Denture base materials

1. DENTUREBASE
M
ATERIALS
▶ Neeraja M Menon
Dept. Of Prosthodontics
Coorg Institute of Dental Sciences

2. CONTENTS
▶ Definition
▶ Ideal denture base
▶ Classification
▶ History
▶ Resin denture base materials
▶ Types of denture base polymers
▶ Metal denture base material
▶ Types of partial denture base
▶ Methods of attaching denture bases
▶ Methods of attaching artificial teeth
▶ Relining and rebasing
▶ Review of litrature

3. DEFINITION
▶ Denture base: the part of a denture that rests on the foundation
tissues and to which teeth are attached - GPT9
▶ Denture base material: any substance of which a denture base may be
made - GPT 9

4. Ideal denture base:
▶ Accuracy to adaptation to the tissue with low volume change
▶ Dense, non-irritating surface capable of receiving and maintain good
finish
▶ Thermal conductivity
▶ Low specific gravity
▶ Sufficient strength
▶ Self cleansing
▶ Aesthetic acceptability
▶ Potential for future relining
▶ Low cost

5. Classification
 Metallic denture base materials
Cobalt-chromium
Gold, Titanium
Stainless steel, Aluminium
 Non-metallic denture base materials
Acrylic resin
Vinyl resin

6. Formerly used materials
Materials used before 18th
1. Wood
2. Bone
3. Ivory
century
Materials used in 18th
1. Gold
2. Porcelain
century
Materials used in the 19th century
1. Tortoise Shell (1850)
2. Gutta Percha (1851)
3. Vulcanite (1851)
4. Cheoplastic (1856)
5. Rose Pearl (1860)
6. Aluminum (1867)
7. Celluloid (1870)

7. Materials used in the 20th century
1. Bakelite (1909)
2. Stainless steel (1921)
3. Cobalt Chromium (1930)
4. Vinyl Resin (1932)
5. Acrylic Resin (1937)
6. Self cure Acrylic Resin
7. Epoxy Resin (1951)
8. Polystyrene (1951)
9. Nylon (1955)
10. Polycarbonates (1967)
11. High impact acrylic (1967)
12. Polysulphones (1981)
13. Visible L.C (1947)Acrylic (1986)
14. Pure Titanium (1998)

8. Resin denture base materials
Chronology of events
▶ Charles Goodyear discovery of vulcanized rubber in 1839.
▶ John hyatt discovered celluloid in 1868
▶ Dr Leo Bakeland discovered phenol-formaldehyde resin
(Bakelite).
▶ In the 1930’s Dr Walter Wright and the Vernon brothers
working at the Rohn and Haas company in Philadelphia
developed Polymethylmethacrylate (PMMA), a hard
plastic.
▶ Although other materials were used for dental prosthesis,
none could come close to PMMA and by the 1940;s 95% of
all dentures were made from this acrylic polymer.
Goodyear
Hyatt
Bakeland

9. Polymers
DEFINITION: A polymer is a long chain organic molecule .It is produced
by the reaction of many smaller molecules called monomers, or
mers.
▶ If reaction occurs between two different but compatible monomers
the polymeric product is called a COPOLYMER.
▶ Resin : A broad term used to describe natural or synthetic
substances that form plastic materials after polymerization (GPT-
9).

10. USES IN DENTISTRY
▶ Denture bases and artificial teeth.
▶ Denture liners and tissue conditioners.
▶ Composite restorative and pit and fissure sealant.
▶ Impression materials
▶ Custom trays for impression
▶ Mouth guards.
▶ Maxillofacial prosthesis.
▶ Space maintainers.
▶ Veneers.

11. CHEMISTRY OF POLYMERIZATION
▶ Monomers react to form polymer by a chemical reaction called
polymerization.
▶ The most common polymerization reaction for polymers used in dentistry
is addition polymerization.
ADDITION POL
YMERIZATION
▶ INDUCTION
▶ PROPOGATION
▶ CHAIN TRANSFER
▶ TERMINATION

12. INDUCTION
1)ACTIVATION
2)INITIATION
ACTIVATION
Free radicals can be generated by activation of radical producing molecule
using.
▶ Second chemical
▶ Heat
▶ Visible light
▶ Ultraviolet light
▶ Energy transfer from another compound that acts as a free radical.

13. Initiator Activator
Heat activated Benzoyl peroxide Heat
Chemical activated Benzoyl peroxide Tertiary amine
Light activated Champhoroquinone Visible light

14. ▶ Commonly employed initiator is Benzoyl peroxide which is activated
rapidly between 50 degree and 100 degree C to release two free
radicals per benzoyl peroxide molecule.
▶ Second type is chemically activated ,consists of two reactants when
mixed undergo reaction eg tertiary amine (the activator) and benzoyl
peroxide (the initiator). Amine forms a complex with benzoyl peroxide
which reduces the thermal energy (and thus the temperature) needed
to split it into free radicals.
▶ Third type is light activated .The visible light light cured dental
restoratives,camphorquinone and an organic amine
(dimethylaminoethylmethacrylate) generate free radicals when
irradiated by light in the blue to violet region.
▶ Light with a wavelength of about 470nm is needed to trigger this
reaction.

15. Initiation
BPO MMA

16. ▶ 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.

17. Chain transfer
▶ The active free radical of a growing chain is transferred to another molecule
(eg monomer or inactivated polymer chain) and a new free radical for further
growth is created termination occurs in the latter.

18. Termination
▶ Can occur from chain transfer.
▶ Addition polymerization reaction is terminated by
-Direct coupling of two free radical chains ends
-Exchange of hydrogen atom from one growing chain to another

19. INHIBITION OF ADDITION REACTION
▶ Addition of small amount of Hydroquinone to the monomer inhibits
spontaneous polymerization if no initiator is present and retards the
polymerization in the presence of an initiator.
▶ Amount added is 0.006% or less
▶ Methyl ether of hydroquinone is generally added.
COPOLYMERIZATION
▶ When two or more chemically different monomers each with desirable
properties can be combined to yield specific physical property of a polymer .eg
small amount of ethyl acrylate may be co-polymerized with methyl
methacrylate to alter the flexibility and fracture resistance of a denture.

20. TYPES OF DENTURE BASE POLYMERS

21. 1)CONVENTIONAL HEAT CURED POLYMETHYL
METHACRYLATE
- Principal
Constituent
- Initiator
- Dyes
Powder form
• PMMA and other co polymers
• Benzoyl peroxide 0.2-0.5%
• Compounds of mercuric sulphide,
cadmium sulphide etc 1%
• Zn or Ti oxide
• Dibutyl phthalate
• Dyed organic filler and inorganic
particles like glass fibers or beads
- Opacifier
- Plastisizer
- For
aesthetics &
enhance
physical properties
Composition

22. Commercial names
Acron
Stellon
Trevelon
Lucitone
Mediodont

23. ▶ As a rule,heat activated denture base are shaped via compression molding
technique.
Polymer monomer interaction
When polymer and monomer are mixed it passes through following stages
▶ Sandy
▶ Stringy
▶ Dough
▶ Rubbery or elastic
▶ Stiff
Dough forming time
▶ The time required for the resin mixture to reach a dough like stage.
▶ In clinical use, the majority of resin reach a dough like consistency in less than 10 min.
Working time
▶ Time that a denture base remains in a dough like stage. ANSI/ADA specification
no 12 requires the dough to remain moldable for 5 min.

24. 2)AUTOPOLYMERIZING/COLD CURE
POLYMETHYL METHACRYLATE
Composition
Powder
 Poly (methyl methacrylate) and other co-polymer(5 %) - Dissolves the monomer to form
dough
- Initiator
- Dyes
 Benzoyl Peroxide
 Compounds of Mercuric sulphide
cadmium sulfide, etc.
 Zinc or titanium oxide
 Dibutyl phthalate
 Dyes organic fillers and inorganic particles like
glass bead fibers or beads
- Opacifiers
- Plasticizer
- Esthetics and to enhance
physical properties

25. Liquid
▶ Methyl methacrylate
▶ Dimethyl-p-toluidine
▶ Dibutyl phthalate
▶ Glycol Dimethacrylate 1 to 2% - Cross
▶ Hydroquinone (0.006%)
- Dissolves/Plasticizes the polymer
polymerization
- Activator
- Plasticizer
- Linking agent (reduces Crazing)
- Inhibitor, prevents premature
polymerization

26. `
▶ Upon mixing tertiary amine causes decomposition of benzoyl peroxide.
▶ Dentures processed have more residual monomer (1-4%),but lower dimensional
change.
▶ Decreased transverse strength (residual monomer act as plastisizer).
▶ Compromised biocompatibility (residual monomer)
▶ Color stability inferior (teriaty amine susceptible to oxidation), stabilizing
agents should be added
▶ Fluid resin and compression molding technique can be
employed for the fabrication of denture.
▶ Also used as repair material

27. 3)HIGH IMPACT RESISTANT ACRYLIC
▶ Similar to heat cured material but less likely to be
broken if dropped.
▶ Produced by substituting the PMMA in the powder with
a copolymer.
▶ Copolymer of butadiene with styrene or methyl
methacrylate are incorporated into the beads.
▶ Phase inversion resulting in dispersion throughout the
beads of tiny islands of rubber containing small
inclusions of rubber/PMMAgraft polymer.
▶ Eg: Hi-Impact Pourable(Excel Formula®), Trevalon Hi
and Lucitone 199

28. 4) Injection molded polymers
▶ These are made of Nylon or Polycarbonate.
▶ The material is supplied as a gel in the form of a putty .
▶ It has to be heated and injected into a mold
▶ Equipment is expensive.
▶ Craze resistance is low .
▶ The SR-Ivocap system uses specialized flasks and clamping presses to
keep the molds under a constant pressure of 3000 lbs

29. 5) RAPID HEAT POLYMERIZED POLYMER
▶ Same as conventional material except that they contain
altered initiation system.
▶ These initiator allow them to be processed in boiling water
for 20 min.
▶ A problem with these is that areas of the base thicker than
approx.6mm have a high level of porosity.
▶ Short duration of heating also leaves a higher level of
residual monomer,3-7 times greater than conventional heat
cured denture base.
▶ Eg: QC 20, Meliodent and Trevalon

30. 6) MICROWAVE POLYMERIZED POLYMERS
▶ Resins are the same as used with conventional material and
are processed in a microwave.
▶ Denture base cures well in Special polycarbonate flask
(instead of metal).
▶ The packed flask is placed inside a microwave oven and
irradiated using the following cycle: 13 minutes on low
power at 90 watts, 1.2 minutes on high power at 500 watts,
and then bench cool for 30 minutes [16].
▶ The advantages are that it greatly reduced curing time (3
min.), shortened dough-forming time, minimal colour
changes, less fracture of artificial teeth and resin bases and
superior denture base adaptability, lower residual monomer
ratio, most stable.
▶ Eg: Material: Nature-cryl
Microwave curing resin: Acron MC

31. 7)Light activated denture base resins
▶ This material is a composite having a matrix of urethane
dimethacrylate, microfine silica and high molecular wt
acrylic resin monomers
▶ Acrylic resin beads are included as organic fillers.
▶ In the visible light-cured material, camphorquinone and an
organic amine (e.g. dimethylaminoethyl methacrylate)
generate free radicals when irradiated by light in the blue
to violet region.
▶ Light with a wavelength of about 400-500nm is needed to
trigger this reaction. Then the denture base is exposed to a
high-intensity visible light source for an appropriate
period.
▶ Can be used as repair material and as custom tray
material.
▶ Single component denture base is supplied as sheet and
rope form in light proof pouches.

32. 8) FIBER –REINFORCED POLYMER
▶ Glass, carbon/graphite, aramid and ultrahigh molecular
weight polyethylene have been used as fiber reinforcing
agents.
▶ Carbon Fibers:
The advantages are increase in transverse and impact strength
of PMMA, increased fatigue resistance when treated with silane
coupling agent
▶ Kevlar (Synthetic Aramid Fiber):
The advantages are increase in modulus of elasticity, increase
in fracture resistance.
The use of 2% by weight Kevlar reinforcement fibers increases
the fracture resistance of acrylic resin. Its disadvantages are
poor esthetics because of yellow color, difficulty in polishing.
▶ Eg: StickTM, Novodent, Alldent

33. Alternatives to methacrylate materials
▶ Most alternatives to polymethacrylate are vinyl acrylic, polysterene,
acrylic styrene, acrylonetrile copolymers .
NEW PLASTIC MATERIAL
▶ High impact methacrylates : These are basically similar to standard
methacrylate but have a higher impact and fatigue strength.
▶ Epoxy resins: The general properties of these materials are strength,
hardness, toughness, low curing shrinkage and good adhesion to metals.
The disadvantages for dental use are the toxicity, the yellow colour
which darkens further, high water absorption, poor adhesion to vinyl
polymers

34. ▶ Nylon materials: They were found to be unsatisfactory for denture base
because of high molding shrinkage which led to warpage, high water
absorption and yellowing.
▶ High impact polystyrene : This is an elastomer graft copolymer with
styrene. It is basically similar to polysterene and injection molded in a
similar way.
▶ High density polythene : This is stiffer, stronger variety of polyether.
▶ Polypropylene : this is a hydrocarbon polymer similar to polyethylene but
stiffer and stronger.
▶ Polyacetal : Also called polyformaldehyde. It has lower water absorption
with good resilience and toughness, and resistance to fatigue

35. ▶ Polycarbonate: It is thermoplastic material with low water absorption
and very high impact strength and toughness.
▶ Chlorinated polyether: It has very low water absorption and low mold
shrinkage with excellent resistance to staining and chemical agents
▶ Eclipse prosthetic resin system: is a new method of fabricating dentures
from Dentsply International. It is being marketed as an indirect build-up
method for fabricating dentures that is monomer-free and flask-free.
Eclipse is a light-cured system that does not contain any ethyl-, methyl-,
butyl-, or propyl-methacrylate monomers.
▶ System uses three resins to form the denture: Baseplate Resin, Set-up
Resin and Contour Resin. The resins were developed to handle like wax,
yet be cured into a denture base material – without investing and flasking.

36. VALPLAST
▶ Valplast is a flexible denture base resin that is ideal for partial
dentures and unilateral restorations.
▶ The material is a specialized form of nylon in the family of
superpolymides (a very pure nylon) that will not deteriorate
chemically when it comes into contact with the fluids, bacteria,
and physical environment of the mouth.
▶ The resin is a biocompatible nylon thermoplastic, it eliminates the
concern about acrylic allergies.
▶ Flexibility of the material allows it to engage the undercut beneath
the bony exostoses, that is not possible in rigid partial dentutres.

37. Metal denture base material
Indication
 Single maxillary complete denture opposing natural mandibular teeth
 Unfavourable occlusion
 Heavy anterior contacts
 Heavy masticatory force

38. Advantages of Metal Bases over Resin Bases:
(1) Accuracy and permanence of form-
▶ Cast more accurately than denture resins and maintain their
accuracy of form without change in mouth.
▶ Internal strains released later to cause distortion not present.
▶ Accuracy – metal base provides intimacy of contact, help in
retention of denture prostheses.
▶ Such intimate contact not seen in acrylic resin bases.

39. (2) Comparative tissue response-
▶ Inherent cleanliness of cast metal base contributes to health of oral
tissue.
▶ Bacteriostatic activity – ionization and oxidization of metal base.
▶ Metal base is naturally cleaner than an acrylic resin base.

40. (3) Thermal conductivity-
▶ Temperature changes transmitted though metal to the underlying
help to maintain health of that tissue.
▶ Patient acceptance.

41. (4) Weight and bulk-
▶ Metal alloy may be cast thinner than acrylic resin and still have
adequate strength.
▶ Certain situations demands use of acrylic denture base.
Extreme loss of residual alveolar bone- fullness to denture base to
restore facial contours.

42. Disadvantage
▶ Aesthetics
▶ Enhancement of retention not possible – lack of weight of metal base
▶ Relining difficult
▶ Restoration of normal facial contour can not be achieved

43. Different metallic denture base
materials
▶ Cobalt-chromium alloys :
▶ As early as 1949 it was estimated that nearly 80% of all partial
denture appliances were cast from Co-Cr alloys.
Composition
Principle elements (approx. 90%):
▶ Cobalt 60%
▶ Chromium 25% to 30%
▶ Other components :Molybdenum silicone, Aluminium nitrogen,
Berylium carbon & manganese

44. ▶ Nickel chromium alloys :
▶ Nickel 70%
▶ Chromium 16%
▶Chromium :
▶ Responsible for the tarnish resistance and stainless.
▶ When the chromium content of an alloy is more than 30% it is
more difficult to cast ; and therefore dental alloys should not
contain more than 28% or 29% chromium
▶ These alloys are considered to be technique sensitive.

45. ▶Cobalt and nickel :
▶ Cobalt increases the elastic modulus, strength and hardness more
than Nickel does
▶ CARBON :
▶ Increase in carbon content increases hardness of Co-based alloys.
▶ If the carbon content is increased by 0.2% more than the desired amount
–results in a too hard and too brittle alloy not suitable for dental
appliances.
▶ Whereas a decrease of 0.2% will decrease the tensile and the yield
strength.

46. ▶ MOLYBDENUM : (3% to 6% )
▶ Contributes to the strength of the alloy.
▶ Initially tungsten was used , but it reduced the elongation ,was
therefore replaced by other hardening elements like molybdenum
▶ ALUMINIUM
▶ Forms a compound with Ni and Al (Ni3Al) which increases the tensile
and the yield strength of the alloys.

47. ▶ BERYLIUM :
▶ About 1% lowers the fusion temperature range of the alloy by about
100 degrees C.
▶ SILICONE AND MANGANESE :
▶ Increase the fluidity and castability of these alloys.
▶ NITROGEN :
▶ If present contributes to the brittle qualities of these alloys

48. ▶ Titanium
▶ Ti was developed by William Gregor of England in
1791,and was named by Martin H. Kalproth of
Germany in 1795.
▶ Welhelm Kroll1930 invented useful metallurgical
processes for Ti and considered to be the FATHER
of Ti dentistry.
▶ It has the advantage of light-weight, strength and
biocompatibility but requires an inert casting
environment and casting defects can be a problem

49. Types of partial denture base
Tooth Supported Partial Denture Base Distal Extension Partial Denture Base

50. Tooth supported partial denture base
▶ In tooth supported prostheses denture base is primarily a span
between 2 abutments supporting artificial teeth.
▶ Occlusal forces transferred to abutments via rests.
▶ It prevent horizontal migration of all abutment teeth in partially
edentulous arch and vertical migration of teeth in opposing arch.

51. Distal extension partial denture base
▶ It is close to the terminal abutment, only a framework
supporting occlusal surface is necessary.
▶ Support from the underlying ridge tissues is very
important.
▶ Maximum support is obtained by using broad accurate
denture bases, which transmit the occlusal load
equally over the entire area
▶ Support should be of primary important in selecting
designing & fabricating distal extension partial
denture base.

52. Methods of Attaching Denture Bases :
▶ Resin bases are attached to the partial denture
framework by means of a minor connector
designed so that a space exists between it and
underlying tissues of the residual ridge.
▶ Relief at least a 20 gauge thickness over basal
seat areas of master cast is used to create raised
platform on the investment cast.
▶ Thus after casting the portion of retentive
framework to which the resin base will be
attached will stand away from the tissue surface
sufficiently to permit a flow of resin base
material beneath the surface.
▶ The retentive framework for the base should be
embedded in the base material with sufficient
thickness of resin. (1-5mm).

53. ▶ Thickness of the resin is essential during the
denture adjustments or during relining procedures
also to avoid weakness and subsequent fracture of
resin base materials.
▶ Metal bases –cast as integral parts of partial
denture framework.
▶ May also be assembled and attached to framework
with acrylic resin.

54. Methods of Attaching Artificial Teeth:
Artificial teeth may be attached denture bases
1) With acrylic resin.
2) Cemented.
3) Processed directly to metal.
4) Cast with framework

55. 1. Porcelain or resin artificial teeth attached with
resin.
▶ Porcelain teeth are mechanically retained.
▶ Posterior teeth are attached retained by acrylic resin in their
diatonic holes.
▶ Anterior porcelain teeth are retained by acrylic resin
surrounding the lingually placed retention pins.
▶ Resin teeth are retained by chemical union of the acrylic resin of
denture base.
▶ Attachment of resin to the metal base may be accomplished by
nail head retention, retention loop, or diagonal spurs placed at
random.
▶ Any junction of resin with metal should be at an undercut
finishing line or associated with some retentive undercut.

56. Plastic mesh work Open lattice
Beads
Nail heads

57. 2.Porcelain or resin tube teeth and facings cemented
directly to metal bases:
▶ Some disadvantages of this type of attachment are the difficulties
in obtaining satisfactory occlusion, lack of adequate contours for
functional tongue and cheek contact and unaesthetic display of
metal at gingival margins.
▶ This can be avoided when the tooth is butted directly to the ridge
and by selecting tube teeth for width but with occlusal surfaces
slightly higher than required.
▶ Recent advance include an attachment of readymade resin teeth to
the metal base with acrylic resin of same shade. This is called
pressing on a resin tooth.
▶ It is particularly applicable to anterior replacements.
▶ After a labial index of the position of the teeth is made. The lingual
portion of the tooth may be cut away or a posthole is prepared in
the tooth for retention on the casting.
▶ Subsequently the tooth is attached to the denture with acrylic resin
of the same shade.
▶ Since this is done under pressure, the acrylic attachment provides
hardness and strength.

58. 3. Resin teeth processed directly to metal bases:
▶ Modern cross linked copolymer enable the dentist to process acrylic resin
teeth that have satisfactory hardness and abrasion resistance for many
situation.
▶ Occlusion may be created without restoring to the modification of
readymade artificial teeth.
▶ Recesses in the denture pattern are either carved by hand or may be
created around manufactured teeth that are only used to form recess in
the pattern.
▶ Occlusal relationship may be established on mouth and then to the
articulator and then the teeth are carved and processed in acrylic resin
of proper shade.

59. 4. Metal teeth
▶ Occasionally a second molar tooth may be repaired as
part of partial denture casting.
▶ This is usually done when space is too limited for the
attachment of an artificial tooth and yet the addition of
second molar is desirable to prevent migration of an
opposing second molar .
▶ Before casting occlusal surface should be waxed properly
minimum
and the area of occlusal contact should be held
the avoid damage to the periodontium of
opposing tooth and the associated discomfort to the
patient.
▶ They should be used only to fill a space and to prevent
tooth migration and no more as they are difficult to
adjust and objectionally hard for use as occlusal surface.

60. 5. Chemical bond :
▶ Direct chemical bonding of acrylic resin metal framework
▶ Sections of metal framework that are to support replacement teeth
can be roughened with abrasives, then treated with vaporized silica
coating.
▶ Upon this surface a resin-bonding agent is applied, followed by thin
film of resin to act as a substrate for latter attachment of
replacement resin or for processing of acrylic resin tissue
replacement.

61. RELINING RESIN DENTURE BASES
▶ Involves replacement of the tissue surface of an existing
denture
▶ Indication
Whenever the denture loses or has poor adaptation to the
underlying tissues, while all other factors as occlusion;
aesthetics; centric relation; vertical dimension at rest and
denture base material are satisfactory:
– Loss of retention.
– Instability.
– Food under denture.
– Abused mucosa

62. Heat cured relining
The fitting surface is cleaned. The undercuts are removed and the
flanges are shortened.
Minor defects and extensions can be corrected with self cured acrylic.
A wash impression is then taken on the fitting surface of the denture
with impression paste, with the patient in light occlusal contact.
Later the impression paste is replaced with heat cured acrylic which is
more durable than the materials used for direct relines.

63. ▶ Chemically cured relining
Cold cured acrylic or tissue conditioner are used
The flanges are trimmed (to reduce danger of over extension) and the
undercuts removed.
The new relining is then mixed and applied to the fitting surface.
The denture is inserted and the patient asked to bite gently on the denture
to ensure that the occlusion is not altered by the procedure.
Border moulding can then be carried out.
The denture is kept in situ for about 5 minutes after which it is removed and
carefully examined

64. REBASING RESIN DENTURES
▶ It’s a process of readaptation of a denture to the
underlining tissues by replacing the denture base
material with a new one without changing its occlusal
relation.
Indications:
When the existing denture base is unsatisfactory; crazed
or porous.

65.  An impression is made with the denture and a cast is obtained.
 An occlusal and incisal index of the teeth is made in plaster using
HOOPER DUPLICATOR, the posts of the lower part of the duplicator are
seated in the upper part to maintain the relationship of the casts to
the plaster index.
 The denture with the impression material are removed from the cast.
Artificial plastic teeth are sectioned from the denture and all base
material around the teeth is removed
 Teeth are placed and held in position in the index using sticky wax on
the labial and buccal surface.
 A layer of base plate wax is placed over the ridge of the cast.
 The upper part of the duplicator is closed and denture teeth are
waxed to the proper thickness and counter to the cast.
 The cast is removed; flasked and processed in the usual manner.
 After deflasking, the cast is reattached to the upper part of the
duplicator to adjust any occlusal errors.
 Occlusion of rebased denture is further perfected by clinical remount.

66. Review Of Literature
Repair strength of autopolymerizing, microwave, and
conventional heat-polymerized acrylic resins
Rached RN et al, J Prosthet Dent 2004
Aim: This study evaluated the transverse repair strength of a conventional heat-
polymerized (Lucitone 199, ‘‘L’’) and a microwave-polymerized (Acron MC, ‘‘A’’) acrylic
resin that were repaired with these same resins and with an autopolymerizing acrylic
resin (Acron MC/R, ‘‘AR’’).

67. ▶ Twenty-four rectangular specimens (65.0 3 10.0 3 3.3 mm) of L or A
and 6 of AR were manufactured and stored in distilled water at 37
degree C for 7 days.
▶ Eighteen specimens of L or A were selected randomly. Six specimens
of each material remained intact (control), each 6 were sectioned in
the middle to create a 10-mm gap and repaired with the materials L,
A, or AR. After an additional 7 days of storage at 37 degree C, the
transverse strength (MPa) of the repaired and intact specimens was
measured using a 3-point bending test.
▶ Conclusion:
The autopolymerizing resin exhibited a repair strength similar to those
found for the conventional heat- and microwave-polymerized materials.

68. In vitro evaluation of the influence of repairing
condition of denture base resin on the bonding of
auto polymerizing resins
Hiroyuki et al, J Prosthet Dent 2003
Aim: This study evaluated the influence of water absorbed in denture
base resin on the bond strength and resistance to cyclic thermal stresses
of autopolymerizing resins bonded to denture base resin

69. ▶ Denture base resin disks were fabricated from heat-polymerized
acrylic resin (Lucitone 199). The disks were divided into groups with 3
conditions of water content: (1) complete water saturation (control),
(2) superficial desiccation by blowing air on the specimen, (3)
complete desiccation.
▶ Each denture base specimen received 1 of 3 surface treatments
including: (1) no treatment, (2) airborne-particle abrasion, or (3)
methylene chloride application.
▶ An autopolymerizing repair resin (Repair Material) or reline resin
(Tokuso Rebase Normal set,) was applied to the bonding area (5 mm
diameter) and polymerized at 37°C for 10 minutes.
▶ The resistance to cyclic thermal stress was determined after
subjecting the specimens to 50,000 thermal cycles between 4°C and
60°C water baths with a 1-minute dwell time. Bond strength (MPa)
was measured by shear bond testing at a 1.0 mm/min crosshead speed
until the applied resin debonded from denture base resin. Data were
statistically analyzed by 3-way analysis of variance and multiple
comparisons among the groups were performed with Bonferroni test
(.05).

70. ▶ Result:
Bond strengths of autopolymerizing resin to denture base resin were not
significantly influenced by water content of denture base resin but were
significantly influenced by resin type, thermal cycling, and surface
treatment.

71. The effect of reinforcement with woven E-glass fibers on
the impact strength of complete dentures fabricated with
high-impact acrylic resin
Sung-Hun Kim et al, J Prosthet Dent 2004
▶ Aim:The purposes of this study were to measure the impact
strength of maxillary complete dentures fabricated with high-
impact acrylic resin and to evaluate the effect of woven E-glass
fiber-reinforcement on the impact strength of the complete
dentures.

72. ▶ Preimpregnated woven E-glass fibers (Stick Net) were used to
reinforce 10 complete denture bases fabricated with a heat-
polymerized high-impact acrylic resin (Lucitone 199). Ten
unreinforced complete dentures served as a control group.
▶ All specimens were stored in water at 378 degree C for 2 months
before testing. The impact strengths (J) of the dentures were
measured with a falling-weight impact test. The impact strengths of
both groups were compared by a repeated measures analysis of
variance (a=.05). The Weibull distribution was also applied to
calculate the cumulative fracture probability as a function of impact
strength.

73. ▶ Result:
The impact strengths of maxillary complete dentures fabricated with
high-impact acrylic resin increased by a factor greater than 2 when
reinforced with woven E-glass fiber.

74. Studies on the effects of titanate and silane coupling
agents on the performance of poly (methyl
methacrylate)/barium titanate denture base
nanocomposites.
Nidal W. et al, J Dent 2017
Aim: The study aimed to fabricate and characterise silanated and titanated
nanobarium titanate (NBT) filled poly(methyl methacrylate)
(PMMA) denture base composites and to evaluate the behaviour of a titanate
coupling agent (TCA) as an alternative coupling agent to silane. The effect of
filler surface modification on fracture toughness was also studied.

75. ▶ Silanated, titanated and pure NBT at 5% were incorporated in PMMA
matrix. Neat PMMA matrix served as a control. NBT was sonicated in
MMA prior to mixing with the PMMA.
▶ Curing was carried out using a water bath at 75°C for 1.5h and then at
100°C for 30min. NBT was characterised via Fourier transform-
infrared spectroscopy (FTIR), Transmission Electron Microscopy (TEM)
and Brunauer-Emmett-Teller (BET) analysis before and after surface
modification. The porosity and fracture toughness of the PMMA
nanocomposites (n=6, for each formulation and test) were also
evaluated.

76. ▶ Result:
Formation of a monolayer on the surface of TCA enhanced the NBT
dispersion, however agglomeration of silanated NBT was observed due to
insufficient coverage of NBT surface. Such behaviour led to reducing the
porosity level and improving fracture toughness of titanated NBT/PMMA
composites. Thus, TCA seemed to be more effective than silane.

77. Effect of Nanodiamond Addition on Flexural Strength,
Impact Strength, and Surface Roughness of PMMA Denture
Base
Al harbi et al, J Prosthet Dent 2018
▶ Aim: To assess the effect of addition of different concentrations of
nanodiamonds (NDs) on flexural strength, impact strength, and
surface roughness of heat-polymerized acrylic resin.

78. ▶ 120 specimens were fabricated from heat-polymerized acrylic resin.
They were divided into a control group of pure
polymethylmethacrylate (PMMA; Major.Base.20) and three tested
groups (PMMA-ND) with 0.5%wt, 1%wt, and 1.5%wt of added ND to
PMMA.
▶ Flexural strength was determined using the three-point bending test.
Impact strength was recorded by using a Charpy type impact test.
Surface roughness test was performed using a Contour GT machine.
One-way ANOVAand Tukey's post-hoc analysis (p ≤ 0.05) were used for
statistical analysis.

79. ▶ Result:
The addition of NDs to acrylic denture base improved the flexural
strength and surface roughness at low concentrations (0.5%), while the
impact strength was decreased with ND addition.

80. REFERENCES:
▶ 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.
▶ Morrow R.M RUDD K.D :Dental Lab procedures CD Vol 3 edition
▶ Wang Russel .R : Titanium for complete application,Quintessence
Int.1996,27:401application,Quintessence Int.1996,27:401
▶ Winkler Sheldon : Esssentials Of Complete Denture Prosthodontics 3r
edition
▶ Peyton F
.A., Anthony D.H., 1963: “Evaluation of dentures processed by
different techniques”. J. Prosthet Dent.; March – April 13(2): 269-282.
▶ Braden M., 1964: “The absorption of water by acrylic resins and other
materials”. J Prosthet Dent.; March/April 14(2): 307-316

81. ▶ Rached, R. N., Powers, J. M., & Del Bel Cury, A. A. (2004). Repair
strength of autopolymerizing, microwave, and conventional heat-
polymerized acrylic resins. The Journal of Prosthetic Dentistry, 92(1),
79–82.
▶ Minami, H., Suzuki, S., Minesaki, Y
., Kurashige, H., & Tanaka, T
. (2004).
In vitro evaluation of the influence of repairing condition of denture
base resin on the bonding of autopolymerizing resins. The Journal of
Prosthetic Dentistry, 91(2), 164–170.
▶ Kim, S.-H., & Watts, D. C. (2004). The effect of reinforcement with
woven E-glass fibers on the impact strength of complete dentures
fabricated with high-impact acrylic resin. The Journal of Prosthetic
Dentistry, 91(3), 274–280. doi:10.1016/j.prosdent.2003.12.023
▶ Al-Harbi, F
.A., Abdel-Halim, M. S., Gad, M. M., Fouda, S. M., Baba, N.
Z., AlRumaih, H. S., & Akhtar, S. (2018). Effect of Nanodiamond
Addition on Flexural Strength, Impact Strength, and Surface Roughness
of PMMA Denture Base. Journal of Prosthodontics.

82. THANKYOU