Dental Materials Packe #5
Terms
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- LESS expansion when adding more water
- Does adding extra water to a plaster mixture cause MORE or LESS expansion of the product?
- Gel
- Continuous solid in a liquid phase. network or chains of polymers with water surrounding everything
- True
- T or F: when an aliginate reaction happens, a SOL turns to a GEL and it is a non-reversible reaction
- sol
- Disperced solid phase (fine particles) in a liquid phase
- Dislocation
- What allows single planes of atoms to move druing deformation instead of large sets of planes?
- Permanent deformation
- when an alginate impression is taken, if it is not filled right away, water will evaporate and it will shrink. this would be what kind of deformation?
- Sodium Phosphate
- Which alginate additive controls setting reaction (retards it). (Potassium sulfate/organic glycol/sodium phosphate)
- Hydrophilic!!! They have a low angle and are easily wet (have good wettability)
- Are molecules with HIGH surface energies considered hydrophilic or hydrophobic?
- True. Weaker plasters expand the most.
- T or F: Most gypsum products show slight setting expansion.
- setting
- Setting and drying reactions are different. In the ______(setting/drying) reaction, only 0.5H20 is used and there is lots of excess H20 in the products
- Setting. after 60 min, impression can be removed from cast
- dont' confuse drying and setting. ____ is when chemical reaction is going on and ends when chemical reaction is complete.
- anhydro-B-D-mannuronic acid
- Alginates are made of Polysaccharides-long chains. Alginate is a linear polymer of what compound??
- Ceramic
- Gypsum material (for study casts) is actually a hydrated form of what compound? (metal/composite/ceramic)
- needle.
- Different types of gypsum materials have differences in strength. This is due to the POWDER PARTICLE SHAPE. This controls how much excess water is needed to form a pourable mass. _____ shaped particles requrire MORE water (needle/spherical
- Long covalently bonded chains...weak bonding between chains and softens when heated
- What characterizes a linear polymer strucuture??
- Retarted elastic deformation and viscous flow---ruins impression. Take out with a SNAP for best results.
- When popping an alginate tray out of a person's mouth, if you take it out SLOWLy, what kind of deformation will you cause?
- Needle-shaped--they require MORE water (remember--stronger materials have LOWER porosities b/c lots of porosity weakens a material
- Dental plaster is the cheapest gypsum material. Therefore, would it have needle-shaped particles or spherical shaped particles?
- drying
- _____(drying/setting) the cast causes it to become much stronger (2x)
- Drying
- In the ______ (setting/drying) reaction, there is 2.0H20 and there is less or ZERO excess H20 in the products
- Model Plaster (Type II)/Model Plaster (type ll)/High Strength Dental Stone (Type IV)
- There are three types of gypsum materials--Model Plaster, Dental Stone and High Strength Dental Stone. Which one is used for study models? Which one has LOW ABRASION RESISTANCE? (material breaks easily). Which one has the HIGHEST abrasion resistance?