This document discusses acetal resin, a thermoplastic material that can be used to create flexible dentures. Acetal resin is an alternative to metal alloys that provides aesthetics and flexibility. It can be used to make dentures that engage deep undercuts for retention. The resin is biocompatible and durable. It comes in various tooth colors and pink shades. Flexible dentures made of acetal resin are indicated for patients with bilateral undercuts or metal allergies. The resin can be used for temporary restorations like dentures or space maintainers. However, it cannot be used for patients with a closed bite due to its flexibility.

1. Thermoplastic Materials
Acetal resin flexible dentures
BY
DR.RAMY MOHSEN
Faculty of dentistry
Suez canal university
2015

2. Changes in dental patient’s attitudes and
awareness have been apparent in all aspects of
dentistry, especially aesthetics. This has
increased the demand for not just improved
functional care, but aesthetically functional care.
In removable partial denture fabrication, unsightly
facial clasps have always been a cosmetic
problem .

3. In such aesthetically demanding
situations, various methods to overcome this
aesthetic dilemma have included :
-painting of clasps with toothcolored resin
-use of lingually positioned clasps
-use of gingival approaching clasps.

4. flexible thermoplastic resins were discovered 50 years
back and presently gaining popularity due to improvement
in their physical and mechanical properites.
Research in polymer science has provided us with an
alternative material called “Acetal resin”. Also known as
Polyoxymethylene (POM), thermoflix , acetal resin is
formed by the polymerization of formaldehyde , it’s a
thermoplastic technopolymer with a monomer-free
crystalline structure.

5. • This material has been shown to have good
biocompatibility and this has fostered its use in
total hip replacement and as artificial heart valve
occluders. It has been used to form a stress-
absorbing component in a dental implant system
(IMZ).
• Flexible dentures based on acetal resin , began
to be used in dentistry in 1971.

6. • The concept of flexible resins is based on their
flexibilty and ability to engage hard and soft
tissue for retention.
• Therefore ,for clinical cases such as kennedy’s
class I & II, which involves distal extensions , the
flexible dentures by engaging severe soft tissue
undercuts and clasping the adjacent teeth
provides excellent retention .

7. Technique
• The material is avaliable
in two forms as
prepackeged cartidges or
granular form .
• Thermoplastic resins are
manipulated by inection
molding technique .

8. • 1 - Flasking , spruing
the pattern.

9. • 2 - Injection molding technique :
The metallic cartridges containing thermoplastic grains
are heated to plasticize the resin. The cartridges are set
in place into the injecting unit and pressure of 6-8 barrs
is used to force the plasticized resin to fill the mold. the
material is injected under pressure into a mold, without
any chemical reactions. Thermoplastic materials is
melted at tempreatures from 200-250°C .Pressure,
temperature and injecting time are automatically
controlled by the injecting unit.

20. Why acital resin?
• Aesthetics :
Thermoflex acetal resin is
available in16 tooth
colors, comparable to the
Vita® Classic Shades ,
and 3 pink tissue colors.

21. • Flexibility :
Thermoflex is flexible enough to accommodate
even the most complex cases, while providing
excellent stability.
Its elastic memory allows the appliance to secure
itself into deep undercuts for a rigid,functional
hold.

23. Durability :
• High-abrasion resistance , Low thermal
conductance and excellent tensile and
shock strength make Thermoflex acetal
resin the preferred material for long lasting
performance .
• Resistance to organic solvents, oils,
alkalis, hot and cold water .
• Non allergenic, non-toxic

24. • Low modulus of elasticity which allow for its use
in larger retentive undercuts than recommended
for Cobalt- Chromium alloys . This may be
advantageous in clinical situations in which
aesthetics or periodontal health are priorities.
• Lighte wight makes patient more comfortable
• High melting point.

25. Versatility :
• Used alone or in combination with other
materials, Thermoflex acetal resin makes all
types of temporary flexible restorations,
including removable partial dentures and
combination cases with metal or flexible
denture bases such as Lucitone® FRS™.

27. Indications of flexible materials
• Bilateral undercuts
• Allergy to acrylic resin or cobalt-chromium
• Patient who don’t want a fixed restoration or metal clasb
• Not enough bone for fitting dental implant
• Patients with comprised neruo-motor function.
contraindications
• Unilateral distal extension
• Lower virtical dimensions and closed bite

28. Another clinical applications
• As direct retainers attached to a cobalt-chromium
removable partial denture framework, as well as the
supportive components of removable partial dentures.
• Removable partial dentures.
• Post-surgery space maintainers .
• Gingival masks , Provisional crowns and bridges.
• Mouthgards , impression try , opturators.

29. Disadvantges :
• A major drawback is de-bonding of the acrylic
teeth from acetal denture base , acetal does not
bond chemically with acrylic resin , so
mechanical undercuts are made in each tooth , it
can’t be used with patients having low vertical
dimensions and closed bite .
• Costly compared to acrylic dentures .
• Difficult to repair ,add teeth to or leline .

30. Thank you
Darawy.Dentist@Gmail.com