CONTENTS: Introduction History Ideal requirements Classification Stages of polymerization Manipulation Properties of Denture Base Resins Processing errors Recent Advancements Conclusion References

1. GOOD
MORNING

2. DENTURE
BASE
RESINS
2

3. CONTENTS
3
✗ Introduction
✗ History
✗ Ideal requirements
✗ Classification
✗ Stages of polymerization
✗ Manipulation
✗ Properties of Denture Base Resins
✗ Advancements
✗ Conclusion
✗ References

4. INTRODUCTION
✗ Denture base (GPT 9) : The part of a denture that rests on the
foundation tissues and to which teeth are attached.
✗ Resin (GPT 9) : A broad term used to describe natural or
synthetic substances that form plastic materials after
polymerization.
4

5. HISTORY

6. 6
MATERIALS USED BEFORE 18th CENTURY
Bone
Ivory
17th century-Pierre Fauchard (1678-1761) He
used human teeth or animal teeth ,& carved
dentures from a single piece of bone.

7. 7
Ivory Dentures

8. 8
MATERIALS USED IN 18TH CENTURY
French dentist Etienne Bourdet (1775)
who made the first reference to the
use of a gold base)
Gold
In 1808 Italian dentist Giuseppangeio Fonzi. Introduced individually baked porcelain teeth

9. 9
1854 Thomas Evan. produced by heating
natural rubber in the presence of sulfur.
It remained the principal denture base
material for the next 75 years
John Wesley Hyatt (1868)the
first organic plastic molding
compound. The advantages
were its translucence and
pink color.
MATERIALS USED IN 19TH CENTURY
• Tortoise Shell (1850) • Cheoplastic (1856) • . Rose Pearl (1860) • Aluminum (1867)
Celluloid (1870)
Vulcanite (1854)

10. 10
Metal denture bases
Used stainless steel, silver and its alloys as
denture base materials. Currently base metal
alloys are gaining popularity in place of gold
alloys and aluminum alloys.
MATERIALS USED IN 20TH CENTURY
PMMA (vernonite)
In 1937 Dr. Walter Wright and Vernon brothers clinically evaluated PMMA and found to fulfill virtually all

11. 11
 Cobalt Chromium (1930)
 Vinyl Resin (1932)
 Acrylic Resin (1937)
 Self cure Acrylic Resin
 Epoxy Resin (1951)
 Polystyrene (1951)
Nylon (1955)

12. Ideal Requirement of Denture Base Resin-
• Be dimensionally stable.
• Be esthetically satisfactory.
• Have enough strength,resilience & abrasion resistance.
• Be tasteless,odourless,nontoxic &non-irritant
• Be easy to fabricate.
Uses of Denture Base Resin-
• Fabrication of dentures.
• Artificial teeth.
• Orthodontics & pedodontics appliances.
• Crown & FPDs facing.
• Inlay & post core patterns.
12

13. PROPERTIES OF
POLYMERS
RHEOMETRIC PROPERTIES
SOLVATION PROPERTIES
THERMAL PROPERTIES
13

14. 14
POLYMERIZATION occurs through a series
of chemical reactions by which the
macromolecule, or the polymer, is formed
from the large numbers of molecules
known as monomers
TYPES:-
CONDENSATION POLYMERIZATION
ADDITIONAL POLYMERIZATION

15. The components are difunctional,
Byproduct is formed.
Not widely used in dentistry
15
CONDENSATION POLYMERIZATION
(Step growth polymerization)

16. All resins employed extensively in dental procedure are produced by
additional polymerization
No change in chemical composition and no by-products are formed
16
ADDITION POLYMERIZATION
(Chain growth polymerization)

17. PHYSICAL STAGES OF POLYMERIZATION
17
Sandy
String
Doughlike
Rubbery/elastic
Stiff

18. CHEMICAL STAGES OF POLYMERIZATION
Induction Propagation
Chain
transfer
Termination

19. 19
INDUCTION: Two processes controls
induction : stage – activation and initiation.
A source of free radical R is required.
Free radicals are generated by activation of
radical producing molecule such as,
chemical, heat, visible light, ultraviolet light
or energy transfer from another compound.
PROPOGATION: The resulting free radical
. monomer complex acts as a new free radical
. center which is approached by another
monomer to form a dimer, which also . .
. becomes a free radical.

20. 20
CHAIN TRANSFER When a free radical
approaches methyl methacrylate molecule
and donates a hydrogen atom to the
methylmethacrylate molecule.
This causes free radical rearrangement to
form a double bond and unreactive.
TERMINATION Addition polymerization
reaction is terminated by
-Direct coupling of two free radical chains
ends.
-Exchange of hydrogen atom from one
growing chain to another.

21. PROPERTIES OF ACRYLIC RESINS
Taste and Odour: Completely polymerized acrylic resin is tasteless and odourless.
Esthetics : It is a clear transparent resin which can be pigmented easily to duplicate
. oral tissue.
strength: The strength of an individual denture base resin is dependent on many
. factors such as- composition, processing technique etc. Self cured resin
generally have lower strength values.
Impact strength: measure of energy absorbed by a material when it is broken by a
. sudden blow ,
Heat-activated resin=0.98-1.27 joules Chemically activated resin=0.78 joules
solubility: Denture base resin are virtually insoluble in the oral fluids
colour-stability: The color stability of heat- cured acrylic resin is superior than other.
Biocompatibility: Completely polymerized acrylic resin are biocompatible.
21

22. CLASSIFICATION

23. 23
Based on
materials
Metallic : Gold and its alloys, aluminium, Cr-Co
alloys
Non metallic: Shellac,baseplate wax, Acrylic &
vinyl resins
Based on
durability
Temporary: Shellac, base plate wax, cold cure
acrylics
Permanent: Gold and its alloys,Cr-Co alloys, light
and heat cure acrylics

24. According to ISO 1567
24
• CLASS 1 Heat processing polymers, powders and liquid
• CLASS 2 Heat processed (plastic cake)
TYPE 1
• CLASS 1 Autopolymerized polymers, powder & liquid
• CLASS 2 Autopolymerized polymers (powder and liquid pour type resins)
TYPE 2
• Thermoplastic blank or powderTYPE 3
• Light Activated MaterialsTYPE 4
• Microwave-Cured MaterialTYPE 5

25. Composition-
Liquid-
✗ Methyl Methacrylate
✗ Dibutyl phthalate
✗ Glycol
dimethacrylate
✗ Hydroquinone
Powder-
✗ Methyl methacrylate
✗ Ethyl methacrylate
✗ Benzoyl peroxide
✗ Dibutyl phthalate
✗ Inorganic fillers
✗ Compounds of
mercuric sulfides
25
HEAT ACTIVATED DENTURE BASE RESIN

26. USES :
Used in the fabrication of nearly all
denture bases.
ADVANTAGES:
They are rigid and accurate.
They are stable, not subject to
distortion.
DISADVANTAGES:
Require considerable time.
More expensive.
26
HEAT CURED DENTURE BASE RESIN

27. 27
Manipulation
Compression
mould
technique
Injection
mould
Technique

28. 28
• Flasking
by: 2 pour
technique /
3 pour
technique
Preparation
of the
mould
• Tinfoil,
Cellulose
lacquers,
solution of
alginate etc
Selection of
separating
medium
• 3:1 ratio by
volume
• 2:1 by
weight
Polymer to
monomer
ratio
• ANSI/ADA
No.12:In clinic,
less than
10min
Dough
forming
time • moldable
for at least
5 min
• Temperatur
e effects
Working
time
• Hydraulic or
mechanical
press
• Trial and final
closure
Packing
•Coupling of two
grouping chains
•Transfer of H2 ion
from one chain to
another
Polymerization
procedure
•Initial heating –
slow
•Temperature > 70º
c(decomposition
rate of benzoyl
perxdTemperature
rise
•Constant temp 74ºC For
8 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
Polymerization
cycle
bench curing
Dewaxing
Bench cooling
Compression mould technique

29. Injection mould technique
In 1946 ,James Watson Henry built
the first screw injection.
ADVANTAGES:
✗ Controlled polymerization with
continuous compensation of the
material
✗ Time consuming adjustments of
occlusion can be eliminated
✗ No mixing or dosing errors
✗ Homogenous mix reduce risk of
possible fractures
DISADVANTAGES:
✗ High technique sensitive ,expensive
29

31. CHEMICALLY ACTIVATED DENTURE RESINS
Often referred as cold curing, self-
curing or autopolymerizing resins.
USES:
✗ Temporary crown and bridges
✗ Special trays(contains more fillers)
✗ Denture repair , relining & rebasing
✗ Temporary denture bases
✗ Inlay and post core patterns etc.
Composition:
Identical to heat cure resin except
polymerization is initiated by tertiary
amine (dimethyl-para-toluidine).
31

32. 32
ADVANTAGE
✗ Exhibit less shrinkage, so greater
dimensional accuracy.
✗ Easy manipulation
✗ Used as repair material
DISADVANTAGE
✗ Increased porosity
✗ Tissue irritation from residual
monomer.
✗ Colour stability-inferior due to tertiary
amine (oxidation)
✗ Decreased flexural strength.

33. 33
Techniques
Sprinkle on
technique
Adapting
technique
Fluid resin
technique
Compression
molding
technique

34. 34

35. 35
Fluid resin technique
Placed in pressurized chamber at room
temperature( air pressure 0.1- 0.2 Mpa)
polymerize – 30 – 45 mins

36. ✗ Polyether urethane
dimethacrylate –
✗ Camphoroquinone
✗ Amine ( dimethyl amino
ethylmethacrylate)
✗ Inorganic ; silicon
dioxide(microfine)
✗ Organic ; acrylic resin
beads
✗ High molecular weight
acrylic resin
36
-Major
constituent
-Photoinitiator
-Photoactivator
-Fillers
-Fillers
-Monomer
Light Activated Materials

37. Light sources – UV Light Argon laser
Light curing chamber – 10 min
Advantages
✗ Less porosity
✗ Extended working time – in vivo also used
✗ Light weight
✗ No allergic reaction
✗ Free of MMA & Non toxic
✗ Reduced polymerisation shrinkage
Disadvantages
✗ Requires high artistic skills
✗ Technique sensitive
✗ Time consuming
37

38. Microwave-Cured Material
NISHII (1968) first used microwave energy to
polymerise denture base resin in a 400 watt
microwave oven for 2.5 mins
Adavantages
✗ Least curing time – 3 min
✗ Good colour stability
✗ Minimal residual monomer ratio
✗ Good denture base adaptation
Disadvantages
✗ Poor bonding to adjacent teeth
✗ Increased porosity
✗ Expensive flasks
✗ Poor durability - flasks
38

39. Thermoplastic blank or powder
Valplast & Flexiplast were firstly
introduced to dentistry in 1950s.
Both materials are similar grades of
polyamides (nylon plastic)
ADVANTAGES
✗ Good retention
DISADVANTAGES
✗ Acrylic teeth do not bond
chemically with bond chemically
with flexible denture base.
✗ Discolouration
39

40. TECHNIQUE
✗ The material is available in
two forms as prepackeged
cartidges or blanks.
✗ Thermoplastic- converted
into fluid form –plasticized
for 15 – 20 min at 550 -
560ᵒ F –Electric cartridge
furnace
✗ Thermoplastic resins are
manipulated by injection
molding technique.
40

41. 41

42. PROCESSING
ERRORS
42

43. The presence of surface and subsurface
voids can compromise
physical, esthetic and hygienic properties of
processed dentures base.
• EXTERNAL POROSITY
-Lack of homogenity
-Lack of adequate pressure
43
POROSITY
-Avoided by proper P:L ratio,mixing ,adequate amount
• INTERNAL POROSITY
-Due to the vaporization of monomer when the temp of the resin
increases above the boiling point of monomer (100.8 degree C)
-avoided by long and low temperature curing cycle

44. 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
44
Crazing

45. 45
✗ 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.
Denture warpage

46. Polymerization shrinkage:
✗ It is partially explained by a volumetric
decrease arising from the con-version of
van der Waals bond into co valent bonds.
✗ The density of the monomer Changes from
0.94 – 1.19 g/cm
It results in volumetric shrinkage of 21%.
✗ By using 3:1 polymer: monomer ratio n the
volumetric shrinkage is brought to 7%.
46

47. ADVANCEMENTS
of
RESIN
47

48. Resins with modified chemical
structure.
Reinforced resins
- High impact resins
- Fiber-reinforced.
Hypoallergenic resins.
Enigma gum toning.

49. 49
:HIGH IMPACT RESINS
• Rubber reinforced (butadiene-styrene
polymethyl methacrylate).
• Rubber particles grafted to MMA for better
bond with PMMA.
CLINICAL APPLICATION:
They are so-called because of greater impact
strength & fatigue properties, hence indicated
for patients who drop their dentures repeatedly
e.g. parkinsonism. Available as powder-liquid
system
E.g Lucitone 199 , D.P.I Tuff, Hiflex H Prevest.

50. 50
Rapid Heat Polymerized Polymer
✗ These are hybrid acrylics which have had the
initiator formulated to allow for very rapid
polymerization without porosity.
✗ The flasks are placed in boiling water
immediately after being packed. The water
is then brought back to a boil for 20 min to
complete the curing cycle.
✗ Fast, high temperature cure makes this
material stiffer than conventional acrylic
processing.

51. RADIO OPAQUE DENTURES
✗ The radiolucent nature of PMMA is
one of its disadvantages as a
denture base material.
✗ Denture wearers can endure
serious complications if their
dentures fractures and a portion is
inhaled or ingested.
✗ Use of sophisticated ultrasound
technique also prove to be difficult
for detection.
51
Chest radiographs in which a segment ofdenture base
has been placed over the lower right half of the chest: (a)
radiolucent DBM(b) radiopaque denture base material.

52. 52
HYPOALLERGENIC RESINS.
• Hypoallergenic denture base materials exhibit significantly lower
residual monomer content than PMMA, thus act as an alternative
in allergic patients
• Diurethane dimethacrylate, Polyurethane,
Polyethylenterephthalate and Polybutylenterephthalate.
• Light activated indirect composite containing urethane
dimethacrylate(UDMA) is an alternative to PMMA for patients
hypersensitive to PMMA

53. Cytocompatible anti-fungal
resin
✗ Inhibition of candida albicans –
preventing denture stomatitis
✗ PMMA – silver nanoparticle discs
were formulated with the
commercial acrylic resin
53

54. Reinforced denture base resins
Metal and metal-reinforced denture
bases
The common metals include
✗ cast gold
✗ aluminium and
✗ chrome based alloys.
Advantages :
thermal conductivity, minimal bulk,
and more strength with high
dimensional stability.
Disadvantages :
heavy, inability of being rebased,
54
poor esthetics and not economical.

55. 55
Fiber-reinforced resin.
Various fibers such as carbon, kelvar,
glass(have best esthetics), and nylon
fibers have been added to PMMA to
improve their flexibility.
Available in two forms (mesh & fiber)
ADVANTAGES :
✗ Highest impact strength
✗ High modulus of elasticity
DISADVANTAGE :
✗ Decreased transverse strength
✗ Finishing and polishing is difficult
✗ Does not bond well with resins

56. 56
COMPARISON OF IMPACT STRENGTH OF RESINS
REINFORCED WITH DIFFERENT FIBERS:
Polyethylene > glass > thick Kevlar>carbon >thin Kevlar > unreinforced.

57. THERMOPLASTIC ACETAL:
POLYOXYMETHYLENE
• CLASPS ENGAGE FIRST THIRD OF
UNDERCUTS: 3-4 TIMES MORE
RETENTION
• BETTER AESTHETICS :METAL
CLASPS AND BARS CAN BE
REPLACED
• CAN BE PLACED MORE GINGIVALLY
• FLEXIBLE , MONOMER FREE-
HYPOALLERGIC
• TEETH AND CLASPS CAN BE ADDED
ON EXISISTING DENTURE BASES.
57

58. NESBIT RPD
✗ One modification of the valplast
partial denture ,which replaces one
to three teeth.
✗ Procedure completed – short visits
✗ Less cost
✗ Easy to get used to
✗ A very realistic appearance
58

59. 59
PEEK
✗ POLYETHER ETHER KETONE (PEEK) BELONGING
TO PAEK(POLYARYL-ETHER KETONE) FAMILY
✗ Introduced in the year 1992- it is a promising
polymeric material that could replace metallic
and ceramic in dental applications
✗ It has an elastic modulus close to human cortical
bone, suggesting more homogenous stress
distribution to bone compares to titanium. (can
also reduce stresses to the abutment teeth)
✗ Ceramic modified PEEK are gentler to enamel ,
and due to it’s low plaque affinity property it
promotes a healthy periodontium.

60. 60

61. 61

62. • Custom shade matching of natural gingival tissue
using ‘Enigma’ colour tones.
• Gives extra confidence to patient in appearance
of their dentures.
• Available in Ivory, Light Pink, Natural Pink, Dark
Pink & Light Brown. Different colors are mixed to
get the desired gum tone.
62
ENIGMA GUM TONING

63. DIGITAL DENTURES
63

64. 64

65. BIOFUNCTIONAL PROSTHETIC SYSTEM
✗ The BPS system is a
standardized system for the fabrication
of high quality removable / complete
dentures.
✗ BPS is the system designed to work with
the body in a biologically harmonious way,
maximizing function, and giving comfort
and natural appearance to the patient.
✗ BPS system uses a controlled
heat/pressure polymerization procedure
during which time the exact amount of
material flows into the flask to
compensate for shrinkage, which ensures
a perfect fit.
65

66. 66
Jaw movements by the Stratos 200
articulator in BPS ensure that BPS
denture meets most exacting requirements.

67. CONCLUSION
67

68. • Kenneth j. Anusavice ; Phillips Science of dental material
.Eleventh edition, Elsevier,2004.
• Robert C. Craig John M. Powers, John C.Wataha ;Dental materials
properties and manipulation,. Eight edition,2004.
References

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