Test review Flashcards by Cutler Frandsen

T/F Polysulfide is accurate but not stable compared to other elastomers because of its biproduct

True

How well did you know this?

Not at all

Perfectly

Which elastomers can be poured multiple times with reasonable accuracy?

PVS

Polyether

How well did you know this?

Not at all

Perfectly

What is the stiffest of the elastomers

Polyether

How well did you know this?

Not at all

Perfectly

What has the best tear strength of the elastomer

Polysulfide

How well did you know this?

Not at all

Perfectly

What is the second best tear strength of the elastomer

PVS

How well did you know this?

Not at all

Perfectly

Why don’t we use alginate for all of our impressions?

-Alginate doesn’t reproduce fine detail well even though it is an accurate impression

How well did you know this?

Not at all

Perfectly

T/F Polysulfide doesn’t smell very good

True

How well did you know this?

Not at all

Perfectly

Which elastomer doesn’t taste very good?

-Polyether

How well did you know this?

Not at all

Perfectly

What are the two variables that relate to create distortion in impression material?

Time

- Compression

How well did you know this?

Not at all

Perfectly

What principles deal with elastic recovery?

Time

- Compression

How well did you know this?

Not at all

Perfectly

How long does it take alginate to rebound (elastic recovery)?

8 - 10 minutes

How well did you know this?

Not at all

Perfectly

How much is an alginate compressed during removal?

10%

How well did you know this?

Not at all

Perfectly

How do we decrease the amount of time alginate is compressed during removal?

-Snap it out (get air into vestibule)

How well did you know this?

Not at all

Perfectly

which temporary material has a higher exotherm?

-Polymethylmetacrylate

How well did you know this?

Not at all

Perfectly

Which temporary material shrinks more?

-Polymethylmethacrylate

How well did you know this?

Not at all

Perfectly

What properties make polymethylmethacrylate desirable?

Great fracture toughness
Not brittle
Easily added to (modify its shape easily)

How well did you know this?

Not at all

Perfectly

What can unifast do that others can’t?

Light curable so you can control the set.

How well did you know this?

Not at all

Perfectly

T/F Polyethylmethacrylate (SNAP) is soft

True

How well did you know this?

Not at all

Perfectly

Would you want to use polyethylmethacrylate for anything other than a single unit?

How well did you know this?

Not at all

Perfectly

What is one method to take a gypsum stone die reinforced and stronger to be more resistant to abrasion?

-Low viscosity cyanoacrylate (basically super glue)

How well did you know this?

Not at all

Perfectly

T/F Calciumsulfatedihydrate is mined out of the ground

-True

How well did you know this?

Not at all

Perfectly

What type of stone is densate used to make?

-Type IV and Type V

How well did you know this?

Not at all

Perfectly

What type of stone is hydrocal used to make?

-Type III

How well did you know this?

Not at all

Perfectly

What is the most refined form of gypsum?

-Calciumsulfatehydrite

How well did you know this?

Not at all

Perfectly

What is the most refined form of gypsum?

-Calciumsulfatehydrite

What are the two most common ways to manufacture ceramic crowns?

- Milled | - Heat pressed ceramic (EMAX/llithium disilicate)

Zirconia is so hard it is milled in its green state?

Yes

Zirconia is in a pre-sintered (green state/larger form) and then is heated, what happens when it is heated (sintered)?

-It shrinks

If the light body is in the setting phase and then you insert the heavy body what happens to your bite record?

-It is inaccurate (open)

If the heavy body material is starting to set but the light body is still fine what happens when you insert the heavy body?

-The die will shrink or be smaller

What are the two biggest draw backs of hydrocolloids?

- Imbibition | - syneresis (sweating)

Dental stone casts reach their maximum strength after how many hours?

24 hours

What does the modulus of elastisitity define?

-The stiffness of a material

What material has the highest elastic modulus?

-Polyether

Clinically the resistance and retention form are satisfied, where is the most ideal place to put your margins with respect to the gingiva (esthetics is not a factor because it is the back of the mouth?

-1 mm above the gingiva (.5 mm pre clinically)

What is alginate made from?

-Potassium alginic salts from seaweed

If you under-reduce occlusaly what are consequences?

- Material to thin | - Over contouring by the lab

If you don't have enough axial reduction what are the consequences?

- Margins to thin - Over contoured axial crown - Create plaque trap with final crown

If you increase taper do you increase or decrease resistance and retention?

-Decrease in both

If you increase the surface area do you increase or decrease resistance and retention?

- Increase retention | - Doesn't always increase resistance

What will the final marginal gap be if everything is perfect (done with the lost wax technique)?

-10 microns

What three things always should be taken into consideration when doing a preparation?

- Biological - Esthetics - Mechanical

Why don't we want you to use a posterior plastic bite tray in the clinic?

-They can bend

Which impression materials can have their setting interfered with latex gloves?

-Addition PVS (sulfur in the latex)

Which impression materials can have their setting interfered with latex gloves?

-Addition PVS (sulfur in the latex)

Why is important to capture the area apical to the margin?

- Makes it easier to trim and find the margin | - Helps make contours

When impressions are set and done what do you want to avoid?

- Extremes of temperature | - Extremes that cause distortion

What are the main things you are trying to capture in your crown impression?

- Die - Prepared tooth - Opposing anatomy - Occlusion - Good adjacent tooth surfaces

What are some of the ways the impression material is kept adherent to trays?

- Perforation - Rim lock - Adhesive sprays

T/F Double sided mouth mirrors are a good retractor and a good visualizer

True

Name some hemostatic chemicals?

- Ferric sulfate - Epinephrine - Aluminum chloride

Why do we use retractions cord?

- Displace soft tissue temporarily | - Carrier of hemostatic agent

T/F Retraction cord can be braided or woven

True

What is the situation where you have to be careful using epinephrine as a hemostatic agent?

- Heart problems | - Lacerated tissues can cause tachycardia

How many ADA recognized gypsum types are there?

-5 types

What is calcination?

-Process of driving water off of gypsum products during refinement process

What type of stones are the hardest stones?

- Type IV | - Type V

Which stone is really hard and expands a lot?

-Type V

What is the advantage of vacuum mixing stone?

- Remove air bubbles - Harder set stone - More dense set stone - More abrasive resistant stone

Which type dental stone exhibits the least amount of expansion?

-Type I MOUNTING Stone

What is the Centrum?

-Cuspal tip against a flat surface at MI

What is tripodisation?

-The mountain engages the valley near the tip but not directly at the tip. Need to have equal contact between the three points or else teeth will move

What is the order that you place your models in the 3 M scanner

1) preparation arch 2) opposing arch 3) together 4) Die

Where is the buccal placed in the scanner?

-The back