The document provides a history of denture materials and techniques from ancient times to modern day. It begins with early dentures made of materials like wood, bone, ivory and human teeth. Important developments include the introduction of porcelain and vulcanite dentures in the 18th-19th centuries. In the 1930s, polymethyl methacrylate (PMMA) was introduced and became the standard denture material due to its strength, biocompatibility and ease of use. The document also describes the compression molding technique for fabricating PMMA dentures, involving steps like flasking, packing, curing and finishing. Alternative techniques like injection molding are also mentioned.

1. 1

2. 2

3. Definitions – GPT 9
Denture : an artificial substitute for
missing natural teeth and adjacent
tissues.
Denture base : The part of a denture
that rests on the foundation tissues
and to which teeth are attached.
3
– GPT 9

4. History
 Skillfully designed dentures were
made as early as 700 BC
 Talmud a collection of books of
Hebrews in 352-407 AD mentioned that
teeth were made of gold ,silver, and wood.
 Egypt was the medical center of ancient world, the
first dental prosthesis is believed to have been
constructed in Egypt about 2500 BC.
Hesi-Re Egyptian
dentist of about
3000 BC
4

5. mandibular fixed bridge, four natural incisor teeth and
two carved ivory teeth
Bound With gold wire found in Sidon-ancient
Phoenicia about fifth and fourth century BC.
5

6.  During medieval times dentures were seldom
considered ,when installed they were hand carved
and tied in place with silk threads.
 Those wearing full denture had to remove them
before eating.
 Upper and lower teeth fit poorly and were held
together by steel springs.
Persian dentist of late eighteen
century
Indian surgeon of mid nineteenth century
6

7. Wooden dentures
 For years, dentures were fashioned from wood .
 Wood was chosen
-readily available
-relatively inexpensive
-can be carved to desired shape
 Disadvantages
-warped and cracked in moisture
-esthetic and hygienic challenges
-degradation in oral environment
7

8. Wooden denture believed to be carved out of box wood in 1538 by
Nakoka Tei a Buddhist priest
Wooden dentures
8

9. Bone
 Bone was chosen due to its
availability, reasonable cost and
carvability .
 It is reported that Fauchard fabricated
dentures by measuring individual arches
with a compass and cutting bone to fit
the arches .
 It had better dimensional stability than wood,
esthetic and hygienic concerns remained
9

10. Ivory
 Denture bases and prosthetic teeth were
fashioned by carving this material to desired
shape
 Not available readily
 Relatively expensive.
 Relatively stable in the oral environment
 Esthetic and Hygienic - comparison with denture
bases carved from wood or bone.
Carved ivory upper denture retained in the
mouth by springs with natural human teeth
cut off at the Neck and riveted at the base.
10

11. Human teeth were also used,
pulled from the deceased or
sold by poor people from their
own mouths
Lower denture with human teeth
England1800-1870
Waterloo dentures
Teeth for dentures from the
bodies of thousands of dead
soldiers on the battlefield at
Waterloo.
11

12.  1788 A.D. Improvement and development of
porcelain dentures by De Chemant.
 G.Fonzi an Italian dentist in Paris invented the
Porcelain teeth that revolutionized the construction
Of dentures.
Partial denture of about
1830,porcelain teeth of Fonzi’s design
have been Soldered to a gold backing.
12

13.  Porcelain denture bases were relatively expensive
 During subsequent years secrets of porcelain denture
became known and it became common and inexpensive.
 ADVANTAGES over wood, bone , ivory were
-Could be shaped using additive technique rather than
subtractive (carving) - facilitated correction of denture base
surface.
-more intimate contact with underlying soft tissues.
-Could be tinted to simulate the colors of teeth and oral
soft tissues.
-stable in oral environment.
-Minimal water sorption, porosity, and solubility.
-Smooth surface provided hygienic properties.
Drawbacks – BRITTLENESS, fractures were common, often
irreparable.
13

14. One piece porcelain upper denture crafted
by Dr John Scarborough,
Lambertville,New Jersey 1868.
14

15. 15

16.  In 1794 John Greenwood began to swage gold
bases for dentures. Made George Washington's
dentures.
George Washington's last dental prosthesis. The palate was swaged
from a sheet of gold and ivory teeth riveted to it. The lower denture
consists of a single carved block of ivory. The two dentures were held
together by steel springs.
16

17. Vulcanite
 In 1839 an important development took place
CHARLES GOODYEAR
discovered VULCANIZATION of natural rubber
with sulphur (30%) and was patented by Hancock
in England in 1843.
 NELSON GOODYEAR (brother of Charles
Goodyear) got the patent for vulcanite dentures in
1864.
 Vulcanite dentures were very popular until the
1940s, when acrylic denture bases replaced them.
17

18.  Advantages
 Well adapted
 Good retention
 Easy to process
 Stable
 Disadvantages
 Lack of translucency
 Poor esthetics
 Porous
 Unhygenic
 Color modification difficult
18

19. A set of vulcanite dentures worn by Gen.
John J. (Blackjack) Pershing, commander
of the American Expeditionary Forces in
France during the First World War
Set of complete dentures having palate of
swaged Gold and porcelain teeth set in
vulcanite.
19

20. celluloid
In 1868 John Hyatt, A US
Printer, discovered the first
plastic molding compound,
called celluloid. He made it
by dissolving nitrocellulose
under pressure
Celluloid upper denture 1880,celluloid as a
Substitute for vulcanite was unsuccessful
as
It absorbs stains and odors in the mouth,
Gradually turns black and was flammable
20

21. In 1909 by Dr. Leo Backeland
 formed by heating and compressing a mixture of phenol
and formaldehyde
Bakelite
Disadvantages
Lack of uniform quality
Variable strength
Variable color
Dimensional instability
21

22. Polyvinyl chloride
 1930 AD
 Flexible
 Mouth guards and denture liners
 Drawbacks – distortion , discoloration
22

23. Polymethyl methacrylate
 IN 1937 Dr. Walter Wright and Vernon brothers
23

24. Advantages
Transparent
Stable
Biocompatible
Tasteless
Easy to repair and
process
Pigmentable
Adequate strength
Low water absorption
and low solubility
odourless
24

25. Disadvantages
Brittle
Poor flexural strength
Large polymerization
shrinkage
High coefficient of
thermal expansion
Radiolucent
Allergic
25

26. 26
• Non toxic, non irritant
Biological
• Inert , insoluble & non
absorbantChemical
• Esthetic
• Dimensionally stable
• Low value of specific
gravity / density
• High value of thermal
conductivity
• Radiopaque
Physical
Requirements

27. 27
• High value of modulus
of elasticity - rigidity
• High value of elastic
limit- permanent
deformation
• A combination of both
• Sufficient flexural
strength
• Adequate fatigue life
and high fatigue limit
• Good impact strength
• Sufficient abrasion
resistance
Mechanical
• Inexpensive
• Long shelf life
• Easy to manipulate
• Easy to repair
miscellaneous

28. 28

29. I . According ISO 1567
Type Class Description
1 1 Heat processing
polymers , powder &
liquid
1 2 Heat processed (plastic
cake)
2 1 Autopolymerized
polymers , powder &
liquid
2 1 Autopolymerized
polymers (powder & liquid
pour type resin)
3 Thermoplastic blank
/powder
4 Light activated material
5 Microwave cured material
29

30. II . According to material system
• Stainless steel denture basesmetallic
• Acrylic resins etcNon- metallic
30
III. According to mode of polymerization
• Acrylic, polyvinyl chloride,
polymethyl methacrylate
Addition
polymer
• Bakelite
• Nylon
Condensati
on polymer

31.  IV. According to method of activation
31
• Heat cure acrylicsThermal
• Self cure acrylicsChemical
Light activated
Microwave
energy

32. Types of denture base
resins
 Based on mode of activation
 Heat activated PMMA
 High impact resin
 Rapid polymerizing resin
 Microwave activated PMMA
 Chemical activated
 Light activated
34

33. Heat activated denture base
resin
35

34. Composition of heat cured acrylic
resin
Ingredient Function
Poly methyl methacrylate Major component
Ethyl or butyl methacrylate Copolymers-improves properties
Benzoyl peroxide Initiator
Compounds of mercuric sulfide,
cadmium sulfide , etc.
Dyes
Zinc or titanium oxide Opacifiers
Di butyl phthalate Plasticizer
Inorganic fillers like glass fibers,
zirconium silicate, alumina, etc.
Improves physical properties like
stiffness etc
Dyed synthetic nylon or acrylic
fibers To simulate small capillaries
36
Powder

35. Ingredient Function
Methyl methacrylate Plasticizes the polymer
Di butyl phthalate Plasticizer
Glycol di methacrylate (1-2%) Cross linking agent (reduces
crazing)
Hydroquinone (0.006%) Inhibitor – prevents premature
polymerization
37
Liquid

36. Manipulation
38
Compression
mould
technique
Injection
mould
technique

37. Compression molding
technique
 Preparation of the waxed denture pattern
 Preparation of the mould
 Selection of separating medium
 Polymer to monomer ratio
 Dough forming time
 Working time
 Packing
 Polymerization procedure
 Temperature rise
 Internal porosity
 Polymerization cycle
39

38.  Three part flask
40

39.  Four part flask
41

40.  Pressure clamps
42

41. Preparation before flasking
 Proper finishing
 Periphery is sealed
 Petroleum jelly inner surface of the flask and on
the Casts
 Adjustment of the plaster model
 Plaster models are wetted
 Wax dentures with casts are soaked with slurry
water
43

42. Preparation of the mould
 Flask is filled with freshly mixed stone
 Place cast on to the mix
 Contour the stone
 After initial set – coat with separating medium
 Another mix of stone poured to the flask (1/4th)
 Incisal and occlusal surface – slightly exposed
 Allow to set – coat separating medium
 Additional increments of stone filled
 Lid is gently tapped to place
 Apply pressure with pressure clamp
44

43. 45
Periphery of flask should be in
level with the rim of the flask
Occlusal plane – parallel to the base of
the flask

44. 46
Retromolar pads and
tuberosity- should be
protected
Devoid of undercut Shaping of the stone –
blade or knife
Distance from top
lid – 6 mm

45. Place the
flask in
boiling
water for 4
mins –
dewaxing
Remove
and
separate
segments
Wax
removed
Prosthetic
teeth
remain
firmly
Cleaned
with mild
detergent
and rinsed
with boiling
water
47

46. Selection and application of
separating medium
 Prevent direct contact b/w denture base resin and
mold
48
Failure
Water may affect polymerization
rate- alter optical and physical
properties
Presence of monomer & free
polymer – fuse investment to
denture base

47. Types of separating medium
 Tinfoil
 Cellulose lacquers
 Solution of alginate compounds
 Calcium oleate
 soft soaps
 Sodium silicate
 Starches
49

48.  Water soluble alginate solution – most popular
separating medium
 Produce thin film of calcium alginate
50
Water soluble
alginate
+ Calcium sulphate
hemihydrates
Calcium alginate

49. Application
 Applied on the exposed surface of a warm clean
stone mold
 Interdental spaces
 Not contact the exposed tooth surface
51

50.  Polymer: Monomer – 3:1 by volume or 2:1 by
weight
 Polymer monomer interaction a workable mass is
produced – pass through 5 stages
52
sandy stringy
Dough
like
Rubbery Stiff

51.  Sandy – coarse / grainy
polymer beads remain unaltered
 Stringy – increased viscosity
monomer attacks polymer beads
 Dough like – pliable dough
increased number of polymer chains
 According to ADA specification no 12 – required
consistency in <40 mins ( clinically < 12 mins)
53

52.  Rubbery / elastic – mass rebounds when
compressed or stretched ; excess monomer is
dissipated by evaporation
 Stiff – due to complete evaporation of free
monomer
54

53. Working time
 Time that the denture base material remain in
dough stage – 5 mins
 Refrigeration – increases WT
 Presence of moisture degrades physical and
aesthetic properties
55

54. Packing
 Placement and adaptation of denture
base resin within the mold cavity
56
Over
packing
Under
packing
Denture with excessive thickness &resultant
malpositioning
Noticeable denture porosities

55.  Resin – dough like stage
 Bent into horse shoe and place in position
 Polyethylene sheet placed over the resin
 Incremental pressure applied
57

56.  Excess material – flash
 Trial closure- repeated – no flash (Hydraulic or
Mechanical press)
 Trial closure pressure – 1500psi
 polyethylene sheet removed before final closure –
Final closure pressure - < 3500 psi
 Flask is carried to a flask carrier maintain
pressure
58

57. Problems & solutions in Flasking
1. Flasks cannot be separated after
dewaxing
-Undercuts in flasking and casts
- Improper application of separating medium
 Solution
- Examining the casts
- Remove undercuts
- Proper application of separating medium
59

58. 2.Heel broken on mandibular cast
Cause Undercut not blocked out
Solution Blocking and protecting the heel area
3.Denture with acrylic blubs
Cause - Investing stone not painted Properly on
waxed denture during flasking
-Improper investing stone mix
Solution Paint investing stone on teeth With brush
- Use of mechanical spatulator
60

59. Polymerization procedure
 When heated above 60º, benzoyl peroxide
decomposes
 Yields free radicals
 Acts rapidly with monomer - chain growth
polymerization
 Additional monomer molecules attach to individual
polymer - rapid
61
Coupling of two
grouping chains
Transfer of H2 ion from
one chain to another
•Heat – activator
•Benzyl peroxide – initiator

60. Temperature rise
 Initially heating – slow – resin occupies the centre
of the mold
 Temperature > 70º c – decomposition rate of
benzoyl peroxide
 Resin & stone – poor conductors of heat – heat
not dissipated
62
Exceeds temp of the boiling point
of monomer (100.8ºC)

61. Polymerization cycle
 Heating process used to control polymerization –
curing cycle
63
Constant temp
74ºC
For 9 hrs or
longer with no
terminal boiling
point
At 74ºC for 2 hrs
& then to
100ºC for 1 hr
Processing at
74C for 8 hrs
& to 100C

62.  Denture flask should be bench cooled for 30 mins
before retrieval
 Rapid cooling – warpage
 Immersed in cool tap water for 15 mins
 Deflasked
 Stored in water until delivery
64

63. Injection moulding
technique
 Developed by Pryor
 1950- Flexible denture base material – Valplast &
Flexiplast
 1970 – Ivoclar – Special resin
 Few dimensional inaccuracies and polymerisation
shrinkage
 Specifically designed flask
65

64. 66
Flexible denture base materials - Super polyamides
(nylon family) – form of granules in cylinders of varying
sizes

65.  Thermoplastic- converted into fluid form –
plasticized for 15 – 20 min at 550 - 560ᵒ F –
Electric cartridge furnace
 Inject into mould under pressure – lever of press
turned rapidly – until springs are fully compressed
– maintain pressure for 3-5 min – bench cool 15 –
20 min
67

66.  Half of the flask is filled with stone
 Contoured and permitted to set
 Sprues are attached to the wax denture base
68

67.  Investment process is completed
 Wax elimination is performed
 Flask is placed under pressure
 Resin mix is introduced into the mold
 Polymerized
69

68. 70

69. Advantages
 Denture bases fabricated by injection molding can
provide slightly improved clinical accuracy
71

70. Disadvantages
Resin viscosity must be considerably lower than that used in
compression molding - to facilitate injection
Smaller polymer-to-monomer ratio, and - results in increased
curing shrinkage.
Hence, the palatal fit is compromised
72

71. Modification of heat activated
acrylic resin
 High impact strength resin
 Reinforced with butadiene styrene rubber
 Rubber particles are grafted to methyl
methacrylate to bond to the acrylic matrix
 Supplied in powder liquid form
 Conventionally processed
73

72.  Rapid heat polymerised resin
 Hybrid resins with both chemical and heat
activated initiators
 No porosity expected
 Polymerized in boiling water for 20 mins
74

73.  Microwave activated PMMA
 NISHII (1968) first used microwave energy to
polymerise denture base resin in a 400 watt
microwave oven for 2.5 mins
 Later carried on by KIMURA et al(1983) and DE
CLERK
75

74. 76

75.  Wax denture investment
 Apply a separating agent - vaseline to the plaster
escape holes.
 Invest the wax denture in the FRP FLASK
 Then remove any excess plaster coming out of the
escape holes
77

76.  Wax removal - usual method.
 Apply GC ACRO-SEP (resin separator) to the
plaster mold.
 Resin packing and trial closure
 Flask nut tightening - force should be 40kg/cm2
78

77.  Cooling and removal of denture
 After polymerizing, allow the flask to cool for at
least 30 minutes in the open air.
 Immerse it in cold water to cool completely.
 Remove the bolts and nuts. Using a wooden
mallet, tap tightly on the thick-walled portion of the
back rim of the FRP FLASK to remove the
embedded denture.
 Never tap the area near the bolt insertion holes of
the upper and lower halves of the flask.
79

78.  Adavantages
 Least curing time – 3 min
 Reduced dough forming time
 Good colour stability
 Minimal residual monomer ratio
 Good denture base adaptation
 Stable
80

79.  Disadvantages
 Poor bonding to adjacent teeth
 Increased porosity
 Expensive flasks
 Poor durability - flasks
81

80.  Technique:
 Heat created – by collision of monomer molecules
– electromagnetic field from microwave
 Self regulatory mechanism – lesser molecules
absorb same energy as reaction proceeds
 Reduced polymerisation time
 Less porosity and shrinkage
82

81.  Saves great amount of time and money in
processing
 Lower residual monomer ratio
 Same physical properties as conventionally cured
resin.
 It requires at least special flasks and a
programmable microwave oven, but specially
designed equipment will give the best results.
83
• Microwave polymerization of acrylic resins used in dental prostheses; J. P.
De Clerck ; j prosthet dent; May 1987;vol57;650-657

82. Chemically activated denture
base resin
84

83. Composition of self cure acrylic resin
85
Ingredients Function
Poly(methyl methacrylate)&
other copolymers
Dissolved by monomer to
form dough
Benzoyl peroxide Initiator
Compounds of mercuric
sulfide,cadmium sulfide
Dyes
Zinc or titanium oxide Opacifiers
Dibutyl phthalate Plasticizer
Dyed organic fillers &
inorganic particles like glass
fibers or beads
Esthetics
Powder

84. Liquid
86
Ingredients Function
Methyl methacrylate
monomer
Dissolves/plasticizes
polymer
Dimethyl-p-toluidine Activator
Dibutyl phthalate Plasticizer
Glycol dimethacrylate Cross linking agent
Hydroquinone Inhibitor

85.  Chemical activators used to induce polymerization
 Cold curing / self curing / auto polymerizing resin
 Chemical used – dimethyl para toluidine (to
monomer)
87
Initiates break down of benzoyl
peroxide to produce free
radicals - polymerization

86. Degree of polymerization not complete – greater
amount of unreacted monomer
 Less color stability due to the presence of amine
susceptible to oxidation
 Less shrinkage and greater dimensional accuracy
compared to heat activated PMMA
88
Plasticizer results in
decreased transverse strength
Potential tissue irritant

87. uses
 For making temporary crowns & FPDs
 Construction of special trays
 For denture repair , relining & rebasing
 For making removable orthodontic appliances.
89

88. Technical consideration
 Supplied in monomer polymer form
 Mixed according to manufacturers instruction –
attain dough like consistency
 Working time is shorter
 Refrigerating monomer increases WT – rate of
polymerisation decreases
90

89. Processing consideration
 Pressure must be maintained throughout
 Initial hardening – 30 mins
 Flask held under pressure – 3hrs
 Low degree of polymerisation – dimensional
instability – soft tissue irritation
91

90. Techniques
 Sprinkle on technique
 Adapting technique
 Fluid resin technique
 Compression molding technique
92

91. Sprinkle on technique
93

92. Finger adapted dough technique
94

93. Fluid resin technique
 Employs a pourable, chemically activated resin
 On mixing – low viscosity resin
 Completed teeth arrangement is sealed to the
underlying cast
 Flask is filled with reversible hydrocolloid
allowed to cool (silicone mold / soft stone)
 After gelation – cast is removed – sprues and
vents are cut on the external surface
95

94.  Wax is eliminated
 Teeth are carefully retrieved and placed in position
 Resin is mixed and poured via sprue channels
 Placed in pressurized chamber at room
temperature( air pressure 0.1- 0.2 Mpa)
 Allowed to polymerize – 30 – 45 mins
 Denture is retrieved , sprues are removed
 Returned to articulator for correction of processing
changes
96

95. 97

96.  Advantage
 No trial packing
 Less expensive
 Less time
 Low water sorption
 Simplified deflasking
 Problems of broken teeth eliminated
 Agar - reused
98

97.  Disadvantage
 High polymerisation shrinkage
 Dimensionally inaccurate
 Low impact strength
 Low fatigue strength
 High creep value
 High solubility
 Low flexural strength
99

98. 100
Self cured Heat cured
-Heat is not necessary for polymerization Heat is necessary for polymerization
-Porosity is greater Porosity of material is less
-Has lower average mol.wt. Higher molecular weights
Higher residual monomer content Lower residual monomer content
-Material is not strong (because of their
lower molecular weights)
Material is strong
-Rheological properties
-Shows greater distortion
-More initial deformation
-Increased creep & slow recovery
Less initial deformation
shows less
Less creep & quicker recovery
-Poor color stability Color stability is good
Easy to deflask Difficult to deflask
Lower rate of monomer diffusion Increased rate of monomer diffusion at
higher temperature
-
-

99. Light activated denture base resin
101

100. Composition
Ingredients Function
Polyether urethane
dimethacrylate
Major constituent
Camphoroquinone Photoinitiator
Amine ( dimethyl amino ethyl
methacrylate)
Photoactivator
Inorganic ; silicon dioxide
(microfine)
Fillers
Organic ; acrylic resin beads Fillers
High molecular weight acrylic resin Monomer
102

101.  Supplied as – sheet / rope form
 Packed in light proof pouches
 Opaque investing material is required – no
conventional method
103

102.  Denture is molded on an accurate cast
 Exposed to a high intensity visible light
 Removed from the mold
 Finished and polished
104

103.  Mechanism of polymerisation
 Camphoroquinone + Organic amine - Free
radicals – irradiated @ 400–500 nm
 Initiates polymerisation
 Light curing chamber – 10 min
 Light sources – UV Light
Argon laser
105

104. Advantages
 Less porosity
 Extended working time – in vivo also used
 Light weight
 No allergic reaction
 Free of MMA
 Non toxic
 Reduced polymerisation shrinkage
106

105. Disadvantages
 Requires high artistic skills
 Technique sensitive
 Time consuming
107

106. 108

107.  Polymerization shrinkage
 Porosity
 Water absorption
 Solubility
 Strength
 Processing stresses
 Crazing
109

108. Polymerization shrinkage
 During polymerization shrinkage the density of the
mass changes from 0.94 g/cm3 - 1.19 g/cm3
 Linear shrinkage – denture base adaptation and
cuspal interdigitation
110
Volumetric shrinkage – 21%

109.  Volumetric shrinkage – 7% , hence linear
shrinkage – 2%
 Initial cooling – resin is soft- contraction at the
same rate as that of dental stone
 At glass transition temperature – contraction
occurs – faster rate than the surrounding stone
111
Glass transition temperature – It is a thermal
change in which the resin passes from a soft,
rubbery stage to a rigid glassy state

110. 112
Fluid resin
technique
Heat /
chemically
activated
resin
Decrease in vertical
dimension
Increase in overall
vertical dimension

111. Porosity
o Contraction porosity
 Generalized
 Localized
o Gaseous porosity
o Granular porosity
o Air inclusion porosity
113

112. Contraction porosity
 Contraction of monomer during polymerization
 Insufficient pressure / material
114

113. Gaseous porosity
 Volatilization of monomer
 In bulkier portion
115

114. Granular porosity
 Localized shrinkage
 Improper mixing / inadequate monomer
116

115. Air inclusion porosity
 Air incorporation
 Fluid resins
117

116. 118
Insufficient pressure
insufficient mixing
rapid heating

117. Water absorption
 Absorbs relatively small amount of water when
placed in water
 Water molecules penetrate the PMMA and occupy
positions between polymer chains forces them
apart
119
Slight expansion in
polymerized mass Water acts as plasticizer

118.  Water absorption value – 0.69 mg/cm2
Interfers with the polymer chain making them more
mobile – releasing stresses
Changes in shape (insignificant)
120

119. Solubility
 Insoluble in oral cavity
 Negligible loss
121

120. Processing stresses
 Natural dimensional change is inhibited – contains
stresses
 Stresses relaxed – distortion occurs
 During polymerization – tensile stresses are
sustained
 Stress is produced during thermal shrinkage also
(cooling < Glass transition temp)
122

121.  Additional factors include
 Improper mixing and handling of the resin
 Poorly controlled heating and cooling of flask
assembly
 Dimensional changes due to small stresses – 0.1
to 0.2 mm
123

122. Crazing
 Crazing is formation of surface cracks on
denture base resin.
 Causes –
 Incorportion of stress
 Attack by solvent (alcohol)
 Incorporation of water during processing.
 Prevention
 Avoidance of solvent
 Proper use of separating media
 Metal moulds
 Use of cross linked acrylic
124

123. Strength
 Load application – stresses within the resin –
change in shape
 Strength α degree of polymerisation shrinkage
 Heat activated resin – lower degree of
polymerisation
125

124. Creep
 Acts as rubbery solids that recover from elastic
deformation once stresses are eliminated – visco
elastic behaviour
 If load is not removed additional plastic
deformation occurs – creep
 Rate at which this deformation occurs – creep rate
126

125. 127

126. Denture warpage
 Denture warpage is change in shape or fit of
denture.
 Causes :incorporation of stress in denture
 Packing in late dough or rubbery stage.
 Stress induced during curing
 Improper deflasking
 Rise in temp while polishing
 Immersion of processed denture in hot water.
128

127. Denture fracture
 Improper deflasking
 Denture base excessively thin
 Accidental dropping at time of polishing
129

128. Change in tooth position
 Care to taken at time of dewaxing procedure
 Rearticulation to be done after processing the
denture to check for occlusal discrepancy.
130

129. Bleaching
 Lightening of pigmentation
 Normal pink color – light /pale
 Clear acrylic – cloudy
 Causes –
 Moisture contamination during mixing and
polymerization
 Use of water glass – separating medium
 Flaming teeth during wax up
 Instability of color pigments
 Bleaching agents for cleaning -patients
131

130. Raised bite
 vertical dimension
 Premature contact in the posterier – instability
 Localised ulcer , TMJ disorder & # of denture
Causes :
 Thick flash
 Too much / too little pressure
 Weak investing plaster
 Hard dough
 Damaged flask
132

131. 133

132. Radio – opaque dentures
 Denture wearers can endure serous complications
if their denture fractures and a portion is inhaled or
ingested
 Most promising – silanated barium fluoride
impregnated powdered glass
 Barium sulphate – improve radiopacity
 Lang et al investigated the potential for triphenyl
bismuth incorporated into injection moulded heat
cure resins to improve radiopacity
134

133. 135
Chest radiographs in which a segment of
denture base has been placed over the lower right half of
the chest: (a) for a radiolucent denture base material; (b)
for a radiopaque denture base material.

134. Cytocompatible anti-fungal
resin
 Inhibition of candida albicans – preventing denture
stomatitis
 PMMA – silver nanoparticle discs were formulated
with the commercial acrylic resin
136

135. Titanium denture base
Commercially
pure titanium
has appropriate
mechanical
properties
Light weight (low
density)
compared with
conventional
alloys
Outstanding
biocompatibility-
prevents metal
allergic
reactions
137

136. Flexible dentures
Available in the
form of granules
in catridges of
varying sizes
First introduced
as valplast and
flexiolast -1956
These are Super
polyamides
belonging to
nylon family
138

137. Advantages
Soft inherent flexibility
Will not warp
Clinically unbreakable
No porosity
Less bulky
Biocompatible
Better esthetics
Better chewing efficiency
139

138. Disadvantages
De-bonding of acrylic
teeth
Discoloration
High surface roughness
Cannot be relined
Difficult to polish
Technique sensitive
Cannot be repaired
140

139. Contraindications
Insufficient inter
arch space (<4mm
space for
placement of teeth)
Prominent residual
ridges
Flat, flabby ridges
141

140. Applications
Management
of xerostomia
patient
Retain
moisture –
better
lubrications
Biocompatible-
safe for
patients with
carcinoma
In conditions
with
inadequate
vertical
dimension
142

141. NESBIT RPD
 Modification of valplast partial denture
 Used to replace one to three teeth onb the same
side of the mouth – much smaller than a
conventional partial denture
143

142.  Procedure completed – short visits
 Less cost
 Easy to get used to
 A very realistic appearance
144

143. High impact acrylic
 Incorporation of a rubber phase – butadiene
styrene
 Improved impact strength
145

144. High impact acrylic resin
reinforced with zirconia
 Transverse strength of high impact acrylic resin –
increased by a factor of 29% and 76%– reinforced
with zirconia in a concentration of 5% and15%
respectively
 In this process , expansion of ZrO2 crystals occurs
and places the crack under a state of compressive
stress and crack propagation is arrested
146

145. Fiber reinforced denture
 To improve physical and mechanical
properties of acrylic resin
1. Carbon fibers
2. Kevlar fibers
3. Glass fibers
147

146.  Carbon fiber
 Larsan et al and sonit – 1991
 Carbon fibers improved flexural and impact
strength ; prevent fatigue fracture and increased
fatigue resistance on treating with silane coupling
agent (yazdanie -1985)
148

147.  Kevlar fibers
 Resistant to chemicals; thermally stable ; high
mechanical stability, melting point and glass
transition temperature
 Studies – Berrang et al (1990) – have shown to
significantly increase the impact strength and
modulus of elasticity – but also unaesthetic
149

148.  Glass fibers
 E-glass , S-glass , R- glass , V-glass and Cemfil
 E-glass fiber – high alumina and low alkali and
borosilicate – claimed to be superior in flexural
strength
 Because the modulus of elasticity of glass fibres is
very high , most of the stresses are received by
them without deformation
150

149. Ceramo polymers
 Color stable with color changes range – 0.34 DE
units & 0.62 DE units
 Decreased shrinkage
 Wear rate similar to enamel
151

150. Incorporation of antimicrobials
 Incorporation of methacrylic acid, apatite coated
titanium oxide photo catalyst & ammonium
compound
152

151. Nano particles reinforced
PMMA
 Zinc oxide , gentamycin & ceramic
 Prevents – Candida & bacterial colonies over the
denture surface
153

152. Repairing fractured acrylic denture
154

153. 155

154. Relining
156

155. Denture liners
 Elastopolymers – flow for an extended period
 Soothing effect on irritated mucosa
 Working time – 2-3 min
 Final gelation time – 15 – 20 min
 Initially plastic – intraorally – elastic
 Short / Long term – amount of plasticizer
 Plasticizer 60 % or more – Soft liners
157

156.  Indications:
 Protect underlying basal tissue
 Dry mouth
 Ill fitting denture – trauma
 Post surgery
 Immediate denture
 Functional impression material
 Aids in retention - engaging in bony undercuts
158

157. Classification
I. Depending upon the plasticizer content and
period for which it remains
A. Tissue conditioners
B. Temporary / short term liners
C. Permanent/long term liners
1. Autopolymerised silicone
2. Heat polymerized silicone
3. Autopolymerised acrylic resin
4. Heat polymerized acrylic resin
159

158. II. Depending on methods of fabrication
A. Chemically activated / direct or chair side liners
B. Heat activated / indirect or lab liners
160

159. Properties
 Viscosity ( 2 at 20ºc and 1.2 at 37.4ºc)
 Elasticity
 Resiliency & dimensional stability
 Adhesion to denture base
 Abrasion resistance
 Color stability
 Biocompatibility
 Good wettability
161

160. Composition of tissue conditioner
Powder
PMMA Polymer beads
162
Liquid
Ethyl alcohol Solvent
Butylphthalyl/ butyl glycolate
(60-80%)
plasticizer

161. Indications
 Conditioning – abused tissues
 Reline material – surgical obturator
 Stabilize & comfort – temporary denture base –
jaw relation
 Functional impression materials
163

162. Composition of temporary liners
Powder Component liquid
Prepolymerised
PMMA beads
Methyl methacrylate
Benzoyl peroxide Initiator
Plasticizer Dibutyl phthalate (50-
60%)
Activator Tertiary amine
Inhibitor Hydroquinone
(0.006% vol)
Color pigments
inorganic salts
164

163.  Advantage
 High peel strength
 Rupture resistant
 Disadvantage
 Poor resistance
 Loses plasticity in time
165

164. Permanent liners
 Indications
 Highly resorbed / atrophied ridges
 Bruxism
 Prosthesis - Maxillo facial defects
 Xerostomia
 Congenital /acquired oral defects
166

165.  Advantages
 Quicker adapatation to new dentures
 Quick healing
 Immediate denture after extraction
167

166.  Disadvantages
 poor wear resistence
 Over time – plasticizer leach out – hard
 Poor color stability
 Require adhesives for bonding
 Silicone – resistent to finishing and polishing
process
 Rough surface – harbors microorganisms
168

167. KOOLINER
 Hard , chair side reliner -
 Low exothermic heat
 110°F at 2mm thickness
 Increases patient comfort
 Completely self-cure in the patient's mouth in appr 10
mins - minimizes distortion ensures fit of the denture
 Dense, stable and color-fast
 Easy to finish and polish
 Can be used to extend denture borders and posterior
palatal seal
169

168. Relining an acrylic denture
170

169. Rebasing
171

170. Rebasing the acrylic denture
172

171. Denture teeth
1. Resin /Acrylic teeth
2. Acrylic teeth with metal inserts
a. Gold solder circular wires
b. Stainless steel circular wires
c. Cleat shaped vitallium occlusal
d. Vitallium occlusal
e. Flat stainless steel castings with holes
f. Metal cutting bar
173

172. 3. Porcelain / ceramic teeth
4. Tube teeth
5. Reinforced acrylic pontics (RAP)
6. Metal
7. Metal with porcelain, acrylic / lab composite
veneering/ facing
174

173. Difference between acrylic and porcelain
teeth
Resin teeth Ceramic teeth
Less resistant to abrasion high
High resilience Brittle and friable
Water sorption can occur Stable
Better bond to denture base
materials
Poor
Natural appearance Natural
No clicking sound Clicking sound
Easy to modify Difficult
175

174. •Toothpaste and brush
Mechanical
• Peroxide solutions
• Mild detergents
• House hold cleansers
• Bleaches
• Vinegar
Chemical
176
Classification

175.  Composition
 Alkaline compounds
 Detergents
 Sodium per borate
 Flavoring agents
LED light irradiation with hydrogen peroxide
photolysis – highly reactive hydroxyl radicals –
bactericidal effect
177

176. Infection control
 Sterilization – ethylene oxide gas
 Disinfection – sodium hypochlorite(1:10)
178

177. Materials for maxillofacial
prosthesis
A) Intra oral
1. PMMA
2. Tantalum ticonium
3. Vitallium
4. Silicones
5. Stainless steel
B) Extra oral
1. PVC
2. PMMA
3. Silicones
4. Polyurethanes
179

178.  Commonly used –
 Acrylic resins – PMMA & MMA
 Latex
 Vinyl polymers and copolymers
 Polyurethane
 Silicone
180

179.  PMMA :
 Hygienic & durable
 Colour matching
 Core for silicone facial prosthesis- LEMON
181

180. Advantage
1. Intrinsic and extrinsic coloration
2. Strength adequate – feather edge margins
3. Compatible – adhesive systems
4. Heat polymerized preferred – less free monomer
5. Serviceable up to 2 yrs
182

181. Disadvantages
 Rigidity – local discomforts
 High thermal conductivity
 Crazing
183

182. Palamed
 Cross linked polymer of methacrylics and acrylics
 Consists of base powder , stain concentrates ,
solvent liquid
 Shade guide is provided
 Produces a soft resilient skin, with a spongy
central mass and light weight
 The sculptured wax is weighed to achieve the
recommended ratio according to the weight ratio
table
184

183. Summary
185

184. References
 Skinners ,science of dental materials
 Rudd and Morrow , dental laboratory procedures,
complete denture
 Craig’s restorative dental materials 13th edition
 Mc Cabe and walls’ applied dental materials 9th
edition
 William J O'Brien Dental materials selection 3rd
edition
 Text book of dental materials , Sharmila Hussain
 Materials used in dentistry , S.Mahalekshmi
186