Denture Base Material

Question 1

What are ideal properties of denture base material?

Answer 1

Low weight
Good aesthetics
Easy to repair
High strength
High resistance to fracture
dimensionally stable
unaffected by oral mucosa
radiopaque
high impact strength
high hardness
non toxic
non irritant

Question 2

What can happen when acrylic dentures are dropped if they dont fracture?

Answer 2

Microcracks can form in acrylic when overtime eventually leads to fracture

Question 3

What is denture acrylic composed of?

Answer 3

Powder

Liquid

Question 4

What is the powder composed of? denture

Answer 4

Initiator = benzoyl peroxide
PMMA particles
Plasticier
Pigments
Copolymers

Question 5

What is the liquid composed of? denture?

Answer 5

Methacyrlate monomer (dissolve the PMMA)
Hydroquinione - to prolong shelf life
copolymers

Question 6

How does denture base material form?

Answer 6

Via free radical addition polymerisation reaction involved:
activation
initiation
propogation
termination

Question 7

Describe PMMA reaction

Answer 7

The methacrylate monomer undergoes free radical addition polymerisation

ACTIVATION- Initiator(BENZOYL PEROXIDE) activates to provide free radicals

INITIATION - free radicals break the carbon to carbon bond in the monomer

propagation - formation of growing polymer chain

termination = rxn ends

Question 8

What is initiator activated by?

Answer 8

Heat >72 or by self cure to produce free radicals which react with monomer and break carbon to carbon bonds

Question 9

What faults can occur during production of acrylic?

Answer 9

Contraction porosity

Gaseous porosity

Crazing

Granular porosity

Question 10

What is contraction porosity?

Answer 10

This is where too much monomer and insufficient excess material which causes polymerisation shrinkage

Question 11

What is gaseous porosity?

Answer 11

This is where monomer is bolling (100) - it has been heated too quickly

Question 12

What is granular porosity?

Answer 12

This is where there is not enough monomer and too much polymer

Question 13

What ifs crazing\?

Answer 13

This is where it is cooled too quickly leading to internal stresses

Question 14

What are some properties of acrylic?

Answer 14

Dimesionally accurate and stable
non toxic and non irriated
unaffected by oral mucosa
poor mechanical properties (need to inc bulk to compensate)
High hardness srength
good thermal expansion
poor thermal conductivity
low density but inc bulk means its higher density