Impression materials

______________ type of impression materials are hydrophilic thus subject to imbibition

-Agar -Alginate

What are all the alternatives to using Lead peroxide as a reactant in Polysulfides? What are the downsides of using these?

-Copper hydroxide -Organic peroxides --> dimensional stability is poor, b/c organic peroxide residues volatilize after material cures

List main reactant & Catalyst of Vinyl polysiloxane

-Dimethyl siloxane w/ Vinyl group termination (C=C) -Dimethyl siloxane w/ Hydrogen terminations +CPAE (chloroplatinic acid ester) catalyst

List the main reactant & catalyst of Polyether rubber:

-Epimine prepolymer -Sulfonate catalyst (+ fluid thinner)

Early Vinyl polysiloxanes had trouble with ________________ because of hydrophobicity

pouring up a BUBBLE-Free die

Define Imbibition

process when the set hydrocolloid gel is immersed in water and takes up water by osmosis and SWELLS.

(Agar/Alginate) is more fluid, thus records FINER surface details & dimensionally more accurate

Agar

Both Agar and Alginate (hydrocolloids) are non-toxic and non-irritating, but with 2 possible exceptions- explain:

Agar - discomfort due to thermal shock Alginate - large amount of diatomaceous earth filler; too much dust can cause respiratory problems ("Silicosis")

Alginates are disinfected by: Agar is disinfected by:

Alginates -SPRAY dilute sodium Hypochlorite solution Agar -Iodophor spray or Ethylene oxide

_____________ in Agar gel is a Micro-organism growth inhibitor

Alkyl benzoate

For _______________, ratio of base/accelerator by manufacturer must strictly be adhered For _______________, ratio of base/accelerator can be variable (as long as it's within its limit)

Polysulfides (b/c Each reactant is in different tube) Condensation silicones (b/c both reactants are in ONE tube)

The role of CaSO4 in Alginate:

Provides Calcium ions to crosslink the gel --> setting

Polysulfide's working/curing time may be extended by adding _______________ ; Polysulfide's working/curing time may be shortened by adding _______________ ;

Retarder (oleic acid) ; Water

Reversible vs. Irreversible Hydrocolloid

Reversible - sol-gel transformation occurs w/ reduction in temperature (cooling) Irreversible - sol-gel transformation occurs by Chemical reaction

Agar is a ____________ type of impression material

Reversible Aqueous hydrocolloids

Under what circumstances do Hydrocolloid impressions undergo Viscoelastic effect:

Slow stress = plastic deformation Quick stress = Elastic deformation

Chemical reaction of Alginate setting reaction

Sodium alginate + CaSO4 --> Calcium alginate (cross-linked form)

_______________ : process in which forces that draw polysaccharide chains together during gelation push an exudate of water out to the surface

Syneresis

Advantages of Agar

<Advantages> -dimensionally accurate -hydrophilic -easy to pour up -Displaces moisture, blood, fluids -no custom tray/adhesives -Pleasant -No mixing required

List 2 major reactants and catalyst of condensation silicone:

<REACTANTS> -Hydroxy-terminated poly(dimethyl siloxane) prepolymer -Tri/Tetra-functional alkyl silicate or hydrogen siloxane -CATALYST: DBTDL (dibutyltin dialaurate) catalyst

Hydrocolloid

A type of Colloid, where the medium is water -sol transforms into gel through agglomeration of molecules to form FIBRILS, which form interlocking network enclosing the water

Out of all elastic impression materials, ______________ has the poorest dimensional accuracy and stability

Condensation silicone

Setting reaction of _______________ gives Ethanol as byproduct (Ethanol=volatile)

Condensation silicone

______________ involves setting reaction w/ Hydroxy (OH) terminated prepolymer or Organo hydrogen siloxane

Condensation silicone

_____________ impression materials are most widely used in operative and crown and bridge

Elastomeric impression materials

Hydrocolloid impression materials have poor shear strength compared to _____________

Elastomers

Setting reaction of ______________ impression material is Self-accelerating

Polysulfide (Water is produced by byproduct - also acts as a accelerator for cure reaction)

In _____________ impression material, Maximum mixing time is NEVER more than 1 minute

Polysulfides

Setting reaction of ______________ impression materials involve Condensation of Thiol groups (-SH) -terminated prepolymer with Lead peroxide

Polysulfides

________________ have the highest tear resistance of the elastomers

Polysulfides

________________ impression material have 4th additional class category with an extremely high putty-like consistency

condensation silicone

Condensation silicones have Poor dimensional accuracy/stability probably due to ______________

evaporation of Ethanol (byproduct)

Lead peroxide gives Brown color in Polysulfides, so this can be replaced by _______________ to give it more pleasant color

Copper Hydroxide (Cu(OH2))

______________ in Alginate powder is added for cohesiveness and increased strength

Diatomaceous Earth powder ("dust")

_____________ is used as a "filler" in irreversible hydrocolloids (Alginate)

Diatomaceous earth filler

Highest tear resistance of elastomers are (Advantageous/Disadvantageous)

Disadvantageous ; (it means it can undergo highest permanent deformation)

______________ type of impression materials are subject to shrinkage, imbibition (swelling), syneresis

Hydrocolloid impressions (agar, alginate)

______________ type of impression materials are subject to viscoelastic effect

Hydrocolloid impressions (agar, alginate)

______________ type of impression materials require that the Cast be poured ASAP

Hydrocolloid impressions (agar, alginate) (due to evaporative shrinkage)

Byproduct of setting reaction of Vinyl polysiloxane:

Hydrogen gas -negligible effect -non-volatile -can create bubbles though (creating porosity)

______________: process when the set hydrocolloid gel is immersed in water and takes up water by osmosis and SWELLS.

Imbibition

In Hydrocolloid impressions, Stone surface can be improved by ______________

Immersion in fixing bath containing SULFATE ions (e.g. potassium sulfate)

Alginate is a ____________ type of impression material

Irreversible aqueous hydrocolloids

______________ Elastic impression material has LOWER range of working/curing times (so requires rapid mixing)

Polyether Rubber

______________ Elastic impression material has no other alternative method to alter the curing time, thus demanding users to strictly adhere to its mixing time limit.

Polyether Rubber

______________ involves setting reaction of cross-linking of difunctional EPIMINE-terminated prepolymer through Alkyl benzene sulfonate catalyst

Polyether rubber

______________ Elastic impression material has NO BYPRODUCT during setting reaction, so dimensional stability is much better

Polyether rubber (and Vinyl polysiloxanes)

______________ Elastic impression material has NO CLASSES available

Polyethers Rubber

Sol vs. Gel state

(2 states of Colloid) -Sol: viscous liquid -Gel: when material "sets" into elastic solid (Jell-O)

Describe how Polyethers are made heavy vs. medium bodied:

(thinners are supplied separately in a tube) -material without thinner = "Heavy bodied" -material w/ thinner added = "medium-bodied"

Disadvantages of Polysulfides:

-Highest tear resistance of elastomers (permanent deformation) -Offensive color/odor

Disadvantages of Agar

-Initial expense of armamentarium -Material needs to be prepared in advance -tears easily -dimensionally UNSTABLE (must immediately pour, single cast) -difficult to disinfect (b/c hydrophilic)

What were the solutions to Making the casting fit with Vinyl polysiloxanes?

-Painting die spacer on model -Use type 5 High expansion die stone -Use material w/ acceptable dimensional stability but "poorer" dimensional accuracy

List All Non-elastic Impression materials:

-Plaster -Impression compound -Waxes -ZOE

3 main Reactants that play a role in setting reaction of Polysulfide :

-Polysulfide prepolymer (-SH) -Lead peroxide -Sulfur

List all compounds used as antimicrobial agents in Alginates:

-Quaternary ammonium compounds -Chlorohexidine gluconate

Condensation Silicone are also called:

-Silicone -Polysiloxane

Define Colloid

-intermediate between solution & suspension -particles so small that most atoms/molecules are exposed on surface -exist in sol or gel state

Vinyl polysiloxane is also called:

-polyvinyl siloxane -addition silicone

Increasing Hydrophilicity of impression material is important in _________________ but has nothing to do with ________________

-pouring up a BUBBLE-FREE cast -ability to DISPLACE MOISTURE

define Syneresis

-process in hydrocolloid, where FORCES that draw these molecules together during gelation do not stop --> enclosed water, low MW polysaccharides, and other ingredients are forced pushed out to form layer on surface (e.g. gello or yogurt)

Composition of Agar Gel

-water -agar -borax -KSO4 -Alkyl benzoate

Explain the steps of Sol-to-gel of Reversible Hydrocolloid

1. Liquefy the gel (Gel--> sol) 2. cool it down to "warm" temp 3. Play in tray 4. Cool w/ water bath 5. Converts sol --> gel

List the component of Vinyl polysiloxane

1. Vinyl functional prepolymer+ catalyst 2. Hydrogen functional prepolymer

List All Elastic Impression materials:

Aqueous Hydrocolloids -Agar -Alginate Non-aqueous elastomers -Polysulfide -Silicones (condensation/addition) -Polyether

List all components of Polysulfides

Base -polysulfide prepolymer -CaSO4 (thickener) -ZnO (pigment, thickener) Accelerator -Lead Peroxide (color) -Dibutyl Phthalate -Sulfur

When you want to shorten/elongate the curing time of Polysulfides, you don't want to change the RATIO of base/accelerator. WHY?

Because Accelerator is NOT a catalyst, it's a REACTANT. So stoichiometry matters, very important. --> also it will drastically affect elastic properties and dimensional stability of product

______________ in Agar gel strengthens the gel

Borax

______________ in Agar gel retards the setting of gypsum ______________ in Agar gel accelerates the setting of gypsum

Borax; KSO4

____________ chemical group of Alginic acid allows reaction w/ sodium to form alginate salt or w/ salt to form cross-linked form

COOH group

______________ in Alginate powder is a Calcium crosslinker (cross-links alginate molecules together) ______________ in Alginate powder precipitates (or "ties up") Calcium to retard gelation rate (allow enough time for mixing, tray loading, insertion)

Calcium sulfate Sodium phosphate

_______________ in Polysulfides is a thickener & reinforcer _______________ in Polysulfides is a Thinner

Calcium sulfate ; Dibutyl phthalate

Name the usages for each class of Polysulfide: -Heavy bodied (I) -Medium bodied (II) -Light bodied (III)

Class I - lower impressions in dentulous pt, tissue displacive technique in edentulous pt Class II - TRAY LOADING for routine dentulous impressions Class III - syringe technique w/ dentulous pts (and sometimes for mucostatic impressions w/ edentulous pt)

Out of all 3 classes of Polysulfides, ____________ have the longest setting time.

Class III (b/c additional time is required to load the syringe)

How does Cold water vs. Hot water affect Gelation rate of Alginate?

Cold water : SLOW down gelation Hot water : SPEED gelation

Polyether Rubber is also called:

Epimine

In polysulfides, ________________ contributes to dimensional instability of cured product

Evaporation of water

In setting reaction of Polysulfide, ______________ is the main reactant; _____________ is a byproduct

Lead peroxide (PbO2) Water + Lead sulfides

Polysulfides are also called

Mercaptan thiokol Rubber base

Impression material is used to form a (negative/positive) form of teeth/tissues

NEGATIVE

In VPS, some manufacturers add _____________ to absorb the hydrogen byproduct as it is formed

Palladium

________________ elastomer had TOO high dimensional accuracy that made the restoration not fit on teeth

Vinyl Polysiloxanes (no space for cement)

"Addition silicone" is commonly called a ________________

Vinyl polysiloxane

__________________ elastic impression material is used with Caulking guns that express the material through mixers

Vinyl polysiloxane

In _______________ elastic impression material, surfactants have been added to increase hydrophilicity

Vinyl polysiloxanes (addition silicones)

_______________ elastic impression material has the best dimensional accuracy, stability, and elastic recovery

Vinyl polysiloxanes (addition silicones)

Impressions of Hydrocolloid material should never be "rocked or eased out of mouth" due to ________________ properties

Viscoelastic property

In polysulfides, ________________ speeds curing/setting reaction

Water (e.g. absorption from humid air)

______________ in Alginate powder strengthen the gel and improve stone surface

ZnO, Borates, Fluorides, silicofluorides, silicates