Polymers for prosthetic applications Flashcards
what is the most important characteristic of monomers/polymers?
their molecular weight–decides their properties
what are the generalized types of polymers?
- hydrophilic
- hydrophobic
what are polymers used in in dentistry?
- impression materials
- compelte and partial denture bases
- artificial teeeth
- preventative sealant materials
- facings on some crowns or bridges
- maxillofacial prostheses
- orthodontic appliances
- mouth guards
what are the criteria for ideal denture base material?
- durable
- natural appearance
- high strength, hardness
- good thermal conductivity
- dimensionally and colour stable
- insolubility
- absence of taste, non-toxic
- resistance to bacterial growth
- biocompatible
- adhesion bw components
- easy to fabricate or repair
- easy to clean, durable
- cost effective
- good shelf-life
what are the common materials used for denture bases
PMMA -- most common UDA: convenient for light curing -polyvinyl chloride - rubber reinforced PMMA and PVC - polycarbonate, nylon
PMMA monomers are mixed with MMA liquid
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what are the adv of PMMA
transparent as a solid, stable in standard oral conditions
- easy to fabricate
- esthetic
- adequate strength
- inexpensive
- satisfactory shelf life
what are the disadv of PMMA
dimensional change upon wetting and drying
- may alter shape during repair
- low thermal conductivity
- radiolucent
what are the stages of polymerization of PMMA?
- sandy
- stringy
- doughy–best for molding, not sticky
- rubbery
- stiff
what are ethe adv of chemically cured polymers?
-better adaptaion to tissue
what are the disadv of chemically cured polymers?
-tooth shifting?? technique sensitive - air bubbles, surface not smooth, -high numer of monomers 0poor bonding to teeth
what are visible-light cured polymers used for?
mainly for record bases, custom trays
disadv of light-cured polymers?
difficult to repair
what are properties pf polymers?
- absorb water–>causes expansion; acts as platicizer
saturation with water depends on thickness, polymer type, temp, and sol’n
- insoluble in oral environment
- crazes in presence of alcohol, polishing heat, or different contraction around porcelain teeth (internal stresses reach surface in form of cracks); x-linking polymer chains reduce crazing; also heat and cool slowly;
- may undergo plastic and elastic deformation during loading; strength depends on degree of pol
- -poor thermal conductivity
- low abrasion resistance
- low impact strength–>dentures may break if dropped
- warping
- poor adhesion to metal/porcelain (worst problem)
describe how to properly care for a denture base
- remove biofilms with hand soap or NON-ABRASIVE denture cleaning paste; immerse in alkaline sol’n (detergents, sodium perborate)
- use white vinegar diluted 1:1
AVOID:
- bleach (attacks metal, may remove colour)
- abrasive powders
- alcohol, acetone
- hot h2o
clean over sink partially filled with water to protect denture in case it’s dropped
