Anatomical considerations and primary impressions

Question 1

How do you make dentures? (2 main stages)

Answer 1

1. Denture construction

2. Denture provision

Question 2

What are the clinical/ technical stages of denture construction?

Answer 2

(a) record shape of supporting tissues
- primary impressions
- secondary impressions
(b) establish correct placement of teeth
- bite registration (check they meet evenly)
- wax try-in
1. record shape of ridges
2. record inter-ridge relationships
3. make wax template
4. covert template to denture

Question 3

What are the clinical/ technical stages of denture provision?

Answer 3

1. fit stage
   - checks: aesthetic and functional
   - check-record
2. post-fit review
   - comfort: sore areas
   - checks: aesthetic and functional
3. 6-12 months post-fit review

Question 4

Disadvantages of primary stock impression trays

Answer 4

Only come in 3 sizes so will never perfectly fit

Question 5

What are the relevant anatomical structures for dentures?

Answer 5

1. those marking the denture periphery - the mandible and maxilla
2. those marking the site of teeth - the maxilla

Question 6

What is the fovea palatini?

Answer 6

Two depressions that lie bilateral to midline of palate, at approx junction of hard and soft palate.
Posterior border of denture (distal margin) should be 1-2mm anterior to these. If denture were to extend to soft palate it would vibrate and dislodge.

Question 7

What is the hamular notch?

Answer 7

Marks distal edge of maxillary denture, where tendon of tensor palatini expands into soft palate

Question 8

How are sulci and fraena relevant to dentures?

Answer 8

They mark functional extent of denture.
Denture doesn’t want to sit on top of fraena, so made to avoid them.
Large fraena may need to be removed surgically

Question 9

What is the retromolar pad?

Answer 9

A triangular area of thick mucosa found distal to last molar. Distal extent of mandibular denture

Question 10

What are mylohyoid ridge and external oblique ridge?

Answer 10

Mylohyoid ridge: attachment of the mylohyoid muscle on mandible
External oblique ridge: bony ridge that runs anter-posteriorly outside buccal shelf
Medial and lateral limits of bony support (distobuccal region)

Question 11

What are the biometric markers for dentures?

Answer 11

Lingual gingival remnant (not usually there)
Incisive papilla is usually 9mm behind incisors
Indicators for lingual margin of posterior teeth and labial surfaces of anterior teeth

Question 12

How do you gain informed consent?

Answer 12

On initial visit:
explain you are a student working under supervision
You are going to carry out an initial assessment to update notes.
Explain:
-diagnosis (what current problem is)
-prognosis (chance of success of new dentures)
-can px’s desires be realistically achieved?
-number of visits and what treatment will be carried out
-proposed changes, benefits, risks
-do they understand? Questions?
-document all this in clinical notes

Question 13

Which insertions should be avoided by the dentures?

Answer 13

Insertion of mentalis (mental fovea) can be problematic (ulceration) when px has atrophic mucosa
Insertion of genioglossus (genial tubercles), otherwise denture would fly out when px opens mouth

Question 14

Why is mental foramen important in dentures?

Answer 14

With resorption it approaches denture-bearing surface. If nerve is compromised could lead to pain and numbness

Question 15

What will the initial assessment cover?

Answer 15

• reason for attendance
• medical history
• social history
• dental history
• observations from extra- and intraoral examination

Question 16

How should consent be gained on subsequent visits?

Answer 16

Explain to px what is going to happen today
Questions? Do they understand?
Re-establish objectives of treatment where appropriate
Write up notes recording all that has been discussed

Question 17

What are the ideal properties of an impression material?

Answer 17

1. Accuracy
2. Resolution (level of detail)
3. Dimensional stability
4. Rigid or elastic

Question 18

What is the purpose of primary impressions?

Answer 18

To record anatomy and permit primary models to be cast

Allows construction of special trays to record working impressions

Question 19

What are the ideal clinical properties for an impression material?

Answer 19

Simple technique, cheap to use, bonds to tray
Viscous during placement
Elastic when set

Question 20

Practical problems of impression materials

Answer 20

Viscoelastic when set
Unstable with time
Can lead to permanent deformation and debonding

Question 21

Name stages of clinical technique for primary impressions

Answer 21

1. Select an impression tray
2. First stage impression
3. Second stage impression
4. Lab prep

Question 22

What does selecting an impression tray comprise of?

Answer 22

Identify type

Select correct size

Question 23

What are the uses of greenstick as an impression compound?

Answer 23

1. Extending trays over retromolar pads or post-dam regions

2. Using inside poorly fitting tray to customise to extent where satisfactory primary impression can be made

Question 24

Problems with greenstick as impression compound

Answer 24

Very difficult to attain ideal T to allow it to work without burning

Question 25

How is greenstick used?

Answer 25

Need very hot water to allow it to soften evenly

Need a flame for ‘stick’ variety and then hot water to temper

Question 26

What does first stage impression comprise of?

Answer 26

Apply bonding agent (mechanical retention via perforations insufficient by itself)
Load with stiff mix (serves to displace soft tissues from denture-bearing area)

Question 27

Where do you stand when taking impressions?

Answer 27

Upper: behind px’s right shoulder, maxilla should be at your elbow height. Px should be at 60 degrees to horizontal (should give clear vision of buccal sulcus and posterior border of tray)
Lower: in front of px, mandible should be at your elbow height

Question 28

How do you insert tray with alginate into mouth?

Answer 28

Hover tray, pull back upper lip then place tray in labial sulcus first - midline labial frenum is key landmark.
Then tip tray upwards posteriorly until alginate can be seen just beyong distal aspect of tray (reduces gagging)
Move soft tissues while it is setting

Question 29

What do you do with newly taken primary impression?

Answer 29

Remove overextensions
Remove obstacles to peripheral flow
Relieve fraena
Check for debonding

Question 30

What is the purpose of a second stage impression?

Answer 30

To perfect the anatomy

To note more precise borders and clear frenal attachments

Question 31

How do you prepare second stage impression for lab?

Answer 31

Mark periphery 2mm inside max depth of impression

This will confirm extent of special tray

Question 32

How long is impression disinfected for?

Answer 32

10 mins