recent advancements in denture base materials for dentists

1. RECENT ADVANCEMENTS IN
DENTURE BASE MATERIALS
AN OPTIMISTIC OUTLOOK TOWARDS NEWER POSSIBILITIES …..
SPECIAL THANKS TO
PROF.DR. T.K.GIRI SIR
&
PROF.DR. S. MUKHERJEE SIR
PRESENTED BY-
DR. DHRUBOJYOTI BANERJEE
1ST YEAR PGT

2. This Photo by Unknown Author is licensed under CC
BY-NC-ND

3. WHAT ARE DENTURE BASE MATERIALS??
IT IS THAT PART OF A DENTURE WHICH
RESTS ON THE SOFT TISSUES & PROVIDES
A SEAT FOR THE ARTIFICIAL TEETH…

4. Should be biologically acceptable
Should be cost efficient

20. ACRYLICS(PMMA)
 INTRODUCED IN 1936 BY DR. WRIGHT AND VERNON BROTHERS
 ADVANTAGES:
 EXCELLENT AESTHETICS
 EASE OF PROCESSING & REPAIR
 COST EFFICIENT

21. DISADVANTAGES:
 RESIDUAL MONOMER ALLERGY
 POOR MECHANICAL STRENGTH
 LOW FATIGUE STRENGTH
 POOR CONDUCTOR OF HEAT
 HIGH COFFICIENT OF THERMAL EXPANSION
 POLYMERISATION AND THERMAL SHRINKAGE
 TO OVERCOME THESE DRAWBACKS SEARCH FOR
NEWER MATERIALS BEGUN

22. NEW ERA IN DENTURE BASE RESINS- A REVIEW
1. Reinforced resins
a. High impact resins
b. Fiber-reinforced
2. Hypoallergenic resins
3. Resins with modified chemical structure
4. Thermoplastic resins
5. Enigma gum toning in denture bases

23. REINFORCED RESINS:
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, senility. Available as powder-liquid system
E.g Lucitone 199 , D.P.I Tuff

24. FIBRE REINFORCED
 Fiber reinforcement result in a 1000% strength increase over non-reinforced
(if there is proper bonding)
A. METAL REINFORCEMENT: PROVIDES BEST REINFORCEMENTS
 NOT USED OF LATE DUE TO:
 1.UNESTHETIC
 2.EXPENSIVE
 3.POOR BONDING WITH ACRYLIC( PMMA).
 4.CORROSION PRONE

25. CARBON/GRAPHITE FIBRE REINFORCEMENT:
 Carbon fibers (65-70 mm length, 5 % by weight & treated
with silane coupling agent) are placed during packing.
 Anisotropic and provides greatest reinforcement of
denture base resin in terms of flexural strength
 Carbon Graphite fibres are available as-chopped,
continuous, woven, braided & tubular

26. ADVANTAGES
 Increases flexural strength, impact strength, prevents fatigue and
strengthens the resin.
DISADVANTAGES
 Unesthetic because of black colour but this can be covered by an
opaquer. The polishing is difficult & also weakens the finished
prosthesis. In addition, there is problem of lateral spreading of
fibers during pressing.

27. ARAMID FIBER REINFORCED
Aramid fiber reinforcement increases the strength
but again they are unesthetic & difficult to polish so
limited to locations where aesthetics is not
important.

28. POLYETHYLENE FIBER REINFORCED
 Multifibered polyethylene strands cut to 65 mm length
& surface treated with epoxy-resin (to improve
adhesion) are placed in resin during packing.
 They develop anisotropic properties to the composite
(i.e. increase strength and stiffness in one direction).

30. ADVANTAGES :
 HIGHEST IMPACT STRENGTH
 HIGH MODULUS OF ELASTICITY
DISADVANTAGE :
 DECREASED TRANSVERSE STRENGTH
 FINISHING AND POLISHING IS DIFFICULT
 DOES NOT BOND WELL TO RESINS

31. HIGHLY DRAWN LINEAR POLYETHYLENE FIBERS (HDLPF)
 Patterns of continuous parallel fibers provide maximum reinforcement to
both maxillary & mandibular bases.
 horizontally positioned fibers in anterior part of labial flange & in region
immediately behind central incisors
 Reinforcement done with 4 layers of fibers (2 in lateral direction sandwitched
between 2layers at 45 degree from middle ones )
 In mandible, maximum stresses appear in labial & lingual second premolar
region & fracture occurs in middle region.
 Thus mandibular bases are reinforced with fibers at right angle to ridge
located close to polished & fitting surface

32. ADVANTAGES :
 HDLPF Have high tensile stiffness & strength
 notch insensitivity & cracks do not propagate
through array of fibers.
 The coherence is maintained even after a
large number of testing cycles.

33. GLASS FIBRES (HAVE BEST
AESTHETICS)
 Continuous parallel fibers provide high strength & stiffness in one direction
(anisotropic) while randomly oriented fibers provide similar properties in all
directions (isotropic properties)
 chopped fibers mixed with denture base acrylic resin enhance isotropic
mechanical properties.
 6 mm chopped glass fibers with 5% fiber in combination with injection
moulding technique result in increase in transverse strength, elastic modulus&
impact strength.
 Glass fibers may be modified by plasma polymerization technique using HEMA,
TEGDME

34. ADVANTAGES
These are the fibres of choice because of well
documented improvement in :
 flexural properties
 fatigue resistance
 the best aesthetics
 excellent polishing characterstics.
 In addition, they resist extreme temperature,
moisture, oil.

35. E-GLASS FIBERS
 Each strand of this E-glass is computer impregnated with a
PMMA (porous polymer) and silane coupler that allows
dissoloution bonding to acrylic. (e.g. Preat Perma Fiber )
ADVANTAGES
 Available in two forms (mesh & fiber)
 are transluscent providing esthetics.
 Because of glass fiber bonding, they also have more
strength.

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

37. POSITION & PLACEMENT OF FIBERS
 1. Place the fiber in the weakest area (On
tension side during mastication)

38. 2. For repairs, place reinforcement 90
degree to the fracture.

39. 3. Unidirectional fibers are stronger, especially
when direction of highest stress is known.

40. Mesh should be placed on the exterior of the
prosthesis, not buried.

41. HYPOALLERGENIC RESINS
 Diurethane dimethacrylate, Polyurethane, Polyethylenterephthalate and
Polybutylenterephthalate.
 Hypoallergenic denture base materials exhibit significantly lower residual
monomer content than PMMA, thus act as an alternative in allergic
patients
 Enterephthalate based (Promysan, thermoplastic) show low water
solubility than PMMA.
 Light activated indirect composite containing urethane dimethacrylate
(UDMA) is an alternative to PMMA for patients hypersensitive to PMMA

42. RESINS WITH MODIFIED CHEMICAL STRUCTURES
 Addition of hydroxy-apatite fillers increases fracture toughness.
 Al2O3 fillers increases the flexural strength & thermal diffusivity
that could lead to more patient satisfaction.
 2% quaternary ammonium compound displays antiseptic properties
& these dentures may be used for geriatric patients to improve their
oral health.
 Addition of ceramic or sapphire whiskers to improve thermal
diffusivity.
 Addition of 11-14% of several compounds of either bismuth or
uranium or 35% of an organo-zirconium compound impart radiopacity
equivalent to that of aluminium.

43. • THERMOPLASTIC
RESINS:
FULLY POLYMERISED BASIC
MATERIAL
SOFTENED BY HEAT WITHOUT
CHEMICAL CHANGES

44. ADVANTAGES
 EXCELLENT ESTHETICS
 UNBREAKABLE ,FLEXIBLE, LIGHT WEIGHT
 STABLE ,HIGH FATIGUE ENDURANCE
 INCREASED CREEP & WEAR RESISTANCE
 NON POROUS: NO BACTERIAL GROWTH BUT RETAINS
ENOUGH MOISTURE TO KEEP IT COMFORTABLE FOR GUMS
 CAN BE RELINED AND REPAIRED

45. MATERIALS USED:
THERMOPLASTIC NYLON
THERMOPLASTIC ACETAL
THERMOPLASTIC ACRYLIC
THERMOPLASTIC POLYCARBONATE

46. THERMOPLASTIC NYLON:
POLYAMIDE(VALPLAST,FLEXIPLAST)
 INJ. TEMP 274-293 DEGREE CENTIGRADE
 TRANSLUSCENT
 TISSUE COLORED CLASPS INSTEAD OF
METAL CLASPS
 UNBREAKABLE & LIGHTWEIGHT
 FLEXIBLE IN NATURE
 DIFFICULT TO POLISH AND ADJUST
 NOT STRONG ENOUGH FOR NORMAL
TOOTH BORNE REST SEATS
 EG: VALPLAST ,LUCITONE FRS(MORE
IMPACT RESISTANCE)

47. THERMOPLASTIC ACETAL: POLYOXYMETHYLENE
 CLASPS ENGAGE FIRST THIRD OF UNDERCUTS: 3-4 TIMES MORE RETENTION
 CAN BE PLACED MORE GINGIVALLY: BETTER AESTHETICS
 18 VITA +3 PINK SHADES: FOR SIMULATING LIFELIKE APPEARANCE
 METAL CLASPS AND BARS CAN BE REPLACED
 FLEXIBLE+MONOMER FREE- HYPOALLERGIC
 TEETH AND CLASPS CAN BE ADDED ON EXISISTING DENTURE BASES

48.  CANNOT BE USED AS MAJOR CONNECTOR
 DOES NOT SEAL THE BASE OF THE DENTURE WHICH ALLOWS
THE SEEPAGE OF FLUID
 CAN NOT BE USED AS CRIB AND CLASP WHERE DIASTEMA IS
ABSENT
 APPLICATION
 PREFORMED CLASP FOR RPDS
 PARTIAL DENTURE FRAMEWORK
 PROVISIONAL BRIDGE
 OCCLUSAL SPLINTS

49. THERMOPLASTIC ACRYLIC
 GOOD FLEXURAL AND TENSILE STRENGTH
 DECREASED WEAR RESISTANCE
 POOR IMPACT RESISTANCE
 EASY TO POLISH
 REPAIRABLE AND RELINEABLE AT CHAIR SIDE
 EXCEPTION: FLEXITE AND MP-a –HIGHEST IMPACT RESISTANCE AMONG
ACRYLICS(VERY POPULAR IN BRUXISM AND PARKINSONISM PATIENTS)

50. THERMOPLASTIC POLYCARBONATE:
POLYMER OF BISPHENOL- A
 STRONG ,FLEXIBLEAND FRACTURE RESISTANT
 LOW WEAR RESISTANT-VDO WONT BE MAINTAINED OVER LONG TERM
 USED AS PROVITIONAL BRIDGE AND CROWN ONLY
CLINICAL ADVANTAGE
 MINIMAL RESIDUAL MONOMER-CAN BE USED IN ALLERGIC PATIENTS
 VERY LITTLE WATER ABSORPTION-LESS SMELL AND BACTERIAL GROWTH
 GOOD ADHERANCE AND COHERENCE

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

53. PEEK(NEWER MATERIAL)
 POLYETHER ETHER KETONE (PEEK) BELONGING TO PAEK(POLYARYL-ETHER
KETONE) FAMILY
 INTRODUCED IN DENTISTRY IN THE YEAR 1992
 STRUCTURE: