temporary materials

Question 1

PMMA e.g. Jet chemistry and uses

Answer 1

indirect
short and long crowns and bridges
free radical addition polymerisation - methacrylate monomer
powder/liquid formulation
self-curing
linear chain like polymer

Question 2

PMMA e.g. Jet advantages

Answer 2

good marginal fit
good transverse strength
polishable

Question 3

PMMA e.g. Jet disadvantages

Answer 3

poor abrasion resistance
high shrinkage
high thermal release
free monomer may be toxic

Question 4

PEMA e.g. TrimII, Snap chemistry and uses

Answer 4

direct
single crowns
based on ethyl methacrylate monomer
powder and liquid

Question 5

PEMA e.g. TrimII, Snap advantages

Answer 5

lower shrinkage

better biocompatibility

Question 6

PEMA e.g. TrimII, Snap disadvantages

Answer 6

mechanically weaker

less colour stability

Question 7

Bis-Acrylic composite

Answer 7

direct
short span bridges
e.g. Protemp4, QuickTemp
bis-GMA monomer
bifunctional i.e. 2C=C - 3D polymer network 
light cure
 - better handling characteristics

Question 8

Urethane dimethacrylate UDMA

Answer 8

e.g. Provipont DC

resin based material

Question 9

Zach and Cohen experimental approach

Answer 9

applied soldering iron for different durations and noted the temp increase at the “pulp side” of dentine

5.5 degree increase - significant tissue changes over first few days
- after 56 days most pulps had overcome thermal trauma but some pulps of smaller teeth more necrotic
11 degree increase - 2/3 of sample suffer irreparable necrosis

missing factor - flaw
- pulpal damage is also affected by duration of the temp rise experienced

amount of heat transferred to the pulp chamber during the polymerisation of resins may be sufficient to cause thermal damage to the dental pulp and odontoblasts
- but careful in predicting clinical consequence from results of an in vitro study without identifying the biologic env

Question 10

clinical significance of heat

Answer 10

depends on:

• health of underlying pulp and gingival tissues
• susceptibility of tissues in direct contact with the exothermic release to inflammation

Question 11

BALDISSARA experiment

Answer 11

use pair of teeth belonging to same individual

11 degree increase does not damage pulp - no signs of inflammation and no reparative processes

Question 12

polymerisation shrinkage

Answer 12

low - good clinical fit

Protemp

Question 13

compressive strength

Answer 13

Protemp good

Question 14

mean marginal discrepancy

Answer 14

protem = integruuty < luxatemp

Question 15

surface roughness

Answer 15

protem

Question 16

mean temp rise

Answer 16

greatest Jet

lowest trim and protemp

Question 17

colour stability

Answer 17

Jet poor

Protemp good

Question 18

DE value

Answer 18

a DE value greater than 3.2 is considered a clinically noticeable change in shade of material
- Protemp excess this