FIXED PROS - Temporary Crowns Flashcards
why are temporary crowns needed? (6)
- restore aesthetics and function
- prevent dentinal sensitivity
- protect from re-infection of a non-vital tooth
- prevent unwanted tooth movements
- to use a provisional crown
- prevent overgrowth of gingiva
why may you get dentinal sensitivity in crown prep?
most of the enamel is removed
dentinal tubules are exposed
what is the hydrodynamic theory?
a mechanism which describes how dentinal sensitivity occurs
describe the hydrodynamic theory.
- dentinal tubules are exposed to external stimuli
- as response, change in fluid flow
- leads to pain and sensitivity in the pulp
why can teeth move if a temp crown isn’t placed?
all contact points, mesially, distally and occlusally are removed
why do we want to prevent unwanted tooth movements?
- adjacent teeth can drift
- the tooth can overerupt to form a new contact point
what is the effect of placing a crown on a over-erupted tooth?
the tooth would be high in occlusion
how do you deal with an over-erupted tooth? what is the biggest issue with this?
re-prep the tooth and start again
- big issue = removing healthy tooth tissue frfr
what is the effect of drifting?
the space designated for the crown is lost
- will be difficult to seat
what is a provisional crown, why is it used?
a temp crown made to test out and try a potential change to aesthetic or occlusion
- patient can either go ahead or decide they dont like it
what are the ideal properties of a temp crown?
- aesthetics
- strong for function
- good contact points and margins to prevent PRF
- retentive, but easily removed when needed
- biocompatible
what are 3 ways of which temp crowns can be manufactured?
- direct custom made
- prefabricated
- indirect lab made
describe how temp crowns are directly, custom made
- chairside technique
- take impression of original tooth using putty index
- crown prep
- place bis-acryl composite on the impression
- place back down onto the tooth
= temp crown - trim off the excess, smooth and finish it
- place on tooth with cement using temp bond
what material is used for a direct custom made temp crown? what’s it called on clinic?
bis-acryl composite AKA Integrity on clinic
what is the excess material called on a temp crown?
flash
what cement is used? what’s it called on clinic?
zinc oxide eugenol temporary cement AKA tempbond
why do we use zinc oxide eugenol temp cement?
- doesn’t chemically adhere to tooth or crown
- retentive enough for function
pros of bis-aryl composite/integrity? (6)
- good strength
- no mixing required
- acceptable aesthetics
- good fit
- shades available
- can repair with composite
con about bis-aryl composite?
will stain easily
what if the tooth has no original morphology to take an impression of? what is the technique called?
Indirect Custom Made with a Diagnostic Wax Up
- still take an impression of current state
- send to lab
- build up tooth shape using wax
- use that as the mould
what is a vinyl mould?
a permanent reusable plastic mould of the dental arch
what are prefabricated temp crowns? describe the process
polycarbonate (anterior) or metal (aluminium or stainless steel for posteriors) crowns that are already pre-made and need altering to suit the patient
- crown prep
- select the crown you need for the tooth from range of sizes
- customise the crown to fit the tooth
3 Pros of Polycarbonate Prefabricated Crowns.
- come ready made
- hard wearing
- durable
when should integrity/zinc oxide eugenol be removed and why?
- when it is in a rubbery phase
- to avoid locking into undercuts - can be hard to remove
describe 2 pros and 4 cons of using metal prefabricated temp crowns for posterior teeth.
pros
- already made
- aluminium can adapt to the occlusion
cons
- margins can be sharp, ouch
- poor contact point
- metal taste
- aesthetics
with a metal prefabricated crown, what can you use to shape it?
BB crown shears
Describe the steps for the Lab Made Technique for Temp Crowns.
what is the purpose of them?
- indirect technique made in the lab on a model
- take impression of original tooth
- send to technician
- technician makes crown prep, temporary crown and returns back
- do the crown prep on the patient
- use integrity to help it fit
- purpose = if you want a longer lasting temp crown of 3-4 weeks
why may you want a temp crown to last up to 3-4 weeks?
if the patient is undergoing perio
- may be changes in gingival margin, changes the
why can lab made temp crowns be more favourable?
- technician uses acrylic materials (PMMA)
= stronger
= more aesthetic than chair side materials
what is the material PMMA?
polymethyl methacrylate
why is polymethyl methacrylate made in a lab? and NOT FOR DIRECT USE IN THE MOUTH?
the polymerisation process is highly exothermic (above 100 degree) and has a large degree of shrinkage
pros of PMMA
- good marginal fit
- strong
- can be polished
- durable
what cement is used for permanent crowns? why cant eugenol be used?
resin cements and non-eugenol cements
- called TempBond NE in clinic
eugenol can retard the polymerisation of resin
