Temporary Materials Flashcards
What are the different types of temporary materials
PMMA eg jet
PEMA e.g trim II
Bis-acryl composite e.g protemp
UDMA e.g provipont DC
Is PMMA a direct or indirect material
indirect
Is PEMA a direct or indirect material
direct/chairside
Is bis-acryl composite a direct or indirect material
direct
What is the duration of PMMA material
long term
What is the duration of PEMA material
short term
What is the duration of bis-acryl composite
long term
Is PMMA used for crowns and bridges
short and long span bridges
Is PEMA used for crowns and bridges
single crowns
Is bis-acryl composite used for crowns and bridges
short span bridges
What is the monomer that makes up PMMA
mono functional monomer
methacrylate monomer
What are the features of PMMA
powder/liquid formulation self curing good marginal fit good transverse strength polishable but: poor abrasion resistance high shrinkage high thermal release free monomer may be toxic
How is PMMA formed
the mono functional monomer with one C=C double bond forms a linear chain-like polymer
How is bis-acrylate composite form
from a bis-GMA monomer
bifunctional (2 C=C double bound)
forms a 3D polymer network
How are all the temp materials formed
polymerisation
powder/liquid or 2 pastes (cartridge system)
What are the sources of scientific information on materials
journals & product literatures
What is the issue with product literature
data is not always complete or accurate
What can product literature be
brochures
websites
product profiles
What are the issue with brochures
made to sell products
superficial
give a positive presentation
What is the issue with websites
it is information rich but this means it takes time to sift through information
it is not always the relevant properties
What is the issue with product profile
scientific info but not definitive
not often supplied for products
When we do an assessment what do we look at
quality of data
competitive performance
What do we look at when looking at quality of data
is the data in house (by manufacturers) or independent
What are key properties that are of dentists concern
temperature of exothermic reaction
material encapsulates tooth prep
safety
What are key properties that are of px concern
aesthetics
ant. teeth
Why is temperature a safety issue
there may be a link between thermal change and pulp damage
What approach did Zach and Cohen use
thermal stimulus applied to teeth using soldering ion and crude and a thermostat was used to record the temperature of the inner tooth surface of pulp chamber
What were Zach and Cohens findings
2 degrees increase - no effect on pulp histology of controls
5.5 degrees increase - significant tissue changes over first few days, after 56 days most pulps had overcome thermal trauma but some pulps of smaller teeth were necrotic
11 degrees increase - most (two thirds) suffer irreparable necrosis
What was the missing factors from Zach and Cohens findings
pulpal damage is also affected by duration of the temperature rise experienced
What did Tjan’s study show
temp taken during fabrication of provisional crown
amount of heat transferred to pulp chamber during polymerization of resins may be sufficient to cause thermal damage to the dental pulp and odontoblasts
Why should Tjan’s results be taken with caution
in vitro study
doesn’t identify biological environment
What did Baldissara’s study show
it contradicts the study that a temperature rise of 11.5 degrees will cause pulp tissue damage
What was the baldissara experiment protocol
use a pair of teeth belonging to same individual
What is the experiment for baldissara
one tooth was exposed to the thermal stimulus believed to be harmful (symptomatically monitored from 68 to 91 days). extracted and examined histologically to identify possible signs of damage to the pulp
second tooth is extracted and exposed to same thermal stimulus as tooth 1. in order to assess the temperature increase induced in tooth 1 (in vitro) i.e record temperature profile applied
What did baldissara results suggest
that an increase of 11 degrees will not damage the pulp as there is no signs of inflammation and no reparative processes at higher temperature
Are any materials above 11 degrees temp change
no
duration also significant
How is color stability measured
coffee test - 3 days immersion in coffee at 36 degrees
pro temp 4 is best
also objective measure - colorimeter measure in detail, lowest for pro temp
What was significant about colors stability of pro temp
objective measure showed it was not as good as coffee test
Why is polymerization shrinkage significant
important for assessing a temp materials accuracy of fit
low PS gives good clinical fit of temp restoration
Which materials have lowest shrinkage
pro temp and integrity
Which materials have highest compressive strength
pro temp
560 newton forces but biting can reach 700 newtons
What material is most resistant material
luxatemp and pro temp
much less resistant than amalgam still
Why is surface roughness significant
influences appearance
Which material has lowest surface roughness
luxatemp
protemp 3 grant
What are other important factors
ease of use
working and setting time
