The document discusses different types of denture bases used in dentistry. Temporary denture bases include materials like autopolymerizing resins, shellac, thermoplastics, and wax. These provide rigidity, stability, and allow for setting teeth and recording jaw relationships. Permanent denture bases primarily use acrylic resin due to its strength, stability, and compatibility. The document outlines the history of denture materials from early natural materials to modern resins, and evaluates different temporary base materials and their advantages for uses like diagnostic trials.
3. WHAT IS A DENTURE BASE ?
Denture base: The part of a denture that rests on the
foundation tissues and to which teeth are attached.
4. HISTORY
Carved by direct observations of ridge contours
hard shell of a coconut
ox femur
hard fruitwood such as teak
hippopotamus tusk
5. 1711 Purman in Poland made the first
recorded impression of the jaw using
bees wax. His cast was also of wax,
probably as a model for fitting by bone
or ivory craftsman.
1756 Pfaff, in Germany, formed the first
plaster cast, described “taking the bite,”
and made and used the first recorded
articulator.
6.
7.
8. Having a working model was a tremendous advance in dentistry
and provided the possibility of
swagging gold denture bases (Bourdet, France 1757)
molding or fusing of porcelain dentures (Delabarre,
France, 1800)
Tin (Hudson, 1820)
Tin with silver or gold plating (Royce, 1836)
Compression molded tortoise shell (Harrington 1847)
A form of Gutta Purcha
Tried as denture bases without much success.
9.
10. 1854 Hard rubber (Vulcanite) was introduced by Evans
in England.
The process for making this material was patented by Nelson
Goodyear in the United States in 1851.
Hard rubber was the first really acceptable denture base
material, or the first one that could be molded by a dentist for a
patient at a reasonable cost.
For the next 80 years, no material displaced vulcanite as the
preferred denture base material.
11.
12.
13. ADVANTAGES
Dimensionally stable.
Adequate strength.
Normally compatible with the tissues.
Possessed a somewhat wettable surface (Some
dentists thought that it produced good retention, others
thought it caused a slight fouling of the denture).
15. Many other materials were tried unsuccessfully during this
period.
They included
Platinum
Swagged aluminum (1867)
Cast gold
Celluloid
Phenol formaldehyde resins
Gyptal resins
Polyvinyl acetate-chloride
16.
17. The next milestone was the introduction of acrylic resin to the
dental profession in the year 1936.
For the next 6 years both vulcanite and acrylic resin were
used as denture bases with the later replacing hard rubber.
VULCANITE ACRYLIC RESIN
By 1942, acrylic resin with its copolymers was considered the
best available denture base material.
18.
19. At a special workshop of Academy of Denture Prosthetics, the
prime clinical requirements of the ideal denture base material
were studied and a list of 58 desirable qualities was
suggested.
Acrylic resin meets 47 of the 58 requirements
Fails in area such as
Instantaneous temperature conductivity
Wettable surface
Easy sterilization
Resistance to abrasion and stain
Choice of hardness and softness
Unbreakability
20. It is estimated that 99% of all complete dentures are fabricated
with one of the acrylic resins.
However, other materials are occasionally used as denture
bases to meet the requirements in certain cases.
22. TEMPORARY DENTURE BASES
Record base: an interim denture base used to support the
record rim material for recording maxillomandibular records,
arranging artificial teeth, or trial placement in the mouth.
Synonyms:
Base plate
Record base
Temporary base
Trial base
Interim denture base
23. PURPOSES OF BASE PLATES:PURPOSES OF BASE PLATES:
KEYWORTHKEYWORTH(1929)(1929)
CARRIERCARRIER
HOLDHOLD
CHECKCHECK
24. REQUIREMENTS OF BASE PLATES:REQUIREMENTS OF BASE PLATES:
ELDERELDER(1955)(1955)
AAdaptationdaptation
AAllow setting of teethllow setting of teeth
BBorder formorder form
CConstructiononstruction
CColorolor
DDimensional stabilityimensional stability
RRigidityigidity
25. TUCKERTUCKER (1966)(1966)
NotNot abrade the cast during removal &abrade the cast during removal &
replacement.replacement.
Take advantageTake advantage of desirable undercuts.of desirable undercuts.
Be of a material thatBe of a material that bondsbonds with that usedwith that used
to block out undercuts on the cast so thatto block out undercuts on the cast so that
it becomes a part of the base plate.it becomes a part of the base plate.
26. Other Requirements for a denture base:
Stable, both on the cast and in the mouth, to ensure the
securing of accurate jaw relation records and the transfer
of these records to the articulator.
Free of voids or projections on the surface that contacts
that contacts the oral mucosa.
Easily removed from the cast.
Reproduce both the contours and the dimensions of the
reflections of the final cast.
Failure to meet these criteria will permit the movement of
the bases in the mouth and result in inaccurate jaw
relationship records.
27. IMPORTANCE OF DENTURE BASES:
Diagnostic use:
The presence of over or underextended borders of the final
impression.
The presence of compression of the mucosa of the residual
ridge, hard palate or soft tissues approximating the borders
of the base.
An indication of the patient’s acceptance of the final denture,
by his early response to the presence of ‘denture-like’ forms
and materials.
The existence of gag reflex that could inhibit adaptation to or
acceptance of the final denture.
28. Therapeutic role:
Aid in recording of maxillomandibular relationship.
Allow the transfer of accurate jaw relationships to an
articulator.
Enabling the setting of artificial teeth for the trial denture.
Reduced or inadequate salivary flow, which may
adversely affect denture retention.
Observation of tongue positions or habits, which would be
unfavorable to the stability of the mandibular prosthesis.
29. CRITERIA FOR THE MATERIAL:
Be readily adapted to the required shape and contours
with a minimum of time, expense and technical skills.
Be rigid and strong in relatively thin sections.
Not exhibit flow at mouth temperature.
Not warp or distort appreciably during the procedures
required for denture fabrication.
Exhibit a color that will not distract from viewing the
arrangement of the teeth of the trial denture as they will
appear in the completed denture.
31. STABILIZED BASE PLATESSTABILIZED BASE PLATES
An interim denture base lined with plastic, or
other material, to improve its adaptation and
stability.
Zinc oxide eugenol impression paste.Zinc oxide eugenol impression paste.
Elastomeric impression materials.Elastomeric impression materials.
Hard or soft curing resins.Hard or soft curing resins.
32. AUTOPOLYMERIZING RESIN BASE PLATESAUTOPOLYMERIZING RESIN BASE PLATES
Require an activator and catalyst.Require an activator and catalyst.
No external heat required.No external heat required.
ADVANTAGES:ADVANTAGES:
Readily availableReadily available
Reasonable costReasonable cost
Set hard and rigid or soft and flexible.Set hard and rigid or soft and flexible.
Ease of use.Ease of use.
33. Most commonly used material.Most commonly used material.
METHODS OF CONSTRUCTION:METHODS OF CONSTRUCTION:
SPRINKLE-ON METHODSPRINKLE-ON METHOD
FINGER ADAPTED DOUGH METHODFINGER ADAPTED DOUGH METHOD
CONFINED DOUGH METHODCONFINED DOUGH METHOD
STONE MOLD METHODSTONE MOLD METHOD
WAX CONFINED METHODWAX CONFINED METHOD
39. KEY POINTS:
EXCELLENT
Performed in an well ventilated area to
minimize exposure to resin fumes.
Use nonfibered powder because it sifts more
readily than a powder with fibers, which will
obstruct the opening of the dispenser.
Use a low speed lathe (1740 rpm) with plenty of pumice
slurry to prevent the build up of heat in the base plate
during polishing.
40. Reinforce base plates with flat ridges by a wire embedded
in resin.
To minimize porosity, keep all areas moist with
monomer to prevent drying when applying resin.
41.
42. FINGER ADAPTED DOUGH METHOD
FASTER
Unless using gloves, needless repeated contact with resin
during adaptation.
Exceedingly difficult to obtain uniform thickness.
Chances of rebound or lift-off of the resin.
Can displace the soft curing resin used to fill undercuts.
47. Elder (1955) described application of pressure using
modelling plastic.
Assadzadik and Yarmond (1975) used the stone mold
method for applying pressure.
ADVANTAGES:
Excellent control of thickness
Reduced finishing time
Minimal porosity
DISADVANTAGES:
Increase in time required to make a mold
Tendency to form voids in the base plate.
48.
49.
50.
51.
52.
53.
54.
55. Described by Lavere and Freda in 1974.
Wax pattern assures the proper thickness of
the base plate throughout, especially in the
palate.
Outer surface of wax makes the record base
neat and pleasing in appearance.
56.
57.
58.
59. Two problems unique to this method:
Controlling the thickness of the resin layer.
Keeping the wax exterior surface free of resin.
60. SHELLAC DENTURE BASE MATERIAL:
Shellac is a commonly used material for denture bases.
Derived from the resinous exudate of a scale insect.( Greener,
Harcourt, and Lautenschlager, 1972).
Powdered talc or mica serves as fillers to increase the strength.
61. The material is brown but can be dyed to a more acceptable
color.
It is supplied commercially in forms shaped to correspond to
the general shapes of the maxillary and mandibular arches.
62. Advantages:
It is inexpensive.
It can be easily and quickly adapted using readily available
laboratory equipment.
If adapted accurately, strengthened, and handled carefully,
it can be effectively used for both mandibular and maxillary
arches.
Disadvantages:
If not adequately strengthened, it tends to warp when
subjected to repeated changes of temperature.
Being a brittle material, it is also subjected to breakage.
Chance of losing their initial adaptation
63.
64.
65.
66.
67. STABILIZED WITH ZINC OXIDE EUGENOL
Fletcher (1951), Jamieson ( 1956), Kapur & Yurkstas (1957)
Exhibits better adaptation and dimensional stability.
DISADVANTAGES:
Thicker base plates
Require additional time
Block-out of undercuts is essential.
68.
69.
70.
71.
72. BASEPLATES STABILIZED WITH ELASTOMERIC
MATERIAL
Freese (1956), Bodine ( 1964) & Malson (1964)
ADVANTAGES:
Inherent flexibility
Smooth surface
DISADVANTAGES:
Increased thickness
Increased cost and construction time
73.
74. BASEPLATES STABILIZED WITH
AUTOPOLYMERISING RESIN
Boos (1956), Jamieson (1956), & Hall (1958).
DISADVANTAGES:
Possible warping of the base plate as the result of
internal stresses being released from the resin liner.
Additional time required.
75.
76.
77. ADVANTAGES:
Excellent thickness control
Reasonably good adaptation to the cast.
Simple technique
Minimal amount of time required.
Satisfactory rigidity.
DISADVANTAGES:
Expense of equipment
Difficulty in achieving intimate adaptation in deep recess
and border reflections.
Difficulty in obtaining smooth round borders.
Editor's Notes
To act as a carrier for occlusal rims on which jaw elations are recorded.
to hold the teeth in the wax setup for tryin.
To check the accuracy of previously recorded records.
Should adapt to the basal seat area as the finished denture base.
Should permit its use as a base for setting up for teeth.
Have the same border form as the finished denture base. Borders should be smooth, rounded and adequately polished to provide maximum patient comfort.
construction should be quick, easy and inexpensive.
Should have no undesirable color.
Dimensionally stable.
Rigid to resisit the biting forces. Rigid, approximately 2 mm in the hard palate area of the maxillary base and the lingual flange of the mandibular base.
3 methods of applying soft curing resin
Mix in dappen dish and apply with a spatula
Sprinkle powder and saturate with monomer.
Place powder and liquid in separate dappen dishe. Dip the brush in liquid and then into the powder and brush this combination on the cast.
To restric the flow of soft curing resin in undercut areas:
warm the surface of resin with warm air frm a chip blower
2. Dip the cast in hot water momentarily.
This will surface set assuring that resin remains in place.
Tilt the cast to prevent pooling of material in a region.
2 mm thickness to be obtained.
Inverted bowl or a presure pot at I warm water at 20 psi for 20 mins.
Porosity reduces rigidity and make denture base unhygienic.
Contact may lead to conatamination of the resin or contact dermatistis.
2. Invariably too thin in convex areas and thick in inaccesible areas.
Two thicknees of shellac base plate.
Described by swenson in 1970
CONTINUE FINGER ADAPTATION UNTILL RESIN NO LONGER SPING AWAY FROM THE CAST.
1 LAYER OF BASE PLATE WAX.
Fill the borders with aditonal wax to make them of unifrom thisvkness.
4 index points at widely seperated points with large round bur.
Boxing wax should extend above the cast to make atone atleast 15 mm thick.
Mix artificial stone with slurry concenrate.
Usually 8 to 10 ml of monomer and 24 to 30 ml of polymer are enough.
Use excess resin to avoid voids.
Confinement and pressure with stone index greatly reduces porosity.
2. Wax 2mm short of the border of the cast.
Make a thin mix using two parts polymer to one part monomer.
Pour some on the borders and the palate of the maxilla.
Carefully press the resin on the cast untill it is 2 mm thick.
Overcome by proper seating of the wax tray and exercising care in adapting and smoothing the resin borders.
Soak the cast in clear slurry water to keep the c=shellac base plate from sticking to the cast when heated.
Or apply powdered talc to the cast before adaptating the base plate.
Undercut blockout with mix of one part of flour and one part of plaster.
If lathe turns too fast and too uch pressure is exerted, it will gum up the trimmer .
Non clogging abrassive wheels are also available for trimming base plates.
As ZNOe is rigid.
Identify and blockout the undercuts with wax or pumice-plaster mix.
2. 0.001 inch thickness Sn foil to coat the cast
to prevent tincfoil from coming off the cast during adaptation small drops of vbase plate wax are added to the cast.
Make a hole in the palate with no. 8 bur. To allow excess imp. Material to escape and to minimise voids.
2. 1mm thick impress. Material.
Alfred et al.in 1968.
Blockout with heat stable blockout compound e.g. Omnidental blockout compound by buffalo, broklyn NY.
0.060 inch thickness
Thicker for mandibular base plates.
Sag approx. ½ inch
Heat for 10 to 15 sec.
Continue vaccum adaptatio for 30 sec. more