FP 7 - Impression Material (Dr. Nui)

Can you box alginate impressions?

No!!!!!!!!!

What is used to obtain accurate replica of soft and hard tissues?

Impression materials

Accurate impressions are dependent upon what two factors?

- Optimal impression material characteristics

- Proper impression technique

These are physical properties of what?

- Good Dimensional Accuracy

- Good Dimensional Stability or Limited Shrinkage during Polymerization, shipping or storage

- Good Tear Strength or High Tear Resistance

- Excellent Flow (Wettability, Hydrophilicity)

- Flexibility and have Good Elastic Recovery when pass undercuts

- Long working time and short setting time

- Non-Toxic or Biocompatible

- Acceptable Odor & Taste

- Long shelf life

- Color should be saturated enough to detect captured margin

Impression materials

These are what types of materials? (rigid or elastomeric?)

- Plaster

- Impression Compound

- Zinc Oxide Eugenol

Rigid

These are what types of materials? (rigid or elastomeric?)

- Agar (Aqueous Elastomeric Impression)

- Elastomer (Non-Aqueous Elastomeric Impression)

Elastomeric

These are what type of material?

- Reversible Hydrocolloid

- Irreversible Hydrocolloid

Agar (Aqueous Elastomeric Impression)

These are what type of material?

- Polysulfides

- Polyether

- Silicone

- - Condensation Silicone

- - Addition Silicone or Polyvinyl Siloxane

Elastomer (Non-Aqueous Elastomeric Impression)

What type of impression material?

- Highly accurate and relatively low cost impression material

- Usually indicated for completely or partially edentulous impressions

- Supplied as base and catalyst pastes

- Available in low, medium, and high viscosities

- Moderate Hydrophilicity

- Condensation Polymerization Type with water as by product

Polysulfide rubber (mercaptan)

Is polysulfide hydrophilic or hydrophobic?

Moderate hydrophilicity

What type of polymerization does polysulfide undergo?

Condensation polymerization with water as a byproduct

What type of impression material has the following composition?

- The base paste contains polysulfide polymer, reinforcing fillers, and plasticizers

- The accelerator paste contains lead dioxide (30%), hydrated copper oxide or organic peroxide as a catalyst, 1% to 4% sulfur as a promoter, and dibutyl phthalate or other nonreactive oils (17%) to form a paste

Polysulfide rubber (mercaptan)

What type of impression material?

Polysulfide rubber (mercaptan)

What type of impression material?

- Equal lengths of base and catalyst

- Mix thoroughly with a stiff tapered spatula

- Mixing time is 45 to 60 seconds

- Working time is 5 to 7 minutes

- Working and setting times can be shortened by higher temperature and humidity

Polysulfide rubber (mercaptan)

A polysulfide rubber impression should be poured up within _______ to minimize water distortion

1 hour

(It requires 30 mins for a recovery time but impression continues to shrink b/c of water evaporation so you should pour a working cast after 30 mins but do not wait more than 60 mins)

What material is being used here?

polyether

What material is being used here?

PVS

What material is used in...

- RPD/CD prosthesis

- Implant to fabricate a soft tissue model

- Aid in registering patient's bite, facebow transfer, or as an index

PVS

What is used to...

- Create mould or a replica in any discipline of Prosthodontics i.e.

- Create a template for provisional restoration

- Create a flexible working when soft/hard tissue have significant undercut

- Create tooth reduction guide

- Create a guide for tooth set- up est.

Silicone

Which surface is hydrophilic: left or right diagram?

Right

(less than 90 degrees = hydrophilic, left is <150 degrees = hydrophobic)

Which material?

- High stiffness (but after year 2000, has become more stiffness than Poyether due to chemistry change in Polyether)

- Short working time

- Available in low, medium, and high viscosities

- Hydrophilic

Polyether

Polyether is hydrophobic or hydrophilic?

Hydrophilic

What type of impression material has the following composition?

- Supplied as two-paste system

- Base paste contains a low-molecular-weight polyether with ethyleneimine terminal groups, along with fillers and plasticizers

- Catalyst paste contains an aromatic sulfonic acid ester plus thickening agents and fillers

Polyether

For polyether, equal amounts of base and catalyst should be mixed rapidly for how long?

30 to 45 seconds

What is the working time of polyether?

2.5 minutes

What is the setting time of polyether?

4.5 minutes

When pouring up a polyether impression, you should wait at least how long?

30-60 min

How long is a polyether impression dimensionally stable for?

1 week

Define the following:

If you pull a spring with too much force and it has passed the yield strength, it won't recoil back to the same position. This is similar situation when the impression passes through the undercuts of both soft and hard tissue. The impression can be permanently distorted, if there were significant hard/soft tissue undercuts.

Spring effect

What is a type of silicone that forms as a result of a condensation reaction?

condensation silicone (has a by-product)

What polyvinyl siloxane is formed from the addition reaction of silicone elastomer?

addition silicone (no by-product)

What type of impression material?

- Used mainly for fixed partial dentures and single-unit partial coverage restorations

- Supplied as either two-paste or paste-liquid systems

- Available in low, medium, high, and very high (putty) viscosities

- Hydrophobic by nature of material

condensation silicone rubber

Condensation silicone rubber is hydrophobic or hydrophilic by nature?

Hydrophobic

What type of impression material has the following composition?

- Base paste usually contains a moderately high-molecular-weight poly(dimethylsiloxane), and orthoalkylsilicate for cross-linking and inorganic filler (30% to 40% filler, with putty containing as much as 75%)

- The catalyst paste (or liquid) will contain a metal organic ester and an oily diluent, plus a thickening agent

Condensation silicone rubber

What is the by-product of the condensation silicone rubber reaction?

Alcohol

What impression material?

- Manipulation same as Polysulfide

- Supply as base and catalyst

- When supplied as baste paste and liquid catalyst, one drop per inch of paste is the recommended ratio

- Setting time is 6-8 mins

- Higher Temperature and humidity shorten the setting time

- Require a very dried field (Hydrophobic material) and are difficult to pour in stone.

Condensation

What is the setting time of condensation silicone rubber?

6-8 min

What shortens setting time for condensation silicone rubber?

high temp, humidity

T/F: Condensation silicone rubber requires a very dried field (hydrophobic material) and are difficult to pour in stone

true

A condensation silicone rubber impression should be poured how soon?

- ASAP or after disinfection

- OR within 30 min of mouth removal to minimize distortion bc ethanol is by product

What impression material?

- Highly accurate impression material, suitable for all dental impression applications

- Available as light, medium, heavy, and putty viscosities

- Expensive

PVS or VPS or Addition (vinyl) silicones

PVS/VPS/Addition silicones are advertised as (hydrophobic or hydrophilic) because Mfg adds cosmetic grade surfactants to improve wetting of the material

Hydrophilic !!!!!

Most PVS are inherently (hydrophobic or hydrophilic)

Hydrophobic !!!!!

What should you avoid wearing when using PVS due to sulfur in the powder which inhibits polymerization of the material?

Latex glove

(Sulfur in the powder of latex glove inhibit polymerization of PVS material)

What type of impression material has the following composition?

- Silicone prepolymers with vinyl and hydrogen side groups

- One paste contains the vinyl-poly (dimethylsiloxane) prepolymer

- Second paste contains a platinum catalyst (chloroplatinic acid)

PVS or Addition (vinyl) silicones

With PVS/Addition (vinyl) silicones, if no hydrogen scavenger (Pt or Pd) is present on the formation, how long should you wait before pouring up?

1 hour

How long are PVS/Addition (vinyl) silicones dimensionally stable for?

1 week

What type of impression material?

Impregum medium viscoisty + Permadyne Low viscosity

What type of impression material?

Imprint Heavy Body + Imprint Low viscosity

Is this an acceptable impression?

No (mix and match material between two companies/ PVS and Polyether)

What is the infection control guidelines in the operatory after an impression?

- Rinse impression using cold running water to remove blood and debris

- Rub impression using Cavi Wipe

- Wrap it with Cavi-Wipe and place in plastic bag

What is the infection control guidelines in the laboratory after an impression?

- Place impression on a paper towel

- Spray with Cavicide in 4th floor Lab and leave it for 3 mins

- Rinse impression using cold running water

- Pour impression with Type III or IV dental stone

What is very common to place when you have moderate to severe undercuts of your prepared tooth (either by dental caries, iatrogenic prep, or pre-existing cervical abrasion) or an existing cervical abrasion on natural dentition that will serve as your abutment?

Reinforcement pin (provides fracture resistance during separation of impression from working cast)