Denture base materials

Question 1

ideal properties

Answer 1

biocompatible
physical (aesthetic, stable, high thermal conducitivtiy)
mechanical (strength,stiffness,toughness)
ease of (processing, repair/adjust, reproduction of surface detail)
cost

Question 2

current materials used for dentures base

Answer 2

PMMa (acrylic)
nylon polyamide
polyetheretherkeleton
Nylon
cobalt chrome alloy
Ti alloy

Question 3

polymerisation of PMMA

Answer 3

benzoyl peroxide (initiator)
splits into 2 fragments, each with 1 unpaired e-
fragments attack the C=C bond
cross linking agent forms additional bonds between polymer chains

Question 4

steps for denture making

Answer 4

1) Make dentures in wax
2) set acrylic teeth into the dentures
3) use brass flask to create a mould of each denture
4) The brass flasks fit together
5) Make a mould of dentures by securing the model into one half of the brass flask
6) Other half filled with plaster, left to set
7) then can heat the flasks up to soften the wax
8) open the flasks, get rid of residual wax by running under boiling water
9) Place separator on the models, mix up the acrylic dough
10) Fill moulds with slight excess, press in big press
11) Placed and cured overnight
12) Can then break open the flasks
13) remove plaster around the model
14) Dentures now ready for finishing

Question 5

processing problems

Answer 5

polymerisation shrinkages
processing stains
volatilisation of the monomer during curing of the temperature

Question 6

alternative processing routes for dentures

Answer 6

injection moulding of acrylic dough
injection of moulding of aryclic above Tg
milling from block
3D printing

Question 7

what is injection moudling

Answer 7

heat material to above Hg

squeeze into mould using high pressure

Question 8

variants of PMMA

Answer 8

cold cure (auto cure)

Question 9

tooth materials

Answer 9

acrylic
highly cross linked acrylic
composite
ceramic

Question 10

indications for flexible denture matierals

Answer 10

repeated denture fracture occurs
presence of large tori
deep undercut
limited mouth opening

Question 11

advantages of flexible materials

Answer 11

• toughness resutling in the dentures being nearly unbreakable
• coloured like mucosa
• thinner than conventional materials
• non allergenic
• no metal clasps, material can be used to create retention
• can be used in areas of deep undercut

Question 12

advances manufacturing for dentures

Answer 12

computer aided design/aided manufacture

Question 13

strain

Answer 13

fractional change in the dimensions caused by the force

Question 14

stress

Answer 14

force per unit cross sectional area, that is acting on the material

Question 15

resilince

Answer 15

amount of energy a material can absorb without undergoing plastic deformation

Question 16

ductility

Answer 16

amount of plastic strain at fracture

Question 17

denture reclining materials

Answer 17

provides a new fitting surface when the denture becomes ill fitting
usually PMMA

Question 18

soft liner materials

Answer 18

plasticised heat cured acrlic
silicone rubber
silicone/acrylate co polymer

Question 19

tissue conditioner

Answer 19

Temporary linings that allow traumatise tissue to recover before carrying out definite treatments
• Polyethylmethacrylate (low Tg)
• Butyl phthalyl glycolate (plasticiser)
• Ethyl alcohol (solvent)