week 5- impressions technique

Question 1

properties of an impression materials

Answer 1

Accuracy 
Elastic recovery
Dimensional stability 
Flow 
Flexibility
Workability 
Hydrophilicity 
A long shelf life
Pt comfort 
Economics 
Tear resistance 
Need to consider the unset,setting and set properties

Question 2

what level of accuracy do we need to record until

Answer 2

25 microns

Question 3

what are the types of impression materials

Answer 3

non elastic

synthetic

Question 4

what are some non elastic impression materials

Answer 4

waxes
compound and plaster
hydrocolloid- reversible/irreversible

Question 5

what are some synthetic impression materials

Answer 5

• Rubbers – polysulphide
• Polyethers
• Condensation polymers
• Addition polymers

Question 6

advantages of addition cured silicones

Answer 6

Accurate 
Suffers little distortion with time
Range of viscosities
Can be withdrawn from large undercuts suffering no plastic deformation 
No taste

Question 7

disadvantages of addition cured silicones

Answer 7

Costly material
Platinum can be poisoned via latex gloves (chloroplatinic acid catalyst is contaminated by sulphur compounds)
Hydrophobic

Question 8

what happens as the filler content increases

Answer 8

dimensional stability and strength increase but their accuracy and flowability decrease

Question 9

how do addition cured silicones work

Answer 9

Setting reaction involves a two paste system
Paste 1 is polydimethylsiloxane containing Si-H GROUPS
Paste 2 is polydimethylsiloxane containing Si-CH=CH2 groups

with a PT catalyst

Question 10

where is the light body impression placed

Answer 10

on the teeth

Question 11

where is heavy body silicone placement

Answer 11

on the tray at the same time

adhesive on the model 10 mins before

Question 12

how do we do soft tissue control

Answer 12

retract gingival cuff with gingival retraction cord - in different sizes

Question 13

how do we place the gingival cord

Answer 13

The cord is placed into the gingival crevice of the tooth all the way round- the condition of the gums and the depth of the sulcus will determine what cord we need to use

Question 14

what is another example of retraction we can use

Answer 14

Components: acidic paste 15% aluminum chloride

Action is- haemostatic- compression of the tissues and astringent action of aluminium chloride

Question 15

what are the contra indications for astringent paste

Answer 15

Diseased periodontium
Open furcations
Exposed bone

Question 16

how do we use the astringent paste

Answer 16

Place 3M ESPE Astringent Retraction Paste into a common composite dispenser, remove cap and discard a small amount of material.
▪ Place the tip of the capsule into the sulcus. While placing the tip into the sulcus the tissue is mechanically retracted from the tooth. The soft edged tip is rounded to prevent
▪ tissue damage.
▪ Extrude retraction paste slowly while going slowly around the prepared tooth. Take care tat the tip of the capsule is subgingival!

Question 17

what else can we do

Answer 17

paste and cord together

Question 18

how long do we leave the paste for

Answer 18

two minutes

Question 19

how do we remove the paste

Answer 19

air-water spray and suction.

Question 20

benefits of the astringent paste

Answer 20

▪ Easy sulcus access due to the fine capsule tip
▪ Effectively opens the sulcus
▪ Enables a clean, dry sulcus area and long-lasting hemostasis
▪ Application with common composite dispenser
▪ Easy and time saving: 50% faster than cords
▪ Lower risk of bleeding/post haemorrhage than with cords
Easier application into the sulcus and interproximal access than others pastes

Question 21

what is electro surgery

Answer 21

Use short, sweeping motions

Question 22

what do we need to consider when doing electro surgery

Answer 22

NO PACEMAKER
no mirror!
burning smell of flesh

Question 23

what are some applications of the electro surgery

Answer 23

▪ Removing localised ginigival tissue
▪ Exposure of subgingival caries 
▪ Exposure of crown margin 
▪ Improve contour and shape of tissues 
▪ Easy retraction for multiple abutments 
▪ Quick 
Predictable healing

Question 24

how do we place retraction cords

Answer 24

1. Having a healthy periodontal status for the patient prior to crown prep there must be a gingival sulcus of 2-3mm
   
   2. Pack the first cord using a flat plastic,wards carver,packer
   3. Push it firmly into the sulcus
   4. Place thr second cord- usually larger than the first cord
   5. Then before placing the light bodied silicone- remove the second cord
   6. Continue to dispense all around the tooth and cover the adjacent teeth be careful of air bubbles
   7. Fill the tray with the medium body silicone and ensure this is seated over the light body prior to setting
      Set for 5 minutes

Question 25

when do we place the light body silicone

Answer 25

right after removing the cords

Question 26

what is the impression assessment

Answer 26

▪ Impression material well-mixed/fully-set
▪ Is the impression still seated in the tray
▪ All teeth in the arch included
▪ No folds between the heavy (or putty) & wash
▪ No drags
▪ No air bubbles
Good impression of adjacent teeth

Question 27

what does the lab need for an impression

Answer 27

A good impression of the prepared tooth in addition cure silicone
Good impression of the opposing arch
Interocclusal record
Prescription of the type of crown needed, design, shade and any characteristics

Question 28

what do we use in shade selection

Answer 28

VITA classical shade selection-
Four groups:
A- brown hues 
B- yellow hues
C- grey hues
D- reddish hues

Question 29

what are the four Cs of patient notes

Answer 29

clear
contemporaneous
concise
complete