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Amalgam Technical considerations

Amalgam Technical considerations. Definition of amalgam. Dental amalgam An alloy of mercury, silver, copper, and tin, which may also contain palladium , zinc and other elements to improve handling characteristics and clinical performance Dental amalgam alloy

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Amalgam Technical considerations

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  1. Amalgam Technical considerations

  2. Definition of amalgam • Dental amalgam An alloy of mercury, silver, copper, and tin, which may also contain palladium , zinc and other elements to improve handling characteristics and clinical performance • Dental amalgam alloy An alloy of silver, copper, tin, and other elements that is formulated and processed in the form of powder particles or compressed pellets. • The term Amalgam is commonly used to mean Dental Amalgam

  3. Associated Terminologies • Amalgamation : - the process of mixing liquid mercury with one or more metals / alloys to produce amalgam • Trituration : - the process of mixing the amalgam alloy particles with mercury in an amalgamator

  4. ADA Specification Number • Silver amalgam alloy – 1 • Mercury - 6

  5. General classification

  6. According to the number of alloys - binary alloys eg. Silver-tin - ternary alloys eg. Silver-tin-copper - quaternary alloys eg. Siver-tin-copper,indium • According to the copper content - low copper alloys ( < 6% copper) - high copper alloys (> 6% copper) • According to the zinc content - zinc containing alloys (> 0.01% zinc) - non zinc containing alloys ( < 0.01% zinc)

  7. According to the shape of powdered particles - spherical alloys - lathe-cut / irregular alloys • According to the size of powdered particles - micro cut alloys - fine cut alloys - coarse cut alloys • According to the addition of noble metals - platinum , palladium and gold are used.

  8. Amalgam in dentistry is supplied in form of powder and liquid.

  9. Basic composition of amalgam includes: - silver 65 wt % - tin 29 wt % - copper 6 wt % - zinc 0.01 wt % • Platinum , palladium , gold , selenium , indium etc. are added in smaller quantities.

  10. Indications • For class I , II and VI restorations. • Restorations that are not in highly esthetic areas of the mouth. • Restorations that have heavy occlusal contacts. • Restorations that cannot be well isolated. • Restorations that extend onto root surface. • As foundations and to restore even badly broken down teeth. • As temporary or caries – control restorations.

  11. Contraindications • Esthetically prominent areas of posterior teeth. • Small to moderate class I and II restorations that can be well isolated. • Small class VI restorations.

  12. Advantages • Ease of use. • High compressive strength. • Excellent wear resistance. • Favorable long term clinical research results. • Lower cost than composite restorations.

  13. Disadvantages • Potential nonesthetic appearance. • Less conservative. • More complex and larger tooth preparation required for an amalgam restoration compared to composite restoration. • Non insulating. • Weakens the tooth structure. • More difficult tooth preparation. • Initial marginal leakage.

  14. considerations

  15. Selection of alloy • Alloy: mercury ratio • Proportioning • Trituration • Mulling

  16. Matricing • Condensation • Burnishing • Carving • Finishing and polishing

  17. Selection of Alloy: • The choice between spherical spheroidal or lathe cut alloy particles can be related to the type of patient population the dentist is involved with. • If quick attainment of amalgam strength is necessary – spherical alloy • But requires fast operators to use them • They exhibit more flow and deformation with time.

  18. 2. Alloy Mercury Ratio • High mercury technique (increasing dryness technique). • The initial amalgam mix contains little more Hg than needed for the powder i.e., (52-53% Hg) - producing a plastic mix. • 2. Minimum mercury or (Eame’s technique) 1:1

  19. Mercury must wet the alloy particles before two components can react. The wetting, is dependant on a number of factors like • Alloy composition • Surface condition • Particle size • Particle shape • In 1959 - Minimal Mercury Technique ( Eames Technique)

  20. 3. Proportioning: Should be done by weight if possible and not by volume Pre amalgamated capsules to monitor correct weighing technique. Disadvantages: Operator has no control over the quantity and expensive

  21. 4. Trituration: • To achieve a workable mass of amalgam within a minimum time, leaving sufficient time for its insertion into a cavity preparation and carving to the predetermined tooth anatomy. • To remove oxides from the powder particles’ surface, facilitating direct contact between the particle and the mercury.

  22. 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.

  23. 5. 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. 6. To keep the amount of gamma – 1 or gamma –2 matrix crystals as minimal as possible, yet evenly distributed throughout the mass for proper binding and consistent, adequate strength

  24. Overtrituration • “hot” mix • decreases working / setting time • slight increase in setting contraction • Undertrituration • grainy, crumbly mix • Normal mix • Appears shiny Warm,homogenous, good strength

  25. 5. Mulling: • Continuation of trituration • Done to get homogeneous mix

  26. 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. This process should not exceed 2 to 5 seconds.

  27. 6. Matricing • It is a procedure ,whereby a temporary wall is created opp to the axial walls and surrounding areas of the tooth structure that were lost during tooth preparation.

  28. AMALGAM CARRIER

  29. 7. Condensation • Condensation is the process of compressing and directing the dental amalgam into the tooth with – condensing instruments (called condensers or pluggers

  30. Condensation: • Done to • To adapt mass to cavity wall • To remove excess mercury • To reduce voids and porosities • To increase density of restoration • To attain maximum strength of restoration • To bring reactive phases together

  31. 3-5 mins for condensation • Pressure: 3-4 pounds • Smaller the size of condenser more will be the pressure • As you come to surface the size of condenser should get bigger • It has been shown that the pressure applied by the condenser nib is inversely proportional to the square of its surface area.

  32. condensors

  33. Forces • lathe-cut alloys • small condensers • high force • spherical alloys • large condensers • less sensitive to amount of force • admixture alloys • intermediate handling between lathe-cut and spherical

  34. For non-spherical amalgam, condensation forces should be at 45 to walls and floors, i.e., bisecting line angles and trisecting point angles • Subsequent increments should be condensed at 90 to the previous portion to avoid shear forces that may displace the already condensed amalgam.

  35. Each portion of amalgam should be condensed from its center to its periphery, in an effort to avoid overlapping or bridging of voids at critical areas. • Mercury which comes to the surface act as a binder for the next increment in the building of the restoration.

  36. Size of condenser: Lathe – cut – smaller Spherical – bigger

  37. 8. Burnishing • It will further reduce the size and number of voids on the critical surface and marginal areas of the amalgam. • It brings 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.

  38. Pre-carve • removes excess mercury • improves margin adaptation • Post-carve • improves smoothness • Combined • less leakage

  39. Pre Carve Burnishing After condensation with amalgam condensers, the amalgam may be further condensed and shaped to occlusal anatomy with large busnisher -----pre-carve burnishing, and it is done immediately after completion of condensation.

  40. 9. Carving. • Is the anatomical sculpturing of the amalgam material • Objectives: • To produce a restoration with no underhangs • To produce a restoration with the proper physiological contours. • To produce a restoration with minimal flash.

  41. Recommended amalgam carvers that satisfy most amalgam carving need are a small cleiod – discoid carver; No: 3: Hollenback , an interproximal carver, NO 14L sickle shaped carver. • In addition, some cutting instruments, such as small spoon excavator, can be - carvers, especially for carving occlusal anatomy in large restorations.

  42. To produce a restoration with functional, non-interfering occlusal anatomy. • To produce a restoration with adequate, compatible marginal ridges.

  43. To produce a restoration with the proper size, location, extent, and inter relationship of contact areas. • To produce a restoration not interfering in any way with the integrity of the periodontium, enhancing its health and amenable for plaque control. • Amalgam carving should be accomplished using sharp instruments and with strokes either proceeding from tooth surface to amalgam surface, or laterally, along the tooth amalgam interface.

  44. Post carve burnishing Is the light rubbing of the surface of a carved amalgam restoration with a burnisher. • Heavy forces should not be used . * purpose is to smooth the surface of the restoration. • After completion - post carve burnishing, the surface may be wiped over with a dry or water- damp cotton ball to provide additional smoothing.

  45. 10. Finishing and Polishing: The most important objective of finishing and polishing is the removal of superficial scratches and irregularities. If this is accomplished properly, it will minimize fatigue failure of the amalgam under the cyclic loading of mastication. And also prevents the adherence of plaque

  46. Principles and procedures for finishing and polishing amalgam restorations. Usually, 24 hours should pass after amalgam insertion before any finishing and polishing commences. Finishing can be defined as the process which continues the carving objectives, removes flash and overhangs, and corrects minimal enamel underhangs. Polishing, on the other hand, is the process which creates a corrosion resistant layer by removing scratches and irregularities from the surface

  47. Finishing is done using descending grade abrasives either in impregnated rubber mounted stones or carried to the tooth on rotary brushes or rubber cups The final polishing act I.e., obtaining metallic lustre is always done with a polishing agent Ex: Precipitated chalk, Tin or Zinc oxide

  48. Thank you

  49. In finishing burs - +ve rake angle • It abrades the restoration • Flutes: more • Polishing done after 24hours • “Passivation of restoration to reduce tarnish and corrosion • Tin oxide – ideally

  50. Purpose • To prevent tarnish and corrosion long run • To get smooth and lustrous surface • To prevent plaque accumulation • To prevent secondary caries

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