PROPERTIES OF AMALGAM IN DENTAL IMPLANT

1. PROPERTIES OF AMALGAM IN
DENTAL IMPLANT
AMALGAM
■ An amalgam is an alloy of mercury with another metal, which may
be a liquid, a soft paste or a solid, depending upon the proportion of
mercury.
■ These alloys are formed through metallic bonding, with the
electrostatic attractive force of the conduction electrons working to
bind all the positively charged metal ions together into a crystal
lattice structure.

2. Dental amalgams
■ Dental amalgam is a dental filling material used to fill cavities caused by tooth decay
■ Dental amalgam is a mixture of metals, consisting of liquid (elemental) mercury and a
powdered alloy composed of silver, tin, and copper. Approximately 50% of dental
amalgam is elemental mercury by weight. The chemical properties of elemental
mercury allow it to react with and bind together the silver/copper/tin alloy particles to
form an amalgam.

3. Properties of metals used in amalgam
■ Zinc prevents the oxidation of other metals in the alloy during manufacturing process.
■ Zinc also inhibits corrosion.
■ Indium containing admixed high-copper amalgam exhibited a reduction in creep and
increase in strength.
■ Palladium reduces tarnish and corrosion. Palladium reduces tarnish and corrosion.

4. Manufacturing of amalgam
■ Liquid mercury is mixed with a powdered alloy mainly comprising tin and silver.
■ Lathe cutting or milling of a cast ingot of the silver-tin alloy is done to produce the
powder. The particles formed are shaped irregularly.
■ Alternatively, the liquid alloy may be atomized and condensed, a process that
causes particles with a spherical morphology.
■ For clinical purposes, amalgam is mixed with mercury in a process called triturating.
Previously, they were formed manually; however, presently vibratory mixers are
present and manufacturers prepare the unmixed amalgam in two chambers of a tiny
capsule.

5. Continue…
■ Before mixing, the thin membrane separating the alloy powder from the liquid
mercury is destroyed and the capsule is placed in the mechanical mixer arm and
vibrated for a specific amount of time to enable thorough mixing of liquid and
powder.
■ The extrusion of the freshly mixed amalgam with a plastic consistency is done
from the capsule into the cavity.
■During the triturating process, the surface layer of the silver-tin alloy dissolves in
the liquid mercury and the reaction causes new phases to be formed. These new
solid phases cause solidification of the plastic amalgam paste.

6. Mechanical analysis
■ The mechanical properties - modulus of elasticity; tensile, compressive, shear,
and bending strength; fatigue strength; indentation hardness; and creep
■ fracture toughness decreased as the alloy copper content increased
■ An amalgam restoration needs to be strong enough so as to resist the biting
forces of occlusion.
■ Dental amalgam has high compressive strength, which is 380MPa for low-
copper amalgam and 414MPa for high-copper amalgams.
■ shear and tensile strengths are quite low.
■ tooth structures support the amalgam to ensure long-term clinical success.

7. Chemical analysis
■ GALVANIC CORROSION
■ In this process corrosion takes place when two dissimilar metals are present in a
wet environment.
■ The flow of electric current between the metals results in one of the metals
getting corroded.
■ Surface corrosion may cause a change of color of an amalgam restoration and
may result in pitting.
■ Surface corrosion fills the amalgam/tooth interface with corrosion products
bringing down micro leakage.
■ Internal corrosion will result in marginal breakdown and fracture. Galvanic
corrosion is promoted by an acidic environment.

8. Ac electrochemical impedance studies
of the corrosion behavior of dental
amalgam
■ high-copper dental amalgams were tested using AC impedance methods.
■ Initially in 0.1% NaCl, both alloys corroded the same when crevice corrosion
was minimized.
■ A 3-fold and a 10-fold increase were observed at 24 hours for the high-copper
and the conventional alloy, respectively, when crevice conditions were imposed.
■ AC impedance is a rapid, nondestructive method which is suitable for use in vivo
and in clinical trials.

9. Biological testing/ biocompatibility:
■ When the amalgam is introduce in our teeth it does not react and biocompatible:
■ Mercury released from dental amalgam restorations does not contribute to systemic
disease or systemic toxicological effects.
■ No significant effects on the immune system have been demonstrated with the amounts
of mercury released from dental amalgam restorations.
■ Only very rarely have there been reported allergic reactions to mercury from amalgam
restorations.
■ No evidence supports a relationship between mercury released from dental amalgam and
neurological diseases.

10. Applications
■ Of all the materials used in dentistry, none has more appeal than amalgam in:
■ The laboratory
■ Clinical researcher.
■ Dental amalgam is used in the following situations:
■ In stress-bearing areas and in small-to-moderate sized cavities in the posterior teeth.
■ When there is severe destruction of tooth structure and cost is an overriding consideration.
■ As a foundation for cast-metal, metal-ceramic, and ceramic restorations.
■ When patient commitment to personal oral hygiene is poor.
■ When moisture control is problematic with patients.

11. Conclusion
■ According to the available articles and data reviewed in this paper, the following
conclusions can be drawn.
■ Mercury released from dental amalgam restorations does not contribute to systemic
disease or systemic toxicological effects.
■ Allergic reactions to mercury from dental amalgam restorations have been demonstrated,
but these are extremely rare.

12. Thank you