Impression Materials/Techniques

Question 1

impressions

Answer 1

negative or positive reproduction of teeth and other oral structures to create a cast or model on which to fabricate an appliance that will reproduce a successful restoration for the patient

Question 2

3 types of impressions

Answer 2

traditional: alginate hydrocolloid, elastomeric materials
digital

Question 3

traditional impression techniques

Answer 3

negative replica -> positive replica

Question 4

digital impression techniques

Answer 4

positive replica of teeth
can then be printed in office or a lab

Question 5

elastomeric impression materials is a _______ polymer

Answer 5

rubber

Question 6

desired properties of elastomeric impression materials (9)

Answer 6

biocompatible
detailed reproduction
dimensional stability
resistance to deformation
high tear strength
long working time/fast set time**
hydrophilic - moisture compatibility**
no taste/odor
ease of use

Question 7

hydrophilic vs hydrophobic contact angles

Answer 7

hydrophilic <90 (desirable)
hydrophobic >90

**figure slide 9

Question 8

4 types of elastomeric impression materials

Answer 8

polysulfide (rubber base) - not used anymore
condensation silicones - not used here
polyethers - used for removables
addition silicones - used for fixed

Question 9

polyvinylsiloxane (PVS) overview

Answer 9

addition silicone type of elastomeric impression material
most used
comes in different consistencies/viscosities - extra low, low, medium, heavy, and very heavy (putty)
base + catalyst
3 different mixing systems

Question 10

mixing systems for PVS

Answer 10

hand mixing
static automixing
dynamic mechanical mixing

Question 11

PVS characteristics

Answer 11

dimensional stability = excellent
wetting/pouring ease = good
permanent deformation = low
reproduction detail = excellent
tear strength = high
taste/odor = none
disinfectant ability = excellent
cost = HIGH**

Question 12

advantages of PVS

Answer 12

most accurate traditional impression material
good tear strength
excellent recovery from deformation
long term dimensional stability **
no unpleasant taste/odor
stable to disinfectants

Question 13

disadvantages of PVS

Answer 13

EXPENSIVE
materials are sensitive to contamination - latex
short delay time for pouring - H gas (about 60 seconds)

Question 14

difference of pouring time between alginate and PVS

Answer 14

alginate = pour up right away
PVS = have to wait at least 60 seconds, could pour up the next day

Question 15

tray prep for PVS

Answer 15

custom tray is best
need perforations/adhesive specific to material (PVS=dimethyl siloxane and ethyl silicate)
even distribution of material is critical
optimal thickness of impression material is 1-3 mm

Question 16

PVS impression steps

Answer 16

dried prepped teeth
light body PVS impression material onto preps
seat impression tray with heavy body PVS
PVS impression of prepped teeth
pour up -> individual stone dies (accurate for crown fitting)

Question 17

PVS setting time

Answer 17

depends on material
fast set - 2.5 minutes
regular set - 4 minutes

Question 18

digital impression applications

Answer 18

exams
nightguard
invisalign
hygiene
single unit crowns
single unit implants
patient education

Question 19

how do digital impressions work?

Answer 19

use projected light to capture images/video that is processed by a software that gives you a 3D model

Question 20

digital impression advantages

Answer 20

more comfortable and convenient for patients
patient education
simplifies clinical and lab workflow
most cost effective (longterm)
less chair time
storage
digital collaboration

Question 21

digital impression disadvantages

Answer 21

soft tissue management
data loss
digitally equipped lab
initial expense
technique sensitive

Question 22

digital impression common errors

Answer 22

capturing unwanted info (ie your finger)
poor isolation (use an isolite)
moving camera too fast/slow or too close/far to teeth

Question 23

what type of digital scanner does Creighton use?

Answer 23

CEREC (chairside economical restoration of esthetic ceramics)
blue cam, omnicam, and now primescan
potential for same day crowns

Question 24

why is it important to know about all the types of impression strategies?

Answer 24

why something might not work
allergic reactions (patients)
first aid measures
competence (ie having a backup plan if wifi is out)