SEM 1 Dental Materials Unit
Model - Study Model - correct answer ✔A positive reproduction used for a
case study or diagnostic purposes.
- Created from an irreversible hydrocolloid. (preliminary impression/alginate).
- Also referred to as study casts or study models
- Are accurate 3 dimensional reproductions of the teeth and surrounding soft
tissues of the maxillary and mandibular arch
Cast- Working Model - correct answer ✔A working model is used in the
fabrication of an appliance or restoration.
- A cast is made from a material that is strong and able to resist wear and
abrasion caused during the fabrication of the appliance.
Edentulous & Dentulous Casts - correct answer ✔A cast is considered to be
a reproduction of a quadrant or an arch which is dentulous or edentulous.
Edentulous = No teeth present
Dentulous = Some teeth present
Die - correct answer ✔Replica of one or more teeth, which is usually a
removable portion of the cast.
- a hand saw is used to cut the die away from the model
,Gypsum - correct answer ✔- Gypsum is a mineral that is mined from earth
- Gypsumproductsare extensively used in dentistry to make dental models
- During manufacturing of gypsum, water is lost from the material
- The calcium sulfate dihydrates are converted to hemihydrates of calcium
sulfate.
Calcium Suldate DIHYDRATE... Take away Water...= calcium sulfate
HEMIHYDRATE
*** - ^ this is important bc The process of removing water results in different
physical and chemical characteristics of stone, plaster, and improved stone
making each material unique in its properties.
We add more water than necessary so we can flow the material into the
impression. The excess water evaporates as the gypsum material sets by an
exothermic reaction
***The shape, size, and porosity of the particles determine the amount of
water needed.
Plaster has larger and more porous particles---requires more water
components of gypsum - correct answer ✔Gypsum Material = calcium
sulfate dihydrate
types of gypsum products - correct answer ✔1.model plaster
2.dental stone
3.improved stone
Model Plaster - correct answer ✔Plaster = WHITE
, - Used for making DIAGNOSTIC STUDY MODELS
- Irregular shape of crystals in plaster make it porous
- Requires more water in the mixing which produces a WEAKER cast.
Dental Stone - correct answer ✔Stone = YELLOW
uUsed when a more durable cast is required-for a WORKING MODEL
u Crystals in stone are more uniform in shape and less porous than plaster
u STRONGER and denser cast
improved stone (high strength) - correct answer ✔improved =
PINK/BLUE/GREEN
uHas strength, hardness and dimensional accuracy
uUsed to create the dies used in the production of indirect restorations
uThe crystals are smooth and very dense and require the least amount of
water for mixing
uSTRONGEST
Initial Set - correct answer ✔Time needed to mix and manipulate the
material.
Look For:
1.Increased viscosity-no longer flowing
2.Loss of gloss
3.Occurs between 8 to10 min
Model - Study Model - correct answer ✔A positive reproduction used for a
case study or diagnostic purposes.
- Created from an irreversible hydrocolloid. (preliminary impression/alginate).
- Also referred to as study casts or study models
- Are accurate 3 dimensional reproductions of the teeth and surrounding soft
tissues of the maxillary and mandibular arch
Cast- Working Model - correct answer ✔A working model is used in the
fabrication of an appliance or restoration.
- A cast is made from a material that is strong and able to resist wear and
abrasion caused during the fabrication of the appliance.
Edentulous & Dentulous Casts - correct answer ✔A cast is considered to be
a reproduction of a quadrant or an arch which is dentulous or edentulous.
Edentulous = No teeth present
Dentulous = Some teeth present
Die - correct answer ✔Replica of one or more teeth, which is usually a
removable portion of the cast.
- a hand saw is used to cut the die away from the model
,Gypsum - correct answer ✔- Gypsum is a mineral that is mined from earth
- Gypsumproductsare extensively used in dentistry to make dental models
- During manufacturing of gypsum, water is lost from the material
- The calcium sulfate dihydrates are converted to hemihydrates of calcium
sulfate.
Calcium Suldate DIHYDRATE... Take away Water...= calcium sulfate
HEMIHYDRATE
*** - ^ this is important bc The process of removing water results in different
physical and chemical characteristics of stone, plaster, and improved stone
making each material unique in its properties.
We add more water than necessary so we can flow the material into the
impression. The excess water evaporates as the gypsum material sets by an
exothermic reaction
***The shape, size, and porosity of the particles determine the amount of
water needed.
Plaster has larger and more porous particles---requires more water
components of gypsum - correct answer ✔Gypsum Material = calcium
sulfate dihydrate
types of gypsum products - correct answer ✔1.model plaster
2.dental stone
3.improved stone
Model Plaster - correct answer ✔Plaster = WHITE
, - Used for making DIAGNOSTIC STUDY MODELS
- Irregular shape of crystals in plaster make it porous
- Requires more water in the mixing which produces a WEAKER cast.
Dental Stone - correct answer ✔Stone = YELLOW
uUsed when a more durable cast is required-for a WORKING MODEL
u Crystals in stone are more uniform in shape and less porous than plaster
u STRONGER and denser cast
improved stone (high strength) - correct answer ✔improved =
PINK/BLUE/GREEN
uHas strength, hardness and dimensional accuracy
uUsed to create the dies used in the production of indirect restorations
uThe crystals are smooth and very dense and require the least amount of
water for mixing
uSTRONGEST
Initial Set - correct answer ✔Time needed to mix and manipulate the
material.
Look For:
1.Increased viscosity-no longer flowing
2.Loss of gloss
3.Occurs between 8 to10 min
