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DENTAL 
AMALGAM
CONTENTS 
1. HISTORICAL BACKGROUND 
2. DEFINITIONS 
3. INDICATIONS 
4. CONTRAINDICATIONS 
5. ADVANTAGES 
6. DISADVANTAGES ...
ALLOY MANUFACTURING 
1. LATHE-CUT ALLOY POWDER 
Main Constituent Metals (Ag, Sn, Cu & Zn) 
melted & 
subjected to 
Homogen...
2. ATOMIZED POWDER (SPHERICAL ALLOY) : 
Molten alloy is forced under inert gas through fine crack in the 
crucible in to t...
PHASES OF AMALGAM 
PHASES FORMULA HARDNESS (VHN) 
1. r Ag3 Sn 250 – 270 
2. r1 Ag2 Hg3 App. 120 
3. r2 Sn7-8 Hg App. 15 
4...
KINETICS OF AMALGAMATION 
• LOW COPPER ALLOYS : 
When Powder (Ag3 Sn) is triturated with 
mercury, 2 processes occur: 
1.A...
• Simplified as: 
r( Ag3 Sn) +Hg r1(Ag2 Hg3) + r2 (Sn7-8 Hg) + r (Ag3 Sn) 
Unreacted
• HIGH COPPER ALLOYS: 
1. ADMIXED ALLOY: 
In 1963,Innes & Youdelis added spherical Ag-Cu 
eutectic alloy (71.9 wt% Ag & 28...
2. SINGLE COMPOSITON ALLOY : 
• First alloy of this type contained of 60 wt% Ag, 27 wt% Sn 
& 13 wt% Cu 
• Total Cu conten...
MANIPULATION FACTORS 
• CHOICE OF ALLOY 
• CHOICE OF MECURY 
• PROPORTIONING OF Hg to Alloy 
• TRITURATION & METHODS 
• IN...
CHOICE OF ALLOY 
• The factors to be considered are: 
1. Alloy composition 
2. Particle shape 
3. Particle size 
4. Speed ...
ALLOYCOMPOSITION 
• The generally accepted specifications for amalgam alloy require the 
composition of the constituent me...
PARTICLE SHAPE 
• The disadvantage of lathe-cut particles is that, although they are 
similar in size as a result of sievi...
PARTICLE SIZE 
• The original particle size alters the character of the finished , carved 
& polished surface. 
• Smaller ...
SPEED OF SET 
• Setting time of an alloy is accelerated by increasing the Ag 
content. 
• Min. Content of Ag is 65% in ADA...
CHOICE OF MERCURY 
• The most recent British standard sp. for dental mercury is B.S.4227 
• Mercury complying with the req...
PROPORTIONING MECURY TO 
ALLOY 
• Philips and Swartz(1949) have shown that regardless of the amount 
squeezed away in the ...
• Eames etal (1961) recognized the advantage of a more plastic mix 
and advise when using a 1:1 ratio of Hg & alloy to ove...
Mechanical instruments 
have now been developed 
which will, in one appliance, 
dispense & triturate the alloy 
& Hg.
• The more common method of dispensing alloy & Hg is the 
Automatic release type of dispenser which proportions 
volumetri...
TRITURATION 
• The purpose of trituration is to bring the particles of alloy into contact with 
the mercury. 
• Prior to 1...
Mortar pestle method 
• Is the oldest method used. 
• Suggested by Dr.Marcus.L.Ward. 
• Here pestle is held in a pen grasp...
RUBBER THUMB-STALL METHOD: 
• In 1934, Mary Gayler advocated this method. 
• This technique has the advantage not destroyi...
Stages of trituration
UNDER TRITURATED 
OVER TRITURATED 
OVER TRITURATED 
TESTING OF MIX 
OVER TRITURATED
MULLING 
• Is a continuation of trituration. 
• Enhances uniformity, coherence & handling ease. 
• In the mortar & pestle ...
PRE-CARVE BURNISHING 
• Large egg shaped burnisher is used. 
• Advantages: 
1) Less Hg 
2) Porosity 
3) r2 phase
CARVING 
• To produce restoration with proper 
physiological & anatomical contour. 
• Use sharp instrument. 
• Don’t attem...
CARVING TECHNIQUE
REMOVAL OF MATRIX BAND
FINISHING & POLISHING 
• Finishing: process which continues the 
carving objectives, removes flash & 
overhang. 
• Polishi...
FINISHING 
• # 12-15 bladed steel burs (worn) 
• Rhein trimmers (gingival area) 
• # 12 BP bald or Blacks knives 
(interpr...
POLISHING 
• Polish all surfaces of restoration 
• Amalgam line (Mosteller” 57) 
• Fine sand paper discs (Buccal & lingual...
• Gingival excess of amalgam: 
1) E.V.A prophylaxis system with safe sided 
& safe edged diamond tip 
2) Ultra sonic scale...
PROPERTIES OF AMALGAM 
1)Dimensional changes 
Effect of moisture contamination 
Mercuroscopic expansion 
2)Strength 
3)C...
1) DIMENSIONAL CHANGES 
• Amalgam undergoes dimensional changes in 3 stages: 
Initial contraction 
Expansion 
Delayed cont...
• Factors affecting dimensional changes: 
1) Constituents 
2) Hg 
3) Particle size 
4) Trituration 
5) Condensation 
• Moi...
• Its clinical consideration: 
1) Protrusion of restoration out of cavity 
Unsupported margins 
# of restoration 
2) Incre...
MECUROSCOPIC EXPANSION 
• By Jorgensen 
• Results from when Hg released from corrosion 
of r2 phase reacts with remaining ...
2) STRENGTH 
• Amalgam has high compressive strength & low 
tensile strength
• The compressive strength of a satisfactory amalgam 
should be atleast 310MPa. 
• ADA SP. Stipulates a minimum compressiv...
CREEP 
• Is a time dependent plastic deformation of crystalline 
material under the influence of a static or dynamic 
stre...
TARNISH & CORROSION 
• Amalgam often tarnish &corrode in oral environment 
• Tendency towards tarnish is unaesthetic due t...
• THERMAL PROPERTY: 
-- GOOD CONDUCTOR OF HEAT 
-- Cf. Of thermal exp, is 3 times greater than 
dentin. 
-- If RDT is <2mm...
MECURY TOXICITY 
• FORMS OF Hg: 
 Organic & Inorganic 
 Most toxic organic forms are Methyl 
Hg & Ethyl Hg 
 Least toxi...
• Chronic exposure – assessed by urinary 
Hg concentration. 
Hg thermometer: 
Hg level 
1000 Pronounced symptoms 
500 Mi...
• Sources of Hg exposure – Dental office: 
Amalgam raw materials being stored 
in use 
During trituration, insertion & i...
Dental Hg hygiene recommendations 
• Train all personals regarding potential hazard of 
Hg vapor & make them aware of its ...
• AVOID skin contact with Hg / freshly mixed 
amalgam 
• USE high volume evacuation 
• Store all scrap amalgam in tightly ...
AMALGAM FAILURES 
• INCLUDE: 
Bulk restoration fracture 
Corrosion & excessive marginal # 
Sensitivity or pain 
Second...
CAUSED OF FAILURE 
• Grouped under 3 headings: 
Faults in cavity design 
- weakened tooth structure 
- sharp internal lin...
 Poor clinical techniques: 
- residual caries 
- poor matrix techniques 
- contamination 
- poor condensation 
- over & u...
RECENT ADVANCEMENT 
IN DENTAL AMALGAM
AMALGAM BONDING SYSTEM 
• Used to seal underlying tooth structure & 
bond the amalgam to enamel & dentin 
• 4-META based b...
Bonding systems used: 
• ALLBOND-2(Bisco) 
• Amalgam bond plus (parkell) 
• Panavia (Kuraray) 
• Scotch bond multi-purpose...
• Potential advantages: 
Improved retention 
Decreased micro leakage 
Improved resistance form 
Decreased post-operati...
GALLIUM BASED ALLOYS 
• Gallium has similar atomic structure and characteristics 
to Hg 
• They consist of Gallium(65%), I...
REFERENCES 
• SKINNER”S- Science of dental materials 
• Sturdevant”s Art & science of operative dentistry 
(4th edition) 
...
Dental amalgam
Dental amalgam
Dental amalgam
Dental amalgam
Dental amalgam
Dental amalgam
Dental amalgam
Dental amalgam
Dental amalgam
Dental amalgam
Dental amalgam
Dental amalgam
Dental amalgam
Dental amalgam
Dental amalgam
Dental amalgam
Dental amalgam
Dental amalgam
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Dental amalgam

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Dental amalgam

  1. 1. DENTAL AMALGAM
  2. 2. CONTENTS 1. HISTORICAL BACKGROUND 2. DEFINITIONS 3. INDICATIONS 4. CONTRAINDICATIONS 5. ADVANTAGES 6. DISADVANTAGES 7. COMPOSITION 8. CLASSIFICATIONS 9. ALLOY MANUFACTURING 10. PHASES OF AMALGAM 11. KINETICS OF AMALGAMATION 12. MANIPULATION FACTORS 13. PROPERTIES OF AMALGAM 14. MECURY TOXICITY 15. AMALGAM FAILURES 16. RECENT ADVANCEMENTS IN AMALGAM 17. ALTERNATIVES TO AMALGAM
  3. 3. ALLOY MANUFACTURING 1. LATHE-CUT ALLOY POWDER Main Constituent Metals (Ag, Sn, Cu & Zn) melted & subjected to Homogenizing Heat Treatment cooled slowly to form Ingot fed to Milling Machine / lathe to produce filings & further broken down by Ball milling Acid treatment Stress – Relief protocols (Annealing Cycle)
  4. 4. 2. ATOMIZED POWDER (SPHERICAL ALLOY) : Molten alloy is forced under inert gas through fine crack in the crucible in to the chamber. If the droplets solidify before hitting a surface, the spherical shape is preserved. Spherical alloy Acid treatment Heat treatment • Average Particle size of modern powder ranges from 15-35 micro meters.
  5. 5. PHASES OF AMALGAM PHASES FORMULA HARDNESS (VHN) 1. r Ag3 Sn 250 – 270 2. r1 Ag2 Hg3 App. 120 3. r2 Sn7-8 Hg App. 15 4. e Cu3 Sn ------ 5. n Cu6 Sn5 --------- 6. silver-copper Ag-Cu ------ eutectic
  6. 6. KINETICS OF AMALGAMATION • LOW COPPER ALLOYS : When Powder (Ag3 Sn) is triturated with mercury, 2 processes occur: 1.Ag & Sn in the outer portion of particles dissolve into Hg. 2. Hg diffuses into alloy particles. • Hg has a limited solubility of Ag (0.035wt%) & Sn (0.6wt%) • When the solubility in Hg is exceeded, 2 binary metallic compounds precipitate in to Hg. They are: 1. Body centered cubic Ag2 Hg3 (r1) phase 2. Hexagonal Sn7-8 Hg (r2) phase. • Later r1 & r2 crystals grow as the remaining Hg dissolves the alloy particles. As Hg disappears, amalgam hardens. • Alloy & Hg in about 1:1 ratio, there is insufficient Hg to completely consume original alloy particles. As a result unconsumed particles are present in the set amalgam (of about 27% of original r phase)
  7. 7. • Simplified as: r( Ag3 Sn) +Hg r1(Ag2 Hg3) + r2 (Sn7-8 Hg) + r (Ag3 Sn) Unreacted
  8. 8. • HIGH COPPER ALLOYS: 1. ADMIXED ALLOY: In 1963,Innes & Youdelis added spherical Ag-Cu eutectic alloy (71.9 wt% Ag & 28.1 wt% Cu) particles to lathe-cut low copper amalgam alloy. This has resulted in increased residual alloy particles & decreased matrix. • Total Cu content ranges from 9wt% - 20wt%. • When Hg reacts with Admixed powder : a) Ag from Ag-Cu particles dissolves Hg. b) Ag & Sn from Ag3 Sn dissolves Hg. c) Sn from Ag3 Sn diffuses Ag-Cu alloy particles and reacts with copper n-phase(Cu6Sn5) around unconsumed Ag-Cu. • Reaction is summarized as: Ag3 Sn +Ag-Cu eutectic +Hg  r1 + n (Cu6 Sn5) + unconsumed alloy particles. • Here r2 phase is eliminated.
  9. 9. 2. SINGLE COMPOSITON ALLOY : • First alloy of this type contained of 60 wt% Ag, 27 wt% Sn & 13 wt% Cu • Total Cu content ranges from 13- 30 wt%. • The alloy particle is composed of a very fine distribution of Ag3 Sn (r) and Cu3 Sn (e). • Simplified reaction with Hg: Ag3 Sn (r) + Cu3 Sn (e) + Hg  Cu6 Sn5(n) +Ag2 Hg3 (r1) • Here also r2 phase is eliminated.
  10. 10. MANIPULATION FACTORS • CHOICE OF ALLOY • CHOICE OF MECURY • PROPORTIONING OF Hg to Alloy • TRITURATION & METHODS • INSERTION OF AMALGAM 1. HAND CONDENSATION 2. MACHANICAL CONDENSATION • PRE-CARVE BURNISHING • CARVING • BURNISHING • FINISHING & POLISHING.
  11. 11. CHOICE OF ALLOY • The factors to be considered are: 1. Alloy composition 2. Particle shape 3. Particle size 4. Speed of set 5. Pre amalgamated or standard alloy 6. Zinc containing or zinc free alloy.
  12. 12. ALLOYCOMPOSITION • The generally accepted specifications for amalgam alloy require the composition of the constituent metals to be : 65% min. Ag 29% max. Sn 6% max. Cu 2% max. Zn • Use of disperse alloy has the advantage of its greater tarnish & corrosion resistance, improved compressive and edge strength with consequent reduction in marginal failure leading to ditching. • Jerman(1970) found that by adding 1.5% SnF to the alloy ,there was an increased fluoride content of the enamel adjacent to the restoration with an associated reduction in the enamel solubility. But there is no evidence that there is continuous leaching of fluoride from the set amalgam.
  13. 13. PARTICLE SHAPE • The disadvantage of lathe-cut particles is that, although they are similar in size as a result of sieving, they are not necessarily similar in shape. • Advantages of spherical particle: 1. Easier to produce 2. Less sensitive to manipulative variables Eg: Breaking up during trituration. 3. Superior 1-hr and final compressive strengths & tensile strengths. 4. Increased plasticity of the mix with mecury.
  14. 14. PARTICLE SIZE • The original particle size alters the character of the finished , carved & polished surface. • Smaller the particle size: 1) Higher the 1hr & 24hr strength 2) lesser the expansion 3) more easily adopted to the cavity walls 4) much less pitted, when carved 5) more easily polished. • Use of fine cut amalgam alloy particle is advocated.
  15. 15. SPEED OF SET • Setting time of an alloy is accelerated by increasing the Ag content. • Min. Content of Ag is 65% in ADA. SP. 1. Quick setting alloys (Ag— 66.7%-74.3%) 2. Slow setting alloys (Ag— 43-48%) • Advantages of fast setting alloy: a) reduces chair side time b) allow to fill approximal cavities at one appointment. • Disadvantage: Rapid crystallization limits removal of Hg from successive condensed portions of amalgam already in the cavity.
  16. 16. CHOICE OF MERCURY • The most recent British standard sp. for dental mercury is B.S.4227 • Mercury complying with the requirements of British &USA Pharmacopoeia or ADA sp.no.6 should be used. • Hg must contain <0.02% by mass, non-volatile residue & there must be no visible surface contamination. • It should have a mirror like surface. • Contaminated Hg by the metals amalgam alloy can only be purified by “Distillation procedures” • Tarnished Hg which comes out from wet mixes after trituration with amalgam alloy can be cleaned by : 1) Passing through pin pricked hole in filter-paper held in a glass filter funnel & allowed to drop in to a carefully cleaned glass dispenser. or 2)Through clean chamois skin to restore its previous brightness.
  17. 17. PROPORTIONING MECURY TO ALLOY • Philips and Swartz(1949) have shown that regardless of the amount squeezed away in the squeeze cloth or removed by condensation, the more the Hg used in the original mix the greater is the amount that will remain in the restoration. • Philips and Boyd(1947) have shown that as the Hg:alloy ratio is increased, the % of residual Hg also increases proportionally. For each additional 15% of Hg used in the original mix, there is an avg increase of 1-1.5% residual Hg. • The residual Hg content of the final restoration should be between 50-55%. • Traditionally Hg:alloy ratio were 7:5 & 8:5 by weight or even higher. • Eames (1959) has fathered the change from using increased Hg:Alloy ratio to using Hg:Alloy ratio of 1:1,which can only be triturated in a mechanical amalgamator. This technique also known as “NO SQUEEZE CLOTH TECHNIQUE” or “MINIMAL MERCURY TECHNIQUE”
  18. 18. • Eames etal (1961) recognized the advantage of a more plastic mix and advise when using a 1:1 ratio of Hg & alloy to over triturate slightly. • The problem then arises which is the best method of dispensing the correct proportions of Hg to alloy. • The Various methods of proportioning alloy & Hg are: 1)By weight eg: Crescent and Ash balances 2)By volume eg: Baker proportioner Amalganom S.S.White proportioner 3)Predispensed eg: S.S.White sigrens Amalcap capsules with mercury in cap Aristalloy tablets.
  19. 19. Mechanical instruments have now been developed which will, in one appliance, dispense & triturate the alloy & Hg.
  20. 20. • The more common method of dispensing alloy & Hg is the Automatic release type of dispenser which proportions volumetrically. • Ryge etal (1958) have analyzed the accuracy of 12 different methods of obtaining the desired proportions of alloy & Hg. According to them, the best method of obtaining an accurate Hg:alloy ratio was to use pre-dispensed alloy produced by manufacturer together with a good Hg volume dispenser. • Hg dispenser should be held vertically and not at 45o. It should be half filled.
  21. 21. TRITURATION • The purpose of trituration is to bring the particles of alloy into contact with the mercury. • Prior to 1940’s Amalgam was triturated by hand in a mortar & pestle. • Its objectives are : 1) to get workable mass in minimum time 2) to remove oxide layer from powder 3) to reduce particle size, increase surface area & thus increasing the rate of amalgamation 4) to keep the r1 & r2 crystals as minimum as possible yet bind the particles. • Methods of trituration are: 1)Mortar & pestle 2) Rubber thumb-stall 3) Mechanical amalgamation / Amalgamator.
  22. 22. Mortar pestle method • Is the oldest method used. • Suggested by Dr.Marcus.L.Ward. • Here pestle is held in a pen grasp with 2-3 pounds load and rapid convenient circular motion is used until a shiny, homogeneous mass is obtained. • WORK = PESTLE SPEED X PESTLE LOAD X TIME • Need 60-120s for trituration.
  23. 23. RUBBER THUMB-STALL METHOD: • In 1934, Mary Gayler advocated this method. • This technique has the advantage not destroying the original particle size, but a higher Hg : alloy ratio is used to obtain amalgamation in 1minute. MECHANICAL AMALGAMATION: • Types of motion: 1) Off-centre-centrifugal action 2) Reciprocating figure of “8”. • Advantages: 1) Trituration is achieved rapidly (20-25sec) 2) More standard mix can be obtained.
  24. 24. Stages of trituration
  25. 25. UNDER TRITURATED OVER TRITURATED OVER TRITURATED TESTING OF MIX OVER TRITURATED
  26. 26. MULLING • Is a continuation of trituration. • Enhances uniformity, coherence & handling ease. • In the mortar & pestle method due to continuous folding off the mass from the side of the mortar to the centre, a layered mass is developed. This is made more cohesive by hand mulling. Mix is kneeded in a piece of rubber dam or between finger & palm For 2-5sec.
  27. 27. PRE-CARVE BURNISHING • Large egg shaped burnisher is used. • Advantages: 1) Less Hg 2) Porosity 3) r2 phase
  28. 28. CARVING • To produce restoration with proper physiological & anatomical contour. • Use sharp instrument. • Don’t attempt to produce deep anatomical fissure (Mahler’ 58). • Marginal ridge – wide, round & carved to the level of adjacent marginal ridge • Use large spoon excavator - Gross occlusal carving.
  29. 29. CARVING TECHNIQUE
  30. 30. REMOVAL OF MATRIX BAND
  31. 31. FINISHING & POLISHING • Finishing: process which continues the carving objectives, removes flash & overhang. • Polishing: process which creates a corrosion resistant layer by removing scratches & irregularites from the surface. • Advantages.
  32. 32. FINISHING • # 12-15 bladed steel burs (worn) • Rhein trimmers (gingival area) • # 12 BP bald or Blacks knives (interproximal areas) • Fused Alumina white stone (marginal adoptation) • Water resistant strip (cervical areas) • Done usually after 24 hrs
  33. 33. POLISHING • Polish all surfaces of restoration • Amalgam line (Mosteller” 57) • Fine sand paper discs (Buccal & lingual embrasures of proximal surfaces) • Linen strips (Proximal surface below the contact area)
  34. 34. • Gingival excess of amalgam: 1) E.V.A prophylaxis system with safe sided & safe edged diamond tip 2) Ultra sonic scaler points • Smooth, highly polished matrix band (contact area) • Final polishing :SnO or Whitening made into paste with alcohol, applied with bristle or goat hair brush. • Temperature should not be raised >65o
  35. 35. PROPERTIES OF AMALGAM 1)Dimensional changes Effect of moisture contamination Mercuroscopic expansion 2)Strength 3)Creep 4)Tarnish &corrosion 5)Thermal property 6)Elastic modulus
  36. 36. 1) DIMENSIONAL CHANGES • Amalgam undergoes dimensional changes in 3 stages: Initial contraction Expansion Delayed contraction • According to ADAsp.1, Amalgam should neither contract nor expand more than 20micro.m/cm at 37o between 5mnts & 24hrs after beginning of trituration • Measured by Interferometer
  37. 37. • Factors affecting dimensional changes: 1) Constituents 2) Hg 3) Particle size 4) Trituration 5) Condensation • Moisture contamination: Delayed expansion: Occurs due to contamination of Zn containing alloys with water during trituration or condensation. Zn+H2O  ZnO + H2 Reaches about >400micro.m
  38. 38. • Its clinical consideration: 1) Protrusion of restoration out of cavity Unsupported margins # of restoration 2) Increased flow & creep 3) causes pulpalgia (2000psi) 4) decreases compressive strength (24%) • Management :  Use Zn free alloys  Isolation
  39. 39. MECUROSCOPIC EXPANSION • By Jorgensen • Results from when Hg released from corrosion of r2 phase reacts with remaining alloy particles. • Mechanism: Sn8Hg + 1/2 O2+ H2O + Cl- Sn4(OH)6Cl2 + Hg • Causes further weakening of the restoration
  40. 40. 2) STRENGTH • Amalgam has high compressive strength & low tensile strength
  41. 41. • The compressive strength of a satisfactory amalgam should be atleast 310MPa. • ADA SP. Stipulates a minimum compressive strength of 80MPa at 1hr. • Factors affecting strength: 1)temperature 2)Trituration 3)Hg 4)Condensation 5)Particle shape &size 6)Porosity 7)r2 phase 8)Interparticular distance 9)Corrosion.
  42. 42. CREEP • Is a time dependent plastic deformation of crystalline material under the influence of a static or dynamic stress. • Can be correlated with marginal breakdown. • Creep rate: 1)Low Cu---0.8-8% 2)High Cu--- <0.1% • Factors affecting creep: 1)Higher condensation forces Creep & Elimination of r2 phase 2) Excess Hg Creep
  43. 43. TARNISH & CORROSION • Amalgam often tarnish &corrode in oral environment • Tendency towards tarnish is unaesthetic due to formation of black AgS • Corrosion occurs in the interface between tooth & restoration. • Corrosion products Oxides & chlorides of Sn • Galvanism (differences in EMF) • Higher Hg:Alloy ratio  corrosion • Smooth& homogeneous surface minimizes tarnish & corrosion
  44. 44. • THERMAL PROPERTY: -- GOOD CONDUCTOR OF HEAT -- Cf. Of thermal exp, is 3 times greater than dentin. -- If RDT is <2mm, protection of pulp is necessary • ELASTIC MODULUS: --High Cu alloys are more stiffer than low Cu alloys. -- 62 GPa
  45. 45. MECURY TOXICITY • FORMS OF Hg:  Organic & Inorganic  Most toxic organic forms are Methyl Hg & Ethyl Hg  Least toxic form of Hg – Inorganic. • Concentration of Hg:  OSHA has set a threshold limit value of 0.05 mg/m3. • Max allowable Hg level in blood  3 micro Gms/L.
  46. 46. • Chronic exposure – assessed by urinary Hg concentration. Hg thermometer: Hg level 1000 Pronounced symptoms 500 Mild to Moderate 100 Subtle changes 25 No known Health effects 4 Upper limit of urinary Hg
  47. 47. • Sources of Hg exposure – Dental office: Amalgam raw materials being stored in use During trituration, insertion & intraoral hardening Amalgam scrap During finishing & polishing During Amalgam removal
  48. 48. Dental Hg hygiene recommendations • Train all personals regarding potential hazard of Hg vapor & make them aware of its potential sources • Working in well ventilated spaces • Periodically monitor dental operatory atmosphere for Hg vapor (DOSIMETERS & Hg Vapor Analyzers) • Facilitate Hg spill contamination cleanup • USE only Pre-capsulated alloys • USE Amalgamator with enclosed arm
  49. 49. • AVOID skin contact with Hg / freshly mixed amalgam • USE high volume evacuation • Store all scrap amalgam in tightly closed container • Recycle amalgam scrap when feasible • Dispose Hg contaminated items in sealed bags • USE trap bottles / tape / freshly mixed amalgam to pick up spilled Hg
  50. 50. AMALGAM FAILURES • INCLUDE: Bulk restoration fracture Corrosion & excessive marginal # Sensitivity or pain Secondary caries(70%) # of tooth structure forming restorative – tooth preparation walls
  51. 51. CAUSED OF FAILURE • Grouped under 3 headings: Faults in cavity design - weakened tooth structure - sharp internal line angles - non-retentive proximal boxes - incorrect cavo-surface design - shallow preparation
  52. 52.  Poor clinical techniques: - residual caries - poor matrix techniques - contamination - poor condensation - over & under filling and over carving  Limitations of the material
  53. 53. RECENT ADVANCEMENT IN DENTAL AMALGAM
  54. 54. AMALGAM BONDING SYSTEM • Used to seal underlying tooth structure & bond the amalgam to enamel & dentin • 4-META based bonding systems are used frequently. • It is important to develop micro-mechanical bonding since no chemical bonding occurs. • Hence bonding system is applied in much thicker layers(10-50mMts).
  55. 55. Bonding systems used: • ALLBOND-2(Bisco) • Amalgam bond plus (parkell) • Panavia (Kuraray) • Scotch bond multi-purpose plus(3M-ESPE)
  56. 56. • Potential advantages: Improved retention Decreased micro leakage Improved resistance form Decreased post-operative sensitivity • Primary indication: when weakened tooth structure remains & bonding may improve the overall resistance form of the restored tooth.
  57. 57. GALLIUM BASED ALLOYS • Gallium has similar atomic structure and characteristics to Hg • They consist of Gallium(65%), Indium, Tin, copper, Palladium. DISADVANTAGE: • 16 Times more experience • Very sticky • High level of corrosion • High level of expansion (1% or 60 mMts/ cm) • Toxicology unknown • Two types of Gallium alloys : • Palladium – Ga – Sn Ag-cu powder mixed with liquid of Ga-In-Sn
  58. 58. REFERENCES • SKINNER”S- Science of dental materials • Sturdevant”s Art & science of operative dentistry (4th edition) • Operative dentistry- Modern theory &practice -- M.A.Marzouk • Pickard”s manual of operative dentistry • Operative dentistry-Gillmore & Lund • Clinical restorative materials & techniques -- Karl. F. Leinfelder • Bonding of amalgam restoration, oper dent, 2000, 25 ,121-129.

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