10 -- Dental Amalgam Structure and Properties

amalgam is _____ to place

easy

is amalgam low or high technique sensitivity

low

amagam has good ____ sealing with time

marginal

amalgam has ______ properties

antibacterial

what is the life span of amalgam

beyond 10 years

amalgam has a lack of _____

esthetics

amalgam has a brittleness that can lead to ______ breakdown and bulk fractures

marginal

amalgam has susceptibility to ____ and galvanic reaction

corrosion

amalgam causes desruction of _____ tooth structure

sound

amalgam can be considered when _____ are not a concern

esthetics

amalgams are indicated for which classes of restorations?

large class I, II and some posterior class V

amalgam can be indicated for ______ prior to

base-up

amalgam is indicated when ___ is an important concern for the patient, including large _____-____ restorations

cost

stress-bearing

amalgam is indicated for patients in whom ____ ____ is difficult

moisture control

can make amalgam even in the presence of saliva and blood it is not as sensitive

amalgam is an ____ containing lqiuid metal (usually Hg) as one of the components

alloy

mecury is needed in amalgam to form a _____ ____

manipulable paste

is mercury needed in amalgam for strength?

Not needed for strength – the amalgam powder is already strong but can’t be shaped without mercury

3 classifications of amalgam

particle (shape)

amount of copper (Cu)

Presence of Zn

particle shape: Lathe cut

Irregular particles from ____ ingot 

AgSn

Lathe cut has low __

Cu

is not clinically used in the US

Particle shape: powder atomization

_____ particles

spherical

spherical is used for all restorations EXCEPT _____ _____

cuspal converage (brown capsule)

Particle shape: Admixed

Combines ____ cut + ______ particles

lathe

spherical

admixed is used for _____ _____

cuspal coverage

Amount of Cu:

Lathe cut has ___ copper - ____ is a filler

low

AgSn

Amount of Cu:

Admixed alloy has ___ Cu

high

Amount of Cu:

Spherical has ___ Cu

high

Presence of Zn:

____ handling

improves

what are the 4 types of particles in amalgam:

Ag, Sn, Cu, Zn

High Cu alloy vs. low Cu alloy:

•  High Cu = ____ GAMA 2

less

since Cu captures Sn, preventing SnHg formation

Process of combining particles (lathe cut, spherical, or admixed) with liquid mercury to form a workable mixture (don’t need to know chemical rxn formula)

amalgamation

which reaction has significant amounts of GAMA 2

Lathe reaction

A. Lathe Cut Rxn

Ag releases 1^st (more abundant) and then reacts with Hg to form _____ _____

silvery mercury

the formation of silvery mercury is called _____

GAMA1

Ag +Hg = silver mercury aka GAMA1

GAMA1 is the ____ component

strong

A. Lathe Cut Rxn

2. Sn releases 2^nd and reacts to form _____ ____

tin mercury

tin mercury (Sn8Hg) is also called ____

GAMA2

GAMA2 is the ____ component

weak

A. Lathe Cut Rxn

3. Copper and tin react to form ____ (minor rxn)

epsilon

B. Admixed Rxn

1. Cu reacts 1^st and reacts with __

Sn - tin

B. Admixed Rxn

2. _____ is almost absent since Cu reacts with the Sn, preventing Sn from reacting with Hg to form _____

GAMA 2 ×2

C. Spherical Rxn

1. __ and _ are together inside the spheres – spheres react too rapidly with Hg to permit working time for cuspal coverage.

Cu and Sn

C. Spherical Rxn

2. No Sn released alone – always together with Cu = No ____

GAMA2

Why we avoid Gama 2

More fracture, wear, chipping, staining, corrosion

Condensing results in ____ ____

marble effect

imagine pressing a fist into a container of marbles – marbles roll away and pile up on the other side)

spherical amalgam

Condense in __ min, sets in _ min

2

3

spherical amalgam

_____ condensation back pressure

low

spherical amalgam

use for ____ to ____ sized restorations

small to moderate

spherical amalgam

Not good for pushing against the matrix to achieve ____

contacts

– better if contacts are already ideal

spherical amalgam

____ early strength

highs

spherical amaglam

_____ carving

smooth

Admixed amalgam

condense in _____ min, set in ____ min

3-4

6-10

admixed amalgam

____ condensation back pressure for ___ packing

higher

firm

admixed amalgam

For _______ restorations and foundations

large/complex

want to use _____ if its hard to get contacts or proximal contours

admixed

Admixed amalgam

Has ____ early strength

low - dont remove band too early

Gama, Gama 1, Gama2 strength rating

Gamma> gama1>> gama2