Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Fixed Prosthodontics > Impressions > Flashcards

Impressions Flashcards

1
Q

What are some common undercut areas that should be blocked out

A
  • Buccal sulcus
  • When there is periodontal bone loss
  • Large interdental spaces
  • Beneath bridge pontics
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Why should we try to block out undesirable undercut areas

A

As addition cured silicones and polyethers are rigid once set and will flow into and become lodged into these undercut areas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

At what point in the crown procedure should we check for and block out undercuts

A

Before taking an impression

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What should we use to block out undesirable undercuts before impression taking

A

Soft wax e.g. ribbon wax

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are some advantages of using normal stock trays

A

They’re commercially available and cheap

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Why should you not use stock trays made from flexible plastic

A

These will flex under load and distort the impression

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

When are adapted stock tray used

A

Sometimes required when taking an impression of a last standing molar

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

When do we need to use a custom/special tray

A

When the shape of the arch, tooth alignment or other anatomical features prevents a stock tray from seating properly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the disadvantages of using a custom/special tray

A
  • Additional lab procedures and costs
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Why should you not use heavy bodied silicones for crown impressions with special trays

A

If the material sets in undercuts, removal will be v difficult and may require sectioning the tray while its in the patients mouth to salvage the situation - can take hours

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the uses of using a triple tray for crown impressions

A
  • Taking an impression of a single prepared tooth where the patient has a stable occlusion and adjacent teeth present
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are the disadvantages of using a triple tray for crown impressions

A
  • Dynamic occlusion/articulation and guidance movements for the whole arch are not replicated
  • Results in a less accurate restoration morphology requiring more occlusal adjustment at the fit appointment
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Why is moisture control important

A
  • Patient comfort
  • Improved operator vision
  • To help obtain an accurate impression
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What can be used to ensure good moisture control

A
  • Wide bore suction
  • Salivary ejector
  • Cotton wool rolls in buccal/lingual sulcus
  • Cellulose pads
  • Rubber dams
  • 3 in 1 air
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the aims of a good impression

A
  • Create an exact replica of the prepared and adjacent teeth from the patient mouth to the dental lab
  • Free of air bubbles, especially on the finishing line
  • There must be no drags or distortion in the impression material
  • Include accurate occlusal surfaces of all teeth in the arch
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Why should the mouth and tooth be dry when using addition cured silicones (elastomers) for crowns

A

The addition cured silicone is hydrophobic

17
Q

What is a light bodied elastomer used for

A

this is a fluid material that is for syringing around the tooth preparation to obtain great surface detail

18
Q

What is a medium bodied elastomer used for

A

Consistency is suitable for syringing and mass filling of the tray

19
Q

What is a heavy bodied elastomer used for

A

Only suitable as a tray borne material

20
Q

Why is a putty less accurate than a heavy bodied elastomer

A
  • Putty is less flowable
21
Q

Why do polyethers need to be stored dry

A

As this material takes up water

22
Q

Why are polyethers only used in a mono phase single stage impression technique

A

As polyethers, unlike silicones, only come in one viscosity

23
Q

What are polyethers particularly suited for

A

For implant prosthodontics

24
Q

AY BAWS CAN I HABE DE NOTE PLZ

A

Polyethers have good elastic properties

Also Hydrocolloids aren’t used for crowns

25
Q

What are hydrocolloids used for

A

Opposing model and study casts (not crowns)

26
Q

What are some of the disadvantages of hydrocolloid materials

A
  • Poor tear resistance
  • Dimensionally unstable - if stored dry, they shrink, if stored in water, they swell
  • Inferior impression detail to addition silicones
27
Q

What is the preferred technique for impression taking

A

2 phase, single stage

28
Q

Describe the 2 phase, single stage method of impression taking

A

2 materials of different viscosity are used to take a single impression with a light bodied wash being syringed around the tooth prep to record fine detail and a heavy bodied loaded into the tray to take up the bulk of the space between the prep and the tray

Take the impression in the supine position

29
Q

What is a good tip to use if you are using a new cartridge of I assume light bodied ting but maybe the heavy one im not sure

A

Syringe a small amount of the impression material onto a mixing pad as there may be some air bubbles present leading to some of the material being in an unmixed state

30
Q

What should be done with the tip of the impression gun when using it and why

A

Always keep it in the syringed impression to help avoid air bubble formation

31
Q

How should you syringe the impression material onto the tooth prep

A
  • Start around the gingival sulcus and finish lines of the prep and work your way around and up the tooth like mr.whippy ice cream
32
Q

How should you try to remove the impression from the mouth

A

Don’t just lever on the mouth and try to break the seal posteriorly first and then remove the impression

33
Q

What are the main differences between the 2 phase, 1 stage and the 2 phase, 2 stage techniques of impression material

A
  1. before tooth prep, take a heavy bodied impression of the arch
  2. After tooth prep, syringe light bodied around prepped tooth and inside the tooth concerned in the original impression, then re-seat the impression and what for the light bodied silicone to set
34
Q

What are the main differences in the 2 stage injection moulding technique and the 2 phase, 1 stage technique

A
  1. Before tooth prep take a heavy bodied impression of the arch
  2. Once set, remove and drill a hole/channel through the impression material, in the area of the tooth which is to be prepared
  3. After preparation, seat the adjusted heavy bodied impression tray and inject the light bodied through the channel and wait for it to set
35
Q

Where can the 2 stage injection moulding technique be useful

A

On lower posterior impressions where moisture control is v difficult to achieve or in patients who have a v active tongue

36
Q

What should you check for in the impression of the prepared tooth

A
  • All prep margins should be clearly visible

- No drags or air bubbles on the prep margins, axial walls, in slots, grooves or boxes

37
Q

What should you check for in the impression of the other teeth besides the prepped one

A
  • Adequate impression of the entire arch to ensure the occlusion and shape of the other teeth are recorded
  • Check for air bubbles on occlusal surfaces
38
Q

What can happen if there are air bubbles on the occlusal surface of the teeth

A
  • It will make the cast rock and will inevitably lead to a crown being made that doesnt fit into the patient’s occlusal scheme

Fixed Prosthodontics (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions