow, setting time -Resists tarnish & corrosion Tin :- - Decreases strength , expansion - Increases flow - Greater affinity for Hg

19. Copper:- - Hardens & strengthens Ag-Sn alloy -Decreases flow -Increases setting expansion Zinc:- -Acts as a deoxidiser Platinum -Hardens the alloy -Increases corrosion resistance Palladium -Hardens & whitens the alloy

20. Mercury:- -The preamalgamation produces a more rapid reaction Indium :- -Improvement in plasticity & compressive strength -Slow setting -Good anti-bacterial activity

21. Amalgamation Reaction

22. Low copper Alloys : - Reaction : - AgSn ( β + γ ) + Hg = γ 1 + γ 2 + AgSn (unreacted) High copper amalgams Setting Reaction: AgSn ( β + γ ) + Ag-Cu eutectic + Hg = γ 1 (Ag 2 Hg 3 )+ γ 2 (Sn 8 Hg)+ AgSn (unreacted) γ 2 (Sn 8 Hg) +Ag-Cu eutectic = Cu 6 Sn 5 ( η )+ Ag 2 Hg 3 ( γ 1 ) b) Single composition Setting reaction Ag-Sn-Cu + Hg = γ 1 + η +unconsumed Ag-Sn-Cu

23. Microstructure of set amalgam :

24. Microstructure of set amalgam :

25. SEM of high copper single composition amalgam fractured shortly after condensation, showing reaction products being formed A- ɣ ,B- ɳ , C- ɳ rods embedded in ɣ

26. TECHNICAL CONSIDERATIONS

27. Proportioning : -  There are different ways of proportioning: Weighing and triturating: 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.

28. DISPENSING : - Precapsulated Amalgam : Some alloys are now available in self-activating capsules, which automatically release the mercury into the alloy chamber during the first few oscillations of the amalgamator. Mechanism of action : mercury and powder seperated by septum that must be perforated before mixing . Fig: Schematic representation of preproportioned capsule

29. Eames technique(1959) : The method for reducing the mercury content of the restoration  reduce the original mercury / alloy ratio. The present day alloys are designated for manipulation with reduced mercury / alloy ratios just enough to get a coherent plastic mass. Also known as the 1:1 or minimal mercury technique Mercury content of the finished restoration to original mercury / alloy ratio, usually about 50 wt % With lesser amounts (~42 wt %) being used with spherical alloys.

30. TRITURATION : - It is the process of mixing the amalgam alloy particles with mercury. Originally the alloy and mercury were triturated, by hand with a mortar and pestle Today mechanical amalgamation saves time and standardizes the procedure. Objectives of the trituration : - To achieve a workable mass To remove oxides To pulverize pellets into particles To increase the surface area by reducing particle size. To dissolve the particles in mercury

31. There are two methods of trituration:- Hand Trituration Mechanical trituration

32. Hand Trituration Glass mortar of parabolic shape, a pestle is used. The fist grip is used. Mixing Time  30-40sec Force  800-900 gm Mixed mass should be: homogeneous, smooth, should not stick to walls of mortar and pestle should form a lump.

33. Mechanical trituration: - The alloy & mercury are dispensed into the capsule & when this is secured in the machine, it is turned on & the arms holding the capsule oscillate at high speed to accomplish trituration.

34. Consistency of the mix : Normal mix Under Trituration Over Trituration

35. Mulling : Mulling is a continuation of trituration. It can be accomplished in two ways; - 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.

36. Condensation Condensation is 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 matrix phase. (Phillips’ science of dental materials- 11 th edition) The force in the range of 13.3-17.8N (3-4 lbs) represent the average force employed for condensation.

37. Goals of condensation:- Compact the alloy  greatest possible density is attained with sufficient mercury present to ensure  complete continuity of the matrix phase (Ag2Hg3) between the remaining alloy particles. To remove any excess mercury from each increment as it is worked to the top by the condensing procedure. Field of operation should be kept absolutely dry  incorporation of the slightest moisture in a zinc containing amalgam  delayed expansion  corrosion, loss of strength and ultimately premature failure of the restoration.

38. The initial condenser should be small enough to condense into the line angles but large enough not to poke holes into the amalgam mass. When the first portion has been condensed, the successive portions of the divided amalgam are added after first squeezing the excess mercury away. It is noted that successive portions require more force to squeeze away mercury. This is because more free mercury is reacting with the alloy particles.

39. Condensation is usually started at the center and then the condenser point is stepped little by little towards the cavity walls. After condensation of an increment, the surface should be shiny in appearance. Indicating  that there is sufficient mercury present at the surface to diffuse into the next increment so that each increment, as it is added, bonds to the preceding one.

40. This is done until the cavity is overfilled by around 1mm.Any mercury rich material at the surface of the last increment is removed when the restoration is carved. If the cavity is larger and extra time is required for condensation, another mix should be made just before the original one loses its plasticity.

41. Burnishing It is a process of rubbing usually performed to make a surface shiny and lustrous It is an adjunct to condensation as it further adapts and compacts the amalgam mass along the walls of the cavity. The objectives of burnishing are : ( Marzouk ) It further reduces the size and number of voids on the critical surface and marginal areas of the amalgam. 2. It brings any excess mercury to the surface,to be discarded during carving. 3. It will adapt the amalgam further to cavosurface anatomy. 4. It conditions the surface amalgam to the carving step.

42. Precarve burnishing After condensing with amalgam condensers, the amalgam maybe further condensed and shaping of the occlusal anatomy is done 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.

43. CARVING Carving is the anatomical sculpturing of the amalgam material. Objectives- - To produce a restoration with no undercuts -To produce a restoration with the proper physiological contours.

44. Amalgam Carving Sequence : A:Removing overfilled occlusal amlagam with large discoid instrument B:Establishing outer incline of marginal ridge with Ward’s C carver

45. C: cervicle overhang is carved with ward’s C carver using adjacent tooth as guideline D: maintaining the anatomic line angle while carving the buccal margin of an extended proximal box

46. E:all overextensions and margins are removed by carving F:developmental grooves are enhanced with anatomical burnisher following carving

47. FINISHING AND POLISHING The objective is to remove superficial scratches, pits & irregularities. This in turn minimizes corrosion & prevents adherence of plaque. The final finishing should be delayed for at least 24 hrs after condensation.

48. Post Carve Burnishing After carving to burnish the surface and margins of the restoration lightly to produce a smooth and satin appearance. Burnishing of the occlusal anatomy can be accomplished with a ball burnisher . One should not rub the surface hard enough to produce grooves on the restoration. Final smoothening can be concluded by rubbing the surface with a moist cotton pellet or by lightly smoothing the surface with a rubber polishing cup and an extremely fine polishing or prophylaxis paste.

49. CLINICAL CONSIDERATIONS

50. Microleakage : Dental amalgam has tendency to minimize marginal leakage due to the corrosion products that forms in the interface between the tooth and the restoration which seals the interface and there by prevents leakage

51. Dimensional Change:- ADA specification No.1 requires that amalgam neither contract nor expand more than 20  m/cm measured at 37°C, between 5 minute and 24 hours after the beginning of trituration.

52. Effect of moisture contamination: Delayed expansion is associated with zinc in the amalgam. It has been demonstrated that the contaminating substance is water. H 2 O+Zn = ZnO+H 2 The contamination can occur at trituration and condensation

53. hydrogen does not combine with the amalgam but collects within the restoration increasing the internal pressure to levels high enough to cause the amalgam to creep producing the observed expansion contamination of the amalgam can occur at almost any time during its manipulation and insertion into the cavity.

54. Strength: Amalgam has high compressive strength & low tensile strength Compressive strength- 310 MPa Tensile strengths- 48 MPa (Low copper) 70 MPa (high copper)

55. Compressive strength 1 HOUR 7 DAYS LOW COPPER 145MPa 343MPa ADMIXED 137MPa 431MPa SINGLE COMPOSITION 262MPa 510MPa

56. Tensile strength -24hr Low copper 60 MPa Admix 48 MPa Single composition 64 MPa

57. Creep :- Time dependant plastic deformation is called as creep Creep rate is co–related with marginal breakdown of traditional low copper amalgam.

58. According to A.D.A specification no. 1 selection of amalgam alloys should be such that the creep rate is below 3%. Creep Values:- Low copper amalgam - 0.8 to 8.0% High copper amalgam - 0.4 to 0.1% Influence of microstructure on creep :– Large gamma1 volume fractions-increases creep L arge gamma1 grain size-decreases creep

59. TARNISH AND CORROSION:- Tarnish is a surface discoloration of on a metal, or as a slight loss or alteration of the surface finish or luster. Corrosion is a process in which deterioration of a metal is caused by reaction with its environment. (Phillips’ science of dental materials- 11 th edition)

60. The space between the alloy and the tooth allows the microleakage of electrolytes and a classic concentration cell (crevice corrosion) process results. The build up of corrosion products gradually seals this space, making dental amalgam a self sealing restoration. The most common corrosion products found with traditional amalgam alloys & high copper amalgams are oxides and chlorides of tin . Corrosion products containing copper can also be found in high copper amalgams (corrosion process is more limited because the η phase is less susceptible to corrosion) Every effort should be made to produce a smooth, homogeneous surface on a restoration to minimize tarnish and corrosion.

61. Corrosion can lead to: Reduced strength Marginal degradation Dimensional changes Increased internal porosities and surface roughness Discoloration

62. Sites Susceptible To Electrochemical And Chemical Corrosion On Amalgam

63. ADVANTAGES Excellent wear resistance Lower cost Ease of use Sealing ability improves Relatively not technique sensitive Bonded amalgams have bonding effects

64. DISADVANTAGES: Non insulating Non esthetic Less conservative Weakens the tooth structure More technique sensitive if bonded & more difficult tooth preparation

65. LIMITATIONS POOR ESTHETICS - polished finish lost with time, due to tarnishing. MERCURY TOXICITY Main sources of mercury exposure arise from: -Accidental spills -Poor mercury hygiene -Direct contact with mercury -Removing old restorations

66. HIGH THERMAL CONDUCTIVITY - Amalgam has very high thermal conductivity. These are dealt with by involving the use of varnishes or liners . GALVANIC EFFECTS - causes patient discomfort -leaves strong metallic taste in mouth - accelerate electro-corrosive breakdown of more electronegative material

67. LACK OF ADHESION Because of this need for retentive cavity designs imposes often removal of large amount of sound tooth structure.

68. Mercury toxicity For the diagnosis of mercury exposure maximum allowable level of mercury- Blood Hg – 1.5  0.5  g/L Urine Hg – 1.6  0.9  g/L Saliva Hg – 41  35  g/L (range 5 – 450 Mg/L)

69. A daily intake of mercury in individuals with amalgam fillings is 8-30 g /day has been estimated & a provisional tolerable weekly intake is 300  g Hg. Threshold limit value (TLV) for exposure to mercury vapour for a 40-hour work in a week is 50 µ g/m 3.

70. Mercury poisoning from amalgam fillings Patient’s signs and symptoms: Concentration disturbances Memory disturbances Headache Arthritic pain Muscular pain and weakness Skin and mucosal changes Stomatitis tendency to cry

71. CLASSIFICATION OF MATERIALS USED AS ALTERNATIVES TO AMALGAM; A. Metallic alternatives; Gallium alloy Direct filling silver Direct gold restorations Cast metal restorations

72. B. Non metallic amalgam alternatives; 1. Composite resins 2. Ceramic 3. Glass lonomer cements a) Metallic inclusions b) Resin modified glass ionomer c) Highly viscous glass ionomer

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

74. References :- Anusavice : Phillips’ science of dental materials- 11 th edition. Eames WB: Preparation and condensation of amalgam with a low mercury/alloy ratio. J Am Dent Assoc 58:78, 1959. Federation Dentaire Internationale , Technical Report 33: Safety of dental amalgam. Int Dent 39:217, 1989. Leinfelder KF: Clinical evaluation of High-copper amalgam. Gen Dent March-April, 1983, p 105. Mahler DB, Adey JD, and Marek M: Creep and corrosion of amalgam. J Dent Res 61:33, 1982. Marshall GW, Marshall SJ, Letzel H: Mercury content of amalgam restorations. Gen Dent, Nov-Dec, 1989, p-473. Mitchell RJ and Okabe T: Setting reactions in dental amalgam. Crit Rev Biol Med7:12-22,1996. Mjor IA: The safe and effective use of dental amalgam. Int Dent J 37:147, 1987. Schoonover JC, and Souder W: Corrosion of dental alloys.J Am Dent Assoc 28:1278, 1941. Sturdevant’s – Art and science of operative dentistry- 5 th Edition.

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