MDA Chapter 47 Laboratory Materials
and Procedures
Anatomical Portion - ANSWER-The structural portion of a dental model created from the alginate
impression
box and pour method - ANSWER-the impression is surrounded by a box made from boxing wax.
Cystallization - ANSWER-Chemical process in whick crystals form a structure
Die - ANSWER-An accurate replica of the prepared portionn of a tooth used in the laboratory during the
fabrication of a cast
Dihydrate - ANSWER-Related to gypsum products and indicating two parts of water to one part of
calcium sulfate
Dimentionally stable - ANSWER-Resistant to changes in width, height, and length
double pour method - ANSWER-the anatomical portion of the cast is poured first. then a second mix of
plaster or stone is used to prepare the art portion. a free-form base may be created by hand, or a
commercial rubber mold can be used
Hemihydrate - ANSWER-Removal of water to become on-half part wter to one part of calcium sulfate,
forming the powder product of gypsum
Homogenous, homogeneous - ANSWER-Having a uniform quality and consistency throughout
how does a vacuum former work? - ANSWER-the upper part of the unit is a heating element that warms
and softens a sheet of thermoplastic resin. the work surface has holes that allow the vacuum to pull and
shape the warmed plastic around the model
how long should you wait before you separate the model from the impression? - ANSWER-wait 46-60
minutes after the impression has been poured
how much should the completed box in a box pour method extend? - ANSWER-at least 1/2 inch above
the palatal area of the maxillary impression and 1/2 inch above the tongue of the mandibular impression
inverted pour method - ANSWER-consists of mixing one large mixture of plaster or stone and pouring up
the impression first then placing a base of material on a tile or a counter to invert the impression in a
single step.
Monomer - ANSWER-A molecule that, when combined with other molecules, forms a polymer
Polymber - ANSWER-Compound of many molecules
recommended powder to water ratios for gypsum products - ANSWER-model plaster (100g) - 45 to 50
ml water
dental stone(100g) - 30 to 32 ml water
high strength stone(100g) - 19 to 24 ml water
, MDA Chapter 47 Laboratory Materials
and Procedures
safety precautions that should be taken in the dental laboratory - ANSWER-1. no eating, drinking, or
smoking permitted
2. keep all cosmetics away from the area
3. wear personal protective equipment
4. keep hair pulled back
5. report all accidents to the dentist immediately
6. follow the manufacturer's instructions for equipment operation
7. clean the work area before/after every procedure
Slurry - ANSWER-Mixture of gypsum and wter used in the finishing of models
Study casts - ANSWER-dental models, aka, study casts are accurate three-dimensional reproductions of
the teeth and surrounding soft tissues of the patients maxillary and mandibular arches.
Volatile - ANSWER-Substance that can evaporate easily and is very expolosive
what are dental models used for? - ANSWER-1. diagnosis for planning a fixed or removable prosthetic
device
2. diagnosis of orthododntic treatment
3.visiul presentation of dental treatment
4. production of custom trays
5.makingt a provisional coverage
6. making of mouth guards
what are gypsum products used for? - ANSWER-to make dental models
what are rubber bowls used for - ANSWER-for mixing of alginate in the treatment area and for mixing of
stone or plaster in the lab setting
what are the chemical properties of gypsum? - ANSWER-dehydrate and hemihydrate
what are the clusters that form when mixing gypsum with water called? - ANSWER-nuclei of
crystallization
what are the three forms of gypsum products used in pouring models? - ANSWER-model plaster, dental
stone, and high-strength stone
what are thee different types of pouring methods - ANSWER-double pour method, box-and-pour
method, and inverted pour method
what are two parts of a dental model? - ANSWER-the anatomical portion and the art portion
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