Tutorial 10a - Properties + choices of materials relevant to RPD constructions Flashcards
LOs
IMPRESSION MATERIALS
Alginate advantages
(irreversible hydrocolloid)
- accurate - good fine detail
- can be used with undercuts - accurately reproduces shape without distortion
- easy to use/ handle
- cheap + affordable
- good shelf like
- flows better + less viscous than silicone putty
- non- toxic/ irritant + acceptable taste/ smell
- compatible with stone/ plaster
- good hydrophilic properties
IMPRESSION MATERIALS
Alginate disadvantages
- need to retake if incorrect
- blow holes can occur - due to incorporating too much air
- tears easily (hard with V deep undercuts
- mixing important - temp, humidity, etc affect composition of materials, qualities, working + setting time
- cannot be recast
- lack of dimensional stability = can swell due to water absorption or shrink due to water evaporation so needs to be cast quickly and kept moist
(- distortion due to syneresis or imbibition - needs to be cast immediately)
IMPRESSION MATERIALS
silicone types
- condensation
- mainly used in lab
- alcohol by-product during
polymerisation causes instability
- 2 phase usu hand mix - addition
IMPRESSION MATERIALS
silicone (condensation) advantages + disadvantages
ADVANTAGES
- cheap
- good elastic recovery
- good detail
- good working time
- pleasant taste/ smell
DISADVANTAGES
- low tear strength
- volatile by-product
- poor dimensional stability
- short shelf life
- hydrophobic
IMPRESSION MATERIALS
silicone (addition) advantages
- diff viscosities available: ultra light, light, medium, heavy + putty
- accurate - with use of different viscosities
- good tear resistance
- dimensionally stable - can be cast some time after not immediately
- non toxic/ irritant, pleasant smell/ taste
- can be recast multiple times
- good shelf life
- good working/ setting time
- automix available (easier to mix + dispense)
- accurate in recording landmarks
- high resistance to deformation
- high elasticity
IMPRESSION MATERIALS
silicone (addition) disadvantages
- expensive compared to alginate
- not common but can lock into deep undercuts
(add notes on cheung’s sheet, cannot read) - can’t use with latex gloves (sulphur contamination impedes setting)
- hydrophobic - surfactants added to make more hydrophilic BUT can then suffer from imbibition
- can be V rigid = be aware of mobile teeth
- more difficult to remove from mould
- longer setting time than alginate
- sensitive to contaminates
IMPRESSION MATERIALS
what area of the alginate is likely to be unsupported? (will require putty)
- palate
- large edentulous saddles where teeth are missing
- distal extension saddles
RPD MATERIALS
1
3 main materials used?
2
other materials used?
1
1. acrylic
2. cobalt chromium (CoCr)
3. thermoplastic - flexible nylon
(add notes on cheung’s sheet, cannot read)
2
1. Type IV gold alloy
2. Titanium
3. Stainless steel
- can be V thin + light, fracture resistant,
corrosion resistant + good thermal
conductivity
4. aluminum
- accurate
RPD MATERIALS
why are gold and titanium not commonly used anymore to make dentures?
Type IV gold alloy
- V expensive + outdated
titanium
- lightweight + biocompatible BUT expensive + complicated casting
RPD MATERIALS
things to consider when choosing RPD material?
RPD MATERIALS
Ideal requirements of a partial denture base material?
- adequate physical + mechanical properties
RPD MATERIALS - ACRYLIC
1
what is acrylic
2
how is it cured
3
which method of curing provides more strength?
1
- Polymethylmethacrylate (PMMA)
2
- can be heat cured or self cured
3
self cured = has 80% strength of heat cured + more residual monomer
RPD MATERIALS - ACRYLIC
indications?
RPD MATERIALS - ACRYLIC
advantages?
- cheap
- good for long span edentulous areas
- easy to reline - for transitional cases
- easily adjustable + can add teeth to it if poor prognosis in arch
- biocompatible
- mainly mucosal support but can add clasps for extra retention (gold/ stainless steel)
- asthethetic (potentially no clasps required)
RPD MATERIALS - ACRYLIC
disadvantages?
RPD MATERIALS - THERMOPLASTIC
advantages?
RPD MATERIALS - THERMOPLASTIC
Disadvantages?
RPD MATERIALS - THERMOPLASTIC
Egs
Polyamide nylon = single polymeric chain)
EGs
- valplast
- flexite
- TCS
- Iflex
- Duralex
RPD MATERIALS - COBALT CHROMIUM (=metal alloy with varying constituents)
advantages?
RPD MATERIALS - COBALT CHROMIUM
Disadvantages?
DENTURE CLASP MATERIALS
Make Q
DENTURE CLASP MATERIALS
What must all clasps provide?
(Make more detailed Q???)
DENTURE CLASP MATERIALS
What does the retentive arm prevent?
Make q
DENTURE CLASP MATERIALS
What does the amount of retention depend om?
DENTURE CLASP MATERIALS
Possible materials?
DENTURE CLASP MATERIALS
What does claps choice depend on?
DENTURE CLASP MATERIALS
What is elastic modulus?
What does a higher and lower modulus indicate?
DENTURE CLASP MATERIALS
Relevance of elastic modulus to clasp
JAW REGISTRATION MATERIALS - pink sheet wax
Advantages
JAW REGISTRATION MATERIALS - pink sheet wax
DisAdvantages
JAW REGISTRATION MATERIALS - zinc oxide eugenol
Advantages
JAW REGISTRATION MATERIALS - zinc oxide eugenol
DisAdvantages
JAW REGISTRATION MATERIALS - hydro bite (light bodied silicone)
Advantages
JAW REGISTRATION MATERIALS - hydro bite (light bodied silicone)
DisAdvantages
