Impression Materials Flashcards
How materials interact with its enviroment & pateitns, properties, contex of use.
Biocompatibility
fundamental requirement for any dental restoration.
The breakdown of mateirals int he oral enviroment
Biodegredation
What are somethigns we look for when choosing dental materials?
- Long term testing & trials
- Internationall reconized spec & standards
- Maximun saftey, durable, effective
- Lower risk due to low knowledge
Whos responsibility is it toweigh the quality of evidence regarding manufacturers’ claims from an informed, intelligent perspective to ensure optimum treatment outcomes for the patients.
The dentist
Dentists are expected to acquire sufficient knowledge of the what 3 things?
of dental materials used in the rehabilitation of the edentulous patient.
- Properties
- Behavior
- Limitations
Of all mateirals
What is the goal of optimal impressions?
- Retention
- Support
- Stability
of denture!
Impression for complete dentures must what?
be capable of capturing and replicating all anatomical peripheral and denture-supporting structures
Just look lol
Just look
an imprint produced by ‘the pressure of one thing upon or into the surface of another
Impression
Active + making
an impression made for the purpose of diagnosis or for the construction of a custom tray.
Preliminary Impression
What mateirals do you need for a preliminary impression?
- Stock tray
- Alginate
An imprint that record the entire functional denture-bearing area to ensure maximum support, retention and stability for the denture during use.
Final Impression
What is the purpose of a final impression?
To record accurately the tissues of the denture bearing areas, in addition to recording the functional width and depth of the sulci.
Anatomy of mouth!
What are the 3 diffrent impression techniques?
- Mucostatic
- Mucocompressive
- Selective Pressure
impression is made with the mucosa in its normal resting position.
* lead to good fitting denture
* During chewing denture will pivot on incompressbale areas and dig into compressible areas
Mucostatic impression
**The impression is made when the mucosa is subject to compression. **
* Denture is most stable during function not at rest
* Hard tissue not compressed
Mucocompressive impression
What we do
The impression is made with stress bearing areas being compressed and stress relief areas being relieved.
Selective pressure impression
What are the 2 main categories of impression materials?
- Ridgid
- Elastics
What kind of impression mateiral?
impression plaster, zinc oxide eugenol paste, and dental impression compound
Ridgid/ non-elastic
What rigid material is used from boarder molding of custom trays?
Compound
What are 2 reasons why ridgid impression materials are bad?
- Inability to withdraw from undercuts= fracture easily
-
No elastic defromation, does not recover past set
3.
What impression mateiral?
used as a mucostatic impression material for making final impressions for edentulous patients
* does not compress or displace tissues
* not used often
Impression plaster
What impression mateiral?
- Rigid
- May fracture in the presence of undercuts.
- Set material does not adhere to set plaster or stone.
- Power, liquid, or paste
- < 0.1% setting shrinkage= impression stored for long time with **no distortion **
Zinc Oxide Eugenol (ZOE) Impression Paste
maining used fro final impression of endentulous ridge
What impression mateiral can be used as a surgical dressing and why?
Zine Oxide Eugenol paste because it is soothing + anti-inflammatory
What are 4 adavantages of ZOE
- Dimensional stability
- Good surface detail
- Can be added on to exsisting ZOE
- Mucostatic or mucocompressive
What are 4 Disadvantages of ZOE
- Can be used with deep undercuts
- sets quickly if thin
- Eugenol allergies
- Stining + burning
What impression material?
- Rigid
- Modeling plastic
- Thermoplastic; heat to mold
- cakes or sticks, with the colors representing different fusing temperatures.
Dental Impression Compounds
green sticks for us
Dental compound is a mixture of waxes and thermoplastic resins plus fillers that increase ____ above mouth temperatures and provide ____ at room temperature.
Above mouth temp= viscosity (heat at 124F by flame or water bath
At room temp= rigidity
WHat type of dental impression compound do we use in lab?
Type 1 lower fusing material for boarder molding
can also be used for pre-liminary impressions
What two was can impression compound be heated?
- Direct flame for sticks
- Waterbath
Whar are the two categories of elastic material?
- Synthetic elastomer
- Hydrocolloids
What material?
considered one of the most accurate impression materials for recording fine details because of their low viscosity and great degree of recovery after deformation around undercuts.
Reversible Hydrocolloids; Agar
What impression material
Most widely used impression materials in dentistry: ease of manipulation, no need for expensive equipment, relatively low cost, and comfort to patients.
Irreverisble Hydrocolloids; Alginate
the setting of a reversible hydrocolloid.
Is a solidification process that involves phase changes from sol to gel states, induced by a change in temperature.
Gelation of Agar
reversible
- Long working time (5 min set)
- can be poured immediatley
- limited use in making fix prosth
Agar; reversible hydrocolloids
Whay is the most commonly used category of impression materials today?
Synthetic Elastomers
What were the were the first synthetic elastomeric material to be introduced in 1950.
Polysulfides
drawback is distorition over time
Silicones and polyethers form the majority of what impression mateira used today?
Elastomeric impression mateirals
What are 3 steps to making impression with elastomeric materias?
- custom trays 2-3 mm short of sulcus
- boarder molded green compoound
- verify proper seal
What impression material?
two-paste system that is available in low, medium, and high consistencies and is made up of a base and accelerator/reactor.
Polusulfide rubber
What occurs when the pasted of polysulfied rubber are mixed together?
Polymerization rxn occurs
How do you know polysulfied rubber is set and why? How soon to pour?
paste has tunred to dark brown rubber, due to prescence of lead oxide; pour within 1 hour
stinks
Characteristics of polysulfied rubber
- great detail
- long working time
- good flexibility
- high tear strength
- hydropphobic so dry tissues prior
- mess, smells bad.
Polysulfied rubber to record the soft tissues for edentulous patients under ____ _____
minimum compression
What impression mateiral
- Highly accurate
- High dimensional stability
- Multiple casts
- Easy to mix
- Pleasant odor
disadvantage:
1. Expensive
2. sulfur inhibit set; no latex gloves
3. short working time
Polyvinylsiloxanes (PVS/VPS)
