2 - 3/11: Denture Base Resins Flashcards
What is resin?
A term to describe natural or synthetic substances that form plastic materials after polymerization
What is acrylic?
A colorless, pungent acid
What are some examples of denture base materials?
Gold
Wood
Bone/animal hooves
Ivory
Ceramics
Metals and alloys
Polymers
How was wood chosen for dentures?
- readily available
- relatively inexpensive
- can be carved to desired shape
What are disadvantages of wood?
- warped and cracked in moisture
- esthetic and hygienic challenges
- degradation in oral environment
How was bone chosen?
Due to availability, reasonable cost, and carvability
Why was bone advantageous for dentures?
Better dimensional stability than wood, esthetic and hygienic concerns remained
Why was ivory beneficial?
Esthetic and hygienic advantage in comparison with denture bases carved from wood or bone
What were advantages of ceramics over wood, bone, ivory?
- could be shaped using additive technique rather than substractive
- additive technique facilitated correction of denture base surface
- intimate contact with underlying soft tissues
- could be tinted
What are base metal alloy denture bases used in?
Automobile industry
What are denture base polymers?
- vulcinate
- polystyrene
- vinyls
- nylons
- polymethyl methacrylate (PMMA)
- urethane dimethacrylate (light activated)
What material had color, taste, and odor that was “less than ideal”?
Vulcanite
What are disadvantages of vulcanite?
- absorbs saliva and becomes unhyginenic due to bacterial proliferation
- poor esthetics
- dimensionally unstable
- objectionable taste and odor
What are disadvantages of celluloid?
- lack of stability
- unpleasant taste
- unpleasant odor
- sustainability
- flammable
What are disadvantages of bakelite?
- lack of uniform quality
- variable strength
- variable color
- dimensional unstability
What are denture bases fabricated with now?
Poly(methyl methacrylate) resins
What is pure PMMA like?
Colorless, transparent solid
What is an advantage of PMMA?
Denture base material is relative ease with which it can be processed
How is PMMA supplied?
Powder and liquid system
What are advantages of PMMA resin?
- excellent esthetic properties
- adequate strength
- low water sorption
- low solubility
- non-toxic, low allergenicity
- easily repaired
- reproduces detail accurately
- simple molding and processing technique
What are PMMA resin ingredients?
Liquid monomer - methyl methacrylate
Powdered polymer - polymethyl methacrylate
Plasticizer - dibutyl phthalate
Initiater - benzoyl peroxide
Pigments
What are the two components of PMMA resin?
- liquid monomer
- Powdered polymer
What is the PMMA liquid?
- methyl methacrylate
- glycol dimethacrylate - a cross linnking agent
- hydroquinone - inhibitor for increased shelf life
What is the PMMA powder?
- PMMA beads
- pigments
- plasticizer
- benzoyl peroxide - initiator of polymerization
What are the steps of curing?
Heat cure
Chemical cure
Light cure
What are heat-activated denture bases used in?
Fabrication of all denture base
What is required for polymerization?
Thermal energy - water bath or microwave oven
What is the composition of heat activated denture base?
PMMA - powder and liquid
Powder - prepolymerized spheres of PMMA and small amount of benzoyl peroxide (initiator)
Liquid - predominantly non polymerized methyl methacrylate with small amount of hydroquinone (inhibitor)
Cross linking agent is added to liquid
How does monomer boils work?
Heat at surface of resin is conducted away into investing medium, hency no porosity on surface of resin
Vaporization of what monomer affects the thick areas of denture base?
Monomer balls
What are reasons that porosity is caused?
Irregular shape, located throughout the base:
- inadequate pressure
- not enough resin in mold
- improperly mixed resin
Resin denture teeth are basically the same composition as?
Denture base resin, except for pigmentation to produce tooth shaed
What two things bond to eachother?
Teeth and base
What does an amine in the liquid react with?
The benzoyl peroxide in the powder to promote polymerization at room temp
What is the fundamental difference between heat-activated vs autopolymerized?
Method of activation of the initiator benzoyl peroxide
What does heat-activated have a greater degree of?
Polymerization
What does heat activated have better stability of?
Color stability
How is color stability of autopolymerized?
The tertiary amine activator (dimethyl-p-toludine) in the liquid oxidizes and turns orange after a few months
What are light activated denture base resins?
Composite matrix of urethane dimethacryate, microfine silica, and high molecular weight acrylic resin monomer
What is the activator for light activated denture base resins?
Visible light
What is the initiator for light activated denture base resins?
Camphorquinone
How is light activated denture base supplied?
In sheet and rope form packed in light proof pouches
Light activated resin cannot be flasked in __________
Conventional manner
What provides the passage of light in light activated denture base?
Opaque investing media
How are teeth arranged and denture base sculpted using?
Light activated resin
