Flexible Dentures in Prosthodontics -An overview

Abstract

There is evidence that Dentistry was practised as far back as 3000 B.C. in Egypt. Dentures are believed to be the mode of treatment for replacing missing teeth around 700 BC. Thereafter, a process began towards improvement in the quality of materials used for fabricating dentures, as the patients demanded better aesthetics, function and comfort. This review tracks the history of flexible materials used as a denture base to the present stage and point towards the research and development in the future. Hard and soft tissue undercuts are frequently encountered in the fabrication of prosthesis in partially as well as complete edentulous arches. This article is an effort to review the various commercially available flexible denture base materials and highlights their indications and special instructions in wearing and maintenance of the same.

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Flexible Dentures in
Prosthodontics - An overview
Prafulla Thumati1, Padmaja S2, Raghavendra Reddy K3
ABSTRACT:
There is evidence that Dentistry was practised as far back as
3000 B.C. in Egypt. Dentures are believed to be the mode of
treatment for replacing missing teeth around 700 BC.
Thereafter, a process began towards improvement in the quality
of materials used for fabricating dentures, as the patients
demanded better aesthetics, function and comfort. This review
tracks the history of flexible materials used as a denture base
to the present stage and point towards the research and
development in the future. Hard and soft tissue undercuts are
frequently encountered in the fabrication of prosthesis in
partially as well as complete edentulous arches. This article is
an effort to review the various commercially available flexible
denture base materials and highlights their indications and
special instructions in wearing and maintenance of the same.
Key words: Flexible dentures, undercuts, Acrylic clasps, Fibre-
reinforced resin
REVIEW
doi: 10.5866/2013.541380
1Professor, Department Head
2Senior Lecturer
Department of Prosthodontics,
Dayananda Sagar College of Dental Sciences,
Bangalore, Karnataka, India
3Senior Lecturer
Department of Prosthodontics
Sri Sai College of Dental Surgery,
Vikarabad, Andhra Pradesh, India
Article Info:
Received: July 8, 2013
Review Completed: August 10, 2013
Accepted: September 9, 2013
Available Online: February, 2014 (www.nacd.in)
© NAD, 2013 - All rights reserved
Email for correspondence:
dr.rajureddy@gmail.com
Quick Response Code
INTRODUCTION
Flexible dentures are custom-made dental installations that rely on unique products to achieve a less
rigid design. These new kinds of dentures are popular for those who struggle with the conventional acrylic
base of dentures that may wear, irritate the gums, induce allergic reactions or generally fail to provide a
comfortable result. Dentists and their patients are often interested in what these newer and more versatile
products can do to better outfit those with a history of tooth decay (Fig. 1 and 2) or who need dental prosthesis
to function or who want to avoid the discomfort due to the rigidity of the denture base.
INDIAN JOURNAL OF DENTAL ADVANCEMENTS
Journal homepage: www. nacd. in
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FLEXIBLE DENTURE BASE MATERIAL (Soft
dentures)
Polymerization shrinkage encountered in
conventionally cured Poly(methyl methacrylate) led
to the development of a special injection-molding
technique. Initially developed as a Fluoropolymer
(1962), Acetal began to be used in 1971. The material
used nowadays is Nylon based plastic (Polyamide).
Elastomeric resins can be added to resin polymer
formulas to create greater flexibility and can be
strengthened with glass fibres.1 Unique features-the
semi-crystalline nylon composition provides
strength, flexibility, transparency, high impact
resistance, colour stability, high creep resistance,
high fatigue endurance, excellent wear
characteristics, good solvent resistance, no porosity,
no biological material build up or odours or stains,
low water sorption and good dimensional stability,
monomer and metal free and the microcrystalline
structure is easy to finish and polish like acrylic.
An alternative denture prosthesis design in
which optimal flange height and thickness can be
achieved is by using flexible denture base material.2
Soft dentures are an excellent alternative to
traditional hard-fitted dentures. Traditionally
relining dentures with a soft base increases comfort
at the cost of chewing efficiency. To make up for the
loss of chewing efficiency, denture wearers would
use denture adhesive, which has its own problems.
A flexible material is now an option that does
not trade off the ability to eat. Flexible denture (soft
dentures) are generally used when traditional
dentures cause discomfort to the patient that cannot
be solved through relining.3 Soft dentures are not
the same as a soft reline for traditional dentures.
Soft relines use a soft putty-like substance to
separate gums from the hard acrylic in dentures.
Flexible dentures use a special flexible resin that
prevents them from chafing the gums, allows the
wearer to chew properly. It also provides a soft base
that prevents the gums from being rubbed raw.
Some of the commercially available products are
Valplast, Duraflex, Flexite, Proflex, Lucitone,
Impak.
Advantages:
Flexible dentures have got various advantages
over the traditional rigid denture bases.
Translucency of the material picks up underlying
tissue tones, making it almost impossible to detect
in the mouth. No clasping is visible on tooth surfaces
(when used in manufacturing of clear clasps)
improving aesthetics. The material is exceptionally
strong and flexible. Free movement is allowed by
the overall flexibility. Complete biocompatibility is
achieved because the material is free of monomer
and metal, these being the principle causes of
allergic reactions in conventional denture and
partial techniques. Flexible dentures will not cause
sore spots as seen with rigid acrylic resins. Flexible
dentures may be used as an alternative treatment
plan in rehabilitating the anomalies such as
Ectodermal dysplasia.
It is nearly unbreakable, pink coloured like the
gums, can be built quite thin, and can form both the
denture base and the clasps as well. The clasps are
built to curl around the necks of the teeth and they
are practically indistinguishable from the gums that
normally surround the teeth due to its Opalescence.
This type of partial denture is extremely stable and
retentive, and the elasticity of the flexible plastic
clasps keeps them that way indefinitely. It has
superior aesthetics, no metallic taste and is non-
allergic. Free movement is allowed by the overall
flexibility and can, therefore, be referred to as “a
built in stress breaker”. Long term health of tissues
and teeth is maintained due to their gentle
massaging action without adversely loading
abutments.
Disadvantages:
Extreme caution is necessary when processing
to avoid skin contact with the heated sleeve,
cartridge, furnace, heating bay, hot cartridge,
injection insert, piston head adapter, hot flasks and
heat lamps. They do discolour due to sorption.
Indications:
Full dentures, partial dentures, Bases and
relines, in cases with bilateral in-operable undercuts
when pre-prosthetic surgery is contraindicated.
Special applications- for TMJ splints, for the
patients allergic to acrylic monomers, as cosmetic
Flexible Dentures in Prosthodontics - An overview Prafulla Thumati, et, al.
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veneers/gum veneers to mask gingival recession
(Fig. 3), in periodontally involved teeth, sensitive
teeth, cancerous mouths or other conditions in which
the teeth are compromised, treatments involving
high torus or cleft palate conditions, as mouth
guards in sports, Bruxisum splints/ Night guards,
Bite splints, Space maintainer, Paediatric cases,
Obturators, Speech therapy appliances and
orthodontic retainers.4
The Flexible dentures in combination with cast
partial framework:
Advantages:
This combination eliminates most of the
difficulty of recurrent sore spots, since the
framework resists movement and pressure from the
clasps, while having the benefit of nearly invisible,
gum coloured clasps (Fig. 4 and 5). It also has the
advantage of being tooth supported.
Disadvantages:
Flexibility is not an advantage where there are
no undercuts in a complete denture situation, as the
retentive peripheral seal can be broken in function.
It is difficult to use with less inter-ridge space, as
bulk of the tooth is needed for mechanical retention.
Insertion:
Denture is placed in very hot water (150 degree
F) for a minute prior to insertion and allowed to
cool to tolerable temperature. This makes the partial
as flexible as it would be at body temperature.
Grinding is done as a last resort at a low speed of
around 250-300 rpm using green stones.
Unilateral or bilateral undercuts are frequently
encountered and may complicate successful
fabrication of denture prosthesis.5,6 Management of
these situations conventionally includes alteration
of the denture bearing area, adaptation of the
denture base; careful planning of the path of
insertion and the use of resilient lining material,
and this can be sorted using a flexible material.
Pro-flex:
Pro-flex is the flexible denture base material
which can be used for Full & Partial flexible denture.
Pickett Dental Laboratory has been offering pro-flex
full and partial flexible dentures since 1998. Pro-
flex is easy to work with the quality, aesthetics and
most importantly the final results. Pro-flex denture
material may be indicated in some of the anatomical
considerations where tooth and tissue undercuts are
a hindrance. It enables the material to effectively
engage those undercuts. Also pro-flex being hypo-
allergenic is recommended for patients with known
acrylic or metal sensitivities. Aesthetically the
material is semi-translucent, allowing the prosthetic
to better blend with the colour of the natural gum
tissue. With pro-flex flexible partials, there are no
metal clasps. Pro-flex full and partial flexible
dentures are easily adjusted by the dentist.
Valplast:
Valplast is a flexible denture base resin that is
ideal for partial dentures and unilateral
restorations. The resin is a biocompatible nylon
thermoplastic with unique physical and aesthetic
properties that provides unlimited design versatility
and eliminates the concern about acrylic allergies.
The valplast flexible partial allows the restoration
to adapt to the constant movement and flexibility
in the mouth (Fig. 6,7,8 and 9). The flexibility
combined with the strength and light weight,
provides total comfort and great looks. The valplast
partial is virtually invisible because there are no
metal clasps and the material itself blends with the
tissue in the mouth. Valplast flexible dentures can
be indicated in case of patients who have acrylic
allergies, history of partial frame breakage,
alternative to implants or fixed prosthesis and
presence of tori.
Sunflex:
The sunflex flexible denture base materials are
virtually invisible, unbreakable, metal-free, light
weight and incredibly comfortable. They are made
from a strong biocompatible nylon thermoplastic
material.
Advantages:
The sunflex flexible denture base materials are
exclusively used in partially edentulous arches
because of its versatile advantages such as-
Flexible Dentures in Prosthodontics - An overview Prafulla Thumati, et, al.
Indian J Dent Adv 2013; 5(4): 1380-1385

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No need of metal clasps-only tissue colored
clasps that blend with natural teeth
More stain-resistant than other flexible acrylics
Has the perfect degree of flexibility
Can be relined and repaired
Will not warp or become brittle
Stands aesthetically superior removable partial
with full functionality and comfort
Ideal for patients considering a removable
partial and those who do not want metal clasps
Are perfect for patients who are allergic to
monomer.
Unbreakable Flexite Plus Dentures:
Flexible dentures created a great deal of
excitement when they were first launched. No more
ugly metal wires, no more broken dentures. What’s
more, the denture can be bent or even twisted, it
springs right back into its original shape. Flexite
Plus is material of choice for all removable partial
dentures. Unlike their predecessors which were
flexible throughout and create problems when they
are long-span, the new material is selectively flexible
and shows rigidity when due.
Advantages:
The biggest advantage of this sort of dentures
is that unlike the hybrid dentures, they are
unbreakable (Fig. 10 and 11) like the former fully
flexible denture systems. Like their fully flexible
predecessors, they also donot have the unsightly
clasps seen in chrome dentures. Flexite Plus is pink
in colour. Flexite Plus plates are not flexible. This
makes them capable of supporting chewing forces
in long-span dentures. Another possibility with
Flexite Plus is the very tiny sectional denture (Fig.
12 and 13). Without the plate covering the entire
roof of the mouth, these dentures tend to be more
comfortable.
Below is another example of a Flexite Plus
denture. It is a sectional prosthesis that shows
remarkably good retention and stability. This was
only a temporary denture which the patient used
while the patient waited for the implant to integrate.
No prosthesis beats an implant restoration in terms
of function.
Above are 2 dentures belonging to the same
patient. On the left is old acrylic denture with metal
clasps (Fig. 14 a), which has cracked a few times
when the patient dropped it. The new denture on
the right uses Flexite clasps which are pink in colour,
which will not break when dropped (Fig. 14 b).
SUMMARY
Flexible dentures help the patients to avoid
some kind of pain associated with the old style
denture models. A flexible resin coating allows for a
custom fit, with hard synthetic teeth still imbedded
in the design to help with chewing food. Flexible
dentures help achieve greater stability and comfort.
Those who have found, for example, that even the
simple back and forth action of chewing causes gum
pain with traditional dentures may be able to find
relief in new and more precise fitting flexible
varieties of denture products.
In addition to these benefits, flexible dentures
are also designed to be porous and to “breathe” better
than some other kinds of dentures. This helps
prevent the build up of bacteria on the dentures and
is another reason that these innovative denture
products are so popular.
CONCLUSION
The fabrication of the optimum restoration is
depending on the clinician’s skill in selection of the
type of the restorations which is required for the
patient. The fabrication of prosthesis for the
partially edentulous arches encountered a special
challenge where many interferences, various path
of placement, tilted teeth and deranged occlusion
will complicate the treatment plan. Flexible
dentures will stand in a superior position in fulfilling
the various patients demand for more retentive and
aesthetic treatment needs. Flexible dentures were
previously selected by few patients and the clinician
but nowadays it has become an elective treatment
option. No more ugly metal wires. No more broken
denture.
Flexible Dentures in Prosthodontics - An overview Prafulla Thumati, et, al.
Indian J Dent Adv 2013; 5(4): 1380-1385

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Figure 1: Cast partial denture
Figure 2: Decayed abutments
Figure 3: Cosmetic veneer masking gingival
Figure 4: Combination of flexible and metal in framework in situ
Figure 5: Combination of flexible and metal framework
Figure 6: Valplast RPD showing thickness and clasps of same material
Figure 7: Valplast RPD on cast
Figure 8: Valplast RPD in mouth
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Figure 9: Valplast RPD in mouth
Figure 10: Unbreakable Flexite Plus Dentures
Figure 11: Unbreakable Flexite Plus Dentures showing its
elasticity
Figure 12: Flexite plus
sectional partial
Figure 14 a: Old acrylic denture
Figure 14 b: Flexite denture
Figure 13: Flexite plus sectional
partial denture with good retention
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Flexible Dentures in Prosthodontics - An overview Prafulla Thumati, et, al.
Indian J Dent Adv 2013; 5(4): 1380-1385