complete dentures

Question 1

What does alveolar resorption involve?

Answer 1

Magnitude
Site and pattern
Time relations
Influencing factors
Problems

Question 2

What is the magnitude of resorption in mandible compared to the maxilla?

Answer 2

4x greater in the mandible than the maxilla

Question 3

How does the residual ridge change as a result of mandibular resorption?

Answer 3

More lingually placed anteriorly
More buccally placed posteriorly
In at the front and out at the back
Labial plate is weaker in front 
Lingual plate is weaker in back

Question 4

Where should mandibular denture teeth be placed in relation to the residual ridge?

Answer 4

Lower anteriors- on or slightly ahead
Canines and premolars- on
First molar- on or just inside
Second molar- on or just outside

Question 5

How does the residual ridge change as a result of maxillary resorption?

Answer 5

More palatial in all regions

Question 6

Where should maxillary denture teeth be placed in relation to the residual ridge?

Answer 6

All slightly buccally/labially rather than on

Question 7

How quick is mandibular resorption over time?

Answer 7

Rapid bone resorption initially when teeth are taken out which then slows over time
Eg. 2.5mm in 4 months
3.5mm in 8 months
4mm in 12 months
4.25mm in 16 months

Question 8

What influences the rate of resorption?

Answer 8

Systemic=quicker eg. Osteoporosis
Local=slower eg. Retained roots and implants preserve bone
Denture induced=quicker (limited evidence)

Question 9

What are the benefits of retained roots and artificial implants?

Answer 9

They preserve the bone around them so the dentures are more stable

Question 10

What is the ‘neutral zone’?

Answer 10

The teeth are placed in balance so that the forces of the tongue and cheek work together to keep the dentures in place

Question 11

What are immediate dentures?

Answer 11

Relates to rapid initial resorption

Question 12

What should happen if the patient has a class 3 molar occlusion?

Answer 12

Lower molar teeth must be placed correctly over the ridge

May have to allow cross-bite for aesthetic purposes

Question 13

Why might patients get a molar crossbite?

Answer 13

Often due to the palatial resorption of maxilla and buccal change of mandible- resorptive pattern

Question 14

How might the mucosa be affected by bone resorption?

Answer 14

It might get compressed between the denture base and the sharp bone ridges leading to pain

Question 15

How might the mental nerve be affected by bone resorption?

Answer 15

May become compressed leading to shooting pain or numbness and paresthesia

Question 16

What happens if there is irregular resorption?

Answer 16

The mucosa might become sandwiched between sharp bony spicules and the denture base- painful

Question 17

How might the patients appearance be affected?

Answer 17

Lack of support of soft tissues may lead to angular cheilitis (fungal infection at corners of mouth) and ages patient significantly

Question 18

What kind of impression would you do with a ridge with minimal/without undercuts?

Answer 18

Rigid impression material in close fitting special tray

Question 19

What kind of impression would you do with a ridge with large undercuts?

Answer 19

Elastic impression material in spaced special tray

Question 20

What is an undercut?

Answer 20

The area between the maximum bulbosity of the ridge compared to the deepest part of the sulcus beneath
The contour that would prevent the placement of a prosthesis

Question 21

Why is zinc oxide-eugenol used?

Answer 21

Cheap, easy to modify and accurate
Mucostatic but if in non-spaced, non-perforated tray= mucocompressive
Sometimes used with one spacer
Mucostatic, two spacers and wide perforations in mild flabby areas

Question 22

What does a close fitting special tray look like?

Answer 22

1-2mm short of final denture border
Minor to moderate undercuts
Mucocompressive impression

Question 23

What does a spaced special tray look like?

Answer 23

Use alginate instead
2-3mm short of final denture border
Moderate to severe undercuts
Mucostatic impression

Question 24

Why might you use tissue stops?

Answer 24

Use for anything but ZnO
Silicone- 1.5-2mm TS
Alginate- 3mm TS
Ask lab to create
For areas that are relatively noncompressive
Stops tray showing through if excessive pressure

Question 25

How do you adjust your tray?

Answer 25

Before taking impression, check tray- cheek traction to see if moves
Overextended- trim back so frenae etc. aren’t impeded and can be recorded
Underextended- add greenstick

Question 26

How far should the tray extend?

Answer 26

Must be short of the deepest part of the sulcus

Question 27

How do you use Zinc Oxide Euganol?

Answer 27

2 tubes- the red and white quantities should be the same to control the setting times
Mix evenly and don’t overload tray

Question 28

What should you tell the patient before taking a ZnO impression?

Answer 28

There is often a burning sensation, it’s sticky and has a strong taste
Let them know that it will get quite warm in their mouth, don’t worry, it’ll set quickly

Question 29

What precautions should you take with ZnO impressions?

Answer 29

If dry mouth, patient should rinse
Elastoplast allergies*

*shouldn’t use ZnO if so

Question 30

How do you record the impression?

Answer 30

Lift the tongue

Must border mold the periphery so that the denture isn’t overextended

Question 31

Why might finger rests be made?

Answer 31

Prevents fingers from distorting the periphery

Question 32

What might you be able to do if the tray penetrates a ZnO impression?

Answer 32

You could add a bit of material to correct this rather than retaking it

Question 33

Why might you want to use a combination of materials?

Answer 33

Selective pressure impression
Eg. Monophase silicone anteriorly for fibrous ridges
ZnO posteriorly for firm tissues

Question 34

What is a flabby/fibrous ridge?

Answer 34

Displaceable/mobile ridge usually in upper anterior region

Often when lower teeth retained against upper edentulous ridge

Question 35

What is the implication of a flabby/fibrous ridge?

Answer 35

Causes instability of denture due to lack of underlying bone

Question 36

How should you record a fibrous ridge?

Answer 36

Should be done in a mucostatic way

Use a ZnO tray with a window box anteriorly to inject light bodied silicone to avoid compression

Question 37

What is an Alma Gauge?

Answer 37

Can give lab a vertical and horizontal reading if there is a good old denture
This is so the bite blocks can come back at the correct dimensions
The plunger should be at the indentation of where the incisive papilla is

Question 38

How should you instruct the lab?

Answer 38

Eg. Please make upper and lower registration rims
Specify- eg. Alma gauge of old upper using incisive papilla as fixed point V12 H7
If not- rough guide 22mm upper and 18mm lower from deepest area of sulcus