DENTURES2

Question 1

What is an Impression?

Answer 1

Negative replica of tissues which is converted into positive model cast in stone or plaster

Question 2

What are the main impression materials used in denture making?

Answer 2

Alginate

Impression compound

Silicone

Polyether

Question 3

What other impression materials may be used to aid denture construction?

Answer 3

ZOE- not elastic

Agar (reversible hydrocolloid)- duplication of casts

Impression plaster

Impression waxes

Question 4

What are the advantages/disadvantages of alginate?

Answer 4

ADV- cheap, easy to use, elastic, accurate

DIS- messy, poor dimensional stability (but ok for dentures)

Question 5

What are the features of impression compound?

Answer 5

Non-elastic (only used for free end saddles)

Poor surface detail

Expensive

Messy

Only used for primary impressions

Can burn patient

Question 6

What are silicones and polyethers used for?

Answer 6

Master impressions- more accurate than alginate

Question 7

What are the features of silicones

Answer 7

Dimensionally stable

Hydrophobic

Variety of consistencies

Can be messy to use

Very accurate

Question 8

What are the features of polyethers?

Answer 8

Dimensionally stable

Hydrophilic (better)

No variety of consistencies (always medium body)

Can be messy to use

Very accurate

Question 9

What is the clinical relevance of impressions?

Answer 9

Allows link and communication between dentist and technician

Question 10

What tray should be used in complete dentures?

Answer 10

Edentulous tray- shallower

Should engage over alveolar ridge and engage full depth of sulcus

Question 11

How do you choose the right tray?

Answer 11

Look and estimate correct size

Try it in:
Too small if flanges hit ridge

Too large- stretches mouth

Question 12

When do you sue elastic impression materials like alginate?

Answer 12

If there are undercuts

Use non-elastic if no undercuts

Question 13

Where should you stand when taking an impression?

Answer 13

Upper- behind

Lower- in front

Question 14

What are the steps in taking an alginate impression?

Answer 14

Rotate the tray in

Position the tray before seating it

Manipulate the tissues (pull lip over etc)

Keep holding the tray until it is set

Question 15

What are the steps in preparing impression compound?

Answer 15

Immerse in water bath at 55-60°C for 4-5 mins- ensures complete softening

Place gauze/paper towel at bottom of bath to prevent sticking

Handle with vaseline on gloves

Question 16

What happened if you knead compound?

Answer 16

Water is incorporated and acts as plastciser

Question 17

What happens if you leave impression compound in bath too long?

Answer 17

Becomes difficult to handle- components leach out and affect properties

Question 18

How do you take an impression using compound?

Answer 18

Rotate the tray into patients mouth

Use firm pressure to seat tray

Tissuemoulding

Remove the impression

Question 19

What should be checked when inspecting impressions?

Answer 19

Is denture bearing area covered

Peripheral seal (should be difficult to remove)

Surface detail- accurate

Can a satisfactory cast be produced

Question 20

How are impression decontaminated in GDS?

Answer 20

Rinse under tap to remove gross debris or saliva

PERFORM- 10mins

Question 21

What should be detailed in the stage and date sections of the prescription card?

Answer 21

Stage- what you want done

Date- when is work required

Question 22

Following a primary impression what should you ask the lab to provide?

Answer 22

Light cured special trays with handles (IO or EO) with spacing

Casts

Question 23

How much spacing is required for different materials?

Answer 23

Alginate- 3mm

Silicone or polyether:
Upper- 2mm
Lower- 0.5-1mm

Question 24

How do you correct an under/over-extended special tray

Answer 24

Over- trim extension

Under- border moulding

Question 25

What is border moulding? (may not be needed for alginate)

Answer 25

Addition of material (greenstick/silicone or wax) to the outside of the periphery of the trays to fill the functional sulcus

Question 26

Where are stops prescribed to be positioned to create space in the upper tray?

Answer 26

In canine and post dam regions (whole posterior border)

Question 27

What are the purposes of occlusal stops?

Answer 27

Allows accurate correction of posterior borders of tray Preform space for impression material Help stabilise special tray

Question 28

How thick should the occlusal stops be for different impression materials?

Answer 28

Alginate- 3mm Light body silicone- 1mm

Question 29

Where are occlusal stops prescribed to create space in the lower tray?

Answer 29

Retromolar pad Ridge in canine areas

Question 30

What do we look for upon inspection of master impression?

Answer 30

Coverage of denture bearing area Good functional sulcus Good surface detail Suitability for master casting

Question 31

What does the replication of the functional sulcus help the technician with?

Answer 31

Getting right flange width

Question 32

What do we want the lab to produce for the next visit?

Answer 32

Master casts Wax record blocks

Question 33

When making replica dentures why is it helpful to modify them temporarily with green stick?

Answer 33

Checks assessment is correct Makes later stages easier

Question 34

What are the steps in modifying a denture with green stick

Answer 34

Heat slowly- wait until it goes matt Place large piece Shape approximately Mould in mouth (finger pressure and swallowing)

Question 35

When temporarily modifying a denture where should green stick not be placed?

Answer 35

On fitting surface Modification should be done on polished surface (often in mylohoid space)

Question 36

What are the objectives when taking replica dentures?

Answer 36

Replica should be dimensionally accurate, have a solid base for recording working impression and have easily modifiable occlusal and polished surfaces

Question 37

What should you ask the lab to produce following replica impression?

Answer 37

Replica blocks in wax or shellac Ready for second impressions and occlusion