Amalgam

At one time, hat makers rubbed mercury into felt with their bare hands to ready it for shaping. Exposure to mercury in that quantity is toxic to nerves and causes ....

"madness" (thus, the Mad Hatter). Fortunately for us, the quantity of mercury in amalgam has decreased a lt over the years (and we wear gloves). Most current products contain around 50 percent mercury. Reducing the amount of mercury in an amalgam increases its strength.

Amalgam is supplied in single-use (at dental offices), disposable capsules that contain measured quantities of alloy and mercury separated by a diaphragm. These capsules are available containing a single spell (400 mg), a double spill (600 mg), and a triple spell ....

(800 mg) of amalgam. As a dental assistant, you may be asked to help the dentist choose the appropriate number of spills depending on the size of the cavity to be filled. Often, the manufactured includes a pestle, a small metal rod, in the capsule to aid in mixing.

Dental amalgam is a direct restorative material that was introduced to the U.S. in the 1800s and was the most popular filling material until very recently. The term amlgamga refers to a blend of metals that includes mercury, the only metal that is liquid at room temperature,. The other metals in amalgam ....

(a combination of silver, copper, tin, and zinc) are called an alloy. Think of alloys as metal blends. If the alloy contains mercury, it is called amalgam.

Steps for placing amalgam (direct restoration):

1. Active the amalgam capsule 2. Place the capsule in the amalgamator 3. Dispense the amalgam in the well 4. Load the amalgam carrier from the well 5. Dispense amalgam into the tooth preparation 6. Condense the amalgam 7. Carve the amalgam 8. Burnish the amalgam

Alloy

A solution composed of two metals that are dissolved in each other when in the liquid state.

Spill

A unit of measurement of amalgam.

1. Fill amalgam well

After the amalgam is mixed, the dental assistant opens the capsule and empties the amalgam into an amalgam well. The empty capsule should be reclosed immediately and disposed of in a general waste container.

A combination of two or more metals:

Alloy.

A blend of metals that contains mercury:

Amalgam.

Amalgam

An alloy, with one of the constituents being mercury.

4. Adapt amalgam to walls of cavity

As the dentist places each measure of amalgam into the tooth, they apply firm pressure to adapt the amalgam to the walls of the cavity. This process is called Condensation and is performed with an instrument called a condenser (or plugger).

Alloy that combine round and irregular particles are called ...... alloys.

Blended (admixed).

Provides strength and corrosion resistance to amalam:

Copper.

Direct restorative materials: Example

Dental amalgam is placed in small quantities in the tooth and then carved into shape.

Tin

Enhances the amalgam's workability.

Indirect restorative materials: Example

Gold is melted under high heat and cast into a mold while molten, a procedure that would be quite painful in the mouth.

Alloy that appears irregular under magnification is called a ....... alloy.

Lathe-cut.

Silver and copper

Make the amalgam stronger. Copper prevents corrosion that can weaken the amalgam in the wet environment of the mouth.

Only metal that is liquid at room temperature:

Mercury.

Pestle

Object that is moved vertically to pound or pulverize a material.

Mercury

Only liquid, it binds the other ingredients together to form a cohesive mass. As a liquid, it provides little in the way of strength to the amalgam. In fact, a greater proportion of mercury results in a weaker amalgam.

A ...... is a metal rod included in an amalgam capsule to increase mixing efficiency.

Pestle.

Zinc

Prevents oxidation of the material.

The ...... of alloy particles in an amalgam determines how they handle in the the tooth.

Shape.

Comprises bulk of amalgam and provides strength:

Silver.

Alloy that appears round under magnification is called a ...... alloy.

Spherical.

A ...... is a measured quantity of amalgam.

Spill

2. Load amalgam into carrier

The dental assistant then loads the amalgam from the well into an amalgam carrier for incremental placement into the prepared tooth.

3. Place amalgam into tooth

The dentist unloads each measure of amalgam from the carrier into the tooth.

Direct restorative materials: Description

These are used to make direct restorations (those shaped in the tooth). These materials are formed into their final shaped and contour directly in the tooth.

Indirect restorative materials: Description

These are used to make indirect restorations. These materials are shaped outside of the mouth and cemented to the tooth in their final form.

Provides workability to amalgam:

Tin.

Trituration

To mix together, as in the process of mixing an alloy with mercury to form an amalgam.

..... is the process of making amalgam from alloy and mercury.

Trituration.

Restorative

Type of dentistry that restores teeth by removing decay and restoring defects.

Suppresses oxidation in amalgam:

Zinc.

Trituration is the process by which the mercury and alloy are mixed to form amalgam. A device known as a triturator (or amalgamator) is used for this purpose. Capsules may require ....

activation before trituration, depending on the manufacturer's design. In this case, the manufacturer will supply an activator that breaks the barrier between alloy and mercury.

Some restorative materials, liek composite resin, can be used for ...

both indirect and direct restorations.

After the tooth is overfilled with amalgam, the dentist uses an assortment of carvers to remove the excess material and shape the amalgam to conform to the remaining tooth structure. Finally, a quick check of the occlusion (bite) is performed, adjustments made to the amalgam, and the amalgam is ...

burnished (rubbed) with a burnisher. Often the tooth being restored is so badly damaged that it requires additional steps to complete the amalgam procedure.

When properly performed, a cohesive mass of dental amalgam is formed that can be compressed into a hole that has been prepared in the diseased tooth. Timing is important because, after a short period of time, the maalgam hardens into a solid that can only be removed with the ...

dental handpiece and a bur. After the tooth is overfilled with amalgam, the dentist uses hand instruments to carve it into a form similar to the missing tooth structure it is replacing.

Different manufacturers' amalgam products have different mixing requirements. Always use the manufacturer's instructions (included in the product packaging) as a starting point for ...

determining the correct mixing time. Greater amalgam quantity requires longer mixing times; hence, a triple spill requires a longer mix than a single spell.

The way the amalgam handles in the tooth is greatly affected by alloy shape. Dentists tend to prefer one product over others based on ...

handling characteristics.

Placement of small portions of amalgam at a time followed by firm condensation of each portion ensures a long-lasting restoration without voids (spaces) in the ...

material. Overfilling of the tooth preparation ensures that the dentist has enough material to carve into a properly fitting restoration.

Amalgams can vary in the shape of their alloy particles. Amalgam manufacturers combine that alloy components (silver, copper, tin, and zinc) in the proper quantities, ....

melt them together, and then form them.

In the early 1800's, an alloy (called d'Arcet's metal) consisting of lead, tin, and bismuth was heated until it melted and poured into the cavity of the ...

patient's tooth. This was before the introduction of local anesthesia.

Early amalgams were made using shavings from ....

silver coins mixed with mercury in a mortar and pestle.

The interaction between the liquid mercury and the alloy particles is responsible for ...

the formation of the solid amalgam.

Mixing Time is Dependent on:

1. Type of amalgam (brand) 2. Quantity of amalgam to be mixed (single, double, or triple) 3. Triturator used for mixing the amalgam