PRD 146: Silver Amalgam

True dentalloy

GV black Produced the first commercial alloy called

Amalgam Formula

Black's Balanced Dental and 1% Zn. Plus Hg __ was incorporated into the ADA Specification for Dental Alloy in 1929

- 67% Ag

- 27% Sn

- 5% Cu

Smaller

In the 60s there were conventional low-copper lathe-cut alloys which had __ particles

lathe-cut

admixture of spherical Ag-Cu eutectic particles with conventional__

Metallic component of amalgam

- silver

- tin

- copper

- zinc

- palladium

- indium

41-51%

Besides the metallic component, how much mercury is in amalgam

Lathe cut alloy

irregularly shaped particles formed by shaving fine particles from an alloy ingot

Spherical alloy

small spheres of alloy particles produced by spraying a fine mist of liquid alloy into an inert gas environment

Admixed alloy

mixture of lathe-cut and spherical alloys

- good all around properties and is common today

gamma 2 phase of amalgam

Tin and Mercury

CuSn now replaces gamma two with the ETA PHASE!

Weakest

The gamma 2 phase is the __ phase

Corrodes

The gamma 2 phase ___ fast and voids form

Hg

The corrosion in gamma 2 forms __ which reacts w/ more gamma

10%

The gamma copper reaction composed __ of volume

Corrosion

The volume decreases w/ time due to

gamma 1 phase

silver and mercury (admixed high copper alloys)

Gamma 2

The gamma 1 phase tries to skip the __ phase

Ivoclar Vivadent

- Palladium enriched

- admixed (dispersed phase) alloy

- high copper

Triturators

dilutions of potent powdered drugs prepared by intimately mixing them with a suitable diluents in 1:10 DILUTIONS

Silamat

The triturator used at pacific

8

The trituration should last at least __ seconds

Over trituration

• Rapid hardening

• Shortened working time

• Setting contraction(<< 1%)

Increased

Over trituration has __ compressive strength

Wet

Over trituration has a __ look

Under trituration

• Crumbly, grainy mix

• Excessive free Hg

Decreased

Under trituration has __ compressive strength

Increased

Under trituration has ___ setting expansion and corrosion

Condensation

- drives out trapped air

- adapt closely to prep wall

- press out excess mercury

- can help create tooth form

Silver amalgam properties

• Compressive Strength

• Tensile Strength

• Corrosion

• Thermal Conductivity

• Creep

20

You must wait __ hours before polishing amalgam

Mercury

During condensation it presses out excess

Compressive strength

Measures the pushing force that one needs to break or

crush a material

Enamel

The strength of amalgam is more than adequate, similar to __ (384 MPa)

Tensile strength

Maximum load that a material can support

without fracture when being stretched,

divided by the original cross-sectional area

of the material

Pupal depth

When prepping for amalgam __ is important so you have enough material for compressive/tensile strength

48 Mpa

Tensile strength of Admixed alloy

thin

Amalgam is brittle when place in __ sections. Amalgam should have sufficient bulk to resist these forces

Corrosion

the deterioration of a metal as a result of

chemical reactions between it and the surrounding

environment. Both the type of metal and the

environmental conditions determine the form and rate of

deterioration.

margins

Corrosion is good for us because when it rusts, the oxidation product seals the __

Creep

Time dependent plastic strain of a solid under a static load or constant stress

copper

Creep is Much lower in high __ alloys but still

present

10; day

The amalgam is Very fragile for the first __ hours and durable after the first __

caries

Amalgam is Resistant to recurrent __

Macromechanical retention

Amalgam is a direct restorative material that is held in place by what? (No bond to tooth structure)

Bulk

Amalgam requires __ and often chips at margins (flash and deformation)

Local

There are __ health effects on amalgam bearers and dental providers

Environment

Health effects of mercury entering the __ from dental sources

Class II lesion

Caries affecting proximal surfaces of molars and premolars

Advantages of amalgam

• Strong, durable, economical

• Easy to use

• Self sealing ability over time (corrosion)

• Wear resistance similar to tooth

• Low micro leakage with time

Disadvantage of amalgam

• Metallic color

• Does not bond to tooth- relies on mechanical retention

• Marginal breakdown

• Controversy over mercury in the alloy as a health concern

GV Black's 7 Steps of Cavity Preparation

1. establish outline form

2. obtain resistance form

3. obtain retention form

4. obtain convenience form

5. remove carious dentin

6. finish enamel walls and cavosurface margins

7. cleaning the preparation

Outline form

• Eliminate carious tooth structure

• Margins should be placed on sound tooth structure

• Leave adequate cuspal support and marginal ridge support

• Include carious fissures and grooves

• Should be able to adequately finish the restoration

• Cavosurface is smooth and fluid

• No sharp angles

Resistance form

The shape and placement of the cavity walls that best

enables both the tooth and the restoration to withstand

occlusal forces without fracture

Occlusal pulpal depth

Amalgam requires proper __ for resistance form

Flat

For amalgam resistance form you must have __ pulpal floor perpendicular to forces of mastication

Bulk

For amalgam resistance form have sufficient __ of material

1.0mm

For resistance form the Isthmus width of __ to prevent fracture of the remaining tooth structure

Retention form

Shape or form of the cavity that best permits

the restoration to resist displacement through

tipping or lifting forces

Truncated

For retention form, Opposing walls being slightly

Length

Increased __ of walls will increase retention

Retention grooves

markings in the surfaces of the tooth that enhance placement and retention of the restoration

Dovetail

For retention you should have a ___

Convenience form

Shape that allows adequate preservation,

accessibility and ease of operation in preparing

and restoring the cavity preparation

DEJ

Extension of the cavity outline should ensure that all caries is removed from the peripheral __

dentin

In small sized lesions, the carious __ is usually removed during the cavity extensions

round bur

Moderate/deep lesions may require removal of carious dentin without further extension of the outline, best removed using an appropriate sized __ in a slow speed handpiece

Smoothen

__ all the walls of the preparation, no sharp angles

desiccate

Do not __ it, clean and remove debris to ensure that it is clean and ready for the restorative material

centered

Preparation should be __ on the central

development groove (outline form)

1mm

All pits and primary grooves should be removed,

__ extension into buccal and lingual grooves,

centered over the grooves (outline form)

Dovetail

Add __ on the opposite proximal wall (outline form)

1/2

Distance from marginal ridge - __ the distance from

distal pit to marginal ridge, parallel to the external surface

of the tooth

0.25-0.5mm

Buccal, lingual and gingival proximal clearances of

__ from the adjacent tooth

"S curve"

Angles of exit are 90 º at the buccal and lingual proximal

walls - some preparations require __ to achieve that

truncated

Buccal and Lingual walls are parallel to slightly

__ and are prepared on the long axis of the

crown

rounded

Buccal, lingual and distal walls meet the pulpal floor at

a slightly __ angle

flared

Distal wall is slightly __** why

parallel

Flat pulpal floor __ to occlusal plane

1.5mm

Pulpal floor __ deep at its shallowest point

90 º

In order to have a __ angle of exit on the

buccal and lingual proximal walls, an "S" curve

may be needed to be given on the outline form

when connecting the occlusal and proximal

box preparations.

triangular ridge

The "S" curve helps to conserve the

0.5mm

Axiopulpal bevel using a hatchet or a #330 bur at axio- pulpal line angle, not more than __ wide

Dentin

You place retention grooves in the ___ and not in the enamel and far away from pulp

1/4 round bur

Place retention groove with

Retention groove

used to improve retention and resistance with excessive taper, prevents rotational tendencies during cementation, helps guide cast into place, 0.5mm distance from finish line at D axial wall, 1.5mm wide at occlusal and 1.0mm wide at cervical (diverges occlusally) and 1.0mm deep pulpally at cervical base (finish line + groove)

Explorer

Check you retention groove with