1. Mercury Toxicity
   1. primary risk to dental personnel is from inhalation of mercury vapours.
   2. maximum level of occupational exposure considered safe is 50 µg of mercury/m of air.
   3. Mercury has an average half life of 55 days for transport through the body .
   4. Causes Acrodynia
      1. characterized by
         1. Pinkish discoloration of skin,
         2. profuse salivation,
         3. ulceration of the mucosa
         4. premature shedding of teeth
2. Amalgam Creep
   1. plastic deformation principally due to very slow metallurgical phase transformations that produces volume increase or expansion.
   2. most common cause of marginal failure.
   3. Creep values:
      1. Low copper
         1. 0.8-8%
      2. High copper
         1. admixed
            1. 0.4-0.1%
         2. Single composition
            1. 0.05-0.1%
3. Corrosion
   1. CHEMICAL CORROSION
      1. Formation of silver sulphide (Ag, S) tarnish.
   2. ELECTRO CHEMICAL CORROSION
      1. Crevice corrosion
         1. occurs in cracks or crevices accumulated by plaque and food debris
         2. due to drop in local pH and decreased oxygen tension
      2. Galvanic corrosion
         1. occurs between dissimilar metals in contact.
         2. The metal with low EMF undergoes corrosion.
      3. Stress corrosion
         1. occurs in the metal at the site of maximum stress.
      4. MERCUROSCOPIC EXPANSION
         1. Electrochemical corrosion of SnHg (y) does not release free mercury into oral cavity. .
         2. Instead mercury reacts with Ag-Sn (y) particles to produce 'Mercuroscopic expansion.
         3. This leads to ditch formation in the margins due to marginal fracture
4. AMALGAM WAR
   1. 1st
      1. In 1843 American society of dental surgeons
   2. 2nd
      1. Mid 1920s, German dentist Alfred stock
   3. 3rd
      1. Dr. Huggins
5. PREPARATION DESIGN
   1. 90 degree CSA.
   2. The walls must be parallel or perpendicular to occlusal loads.
   3. A definite gingival seat of 1.5-2 mm. in depth for compound cavities.
   4. Rounded internal line angles.
   5. Sufficient bulk at the isthmus area
   6. Each portion must have its own independent retention and resistance.
6. Miscellaneous Points
   1. cavosurface angle-
      1. 90°
   2. axiopulpal line angle
      1. bevelled to prevent fracture of amalgam
   3. strongest phase is original Gamma phase (Ag3sn)
   4. weakest phase of amalgam = Gamma2 phase
      1. Indium is added to reduce this phase
   5. Polishing Agent
      1. Tin Oxide
   6. Cavity made with
      1. Pear shaped bur
   7. Minimum Occlusal Thickness
      1. 1.5 mm to provide resistance to fracture
7. PIN RETAINED AMALGAM
   1. restoration requiring the placement of one or more pins in the dentin to provide adequate retention form and/or resistance form
   2. ADVANTAGES
      1. Conservation of tooth structure.
      2. Completed in one appointment whereas cast restoration requires atleast two appointments, Increased retention and resistance forms.
      3. Economical when compared to cast restorations
   3. DISADVANTAGES
      1. Dentinal microfractures
      2. Microleakage
      3. Decreased strength of amalgam
      4. Resistance form is difficult to develop than cast
      5. restorations.
      6. Perforations.
   4. TYPES
      1. cemented
         1. Least retentive Produces least crazing of dentin
         2. The pin should extend 3mm into dentinand 2mm into amalgam
         3. The pinhole should be 0.025 to 0.05mm larger than the diameter of pin
         4. Used mostly in nonvital teeth.
      2. friction lock
         1. It is intermediate retentive
         2. Produces crazing and cracks in dentin
         3. The pin should extend 3mm into dentin and 3mm into amalgam
         4. The pinhole is 0.025mm smaller than the diameter of the pin
         5. The pins are retained by the resiliency of dentin
      3. self threading
         1. Most retentive pin
         2. Most frequently used pin
         3. The pinhole is 0.0015 to 0.004 inch smaller than the diameter of the pin
         4. Retained by the resiliency of the dentin
         5. Produces maximum crazing in dentin.
         6. The pin should extend 2mm into dentin and 2mm into amalgam
   5. TMS Pin Sizes
      1. Minikin
         1. 0.48 mm (0.019 inch)
      2. Minim
         1. 0.61 mm (0.024 inch)
      3. Minuta
         1. 0.38 mm (0.015 inch)
8. FAILURE OF AMALGAM
   1. Bulk fractures of restoration
   2. Corrosion
   3. Excessive marginal fracture
   4. Sensitivity or pain
   5. Secondary caries
   6. Fracture of tooth structure
9. CONTRAINDICATIONS
   1. Anterior teeth where esthetics is a prime concern
   2. Aesthetically prominent areas of posterior teeth.
   3. Small-to-moderate classes I and II restorations that can be well isolated.
   4. Small class VI restorations
10. INDICATIONS
    1. Moderate to large restorations.
    2. Restorations that are not in highly esthetic areas of the mouth.
    3. Restorations that have heavy occlusal contacts.
    4. Restorations that cannot be well isolated.
    5. Restorations that extend onto root surface.
    6. Abutment teeth for RPD.
    7. Temporary or caries control restorations.
11. CLASSIFICATION
    1. Based on Copper content
       1. Low copper
       2. High copper
          1. Admixed
          2. Single composition
    2. Based on Zinc content
       1. Zinc containing
          1. contain more than 0.01% of zinc.
       2. Zinc free
          1. contain less than 0.01% of zinc.
    3. Based on Alloy Particle Shape
       1. Lathe cut
          1. irregular shape
       2. Spherical
       3. Admixed-
          1. contain both lathe cut and spherical alloys.