Interim restoration and protection of teeth undergoing endo therapy

Question 1

Eight steps to successful endo

Answer 1

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

Question 2

Failure to comply with steps to successful endo will risk potential for

Answer 2

Bacteria already in tooth to survive and proliferate
New organisms to enter the tooth and establish colonies
–> outcome of this will be continuation of apical periodontitis which was already present, or development of new apical periodontitis lesion

Question 3

Interim restoration definition

Answer 3

A restoration that has been placed in tooth after previous restoration, caries, cracks etc have been removed at commencement of endodontic tx
Will remain in place whilst endo tx is being performed and after the RCT has been completed until definitive coronal restoration placed

Question 4

Temporary restoration definition

Answer 4

A restoration placed in an endo access cavity

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

Question 5

What is the main cause of pulp and perapical disease

Answer 5

Presence of bacteria within tooth

• important to determine how bacteria entered tooth initially
• clinician must then remove pathway of entry to prevent further bacterial ingress

Question 6

Most common pathways of entry for bacteria

Answer 6

Caries
Cracks
Exposed dentine
Broken down restoration margins

Question 7

Indentifying pathway of bacterial entry to tooth

Answer 7

Initial clinical and rad assessment often fails prior to endo
For this reason existing restoration should ideally be replaced with a good quality, well-sealed restoration
-can be considered ‘investigation’ of tooth to assess restorability and overall prognosis
Endo should never be undertaken through failing or poor quality restoration, or through a temp

Question 8

Advantages to good interim restorations prior to endodontic treatment

Answer 8

Structural integrity to tooth
Support for weakened cusps
Coronal seal
Rubber dam will be easy to apply, with appropriate tooth/ restoration structure for clamp to grip to
An ‘ideal’ access cavity can be cut
No risk of leakage through coronal restoration when using irrigants
Temporary restoration will be retained better
Well restored tooth will be more comfortable and functional to patient
Restoration can be used as core restoration if indirect restoration is required later

Question 9

When may an interim restoration not be required?

Answer 9

If the tooth is unrestored (for example a none vital pulp following trauma) or has only a small-intracoronal restoration
However, if there is any suspicion that intra-coronal restoration is compromised, this should still be replaced

Question 10

Appropriate material interim restorations are

Answer 10

Composite
Resin-modified glass ionomer cement
Amalgam

Question 11

Inappropriate material interim restorations are

Answer 11

IRM

Glass ionomer cement

Question 12

Large restorations or teeth with cracks may need to be

Answer 12

Supported by a metal band e.g.
-an orthodontic band
-copper rings
Occlusal surface could be reduced and rebuilt strong restorative e.g. amalgam or composite but NOT RMGIC

Question 13

Advantages of metal band placement

Answer 13

Support of weakened tooth structure, especially cusps

Prevent progression of cracks

Question 14

Principles for metal band placement

Answer 14

Ensure the band is the correct size for the tooth
Chemically curing cement (e.g. GIC or RMGIC) should be used when luting the band
Provide good margins to allow adequate OH
Ensure restoration harmonises with occlusion

Question 15

Interim restorations - teeth with full-coverage crowns

Answer 15

Ideally, full coverage crowns should be removed prior to commencing endo
Should only be left in-situ if it is certain that there is no chance of coronal leakage or pathology under the crown

Question 16

Advantages of removing ful coverage crowns

Answer 16

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

Question 17

Removing crowns

Answer 17

Take sectional putty impression of the tooth prior to removing the crown to use as a stent to make temp
Make groove through crown through to tooth tissue/ core material and twist instrument into groove
If unsuccessful, continue groove occlusally, then if still successgul, lingually

Question 18

Making a provisional crown

Answer 18

 Ideally use a temporary crown composite
material (eg Protemp or Quicktemp) or coldcure acrylic (Trim or Snap) in the putty stent
 Ensure the crown is well fitting with excellent
margins
 Consider cementing with zinc phosphate
rather than Tempbond
 Consider sealing the dentinal tubules with a
dentine bonding agent
 Alternatively, construct a provisional crown
using a pre-formed metal crown, adapted to fit
with provisional crown material

Question 19

Provisional crowns, temporary restorations during endo

Answer 19

 Provisional crowns should be removed prior to
undertaking endodontic treatment and replaced
between appointments and at the end of treatment
 The access cavity cut into the underlying tooth
structure should be restored with a temporary
restoration (eg IRM, GIC etc) and not left open – If the
temporary crown falls off the tooth will still be sealed
 Once treatment is completed, provision should be
made for a definitive crown to be placed as soon as
practicable

Question 20

Teeth with post crowns - options

Answer 20

Interim restorations for teeth with post crowns can be very challenging- some research suggests that teeth with temp post crown has as much contamination as teeth with no restoration in situ
 Prior to cementing a temp post crown it may be prudent to place cavit at base of post crown
prep to improve seal, however this can pose
challenges in removal
 Ideally, if pt will allow, the best solution is to
provide no temp post crown and simply restore the
access with an adhesive restoration such as GIC
 Alternatively, a temporary partial overdenture can be
provided and the access sealed as above

Question 21

What role do temporary restorations play?

Answer 21

Occupy access between apts

Question 22

Properties and requirements of temporary restorations

Answer 22

Effective and durable coronal seal
Ease of removal at next apt
Obvious difference between tooth tissue interim restoration to allow removal without of removing more tooth tissue
Inexpensive

Question 23

Potential materials for temporary restorations

Answer 23

Zinc-oxide/ calcium-sulphate based material e.g. Cavit, Coltisol
Zinc-oxide based reinforced intermediate restorative materials e.g. IRM
GIC
Resin-modified GIC
Reinforced GIC e.g. Ketac Fil, Ketac Silver
Composite

Question 24

What goes under IRM but over CaOH paste?

Answer 24

Either
1. Sponge pellet (compressed under temp allowing easier removal)
2. Soft temporary material e.g. Cavit or Coltosol (excellent ‘double seal’ but can be more diificult to remove
Cotton wool should not be used underneath as it ‘wicks’ saliva (and therefore bacteria) through restoration

Question 25

Dimensions of temps

Answer 25

At least 3mm in depth in order to provide adequate seal

Question 26

What if temp is lost between apts?

Answer 26

Pt should be told to return in order to minimise bacterial contamination

Question 27

Temporary restorations on completion of endo

Answer 27

 Cut the gutta percha back to the ADJ
 Place GIC in the access cavity but leaving at least 3mm more coronally
 Restore the coronal aspect with composite or amalgam
 If an indirect restoration is required decide if this is to
be undertaken immediately or following a period of
monitoring

Question 28

Why do posterior teeth undergoing endodontic

therapy require protection?

Answer 28

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

Question 29

Occlusal terminology of relevance to endodontically

treated posterior teeth

Answer 29

ICP: will generally direct forces axially down posterior teeth
Lateral guidance: teeth which are involved in guiding lateral excursions, can be either canine guided, or group function

Question 30

Canine guidance or group function for protection of posterior teeth?

Answer 30

 Canine guidance is usually ideal as it protects the posterior
teeth
 Group function is damaging to posterior teeth, especially if
they have been root treated
 Premolars are most at risk as they are more commonly
involved in group function compared to molars
 Premolars are often also weaker due to comparatively more
tooth tissue loss
 Other forces, such as non-working side interferences are
also extremely damaging for root treated teeth

Question 31

What may forces on posterior teeth eventually lead to?

Answer 31

Cusp fracture, the risk of which increases as tooth becomes more heavily restored

Question 32

Options for protecting posterior teeth with weakened structure:

Answer 32

Interim measures
 occlusal adjustment to reduce loading
 cusp reduction and overlay restoration
 cemented orthodontic band
 interim crown (metal/composite/acrylic)
Definitive measures
 cusp reduction and overlay restoration
 onlay/ overlay indirect restoration
 full crown

Question 33

Protection of posterior teeth: occlusal adjustment to reduce occlusal loading

Answer 33

Use occlusal marking foil to highlight contacts in ICP - first colour
Use a different colour of marking foil to highlight contacts in lateral
excursion - second colour
Use a diamond bur to:
-keep ICP contacts
-remove lateral excursive contacts
Need to be careful when adjusting occlusal contacts
Ideally, occlusal adjustments should first be
undertaken on study casts mounted on a semiadjustable articulator, mounted with a facebow

Question 34

Every change that you make can have a knock-on effect for other teeth, e.g.:

Answer 34

Transfer of guidance to other teeth
Introduction of interfering contacts
Accidental loss of ICP contacts

Question 35

Protection of posterior teeth: cusp reduction and overlay restoration

Answer 35

Reduce cusps by 2-3mm with a bur
 use composite or amalgam to build tooth up
 ensure ICP contacts are restored
 keep excursive contacts to a minimum
Onlay/ overlay indirect restoration
 provides a strong, indirect
restorative option, whilst still
conserving tooth tissue compared
to a full coverage crown
 traditionally made from gold, but can also be constructed from highstrength porcelain or composite
 can be cemented with an adhesive
cement

Question 36

Protection of posterior teeth: full crown

Answer 36

Provides full coverage and
therefore good seal, however, at the expense of more tooth tissue reduction
Remember – the tooth will have an access restoration AND full coverage preparation which will
leave very thin walls of dentine remaining