Dental Materials Chapter 16 - Gypsum and Wax Products
Terms in this set (32)
When working models for cast restorations are being made, a die of high-strength stone (Type IV) is often poured with a base and adjacent teeth of Type _____ stone.
An increase in the recommended water-to-powder ratio will result in a _____ accurate model.
Which of the following statements is true regarding dimensional accuracy of gypsum products?
High-strength stones have the least amount of setting expansion.
Which of the following is an example of a pattern wax?
An increase in spatulation time and rate will _____ the setting time and _____ the rate of setting expansion.
shorten ; increase
Which of the following statements is true of inlay waxes?
They may be used directly in the mouth and placed onto the prepared tooth in the direct waxing technique.
Which of the following gypsum products is ideal for making full or partial denture models, orthodontic models, and casts requiring higher strength and abrasive resistance?
Dental stone (Type III)
Sheets of baseplate wax are usually layered to:
Produce the form on which denture teeth are set.
As the temperature of the wax increases, the _____ of the wax decreases until the wax becomes a liquid.
For regular-set gypsum products, the initial set occurs within _____ minutes from the beginning of the mix.
7 to 9
Utility wax may be used to:
1. adapt the periphery of an impression tray.
2. provide a better fit into the vestibule of the impression material.
3. cover sharp brackets and wires for orthodontic patients.
1, 2, 3
What could occur if excess residue remains in the investment mold after the wax pattern is melted out?
This may result in inaccuracies in the object being produced.
Which of the following statements is true concerning the mixing of plaster and stone materials?
The measured amount of water is placed into the mixing bowl and the powder is slowly sifted into the water.
b-Hemihydrate is commonly used for:
Which of the following is true concerning the chemical properties of gypsum materials?
The amount of water required to mix the calcium sulfate hemihydrate is greater than the amount required for the chemical reaction.
Model plaster has a water-to-powder ratio of approximately _____ (mL/g).
Increased porosity of the gypsum particles makes it necessary to use _____ water to convert the _____ when mixing gypsum products.
more ; hemihydrate particles back to dihydrate particles
Wax patterns should be invested within _____ of carving.
Which of the following is true of boxing wax?
Boxing wax is slightly tacky at room temperature.
Which of the following dental gypsum products will require the least water for mixing and will have the highest final density?
Dental stone, high strength (Type IV)
Which kind of wax is used to construct the metal framework of partial and complete dentures?
Which of the following represents the correct sequence for creation of a casting using the lost wax technique?
1. The pattern and sprue are encased in an investment ring.
2. A wax or plastic sprue is attached to the pattern.
3. A wax pattern of the restoration is carved on the die.
4. The enclosed pattern and sprue are heated in a burnout oven at high temperatures.
3, 2, 1, 4
Which of the following is true of the double-pour method for fabricating and trimming diagnostic/working casts?
This technique involves two separate mixes.
Which of the following is true regarding trimming of models with a model trimmer?
The casts should be trimmed so that proportionately the base makes up one third and the anatomic portion two thirds of the total depth.
Type I: Rarely used today
Type II: frequently used for diagnostic casts ; durable but relatively weak material
Type IV: often referred to as die stones or densite ; used to fabricate crowns and bridges
Dental stone, high-strength/low-expansion
Type V: good to use with the newer base metals because of casting shrinkage
Dental stone, high-strength/high-expansion
Which of the following would not alter the setting time of gypsum?
Using a mechanical mixer
When stone is mixed with silica, this is referred to as ______.
In the lost wax technique for casting gold for dental restorations, a _____ is attached to the pattern to form the channel into which the molten metal will be forced.
The _____ the particles of gypsum powder are, the weaker and less resistant to abrasion is the final product.
larger, more irregular, and more porous