1. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Dental Amalgam Dental Amalgam Dental Materials DEN 256 Chapter 10

2. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Dental Amalgam  Dental amalgam has been used successfully for longer than 170 years for the restoration of teeth.  Approximately 50 million amalgam restorations are placed each year.  Lack of esthetics and patient concerns about amalgam safety have prompted an approximately 40% drop in its use over the past 15 years.

3. Copyright © 2011 by Saunders, an imprint of Elsevier Inc.  Amalgam consists of several different metals, with silver being the predominant metal ◦ Metals are in a powder form and then mixed with mercury to form a soft, pliable mixture ◦ When placed into a prepared tooth, condensed, carved, and allowed to harden, the mixture becomes a permanent amalgam restoration  Amalgam is a safe, affordable, and durable material used predominantly to restore premolars and molars 3

4. Copyright © 2011 by Saunders, an imprint of Elsevier Inc.  The controversy has evolved in two directions: ◦ Potential harm to patients from mercury within the amalgams placed in their teeth ◦ Toxicity level of mercury vapors affecting dental personnel exposed over a long period 4

5. Copyright © 2011 by Saunders, an imprint of Elsevier Inc.  The ADA and the National Institute of Health- Nations Administration have agreed that there is no basis for claims that amalgam is a significant health hazard  The health risk for dental personnel is greater than that for a patient: ◦ The dentist and assistant who are exposed to mercury vapors daily should be aware of their toxic effects ◦ An increase in exposure can result in tremors, kidney dysfunction, depression, and central nervous system disorders 5

6. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Alloy Versus Amalgam  An alloy is a mixture of two or more metals.  The alloy used in dental amalgam is composed predominantly of silver but also contains copper and tin.  A variety of other metals, such as palladium, iridium, or zinc, may be added in smaller quantities.  When the silver-based alloy is mixed with mercury, the reaction that occurs is called amalgamation.

7. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Amalgam Restorations 42?” A & F: canines and anterior teeth B & C: highly adaptable with longevity D: Build up prior to crown preparation E: Deterioration of margins

8. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. are placed in posterior teeth where esthetic concerns are secondary. have highly adapted margins and longevity. are rarely used on canines or other anterior teeth. Used to build up the tooth prior to a crown preparation Can be placed with good clinical success when isolation of the tooth is impossible and bonding of composites would be compromised. Most of generally fail because of deterioration of its margins with the tooth with or without development of secondary caries. Amalgams :

9. Copyright © 2011 by Saunders, an imprint of Elsevier Inc.  Can withstand high chewing forces  Biocompatible  Useful when isolation is difficult  Easy to manipulate  Very durable  Relatively inexpensive

10. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Primary and permanent teeth Stress-bearing areas of the mouth Small to moderate-sized cavities in the posterior teeth Severe destruction of tooth structure As a foundation for cast-metal, metal-ceramic, and ceramic restorations When a patient’s commitment to personal oral hygiene is poor When moisture control is problematic When cost is an overriding patient concern

11. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. May require more tooth structure removal to retain the restoration. Cannot chew on it immediately after placement Possible temperature sensitivity after placement Possible galvanic reaction with other metals in the mouth Requires mercury hygiene measures with scrap material.

12. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Silver-Based Amalgam Alloy Particles  Silver-based amalgam alloys are classified according to the shape of the particles in the powder as lathe- cut, admixed, or spherical.  Each of these particle shapes contributes certain handling characteristics to the amalgam.

13. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Silver-Based Amalgam Alloy Particles (cont’d)  Lathe-cut particles are formed by shaving fine particles off an ingot of the alloy with the use of a lathe.  The particles are sifted to separate them into fine and ultra-fine particles.

14. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Silver-Based Amalgam Alloy Particles (cont’d)  Spherical particles are produced by spraying molten alloy into an inert gas.  Spherical particles are formed as the atomized droplets cool.  Admixed particles consist of a mixture of lathe-cut and spherical particles.

15. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Composition  Modern dental alloys are considered to be high in copper content (10% to 30%) compared with their predecessors (2% to 4%).  They generally contain 40% to 70% silver.  Approximately 12% to 30% tin is included  They are mixed with mercury 43% to 50% by weight.

16. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Strength Strength  Amalgam is among the strongest of the directly placed restorative materials.  Amalgams are stronger in compression than are composites or glass ionomers.  If they are too thin in areas, however, amalgams may be broken by the biting forces.

17. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Tarnish Tarnish  The oxidation that attacks the surface of the amalgam and extends slightly below the surface  Results from contact with oxygen, chlorides, and sulfides in the mouth  Causes a dark, dull appearance that is not destructive to the amalgam

18. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Corrosion Corrosion  Corrosion can be caused by a chemical reaction between amalgam and substances in saliva or food that results in oxidation.  Corrosion can occur when two dissimilar metals interact in a solution that contains electrolytes.  An electrical current is generated between the metals (galvanism), resulting in corrosion.

19. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Delayed Expansion of Amalgam  margins of the restoration stand up from the tooth.

20. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Dimensional Change Dimensional Change  Ideally, the dimensions of a newly placed amalgam should not change.  If it contracts excessively, it will open gaps at the margins and contribute to microleakage.  If the material expands excessively, it puts pressure on the cusps that can cause fracture.

21. Copyright © 2011 by Saunders, an imprint of Elsevier Inc.  Creep in amalgam results from the application of nondestructive occlusal forces over a period of months to years. (vertical arrows)  These occlusal forces gradually change the shape, results in loss of marginal integrity and ultimately leading to fracture. Occlusal Forces Tooth Vertical Fracture

22. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Operating Zones: Right Handed Dentist

23. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Operating Zones: Left handed dentist

24. Copyright © 2011 by Saunders, an imprint of Elsevier Inc.

25. Dispensing of Alloy and Mercury  The amalgam must be handled properly from the start through the entire placement process if the restoration is to be successful.  Use of premeasured capsules is the most hygienic way to work with these materials.  Chances for contamination of material or for spills are fewer.

26. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. 26 From Heymann HO, Swift EJ, Ritter AV: Sturdevant’s art and science of operative dentistry, ed 6, St Louis, 2013, Mosby.

27. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. 1. Gamma Phase (y) Silver alloy phase, is the strongest phase and has the least corrosion. 2. Gamma-1phase (y) Consisting of mercury reacting with the silver. It is strong and corrosion resistant. 3. Gamma-2 phase (y2) the reaction of mercury with tin. Weak and corrodes readily. Tin controls the rate of setting time. Can take up to 24 hours.

28. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Trituration  Powder and mercury are mixed together in a mechanical device called a triturator, or amalgamator.  Each manufacturer of amalgam materials provides specific time and speed specifications regarding the mixing of a particular material.

29. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Trituration (cont’d)  Under-triturated amalgam appears dry and crumbly and sets too quickly.  Over-triturated amalgam appears wet and sets quickly, producing heat.  Properly triturated amalgam has a satin-like appearance.

30. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Do not activate the capsule before you are ready to begin mixing it. The dentist will tell you when he/she is ready to fill the cavity preparation. Follow the manufacturer's recommended trituration time and speed for optimum properties. Improper mixing can adversely affect the longevity of the restoration. When the capsule is activated, it will have a certain amount of working time. Several capsules may be needed to fill larger cavity preparations.

31. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Setting Transformation  When the alloy in powder form is mixed with the mercury, a chemical reaction occurs.  The mixture has a putty-like consistency that can be packed into the cavity preparation.  It gradually becomes firmer.

32. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Setting Transformation (cont’d)  During the firming phase, the amalgam can be carved to the anatomic shape of the tooth.  Once it reaches its initial set, it no longer can be carved.  It is firm but is not fully reacted.  It is relatively brittle at this point. ◦ 24 hours is needed for a full set.

33. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. The ability of holding two things firmly together when they will not adhere to each other naturally Dental restorations, castings, and appliances must be held in place with the use of materials and retention methods Even though retention holds the material in place, it does not completely seal the two structures together Microleakage can occur if an additional material such as a bonding material is not placed to create a seal Retention

34. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Retention is very important in the preparation of teeth that are to receive amalgam fillings. One of the ways in which retention is achieved is preparing the opposing inside walls of the tooth to slant slightly inward so that when amalgam is placed and set it will not slide out. Retention (con’t)

35. Copyright © 2011 by Saunders, an imprint of Elsevier Inc.  Amalgam is retained in the cavity preparation by parallel walls or undercut walls.  It is not bonded to the tooth surface but is retained mechanically.  Recently, many dentists have begun bonding amalgam with resin bonding agents.

36. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Retention of Amalgam

37. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Dycal Cement is sometimes used under amalgams, acting like an insulator, to protect the pulp.

38. Copyright © 2011 by Saunders, an imprint of Elsevier Inc.  Amalgam is supplied by the manufacturer in sealed single-use capsules with the proper ratio of alloy powder in one side of the capsule and mercury on the other side, separated by a thin membrane  Capsules are available with: ◦ 600 mg of alloy for small or single-surface restorations ◦ 800 mg of alloy for larger restorations  If more amalgam is required, additional capsules are triturated as needed 38

39. Copyright © 2011 by Saunders, an imprint of Elsevier Inc.

40.  After mixing, the amalgam is removed from the capsule and is placed into an amalgam well.  The amalgam is picked up in small increments with the use of an amalgam carrier.  Condensers are used to work the material into all areas of the preparation.  The preparation must be overfilled to allow room for carving of the anatomy.

41. Copyright © 2011 by Saunders, an imprint of Elsevier Inc.

42. Placement of amalgam into tooth Amalgam Carrier

43. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Packing the amalgam into the tooth using a plugger/condenser Condenser/Plugger

44. Copyright © 2011 by Saunders, an imprint of Elsevier Inc.  Amalgam is condensed with overlapping steps of the condenser to avoid voids within the amalgam that might weaken it.

45. Copyright © 2011 by Saunders, an imprint of Elsevier Inc.  Burnishing before carving produces a much smoother and denser surface.  Burnishing also helps to seal margins and enhances the longevity of the restoration.  Carving removes extra material from the cavosurface margins and allows the missing anatomy to be reformed.

46. Copyright © 2011 by Saunders, an imprint of Elsevier Inc.  Hand carving instruments carve back the amalgam material to the tooth’s normal anatomy, which was removed during cavity preparation  A burnisher is used to smooth the amalgam once most of the carving has been completed.  46

47. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Amalgam is being carved using a cleoid discoid Carving

48. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Flossing interproximally gets rid of any excess amalgam and smoothes and adapts the amalgam to the tooth Flossing

49. Copyright © 2011 by Saunders, an imprint of Elsevier Inc.  Finishing is best done 24 hours or longer after initial placement, to allow crystallization within the amalgam to go to completion.  Because a second visit is involved for finishing and polishing amalgam restorations, many clinicians do not polish them.

50. Copyright © 2011 by Saunders, an imprint of Elsevier Inc.  Articulating Paper is used to check occlusion - is used to check how the restoration occludes with the opposing tooth. - the patient is instructed to bite down lightly on the articulating paper (carbon paper). -this technique is done multiple times to insure the final carvings are accurate.

51. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Finished Amalgam

52. Copyright © 2011 by Saunders, an imprint of Elsevier Inc.

53. Mercury-Free Amalgam Mercury-Free Amalgam  A mercury-free metal compound was developed that has an appearance and handling characteristics similar to those of amalgam.  This was not a good alternative because it was highly corrosive.  It is no longer used in the United States.

54. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. It may be more detrimental to remove more than one tooth by replacing a sound amalgam restoration than to leave it alone. The oral environment may be re-exposed to mercury with removal. Do not touch mercury with your bare hands. Do not vacuum up spilled mercury. Get a mercury spill kit with a magnet. Facts Regarding Removing Amalgam

55. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Mercury Safety  Mercury is toxic at high levels.  The amount of mercury that is released from a set amalgam is minimal.  No substantiated research has proved otherwise.  When old restorations are removed, it is important to use a water spray to minimize vapor.

56. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Mercury Safety (cont’d)  When one is disposing of amalgam waste, it is important to do so properly. ◦ Commercial containers can be purchased for scrap amalgam disposal and recycling. ◦ Although some offices do so, scrap amalgam should never be thrown into the trash can.

57. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. Summary Summary  Dental amalgam plays a large role in restorative dentistry. ◦ It is an economical, durable, and versatile material.  Patients should be educated about the pros and cons of a material so that they can make informed decisions.

58. Copyright © 2011 by Saunders, an imprint of Elsevier Inc.  A PROPERLY MIXED AMALGAM SHOULD APPEAR a. Dry and crumbly b. Soupy and shiny c. As a homogeneous mass with a slight shine d. Liquid-like and should pour easily out of the capsule.

59. Copyright © 2011 by Saunders, an imprint of Elsevier Inc.  C. As a homogeneous mass with a slight shine

60. Copyright © 2011 by Saunders, an imprint of Elsevier Inc.  IN THE AMALGAM A RESTORATION, THE TWO MAIN COMPONENTS ARE: a. Silver and copper b. Mercury and tin c. Silver and mercury d. Mercury and zinc

61. Copyright © 2011 by Saunders, an imprint of Elsevier Inc.  C. Silver and Mercury

62. Copyright © 2011 by Saunders, an imprint of Elsevier Inc.