Intro to restorative 3/ impressions

which impression material is reversible

agar hydrocolloid

which impression material is irreversible and hydrophilic

alginate hydrocolloid

alginate hydrocolloid is used for what

-case study models

-ortho models

-opposing models

-semi direct restorations

agar hydrocolloid is used for what

crown and bridges

synthetic elastomeric is used for what

all dental impression techniques

-crown and bridges

-indirect restos

-implant restorations

-denture impressions

for alginate hydrocolloid, accurate casts are transferred to

semiadjustable articulator --> essential for fixed prosth planning

what precipitates out of alginate hydrocolloid as a porous network

Ca-alginate

what remains in the porous network

water

water is NOT bound to alginate and can freely come into or leave the Ca-Alg network

what tray should be selected for a pt

largest tray that fits comfortably

potential tray modifications

-modeling compounds or wax extension

-use an S cutter to modify

-reshape with heat

what needs to be applied to tray before adding alginate for the impression

adhesive

after applying adhesive, let dry for how long

air dry for 15 min or air stream for 1 min and 2 min air dry

steps after taking impression

rinse --> disinfect --> rinse again --> dry lightly with air stream --> pour cast within 30 min

if immediate pouring is not possible, what can you do

wrap impression in paper towel and put in plastic bag or humidor (pour within 60 min)

when adding water to alginate material, what temp should water be

room temp

warm water will ___ the rxn and cold water will ___ the rxn

speed up the rxn; slow down the rxn

for impressions, what is poured first: water or powder

powder in bowl first

when pouring diagnostic casts with microstone, what is poured first: water or power

water

mixing time for alginate

60 sec

when pouring alginate impression and it's setting, the the poured impression tray must be stored...

tray side down

alginate advantage

cheaper

alginate disadvantage

have to pour quick

PVS advantage

more sophisticated and can wait longer before having to pour cast

PVS disadvantage

more expensive

2 types of mandibular movements

1. rotation around an axis

2. translation --> md is forced to translate after 12mm of incisal opening

bennet angle on articulator

15 degrees (red)

protrusive condylar inclincation angle of articulator

30 degrees (black)

benefit of using semi adjustable articulator

indicated for more routine fixed prosth procedures

why do we not use a fully adjustable articulator

it is too complex and requires a high level of skill and not required for more procedures

what is the purpose of a facebow

record AP and mediolateral spatial position of max occlusal surfaces in relation to transverse opening and closing axis of pts mandible

where should the AP reference point be marked

43mm above incisal edge of right central or lateral incisor

where should regisil be places on the bitefork for max imprint

where incisal edge of central incisors and cusp tips of molars are recorded

facebow should be ____ to the inter-pupillary line

parallel

what is centric relationship

relationship of mandible to maxilla when properly aligned when the condyle/disk are in most superior position against articular eminence

in CR, TMJ can do what

resist maximum loading

CR happens when

at first contact

what is MIP

complete intercuspation of opposing teeth independent of condylar position