Dental Materials Unit 3 Study Guide

are used to obtain a reproduction of the teeth, surrounding oral tissues, or both

impression materials

negative reproduction

impression

positive reproduction

model

what are the two impression techniques

1. traditional/material-based

2. digital

what are the 3 classifications of material-based impressions

1. preliminary

2. final

3. occlusal

what are preliminary impressions used for

• diagnostic models/casts

• custom trays

• provisional coverage

• orthodontic appliances

produces the most accurate reproduction of the teeth and surrounding tissues

final impressions

what are final impressions used for

• indirect restorations

• partial or full dentures

• implants

also called bite registration

occlusal impression

records the relationship between the maxillary and mandibular teeth when the mouth is occluded

occlusal impression

provides an accurate registration of the patient’s centric relationship between the maxillary and mandibular arches

occlusal impression

preliminary → ?

diagnostic

final → ?

accurate/detailed

occlusal → ?

bite registration

hold the impression material during the impression procedure

impression tray

an impression tray but be rigid enough to ____?

• carry material into mouth

• hold material close to the teeth

• avoid breaking during removal

• prevent warping or distortion

impression trays are rigid for all of the following reason except to?

prevent warping or distortion

available in many sizes

stock trays

types of stock trays

• quadrant

• section

• full arch

quadrant stock tray → ?

half arch

section stock tray → ?

anterior portion

full arch stock tray → ?

entire max or mand arch

impression material mechanically locks into the holes

perforated tray

requires tray adhesive

smooth tray

the tray should : ?

• be comfortable

• extend slightly beyond teeth

can be used to modify a stock tray

utility wax

utility wax can be used to _____?

• extend length of tray

• increase height of tray borders

• accomodate unusual anatomy

• accommodate a high palatal vault

• extend posterior portion of mandibular tray

made specifically for one patient

custom tray

what is a custom tray constructed from

diagnostic model made from preliminary impression

materials used for custom trays: ?

• acrylic resin

• light-cured resin

• thermoplastic resin

used for final impressions

custom trays

custom trays are used for final impressions, including?

• dentures

• inlays

• crowns

• bridges

• partial dentures

stock tray → ?

standard size

custom tray → ?

made for one pt

blue adhesive

VPS wh

what is VPS adhesive used with

polyvinyl siolxane and polyether

brown

rubber base adhesive

what is rubber base adhesive used with

polysulfide

orange/pink

silicone adhesive

what is silicone adhesive used with

polysiloxane

hydro = ?

water

colloid = ?

gelatin substance

hydrocolloids change between a ?

sol → gel

what are the two types of hydrocolloids

1. irreversible

2. reversible

what kind of hydrocolloid is alginate

irreversible

once alginate changes from a sol → gel, it cannot return to the ___ state

sol

most widely used irreversible hydrocolloid for preliminary impressiosn

alginate

physical phase of sol

liquid or semiliquid

physical pahse of gel

semisolid

has less gel strength than elastomeric impression materials

alginate

ingredients of alginate

• potassium alginate

• calcium sulfate

• trisodium phosphate

• diatomaceous earth

• zinc oxide

• potassium titanium fluoride

derived from seaweed; thickens alginate

potassium alginate

reacts w/ potassium alginate to form the gel

calcium sulfate

slows the reaction

trisodium phosphate

adds bulk

• diatomaceous earth

• zinc oxide

prevents interference with setting and improves surface strength

potassium titanium fluoride

must be completely set before removal

alginate

strength increases over time

alginate

leave the alginate impression in the mouth for the ___?

full recommended time

dimensional changes of alginate

imbibition → water absorption → expansion

syneresis → water loss/open-air storage → shrinkage

imbibition = ?

water enters

syneresis = ?

water leaves

alginate can deteriorate quickly when exposed to : ?

• elevated temp

• moisture

what is the shelf life of alginate

1 yr

packaged in containers about the size of a coffee can

alginate

cost more but save time by eliminating powder measurement

premeasured individual alginate packages

working/setting time of normal-set alginate

2 working - 4 ½ minutes setting

working/setting time of fast-set alginate

1 ½ working - 1-2 minutes setting

good choice for a pt with a strong gag reflex

fast-set alginate

time available for mixing the alginate and loading the tray

working time

time required for the chemical reaction to be completed

setting time

cooler water → ?

longer setting time

warmer water → ?

shorter setting time

always use the scoop and measuring device supplied by ?

the manufacturer

measurements for adult mandibular impression

2 scoops poweder + 2 measures water

measurements for adult maxillary impressions

3 scoops powder + 3 measures water

what is the most common technique for mixing alginate

rubber bowl

beavertail/wide spatula

flexible rubber bowl attached to an electrical component that mixes the alginate at low or high speed

alginator

when taking an alginate impression the EFDA should be able to: ?

• mix alginate

• load the tray

• seat the tray posterior first

• keep pt comfortable

• explain procedure

• evaluate complete impression

after the the alginate impression is taken what should you do

• spray w/ intermediate level disinfectant

• place in a plastic bag

• pour within 1 hour

reversible hydrocolloid changes

sol → gel → sol

what is the reversible hydrocolloid change caused by

temp

describes the temp change that causes the transformation

hysteresis

what is required for reversible hydrocolloid

special conditioning bath

what are the 3 bath compartments

• liquefying

• storage

• tempering

• before the impression

• approximately 212 F

liquefying bath

keeps material ready for the impression

storage bath

• used after material is placed in the tray

• approximately 110 F

tempering bath

for reversible hydrocolloid tray and syringe what is used

water cooled stock tray

are used when an accurate final impression is essential

elastomeric material

types of elastomeric material

• light-bodied

• regular/heavy-bodied

other names for light bodied material

• syringe type

• wash-type

used to flow around the details of the prepared tooth

light bodied

applied first

light bodied

thicker material used to fill the tray

regular/heavy-bodied

paste begins to stiffen but does not yet have elastic properties

initial set

elasticity appears and the material becomes a solid, rubbery mass

final set

last stage occurs within approximately 1-24 hours

final cure

uses an extruder/dispenser gun

automix system

uses cartridges

automix system