Diagnostic Casts
Positive replicas of the teeth produced from impressions that create a negative representaton of the teeth; commonly called study models and used for diagnostic purposes and numerous chairside and laboratory procedures.
Bite Registration
an impression of the occlusal relationshio of opposing teeth in centric occlusion (pt's normal bite).
Colloid
glue-like material composed of two or more substances in which one substance does not go into solution but is suspensed within another substance; it has at least two phases, a liquid phase called a sol and a semisolid phase called a gel.
Hydrocolloid
a water-based colloid used as an elastic impression material.
Reversible Hydrocolloid
an agar impression material that can be heated to change a gel into fluid sol state that can flow around the teeth, then cooled to gel again to make an impression of the shapes of the oral structures.
Irreversible Hydrocolloid
an alginate impression material that is mixed to a sol state and as it sets converts to a gel by a chemical reaction that irreversibly changes its nature.
Agar
a powder derived from seaweed that is a major component of reversible hydrocolloid.
Sol
liquid state in which colloidal particles are suspended ; by cooling or chemical reaction, it can change into a gel.
Gel
a semisolid state in which colloidal particles form a frameworkthat traps liquid (e.g., Jell-O)
Hysteresis
the property of a material to have two different temperatures for melting and solidifying, unlike water, which has one temperature for both.
Syneresis
a characteristic of gels to contract and squeeze out some liquid that then accumulates on the surface.
Alginate
a versatile irreversible hydrocolloid that is most-used impression material in the dental office; it lacks the accuracy and fine surface detail needed for impressions for crown and bridge procedures.
Elastomers
highly accurate elastic impression materials that have qualities similar to rubber; they are uses extensively in indirect restorative techniques, such as crown and bridge procedures.
Imbibition
the act of absorbing moisture.
Surfactant
a chemical that lowers the surface tension of a substance so that it is more readily wet; for example, oil beads on the surface of water, but soap acts asa surfactant to allow the oil to spread over the surface.
Polysulfide
an elastic impression material that has sulfur-containing (mercaptan) functional groups; it has also been referred to as rubber base impression material.
Condensation Silicone
a silicone rubber impression material that sets by linking molecules in long chains but produces a liquid by-product by condensation.
Addition Silicone
a silicone rubber impression that also sets by linking molecules in long chains but produces no by-product; the most commonly used addition silicones are the polyvinyl siloxanes.
Polyvinyl Siloxanes (PVS)
very accurate addition silicone elastomers impression material; it is used extensively for crown and bridge procedures because of its acccuracy, dimensional stability, and ease of use.
Polyether
a rubber impression material with ether functional groups; it has high accuracy and is popular for crown and bridge procedures.
Impression Compound
an impression material composed of resin and wax with fillers added to make it stronger and more stable than wax.
Impression Plaster
an impression material composed of gypsum product similar to plaster of Paris.
Zinc Oxide Eugenol (ZOE)
a hard and brittle impression material used in complete denture procedures.
1) A dental impression material
a. Forms a positive imprint of the oral structures involved.
b. Allows the creation of a replica of the structures involved.
c. Always flexible for easy removal from the mouth.
d. Is used only for crown and bridge procedure
b. Allows the creation of a replica of the structures involved.
2) Which of the following impression materials is/are transformed from a sol to a gel state when set?
a .Alginate and agar hydrocolloids
b. Polysulfide
c. Zinc oxide eugenol
d. Condensation silicones
a. Alginate and agar hydrocolloids
3) Which of the following is an example of an inelastic impression material?
a. Alginate
b. Polyether impression material
c. Dental compound
d. Polyvinyl siloxane (PVS) impression material
c. Dental compound
4) The types of impression materials that are considered hydrophilic are those that
a. Have a lot of water in them.
b. Can be immersed in water without absorbing.
c. Cause water to bead up on the surface.
d. Have good surface wetting characteristics.
d. Have good surface wetting characteristics.
5) Hydrophobic impression material
a. Absorb moisture only after their final set.
b. Are the best types of material to use in the mouth.
c. Need a dry field to get the best results.
d. Provide the best surface of gypsum casts, because they resist the upta
c. Need a dry field to get the best results.
6) Alginate impression material
a. Is accurate enough to be used for crown and bridge material procedures.
b .Has very few uses in the modern dental practice.
c. Is dimensionally stable during the first 24 hours.
d .Can be immersed in an appropriate disin
d .Can be immersed in an appropriate disinfectant for up to 30 minutes without distorting.
7) Agar hydrocolloid
a .Works well in a moist field.
b. Is hydrophobic.
c. Has excellent tear strength in deep, narrow spaces.
d .Can be poured up after several days if kept immersed in water.
a .Works well in a moist field.
8) An irreversible hydrocolloid
a. Is one that goes from a gel to a sol when it is heated.
b. Commonly used in the dental offices is agar hydrocolloid.
c .Is hydrophobic.
d. Cannot reverse from a gel to a sol because a chemical reaction prevents it.
d. Cannot reverse from a gel to a sol because a chemical reaction prevents it.
9) Polyvinyl impression materials are of the class known as
a. Inelastic materials
b. Mucostatics
c. Hydrocolloids
d. Elastomers
d. Elastomers
10) Polysulfide impression materials
a. Are easy to mix.
b. A rapid setting time.
c. Are the most accurate impression materials.
d. Have excellent tear strength.
d. Have excellent tear strength.
11) Which of the following elastomers will imbibe water when immersed in it and swell?
a. Polysulfides
b. Condensation silicones
c. Addition silicones
d. Polyethers
d. Polyethers
12) Which of the following materials produce alcohol as a by-product of it setting reaction and is subject to distortion as it evaporates?
a. Agar hydrocolloid
b. Polysulfide
c. Condensation silicone
d. ZOE
c. Condensation silicone
13) Which of the following statements is true about the addition silicones?
a. They are good material for complete denture impressions but are not accurate for crown and bridge procedures.
b. They are very dimensionally stable.
c. They cost about the same
b. They are very dimensionally stable.
14) The most rigid of the impression materials listed below is
a. Alginate
b. Polysulfide
c. Polysulfide polyvinyl siloxane
d. Compound
d. Compound
15) The least accurate of the elastic impression material is
a. Agar hydrocolloid
b. Condensation silicone
c. Polyvinyl siloxane
d. Alginate
d. Alginate
16) Which two of the following elastomers do NOT need to be poured with gypsum within a few hours after the impression is made?
a .Polysulfide and polyvinyl siloxane
b. Condensation silicone and polyether
c. Polyvinyl siloxane and polyether
d. Condensatio
c. Polyvinyl siloxane and polyether
17) Dental compound impression material can change from a solid to a soft material when it is heated. Its greatest use today is for which procedure?
a. Border molding custom trays for denture impressions.
b. Making impressions of teeth for single crowns.
a. Border molding custom trays for denture impressions.
18) Which one of the following when used for denture impressions, is broken into pieces to remove it from the mouth and is reassembled in the laboratory to pour the impression?
a. Impression plaster
b. Dental compound
c. Impression wax
d. Zinc oxide eugen
a. Impression plaster
19) Zinc oxide eugenol impression material is
a.Mixed to the same consistency as zinc oxide eugenol provisional filling material.
b. Useful for impression of a crown preparation in the presence of inflamed gingiva because of the healing capacity of the eu
d. Used alone in a custom acrylic resin impression tray as a wash material.
20) Disinfecting of impressions
a. Is done to protect the patient from surface bacteria.
b. Must be done for all impressions.
c. Is done only with impressions for patients with known infectious diseases.
d. Does not need to be done for the new alginates t
b. Must be done for all impressions.