ch 46-47

negative production

a dental impression is this of the patient’s oral structures

positive production

a dental model is this of the patient’s oral structures

preliminary impressions

taken with alginate or a monophase impression material and a stock impression tray

final impressions

taken with an elastomeric impression material and a custom impression tray or a triple tray

bite registrations

taken with wax registration material, polysiloxane bite registration paste, or zinc oxide eugenol

what is alginate made from

seaweed known as kelp

what is alginate known as

irreversible hydrocolloid impression

what is alginate supplied with

a powder and is mixed with cold water

what will speed up the setting process?

mixing alginate with warm or hot water, acting as a catalyst or accelerator

imbibition

alginate impressions that are allowed to absorb additional water

syneresis

alginate impressions that are allowed to dehydrate

what are preliminary impressions commonly taken with?

stock metal perforated impression trays

what chemical forms do elastomeric impression materials come in

1. Polysulfide

2. Polyether

3. Polyvinyl Siloxane (PVS)

what are elastomeric impression materials supplied with

a two-paste system, which includes a base and a catalyst

what does the catalyst do in the two-paste system

it initiates and speeds up the chemical reaction or POLYMERIZATION

what are elastomeric impression materials used for

to take final impressions

polymerization

chemical process by which elastomeric impression materials set or harden

light bodied viscosity (wash-type)

also known as syringe-type. this is the lowest viscosity (thinest) , picks up the most detail, loaded into a COE syringe

regular bodied (tray-type)

also known as heavy-bodied BUT it doesn’t have the highest viscosity. It is loaded into an impression tray

putty

it has the highest viscosity (thickest) and is hand mixed

how can an elastomeric impression be mixed ?

1. through an extruder gun with a mixing tip

2. by kneading the base and catalyst together by hand

initial set of an elastomeric impression

this impression must be placed into the patient’s mouth during the initial set

final set

the impression can be removed from the patient’s mouth at the end of the final set stage

tray adhesive

painted on the internal portion of an impression tray to lock the impression to the impression tray, thus preventing separation and distortion

one-step technique

wash type and tray type taken at the same time after the tooth is prepared

two-step technique

the final impression is taken with the wash type after the tooth has been prepared by inverting the putty-filled customized tray over the wash

triple-tray technique

taken after the tooth is prepared, a special triple tray is required. triple impression = opposing arch, final impression, and bite registration all in one step

homogeneous

upon completion of mixing a material, there should be consistency throughout the material

articulator

an articulator is a device to which study models are mounted

gypsum

used to created the materials stone and plaster

calcination

during this production process, water is evaporated out of the material

what comes in different colors?

stone materials

vibrator

used to remove the air bubbles from stone and plaster after the mixing process. it is also used to flow plaster or stone as it's being poured into an impression

model trimmer

used to trim study models

dental lathe

used to trim and polish temporary restorations, orthodontic and removable appliances (dentures)

border molding

accomplished by adding soft utility wax to the borders of an impression tray to make it better fit the patient’s mouth

undercuts throughout the patient’s dentition

 must be waxed out with soft utility wax prior to taking impressions