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AMALGAM RESTORATIONS (1) DEFINITION OF DENTAL AMALGAM It is the combination of dental amalgam alloy composed of silver, tin and copper with mercury (sometimes.

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Presentation on theme: "AMALGAM RESTORATIONS (1) DEFINITION OF DENTAL AMALGAM It is the combination of dental amalgam alloy composed of silver, tin and copper with mercury (sometimes."— Presentation transcript:

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2 AMALGAM RESTORATIONS

3 (1) DEFINITION OF DENTAL AMALGAM It is the combination of dental amalgam alloy composed of silver, tin and copper with mercury (sometimes it contains zinc). It is the combination of dental amalgam alloy composed of silver, tin and copper with mercury (sometimes it contains zinc). DEFINITION OF AMALGAMATION PROCESS It is the process of alloying of mercury being in liquid state to Ag-Sn metal alloy being in the solid state. It is the process of alloying of mercury being in liquid state to Ag-Sn metal alloy being in the solid state.

4 (II) TYPES OF AMALGAM 1) According to copper content: 1) According to copper content: 1- Conventional amalgam (Cu is less than 6%) 1- Conventional amalgam (Cu is less than 6%) 2- High copper amalgam (Non-∂ 2 amalgam) (Cu is more than 6%). 2- High copper amalgam (Non-∂ 2 amalgam) (Cu is more than 6%). 2) According to Zinc content: 2) According to Zinc content: 1- Zinc containing amalgam. 1- Zinc containing amalgam. 2- Zink- free amalgam. 2- Zink- free amalgam. When zinc comes in contact with moisture (saliva) delayed 2 ndry expansion will occur. Zn + H 2 O ZnO + H 2 Zn + H 2 O ZnO + H 2

5 CLINICAL EFFECT OF MOISTURE 1- Secondary delayed expansion. 1- Secondary delayed expansion. 2- Delayed pain. 2- Delayed pain. 3- Overhanging margins. 3- Overhanging margins. 4- Recurrence of decay. 4- Recurrence of decay. 5- Weak & corrodible amalgam. 5- Weak & corrodible amalgam.

6 ACCORDING TO PARTICLES SHAPE 1- Lathe – cut alloy particles [Irregular shape needles]. 1- Lathe – cut alloy particles [Irregular shape needles]. 2- Spherical alloy particles. [Particles are rounded or spherical in shape] 2- Spherical alloy particles. [Particles are rounded or spherical in shape] 3- Admixed alloy particles. 3- Admixed alloy particles.

7 Lath-cut

8 Spherical all0y

9 Admixed alloy

10 (1) IN CASE OF THE LATHE-CUT TYPE: METHOD OF MANUFACTURING: All the alloy ingredients are melted forming an ingot (cast) then after cooling & solidification, we subject the ingot to a milling machine & so, we get fillings, needle shaped type. All the alloy ingredients are melted forming an ingot (cast) then after cooling & solidification, we subject the ingot to a milling machine & so, we get fillings, needle shaped type.

11 (2) IN CASE OF THE SPHERICAL ALLOY PARTICLES: METHOD OF MANUFACTURING: Pour the melted ingot into an inert gas chamber (N 2 gas) [no O 2 to prevent the oxidation] by spraying [Atomization] when they are sprayed by inert gas upon solidification, they will solidify in the form of spheres. Pour the melted ingot into an inert gas chamber (N 2 gas) [no O 2 to prevent the oxidation] by spraying [Atomization] when they are sprayed by inert gas upon solidification, they will solidify in the form of spheres.

12 (3) IN CASE OF THE ADMIXED TYPE: They manufacture lathe-cut alone & spherical alone & then they are mixed together. They manufacture lathe-cut alone & spherical alone & then they are mixed together.

13 (4) ACCORDING TO PARTICLE SIZE: 1- Micro-cut alloy particle. 1- Micro-cut alloy particle. 2- Fine-cut alloy particle. 2- Fine-cut alloy particle. 3- Coarse-cut alloy particle. 3- Coarse-cut alloy particle. The best form is the Fine-cut.

14 SHERICAL AMALGAM ALLOY PARTICLES CHARACTARISTICS: 1- Zinc content not required. 1- Zinc content not required. 2- Less amount of Hg is needed. 2- Less amount of Hg is needed. 3- Amalgamates more easily. 3- Amalgamates more easily. 4- Less technique sensitive (adv.). 4- Less technique sensitive (adv.). 5- Increased early compressive strength. 5- Increased early compressive strength. 6- Easier to condense, carve & polish. 6- Easier to condense, carve & polish.

15 MICRO-CUT AMALGAM ALLOY PARTICLES less than 10 microns less than 10 microns * CHARACTARISTICS : * CHARACTARISTICS : - Greater amount of Hg required (Greater S.A: Surface appear granular). - Greater amount of Hg required (Greater S.A: Surface appear granular). - Less plastic mass. - Less plastic mass. - Decreased compressive strength. - Decreased compressive strength.

16 FINE-CUT AMALGAM ALLOY particles [10-30 microns] particles [10-30 microns] * CHARACTARISTICS : * CHARACTARISTICS : - Improved adaptation. - Improved adaptation. - Smoother surface texture. - Smoother surface texture. - Easier carving & polishing. - Easier carving & polishing. - Increased compressive strength. - Increased compressive strength.

17 COARSE-CUT AMALGAM ALLOY PARTICLES [Greater than 30 microns]. [Greater than 30 microns]. * CHARACTARISTICS : * CHARACTARISTICS : - Less amount of Hg required (adv but as particles are rough & large less adaptation) - Less amount of Hg required (adv but as particles are rough & large less adaptation) - Rough surface texture. - Rough surface texture. - Decreased adaptation to cavity walls. - Decreased adaptation to cavity walls. - Increased compressive strength. - Increased compressive strength.

18 [III] COMPOSITION OF AMALGAM ALLOY 1- Conventional alloy (Traditional). 1- Conventional alloy (Traditional). 2- High-Cu alloy (non-σ 2 amalgam) 2- High-Cu alloy (non-σ 2 amalgam)

19 (1)*COMPOSITION OF CONVENTIONAL SILVER/ TIN AMALGAM ALLOY: * Silver : not less than 65% by wt. * Silver : not less than 65% by wt. * Tin : not less than 25% by wt. * Tin : not less than 25% by wt. * Copper: not more than 6% by wt. * Copper: not more than 6% by wt. * Zinc : not more than 2% by wt. * Zinc : not more than 2% by wt.

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21 * Silver : It is the main ingredient of amalgam used to: * Silver : It is the main ingredient of amalgam used to: - strength & hardness of amalgam. - strength & hardness of amalgam. - flow. - flow. - Some expansion. - Some expansion.

22 * Tin: tin is introduced to give plasticity of mass as tin has a great affinity to Hg so. It is attracted to Hg & so it gives plasticity to mass allows amalgamation process to take place easily * Tin: tin is introduced to give plasticity of mass as tin has a great affinity to Hg so. It is attracted to Hg & so it gives plasticity to mass allows amalgamation process to take place easily * Strength * Strength * Flow * Flow * Cause contraction * Cause contraction

23 *Copper: (like Ag) *Copper: (like Ag) * strength * strength * flow * flow * produces expansion * produces expansion * Improves setting characteristics. * Improves setting characteristics.

24 * Zinc: * Zinc: Acts as a scavenger or deoxidizer during Acts as a scavenger or deoxidizer during manufacturing. manufacturing. It prevents the formation of oxides on Cu, Ag & Sn. It prevents the formation of oxides on Cu, Ag & Sn. Disadv.: if amalgam is applied below free gum margin, moisture contamination will cause excessive delayed secondary expansion ( 3-5 days after placement of restoration). Disadv.: if amalgam is applied below free gum margin, moisture contamination will cause excessive delayed secondary expansion ( 3-5 days after placement of restoration).

25 * Reaction of conventional amalgam: * Reaction of conventional amalgam: It is a crystallization reaction: It is a crystallization reaction: Ag 3 + Hg Ag 2 Hg 3 + Sn 7 Hg + Ag 3 Sn. Ag 3 + Hg Ag 2 Hg 3 + Sn 7 Hg + Ag 3 Sn. σ + Hg σ 1 + σ 2 + unreacted σ σ + Hg σ 1 + σ 2 + unreacted σ intermediate weakest strongest intermediate weakest strongest strength phase phase strength phase phase

26 - The strongest phase is σ, it gives very strong amalgam restoration followed by σ 1 then the weakest phase is σ 2 which is susceptible to corrosion. - The strongest phase is σ, it gives very strong amalgam restoration followed by σ 1 then the weakest phase is σ 2 which is susceptible to corrosion. - We have to eliminate Sn-Hg phase as much as possible to avoid weak amalgam restoration. - We have to eliminate Sn-Hg phase as much as possible to avoid weak amalgam restoration.

27 (2) COMPOSITION OF HIGH COPPER AMALGAM ALLOY: * Silver : not less than 40% * Silver : not less than 40% * Tin : not less than 25% * Tin : not less than 25% * Copper : 10 – 30% * Copper : 10 – 30% * Zinc : 0-2% * Zinc : 0-2% - We cannot remove tin from the ingredients otherwise amalgam will be granular. - We cannot remove tin from the ingredients otherwise amalgam will be granular. - The increase in the % of copper is on the expense of Ag. - The increase in the % of copper is on the expense of Ag.

28 ** CHARACTARISTICS OF HIGH COPPER AMALGAM: (1) Higher early compressive strength. (1) Higher early compressive strength. (2) Increased corrosion resistance. (2) Increased corrosion resistance. (3) Improved marginal integrity (3) Improved marginal integrity (4) Lower creep value (4) Lower creep value

29 ** TYPES OF HIGH COPPER AMALGAM: ( 1) Admixed ( Lathe cut + Spherical) ( 1) Admixed ( Lathe cut + Spherical) (2) Single composition (Spherical or Lathe –cut) (2) Single composition (Spherical or Lathe –cut)

30 (1) Admixed high copper amalgam: * Composition: * Composition: 10-20% copper 10-20% copper - it is called Admixed type because some particles are spherical & some are lathe- cut. - it is called Admixed type because some particles are spherical & some are lathe- cut. - 2/3 lathe-cut. - 2/3 lathe-cut. - 1/3 spherical Ag-Cu (eutectic phase). - 1/3 spherical Ag-Cu (eutectic phase).

31 * Reaction : Mercury will penetrate bet. The particles * Reaction : Mercury will penetrate bet. The particles * Ag 3 Sn (σ ) + Hg Ag 2 Hg 3 (σ 1 ) + Sn 7 Hg (σ 2 ) + Ag 3 Sn (σ ). * Ag 3 Sn (σ ) + Hg Ag 2 Hg 3 (σ 1 ) + Sn 7 Hg (σ 2 ) + Ag 3 Sn (σ ). * Sn 7 Hg (σ 2 ) + AgCu Ag 2 Hg 3 (σ 1 ) + Cu6Sn5(E) * Sn 7 Hg (σ 2 ) + AgCu Ag 2 Hg 3 (σ 1 ) + Cu6Sn5(E) * σ 2 in the 1 st reaction would be attacked by AgCu of the eutectic. * σ 2 in the 1 st reaction would be attacked by AgCu of the eutectic. * Cu has a very great affinity to Sn so, it forms a compound called Cu 6 Sn 5. * Cu has a very great affinity to Sn so, it forms a compound called Cu 6 Sn 5.

32 - The aim of this reaction is: How to get rid of Ag 3 Sn but at the same time presence of Sn is v.imp as it has more affinity to Cu than Hg so, it will react with Cu & form E form. - The aim of this reaction is: How to get rid of Ag 3 Sn but at the same time presence of Sn is v.imp as it has more affinity to Cu than Hg so, it will react with Cu & form E form. * σ2 phase is eliminated & the net result is: * σ2 phase is eliminated & the net result is: σ 1 + σ 1 σ E σ 1 + σ 1 σ E Resultant is Cu 6 Sn 5 phase. Resultant is Cu 6 Sn 5 phase.

33 (2) Single COMPOSITION high copper amalgam : * COMPOSITION : * COMPOSITION : 13-30% copper. 13-30% copper. - Ternary Ag-Sn-Cu. - Ternary Ag-Sn-Cu. - Indium or palladium 10% ( to creep & corrosion resistance) - Indium or palladium 10% ( to creep & corrosion resistance) - it is made of one type only of alloy lathe cut or spherical not a mixture. - it is made of one type only of alloy lathe cut or spherical not a mixture. - Each alloy particle contains Ag-Sn-Cu whether it. - Each alloy particle contains Ag-Sn-Cu whether it. spherical or lathe – cut this is called ternary alloy. spherical or lathe – cut this is called ternary alloy. - Indium corrosion resistance. - Indium corrosion resistance.

34 * Reaction : * Reaction : Ag- Sn Cu + Hg Ag 2 Hg 3 (σ)+Cu 6 Sn 5 (E). Ag- Sn Cu + Hg Ag 2 Hg 3 (σ)+Cu 6 Sn 5 (E). - Sn has more affinity to Cu than Hg So, we have no σ 2 phase no SnHg phase as it will not leave Cu& bond with Hg. - Sn has more affinity to Cu than Hg So, we have no σ 2 phase no SnHg phase as it will not leave Cu& bond with Hg.

35 (IV) PROPERTIES OF AMALGAM RESTORATION: Advantages : Advantages : (1) Adequate compressive strength. (1) Adequate compressive strength. (2) High abrasion resistance. (2) High abrasion resistance. (3) Insolubility in oral fluids. (3) Insolubility in oral fluids. (4) Adaptability to cavity walls. (4) Adaptability to cavity walls. (5) Convenience of manipulation. (5) Convenience of manipulation. (6) Biocompatibility with oral & dental tissues. (6) Biocompatibility with oral & dental tissues.

36 Disadvantages: [1] Dimensional changes. [1] Dimensional changes. [2] Creep or flow tendency. [2] Creep or flow tendency. [3] Inadequate tensile strength. [3] Inadequate tensile strength. [4] Low edge strength. [4] Low edge strength. [5] Thermal conductivity. [5] Thermal conductivity. [6] Galvanism. [6] Galvanism. [7] Tarnish & corrosion. [7] Tarnish & corrosion. [8] Inharmonious color. [8] Inharmonious color. If it is properly manipulated we can overcome some if not all of these dis-adv.

37 [1] Dimensional changes: - Regarding the dimensional changes amalgam undergoes.3 stages: - Regarding the dimensional changes amalgam undergoes.3 stages: a) First stages: a) First stages: When Hg is added to the alloy powder & after trituration by 10 min. Amalgam undergoes slight contraction due to the penetration of Hg into the alloy particles. When Hg is added to the alloy powder & after trituration by 10 min. Amalgam undergoes slight contraction due to the penetration of Hg into the alloy particles.

38 b) Second stage: b) Second stage: After 10 min. of triturition & till the first 8 hours, there will be sever expansion due to the formation of σ 1 phase or silver – mercury phase. After 10 min. of triturition & till the first 8 hours, there will be sever expansion due to the formation of σ 1 phase or silver – mercury phase. c) Third stage: c) Third stage: After 24 hours there will be very slight contraction as a result of the setting of amalgam mass, all the phases of amalgam approach each other. After 24 hours there will be very slight contraction as a result of the setting of amalgam mass, all the phases of amalgam approach each other.

39 [2] Creep or flow tendency: Deformation of amalgam under load. Deformation of amalgam under load. * Creep: Deformation of amalgam restoration under load after it has completely set. * Creep: Deformation of amalgam restoration under load after it has completely set. * Flow: Deformation of amalgam restoration under load before it has set. * Flow: Deformation of amalgam restoration under load before it has set.

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41 Disadvantages : 1- Flattening of contact area. 1- Flattening of contact area. 2- Over hanging. 2- Over hanging. 3- Protrusion of restoration. 3- Protrusion of restoration.

42 [3] Inadequate tensile strength: - Amalgam can fracture at the isthmus (junction bet. Occlusal & proximal parts) due to its low tensile strength under tension load. - Amalgam can fracture at the isthmus (junction bet. Occlusal & proximal parts) due to its low tensile strength under tension load.

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44 [4] Low edge strength: - The low edge strength is responsible for the fracture at the margins. - The low edge strength is responsible for the fracture at the margins. (1) Amalgam ditch can occur I.e. v-shaped groove that occurs as a result of fracture of the margins of amalgam between amalgam & cavity walls at the cavosurface margin. (1) Amalgam ditch can occur I.e. v-shaped groove that occurs as a result of fracture of the margins of amalgam between amalgam & cavity walls at the cavosurface margin. To prevent this, the cavosurface angle must be 90 o to increase the bulk of amalgam at this area To prevent this, the cavosurface angle must be 90 o to increase the bulk of amalgam at this area

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46 [5] Thermal conductivity: [5] Thermal conductivity: Amalgam can transmit thermal impulses to the pulp & this can be overcome by putting cement. Amalgam can transmit thermal impulses to the pulp & this can be overcome by putting cement. - In deep cavities we put a liner to protect pulp from Thermal conductivity. - In deep cavities we put a liner to protect pulp from Thermal conductivity. - In shallow cavities there is enough dentin to protect pulp. - In shallow cavities there is enough dentin to protect pulp.

47 [6] Galvanism - If we have two dissimilar metals on the same side ex: amalgam & the other is gold, saliva acts as the electrolyte, amalgam acts as a node & gold acts as cathode so, when they come in contact ions are transmitted from amalgam to gold & this causes pain. As an electric current will pass. - If we have two dissimilar metals on the same side ex: amalgam & the other is gold, saliva acts as the electrolyte, amalgam acts as a node & gold acts as cathode so, when they come in contact ions are transmitted from amalgam to gold & this causes pain. As an electric current will pass. - This is associated with corrosion & it is called galvanic corrosion. - This is associated with corrosion & it is called galvanic corrosion.

48 [7] Tarnish & corrosion Tarnish Tarnish *It is an oxide film that causes discoloration (blackening). corrosion * It is the disintegration of the outer surface. * It is the disintegration of the outer surface.

49 * Indications: * Indications: - Class I - Class I - Class II - Class II - Class v - Class v - and distal cavities of canine in class III. - and distal cavities of canine in class III. * Contra Indication: * Contra Indication: - Anterior cavities. - Anterior cavities. - In the presence of other metallic restoration. - In the presence of other metallic restoration. To avoid galvanism. To avoid galvanism.

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52 [VI] Clinical application of amalgam restoration [1] Cavity preparation & pulp protection. [1] Cavity preparation & pulp protection. [2] Matrix & wedge application. [2] Matrix & wedge application. [3] Alloy selection & proportioning. [3] Alloy selection & proportioning. [4] Triturition & condensation. [4] Triturition & condensation. [5] carving & burnishing. [5] carving & burnishing. [6] Wedge & matrix removal. [6] Wedge & matrix removal. [7] Finishing & polishing. [7] Finishing & polishing.

53 Manipulation The ratio (or the alloy / mercury ratio): The ratio (or the alloy / mercury ratio): The amount of mercury needed is to coat all the particles to produce homogeneous coherent mass of amalgam. The amount of mercury needed is to coat all the particles to produce homogeneous coherent mass of amalgam. 1- Ratio 1:1 or 5:5 technique. 1- Ratio 1:1 or 5:5 technique. 2- Ratio 5:8 technique. 2- Ratio 5:8 technique. * The ratio is by weight and not by volume. * The ratio is by weight and not by volume.

54 Excess mercury leads to : Excess mercury leads to : 1- strength. 1- strength. 2- Flow and creep. 2- Flow and creep. 3- Expansion. 3- Expansion. 4- Tarnish and corrosions. 4- Tarnish and corrosions.

55 Less mercury leads to : Less mercury leads to : 1- non-coherent. 1- non-coherent. 2- Weak. 2- Weak. 3- Less resistance to tarnish and corrosion. 3- Less resistance to tarnish and corrosion. N.B: Each in Hg by 15% results in 1.5% excess in the final restoration.

56 Methods of proportioning: Methods of proportioning: 1- Simple weighing balance. 1- Simple weighing balance. 2- Tablets or pellets where amount of Hg is measured according to the manufacture by a mechanical dispenser. 2- Tablets or pellets where amount of Hg is measured according to the manufacture by a mechanical dispenser. 3- Automatic mechanical dispenser. 3- Automatic mechanical dispenser. Dispenser should be 1) clean and dry. 1) clean and dry. 2) Vertical to obtain proper measurement. 2) Vertical to obtain proper measurement. 3) Half filled. 3) Half filled.

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59 Disadvantages: a) Some alloys can cling to the wall of the dispenser. b) Each dispenser is for one type of alloy l.e. can’t be used universally for all types of alloys

60 4- Preproportioning capsules (the best method) proper alloy and Hg ratio is done by manufacturing and are put in a capsule. 4- Preproportioning capsules (the best method) proper alloy and Hg ratio is done by manufacturing and are put in a capsule. A disc or membrane separates Hg and alloy to prevent premature amalgamation. A disc or membrane separates Hg and alloy to prevent premature amalgamation. Activation is done before trituration. This is done by removal of the membrane, and provide contact between alloy and Hg. Activation is done before trituration. This is done by removal of the membrane, and provide contact between alloy and Hg. This could be done by - Pressure. This could be done by - Pressure. - Twisting cover of capsule - Twisting cover of capsule

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63 5- Self-activated capsules: 5- Self-activated capsules: The process of amalgamation activates the capsule The process of amalgamation activates the capsule Advantages of proportioning capsule: Advantages of proportioning capsule: 1- More convenient. 1- More convenient. 2- Proper Hg alloy ratio variables of dentists are eliminated. 2- Proper Hg alloy ratio variables of dentists are eliminated. 3- Prevent spill of Hg preventing Hg hazards. 3- Prevent spill of Hg preventing Hg hazards.

64 II- Trituration: * Definition: * Definition: It is the process by which the alloy and mercury are amalgamated together into: - Coherent. - Coherent. - Homogeneous. - Homogeneous. - Smooth. - Smooth. - Plastic mass of amalgam. - Plastic mass of amalgam.

65 * Methods of trituration: * Methods of trituration: a. Manual trituration using Mortar and Pestle. a. Manual trituration using Mortar and Pestle. b. Mechanically using electric amalgamator. b. Mechanically using electric amalgamator. A. Hand trituration: i- Glass mortar and pestle are used. i- Glass mortar and pestle are used. ii-Should be cleaned to prevent contamination. ii-Should be cleaned to prevent contamination. iii-The face of the Pestle must have the same shape as the surface of the mortar for effective trituration. iii-The face of the Pestle must have the same shape as the surface of the mortar for effective trituration. iv- Both Mortar and Pestle should present an even rough working surface for effective trituration. iv- Both Mortar and Pestle should present an even rough working surface for effective trituration. v- The trituration process must be standardized by rate, time and pressure. v- The trituration process must be standardized by rate, time and pressure. e.g: 2kg or 4 kg is 1 min. In 60 revolution. e.g: 2kg or 4 kg is 1 min. In 60 revolution.

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70 Aims of trituration. a. To rub off the oxide layer on the alloy particles. a. To rub off the oxide layer on the alloy particles. b. For further reduction of the size of the alloy particles. b. For further reduction of the size of the alloy particles. c. To bring the mercury into contact with the alloy particles to start the reaction. c. To bring the mercury into contact with the alloy particles to start the reaction.

71 * Properly triturated amalgam will appear: * Properly triturated amalgam will appear: A. Homogeneous. A. Homogeneous. B. Smooth. B. Smooth. C. Climb along the side of the mortar and form a curl at its top. C. Climb along the side of the mortar and form a curl at its top.

72 * Under triturated leads to: A. Weak. A. Weak. B. Non-homogeneous. B. Non-homogeneous. C. Excess mercury. C. Excess mercury. D. Appear dull. D. Appear dull. E. Non-coherent. E. Non-coherent. F. Undergo more expansion. F. Undergo more expansion. G. More tarnish and corrosion. G. More tarnish and corrosion.

73 Over triturated leads to: A. Sets faster. A. Sets faster. B. Greater one hour strength. B. Greater one hour strength. C. Smooth surface. C. Smooth surface. D. Less flow. D. Less flow. E. More tarnish and corrosion resistance. E. More tarnish and corrosion resistance. F. The only disadvantages is that it may undergo contraction farther than expansion. F. The only disadvantages is that it may undergo contraction farther than expansion.

74 B. Mechanical Trituration:. This method: 1- Saves time. 1- Saves time. 2- Gives better standardization, for the triturated amalgam. 2- Gives better standardization, for the triturated amalgam. * Mulling of amalgam: * Mulling of amalgam: It is a process of mulling the properly triturated amalgam for few sec. In a piece of rubber to acquire a max. degree of plasticity. It is a process of mulling the properly triturated amalgam for few sec. In a piece of rubber to acquire a max. degree of plasticity.

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77 II. Condensation: * Definition: * Definition: It is the process of packing of the properly triturated amalgam in the prepared cavity. It is the process of packing of the properly triturated amalgam in the prepared cavity. *Aims: *Aims: 1. The adaptation of amalgam to cavity walls and margins. 1. The adaptation of amalgam to cavity walls and margins. 2. The adaptation between successive layer of amalgam. 2. The adaptation between successive layer of amalgam. 3. Express excess mercury and density of the alloy. 3. Express excess mercury and density of the alloy. 4. The compressive strength of amalgam. 4. The compressive strength of amalgam.

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81 * Requirements for proper condensation: 1. Only fresh mixes should be used. (Mixes more than 3.5min. Should be discarded, this is to avoid layering of amalgam. 1. Only fresh mixes should be used. (Mixes more than 3.5min. Should be discarded, this is to avoid layering of amalgam. 2. We must use successive increments for effective condensation. 2. We must use successive increments for effective condensation. 3. Great condensation pressure is required, directed, towards cavity wall, and margins. 3. Great condensation pressure is required, directed, towards cavity wall, and margins. 4. Each condensed layer must be properly stable other wise weak amalgam will result. 4. Each condensed layer must be properly stable other wise weak amalgam will result.

82 5- A proper sized and designed condenser must be used: 5- A proper sized and designed condenser must be used: i. It should be small enough to exert great pressure, but not too small to cause holes in the amalgam. i. It should be small enough to exert great pressure, but not too small to cause holes in the amalgam. ii. It should be properly angulated to reach all areas of the cavity. ii. It should be properly angulated to reach all areas of the cavity. iii. The face of the condensed must be either flat, smooth or serrated. iii. The face of the condensed must be either flat, smooth or serrated. 6- Condensation should be completed under clean dry condition. 6- Condensation should be completed under clean dry condition.

83 * Condensation technique: * Condensation technique: 1- By hand condensation and it should be as follows. 1- By hand condensation and it should be as follows. a. The restoration is built from small successive increment. a. The restoration is built from small successive increment. b. In case of compound cavities, the box should be filled first to the level of pulpal floor, then the occlusal. b. In case of compound cavities, the box should be filled first to the level of pulpal floor, then the occlusal. c. Small piece of amalgam is carried by amalgam carrier and forced into the cavity. c. Small piece of amalgam is carried by amalgam carrier and forced into the cavity. d. The first layer is condensed with great force using small condenser from the center of the cavity to cavity margins. d. The first layer is condensed with great force using small condenser from the center of the cavity to cavity margins.

84 e- The mercury rich amalgam on the surface is removed with spoon excavator. f- The process is repeated until the cavity is completely filled. g- A final dry piece is condensed to over fill the cavity and over come the excess mercury of the last layer and then this layer is removed leaving the surface of amalgam with no excess mercury.

85 2- Mechanical condensation: by ultrasonic device * Advantages of mechanical condensation: * Advantages of mechanical condensation: 1- It is more standardized. 1- It is more standardized. 2- Less fatigue to the operator. 2- Less fatigue to the operator. 3- It produces homogenous amalgam. 3- It produces homogenous amalgam. 4- More strength property for the final amalgam. 4- More strength property for the final amalgam. 5- Less flow. 5- Less flow. 6- More stability. 6- More stability. 7- Less expansion. 7- Less expansion.

86 Carving of Amalgam: Carving of Amalgam: 1- We use suitable amalgam carver. 1- We use suitable amalgam carver. 2- Amalgam must not be carved unless it becomes hard enough to resist carving instrument ( for about 3.5 min). 2- Amalgam must not be carved unless it becomes hard enough to resist carving instrument ( for about 3.5 min). 3- Sharp instrument must be used for carving, to not disturb the matrix. 3- Sharp instrument must be used for carving, to not disturb the matrix. 4- Avoid carving towards cavity margins to avoid under filling and expression of excess mercury towards the margin. 4- Avoid carving towards cavity margins to avoid under filling and expression of excess mercury towards the margin.

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88 Excess Hg at the margins may cause: a- Marginal disintegration. a- Marginal disintegration. b- Marginal leakage. b- Marginal leakage. c- Tarnish and corrosion. c- Tarnish and corrosion.

89 5 - In compound cavities, the occlusal portion is carved 1 st before removal of matrix. 5 - In compound cavities, the occlusal portion is carved 1 st before removal of matrix. 6- After carving of the occlusal portion, the matrix holder is unscrewed and band is removed either buccally or lingually. Avoid its removal occlusally to avoid fracture of the margins. 6- After carving of the occlusal portion, the matrix holder is unscrewed and band is removed either buccally or lingually. Avoid its removal occlusally to avoid fracture of the margins. 7- The proximal contour is carved and then contact is checked by using dental floss silk. 7- The proximal contour is carved and then contact is checked by using dental floss silk.

90 Double burnishing technique Means the amalgam is pre and post carving burnished Pre carving burnishing Using large sized burnisher with heavy pressure

91 Benefits of precarving burnishing A-Increase adaptation of amalgam to cavity walls and margins B-Bring the mercury to the surface C- More cohesive amalgam D-Continue the process of condensation

92 Post carving burnishing Small sized burnisher with gentle strokes just to smoothen the amalgam

93 Finishing and polishing of Amalgam: It should be done to give a luster-like smooth surface after at least 24 hrs. It should be done to give a luster-like smooth surface after at least 24 hrs. * Finishing and polishing is achieved by using: * Finishing and polishing is achieved by using: 1- Rotating finishing instruments which include: a- Finishing stones as carburundum green stones in form of : coarse. a- Finishing stones as carburundum green stones in form of : coarse. medium medium fine fine they are used to correct surface discrepancies. they are used to correct surface discrepancies.

94 b- Interproximal finishing instruments as: i- finishing strips in form of : coarse. i- finishing strips in form of : coarse. medium medium fine fine ii- Abrasive discs. ii- Abrasive discs. they are used to correct over hangs and give smooth interproximal surface. they are used to correct over hangs and give smooth interproximal surface. c- Finishing burs12 fluted. c- Finishing burs12 fluted.

95 2- Rotating polishing instruments include: a- Rubber cups in form of coarse, medium or fine applied with polishing paste at low speed. a- Rubber cups in form of coarse, medium or fine applied with polishing paste at low speed. b- Rotating soft brush applied with polishing paste. b- Rotating soft brush applied with polishing paste.

96 * If amalgam restoration is not finished and polished, then the surface remains rough leads to: a- Surface porosities. a- Surface porosities. b- Food and plaque accumulation. b- Food and plaque accumulation. c- Tarnish and corrosion. c- Tarnish and corrosion. d- Concentration of stresses. d- Concentration of stresses.

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103 ADVANTAGES: 1- High compressive strength properties (45000PSI). 1- High compressive strength properties (45000PSI). 2- Low coefficient of thermal expansion. 2- Low coefficient of thermal expansion. 3- Indestructibility in oral fluid. 3- Indestructibility in oral fluid. 4- Easy of manipulation. 4- Easy of manipulation. 5- It is capable to take and maintain a good polish. 5- It is capable to take and maintain a good polish.

104 DISADVANTAGES : 1- Low tensile strength. 1- Low tensile strength. 2- Bad esthetics due to unnatural color and the tendency for corrosion. 2- Bad esthetics due to unnatural color and the tendency for corrosion. 3- High thermal conductivity. 3- High thermal conductivity. 4- Slight changes in dimension during setting. 4- Slight changes in dimension during setting.

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107 THANK YOU


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