Interim Restorations for Teeth Undergoing Endo Therapy

Question 1

Endo tx aim?

Answer 1

Eliminate bac from the tooth

Tooth maintained in disinfected state by preventing any further ingress of bac during and after tx

Question 2

Steps to successful endo?

Answer 2

1. Diagnose and remove the cause of disease
2. Use an antiseptic technique
3. Mechanically instrument the canals to enlarge them
4. Irrigate the canals with one or more antibac soln
5. Medicate the canals with an antibac agent
6. Temporarily restore the tooth to avoid bac ingress during and after tx
7. Fill the root canal system once disinfected
8. Restore the tooth to normal function

Question 3

What can occur if you do not follow these steps?

Answer 3

Risk the potential for:

• Bac already in the tooth to survive and proliferate
• New organisms to enter the tooth and establish colonies

= Continuation of apical periodontitis or the development of a new apical periodontitis lesion

Question 4

Define interim restoration

Answer 4

A restoration which has been placed in the tooth after the previous restoration, caries, cracks etc have been removed at the commencement of endo tx
This restoration will remain in place whilst the endo tx is being performed and after the RC filling is complete until the definitive coronal restoration is placed

Question 5

Define temporary restoration

Answer 5

Restoration placed in an endo access cavity

Likely to have been cut through an interim restoration in most cases

Question 6

What are the most common pathways of bac entry?

Answer 6

Caries
Cracks
Exposed dentine
Broken down restoration margins

Question 7

When should endo tx never be performed?

Answer 7

Through a failing or poor quality restoration

Or through a temporary restoration

Question 8

What advantages does an interim restoration prior to endo tx provide?

Answer 8

Structural integrity of tooth
Support for weakened cusps
Coronal seal
Rubber dam will be easy to apply, with appropriate structure for the clamp to grip
No ideal access cavity can be cut
No risk of leakage through the coronal restoration when using irrigants
A temp restoration will be retained better
A well restored tooth will be more comfortable and functional for pt

Question 9

When may an interim restoration not be required?

Answer 9

If the tooth is unrestored or has only a small intracoronal restoration (not compromised) (large or medium restorations should be replaced)

Question 10

List the appropriate materials for interim restorations

Answer 10

Composite
RMGIC
Amalgam

Question 11

What materials are NOT suitable for interim restorations?

Answer 11

IRM

GIC

Question 12

What may be needed for large restorations or cracked teeth?

Answer 12

Support by metal bands

• An ortho bad
• Copper rings

OR

Reduce occlusal surface and rebuild the tooth using composite or amalgam (RMGIC not suitable)

Question 13

What will a metal band provide?

Answer 13

Support of weakened tooth structure, esp cusps

Prevent progression of cracks

Question 14

What principles should be applied when using a metal band?

Answer 14

Ensure band is correct size for tooth
GIC or RMGIC should be used when luting the band
Provide good margins = good hygiene
Ensure restoration harmonises with the occlusion

Question 15

How to manage teeth with full coverage crowns? Why?

Answer 15

Removed prior to endo tx

Allows assessment of underlying tooth structure
Identification of hidden pathology
Better orientation when undertaking endo tx
Better coronal seal

Question 16

When should crowns be left prior to endo tx?

Answer 16

If it’s certain that there is no chance of coronal leakage or pathology hidden under the crown

Question 17

How to remove crowns?

Answer 17

Take a sectional putty impression of the tooth prior to removing the crown = stent to make temp restoration
Make a groove through the crown to tooth tissue and twist instrument into the groove
If unsuccessful, continue the groove occlusally, if still unsuccessful, lingually

Question 18

How to make a provisional crown?

Answer 18

Protemp/quicktemp or trim/snap in the putty stent
Ensure crown is fitting well, good margins
Can cement with zinc phosphate rather than tempbond
Can seal dentinal tubules with a dentine bonding agent
OR construct a provisional crown using a pre-formed metal crown

Question 19

How to manage provisional restorations during endo tx?

Answer 19

Should be removed prior to undertaking endo tx and replaced between appts and at end of tx
Access cavity filled with IRM/GIC - crown falls off = tooth is sealed
RCT complete - provisional - definitive crown asap

Question 20

How to manage teeth with post crowns?

Answer 20

Temp can be very challenging
No temporary and restore the access with an adhesive restoration e.g. GIC
OR
Temporary partial overdenture and seal the access

Question 21

RCT temporary restoration desirable properties?

Answer 21

Durable and effective coronal seal
Cheap
Easy to remove
Obvious difference between tooth tissue/interim restoration to ensure no more tooth tissue is removed upon removal

Question 22

Examples of temporary restoration materials?

Answer 22

Zinc phosphate or Calcium sulphate based materials e.g. cavit/cortisol
GIC
RMGIC
IRM
Composite

Top layer - gic, irm etc
2nd layer - sponge or soft temp material (cavit/cortisol)
Then calcium hydroxide paste in the canal

Question 23

Criteria for temporary restorations?

Answer 23

3mm in depth to provide adequate seal
Cotton wool wicks saliva and bac through the restoration
Foam pellets do not do this and are compressed under the temp restoration allowing easier removal
Cavit/cortisol - excellent double seal but more difficult to remove
Pt return if temp comes off to minimise bac contam

Question 24

What to do upon completion of endo tx/how to place a temp restoration?

Answer 24

Cut GP points back to ADJ
Place GIC in access cavity but leave at least 3mm more coronally
Restore coronal aspect with amalgam/GIC
Indirect restoration - immediately or following a period of monitoring

Question 25

Why do posterior teeth undergoing endo tx need protection?

Answer 25

Reduced tooth structure
Loss of marginal ridge
Access cavity
Axial forces can flex cusps 
Non-axial forces are even more damaging

Question 26

How does occlusion impact the protection of posterior teeth?

Answer 26

ICP - directs forces axially down posterior teeth
Lateral guidance can either be group function or canine guided
Canine guided = protects posterior teeth
Group function = damaging to posterior teeth, premolars more at risk, premolars weaker due to more tooth tissue loss
Non-working side interferences are damaging for root treated teeth
Forces on posteriors can lead to cusp fracture

Question 27

When does the risk of posterior tooth fracture increase?

Answer 27

When more heavily restored = weakened tooth
Occlusal
Occlusal plus 1 marginal ridge loss
Occlusal, both MR loss
Occlusal, both MR, MOD
Occlusal, both MR, MOD, palatal/buccal restoration

Question 28

How to protect posterior teeth with weakened tooth structures?

Answer 28

Interrim measures

• Occlusal adjustments to decrease loading
• Cuspal reduction with overlay restoration
• Cemented ortho band
• Interim crown

Definitive measures

• Cusp reduction and overlay restoration
• Full crown
• Onlay/overlay indirect restoration

Question 29

How to make occlusal adjustments to decrease loading?

Answer 29

Articulating paper - 1 colour records ICP, another records lateral excursions
Remove lateral excursions with rugby bur

Question 30

Why be careful with adjusting the occlusion?

Answer 30

Can introduce interfering contacts
Loss of ICP contacts
Transfer guidance to other teeth

Question 31

How to reduce the cusp and provide an overlay restoration?

Answer 31

Reduce cusps by 2-3mm with a bur
Build up tooth with composite/amalgam
Restore ICP contacts
Keep excursive contacts to a minimum

Question 32

Onlay/overlay indirect restoration?

Answer 32

Conservative compared to full crown
Strong
Can be cemented
Gold/high strength porcelain/composite

Question 33

Full crown protection?

Answer 33

Full coverage = good seal

Destructive - v thin dentine walls remaining