............. ........................ is a mixture of mercury, silver, tin, copper, and other elements

Amalgam has several characteristics that make it popular

AMALGAM

Lack of Biocompatibility, specifically the toxic and allergenic potential, has received attention

Uses of Amalgam

Classification of amalgam is according to .........A.......... and ................B.................

(Comminuted)-made by filing silver-tin alloy on a lathe.

Irregular shape (200 microns) • Less mushy

Alloy melted and sprayed through a nozzle to form small droplets, quickly cooled to preserve shape (100 microns)

• More mushy

Require less condensation

• Requires heavier wedging

• Require less Hg

• Faster set

Require greater condensation

• Better proximal contacts

• Easier to carve

• Longer working time

Causes setting expansion and increase strength and corrosion resistance

causes setting contraction and decrease strength and corrosion resistance

longer clinical life expectancy than non-zinc

corrosion resistance

High Copper Amalgams

• Virtually all amalgams placed today are of this kind

Silver~ 40-70%

Tin~ 22-30% + Copper~ 13-30 %

Zinc~ 0-1%

Mercury~40-45% slightly lower

Dental Amalgams are a mixture of elements and Phases/rxns:

• All 3 phases combined produce the dental

amalgam. Levels of the different elements can be

changed to improve clinical performance

Strongest and most corrosion resistant. ~¼ of the volume of the dental amalgam

Somewhat strong, but brittle. Corrosion resistant.

~½ of the volume of the dental amalgam.

This phase is the matrix phase that holds this multi-phase material together.

The weakest phase and MOST CORROSION PRONE.

~1/10 of the dental amalgam.

The weak link in the structure

Low copper amalgams(more Hg):

• Tin reacts with mercury to form tin-mercury compound called Gamma-2 (Sn-Hg) rxn. *.......A...... and more .......b......... to corrosion

High copper amalgams (less Hg):

• Tin reacts with copper to form Sn-Cu compound. This is part of the Gamma 1 (Ag-Hg) rxn. *..........a.......... and ........b........... to corrosion

3 Main Factors affecting handling

Trituration: the process of mixing mercury with a silver alloy in a mechanical device at high speed to produce a dental amalgam

Amalgam is somewhat plastic (moldable) and condensable and remains so for ...... to ....... minutes

Free mercury is no longer present in amalgam after the first few hour's post-trituration

Gap closes over a few months after being submerged in saliva

Defined as flow or dimensional change produced under constant stress

High modulus of elasticity, strong in compression-STRONGER COMPRESSIVE STRENGTH THAN ................................

All amalgams corrode in saliva

•Poorly condensed, pitted, porous, and rough amalgams are going to corrode quicker

COMPOSITES

Types of wear

from the movement of objects such as food or toothpaste across surface, more uniform

COMPOSITE TYPES OF WEAR

direct contact with opposing teeth, more aggressive wear

COMPOSITIES

Clinical Success

Average lifetime for composites ............. years for class I and II restorations

Strain Hardening GOLD

The process of imposing stress on a metal and inducing a dimensional change or strain. Soft metal, like Gold, will undergo these forces causing a 100 times increase in hardness and strength.

•It is simply the use of permanent deformation to increase the strength of a metal.

Results of Poor Carving

Temporary restorative must be

Types of Temporary Materials

Zinc Oxide Eugenol

Generally PREFERRED BECAUSE considered to be non-irritating - eugenol has a neutral pH and an ....................... (sedative) effect on pulp tissue.

Has antibacterial properties

Seals cavities (little dimensional change)

Some formulations (IRM) are REINFORCED (strengthened) with polymethyl methacrylate (PMMA) beads (polymer modified) Some have aluminum oxide particles with ethoxybenzoic acid (EBA) in liquid portion

ZOE materials set by a

Properties of Zinc Oxide Eugenol

All breakdown and wear excessively and should be limited to a maximum of 1 year

Used as temporary crown and bridge material

Direct and Indirect techniques

Both require an alginate impression prior to prep. Both use a template

Direct-place template with acrylic on prepped teeth in mouth

Indirect-place template with acrylic on model of prepped teeth

Light-curing composite can be used w/ either technique as well.

Crown & Bridge Temporaries Techniques

Zinc Oxide Eugenol (ZOE) Uses

when one or more cusps are restored, but not the entire tooth crown.

portion of tooth restored is within the cusps

Veneers-Thin layer of material that covers another material

............A.............. Use bonded composites; very little or no tooth structure removed; considered reversible

..........B.......... Use porcelain; facial surface is prepped; not reversible.

Retainer-the seated .............. portion of a dental bridge.

Pontics: the replacement of a missing tooth

Dental Bridge: replaces missing teeth.

Abutment-the ................ teeth used as support

Choice for a given restoration must be based on :

Type and size

Location in the mouth

Oral habits of the patient

Patient’s wishes

Opinion of the clinician/DDS

process by which inlays, crowns, bridges, and partial denture frameworks are made. Wax pattern is heated, vaporized, and subsequently replaced by metal

Are the replicas of the shape of a Prep to aid in construction of a restoration or appliance. ie: crown, inlay/onlay

refers to the process of pouring a liquid metal into a cavity prep in a mold to produce a restoration or appliance. Reproduces the shape of the lost tooth structure.

Proper Sequence in casting a restoration for a patient

1. Polish

2. Burn out (wax)

3. Cast w/ alloy

4. Wax pattern

5. Invest (gypsum)

w/ alloy  5. Polish

Overall technique

Impression made of prepared tooth Stone model (cast) formed to create a Die of the prepped tooth

DIE: ................. replica of a single tooth is then trimmed.

Investment heated during burn-out to vaporize/remove wax: causes thermo expansion of the investment and raises the temperature of the investment closer to that of the heated metal.

1. Has a small tube connecting a wax pattern to a sprue base

2. Provides a channel for molten metal to flow through during the casting process 3. Serves as a route creating an opening or ingate for the mold

Uses of Waxes in Dentistry

...................... major component of most dental waxes

used to make inlays, onlays, crowns, bridges, partial denture attachments, setting denture teeth

Thermoplastic reaction (ALL Waxes soften and harden on heating & cooling)

........................................... used for bordering impression trays, temporarily attaching objects.

2 Types:

Boxing (utility)waxes- are soft with low melting temperature (rope wax) Extend alginate tray

Sticky waxes - are hard with higher melting points

.............................................. used for taking edentulous impressions, bite registrations  Minimal stability, are not used very much for impressions

Inlay pattern waxes are hard at room temperature and ................ or .................. in color, used to fabricate crowns

Casting pattern waxes are softer and used for partial frameworks and are ................. red or blue in color

Baseplate waxes tend to be harder and more brittle, supplied in sheets, and are .................... in color, used in processing of dentures

Use of metals based on

..................................... (recoverable strain, atoms move but return). Example: spring

(permanent, atoms move but do not rebound when force is removed). Example: bent spoon

describes stiffness

stress required to produce permanent (plastic) deformation

Strain Hardening (cold working)-process of bending (straining) a metal beyond its maximum flexibility to increase hardness

heating process to eliminate the effects of strain hardening, returns the metal back to the starting value.

Some of the metals used in Dental Alloys

Primary Reason for polishing: Reduce surface tarnish and potential for plaque accumulation