FIXED PROS - Temporary Crowns

Question 1

why are temporary crowns needed? (6)

Answer 1

• 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

Question 2

why may you get dentinal sensitivity in crown prep?

Answer 2

most of the enamel is removed
dentinal tubules are exposed

Question 3

what is the hydrodynamic theory?

Answer 3

a mechanism which describes how dentinal sensitivity occurs

Question 4

describe the hydrodynamic theory.

Answer 4

• dentinal tubules are exposed to external stimuli
• as response, change in fluid flow
• leads to pain and sensitivity in the pulp

Question 5

why can teeth move if a temp crown isn’t placed?

Answer 5

all contact points, mesially, distally and occlusally are removed

Question 6

why do we want to prevent unwanted tooth movements?

Answer 6

• adjacent teeth can drift
• the tooth can overerupt to form a new contact point

Question 7

what is the effect of placing a crown on a over-erupted tooth?

Answer 7

the tooth would be high in occlusion

Question 8

how do you deal with an over-erupted tooth? what is the biggest issue with this?

Answer 8

re-prep the tooth and start again

• big issue = removing healthy tooth tissue frfr

Question 9

what is the effect of drifting?

Answer 9

the space designated for the crown is lost
- will be difficult to seat

Question 10

what is a provisional crown, why is it used?

Answer 10

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

Question 11

what are the ideal properties of a temp crown?

Answer 11

• aesthetics
• strong for function
• good contact points and margins to prevent PRF
• retentive, but easily removed when needed
• biocompatible

Question 12

what are 3 ways of which temp crowns can be manufactured?

Answer 12

1. direct custom made
2. prefabricated
3. indirect lab made

Question 13

describe how temp crowns are directly, custom made

Answer 13

• chairside technique

1. take impression of original tooth using putty index
2. crown prep
3. place bis-acryl composite on the impression
4. place back down onto the tooth
   = temp crown
5. trim off the excess, smooth and finish it
6. place on tooth with cement using temp bond

Question 14

what material is used for a direct custom made temp crown? what’s it called on clinic?

Answer 14

bis-acryl composite AKA Integrity on clinic

Question 15

what is the excess material called on a temp crown?

Answer 15

flash

Question 16

what cement is used? what’s it called on clinic?

Answer 16

zinc oxide eugenol temporary cement AKA tempbond

Question 17

why do we use zinc oxide eugenol temp cement?

Answer 17

• doesn’t chemically adhere to tooth or crown
• retentive enough for function

Question 18

pros of bis-aryl composite/integrity? (6)

Answer 18

• good strength
• no mixing required
• acceptable aesthetics
• good fit
• shades available
• can repair with composite

Question 19

con about bis-aryl composite?

Answer 19

will stain easily

Question 20

what if the tooth has no original morphology to take an impression of? what is the technique called?

Answer 20

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

Question 21

what is a vinyl mould?

Answer 21

a permanent reusable plastic mould of the dental arch

Question 22

what are prefabricated temp crowns? describe the process

Answer 22

polycarbonate (anterior) or metal (aluminium or stainless steel for posteriors) crowns that are already pre-made and need altering to suit the patient

1. crown prep
2. select the crown you need for the tooth from range of sizes
3. customise the crown to fit the tooth

Question 23

3 Pros of Polycarbonate Prefabricated Crowns.

Answer 23

• come ready made
• hard wearing
• durable

Question 24

when should integrity/zinc oxide eugenol be removed and why?

Answer 24

• when it is in a rubbery phase
• to avoid locking into undercuts - can be hard to remove

Question 25

describe 2 pros and 4 cons of using metal prefabricated temp crowns for posterior teeth.

Answer 25

pros
- already made
- aluminium can adapt to the occlusion

cons
- margins can be sharp, ouch
- poor contact point
- metal taste
- aesthetics

Question 26

with a metal prefabricated crown, what can you use to shape it?

Answer 26

BB crown shears

Question 27

Describe the steps for the Lab Made Technique for Temp Crowns.

what is the purpose of them?

Answer 27

• indirect technique made in the lab on a model

1. take impression of original tooth
2. send to technician
3. technician makes crown prep, temporary crown and returns back
4. do the crown prep on the patient
5. use integrity to help it fit

• purpose = if you want a longer lasting temp crown of 3-4 weeks

Question 28

why may you want a temp crown to last up to 3-4 weeks?

Answer 28

if the patient is undergoing perio
- may be changes in gingival margin, changes the

Question 29

why can lab made temp crowns be more favourable?

Answer 29

• technician uses acrylic materials (PMMA)
  = stronger
  = more aesthetic than chair side materials

Question 30

what is the material PMMA?

Answer 30

polymethyl methacrylate

Question 31

why is polymethyl methacrylate made in a lab? and NOT FOR DIRECT USE IN THE MOUTH?

Answer 31

the polymerisation process is highly exothermic (above 100 degree) and has a large degree of shrinkage

Question 32

pros of PMMA

Answer 32

• good marginal fit
• strong
• can be polished
• durable

Question 33

what cement is used for permanent crowns? why cant eugenol be used?

Answer 33

resin cements and non-eugenol cements
- called TempBond NE in clinic

eugenol can retard the polymerisation of resin