week 5- impressions technique Flashcards Preview

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Flashcards in week 5- impressions technique Deck (29)
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1

properties of an impression materials

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

2

what level of accuracy do we need to record until

25 microns

3

what are the types of impression materials

non elastic
synthetic

4

what are some non elastic impression materials

waxes
compound and plaster
hydrocolloid- reversible/irreversible

5

what are some synthetic impression materials

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

6

advantages of addition cured silicones

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Can be withdrawn from large undercuts suffering no plastic deformation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

7

disadvantages of addition cured silicones

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

8

what happens as the filler content increases

dimensional stability and strength increase but their accuracy and flowability decrease

9

how do addition cured silicones work

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

10

where is the light body impression placed

on the teeth

11

where is heavy body silicone placement

on the tray at the same time
adhesive on the model 10 mins before

12

how do we do soft tissue control

retract gingival cuff with gingival retraction cord - in different sizes

13

how do we place the gingival cord

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

14

what is another example of retraction we can use

Components: acidic paste 15% aluminum chloride
Action is- haemostatic- compression of the tissues and astringent action of aluminium chloride

15

what are the contra indications for astringent paste

Diseased periodontium
Open furcations
Exposed bone

16

how do we use the astringent paste

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!

17

what else can we do

paste and cord together

18

how long do we leave the paste for

two minutes

19

how do we remove the paste

air-water spray and suction.

20

benefits of the astringent paste

▪ 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

21

what is electro surgery

Use short, sweeping motions

22

what do we need to consider when doing electro surgery

NO PACEMAKER
no mirror!
burning smell of flesh

23

what are some applications of the electro surgery

▪ 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

24

how do we place retraction cords

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

25

when do we place the light body silicone

right after removing the cords

26

what is the impression assessment

▪ 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

27

what does the lab need for an impression

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

28

what do we use in shade selection

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

29

what are the four Cs of patient notes

clear
contemporaneous
concise
complete