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ACS > Restoration of a root filled tooth II > Flashcards

Restoration of a root filled tooth II Flashcards

1
Q

Challenges of total crown replacement?

A

Restoration needs to be retained by the root
It must allow stress distribution
Must not cause root fracture
Must be durable

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2
Q

Principles in crown retention?

A

Retain as much dentine mass as possible
Restore dentine mass with a suitable material
Use an intra-radicular post in combination with the above if retention is compromised

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3
Q

Core build up materials materials?

A

Amalgam
Core composite
Glass ionomers
Compomers

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4
Q

Core build up: features of amalgam?

A

Strong
Reliable
Successful
Adhesion?

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5
Q

Core build up: features of composite?

A

Strong
Adhesive
Predictable?
Mismatch in thermal expansion

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6
Q

Core build up: features of glass ionomers?

A 
Low tensile strength - brittle
Unreliable
Poor adhesion
Excellent thermal match to tooth 
Dimensionally stable 
Reserve for patches only
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7
Q

Intra-radicular posts

A

Retain and support the core and coronal restoration
Aid in transferring functional loads to as wide an area as possible
Posts do not increase tooth fracture strength
Ideally a rigid material or elastic with a ferrule
Appropriate dimensions

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8
Q

What to consider with an intra-radicular post?

A 
Parallel sided or tapered
Surface configuration
Active or passive fit
Length, width
Ferrule
Anti-rotation
Choice of material
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9
Q

Why are some intra-radicular posts parallel sided?

A

Resistance to axial forces

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10
Q

Tapered intra-radicular posts - what can they create?

A

A wedge effect

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11
Q

What to consider with surface configuration?

A 
Casting roughness
Sandblasted
Etched
Grooved 
Fluted

= Want to increase the surface area e.g. by increasing the casting roughness or sandblasting it = mechanical retention

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12
Q

How to aid retention of a post with an active system?

A

A thread cuts into the post-hole wall to aid post retention

= Greater stresses into the system

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13
Q

How to aid retention of a post with a passive system?

A

Post is retained in the hole by means of an adhesive lute

Surface of the post may be configured to aid adhesion

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14
Q

Pros and cons of the post being deeper in the tooth?

A

Deeper poles distribute stress better and increase retention
BUT
Disturb apical seals and destroy tooth substance

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15
Q

What should the post design be?

A

3-4mm short of apex OR
2/3 of total root length
1/2 greater than crown height

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16
Q

Why should posts be as narrow as possible but within the strength limits of the material?
What is wrong with this?

A

Strength is more dependent upon the outer perimeter of the root and are conservative
BUT narrow posts are weak and easily rotated

17
Q

Ferrule (most important) - what is it?

A

Distance between the crown margin and interface between core and dentine
Greater ferrule = greater resistance to breakage of the crown
Improves retention and prevents post from bending and fracturing

18
Q

Ferrule - what should it be?

A

At least 1.5mm of vertical sound tooth structure between the crown margin and the dentine-core interface that wraps around the whole tooth

19
Q

Wha can provide the anti-rotation requirement of the post?

A

The irregular shape of the access cavity

Or can insert an anti-rotational pin

20
Q

Prefabricated posts - what are they good for?

A

Circular post holes
Divergent roots
Narrow post holes - use SS

21
Q

Cast posts - when to use?

A

Non-circular root canals
Direct/indirect technique
Choice of alloy - cobalt chrome, gold, nickel chrome
Path of withdrawal and insertion

22
Q

What materials are used for posts? Characteristics?

A

Metal alloys

  • Strong, corrosion resistant
  • Prefabricated: SS, TiVAL
  • Cast - gold alloys, nickel-chrome

Other prefabricated materials:

  • Resin reinforced carbon fibre
  • Ceramics
  • Composite fibre
23
Q

Which post system - rigid and elastic materials?

A

Rigid:

  • SS
  • Gold alloys
  • Ni-Cr alloys
  • Zirconium ceramics

Elastic

  • Titanium
  • Ti alloys
  • Carbon fibre
  • Composite fibre
24
Q

Zirconia features?

A

High modulus of elasticity = extreme stiffness

Acceptable strength

25
Q

Carbon fibre?

A

Low modulus of elasticity

V difficult to remove

26
Q

What is the parapost system?

A 
Complete integrated system
Parallel posts
Matching instruments and posts 
Anti-rotational pins
Multiple clinical techniques 
Multiple materials and combinations
27
Q

Parapost XP?

A

1 visit technique
Traditional parapost head design with X pattern
Indicated for amalgam cores and multi-rooted teeth where space is limited
Titanium or SS
19mm long

Parallel sided
- Evenly distributes functional forces, eliminating wedging effect of a tapered post

Passive fit
- Eliminates stress in the dentine compared to a screw post

28
Q

Aesthetic crown materials?

A

All ceramic

Ceramic bonded to metal

29
Q

What to do when a root filled tooth fails?

A

Cause analysis - biological or mechanical
Elimination of cause
Prevention of recurrence
Restoration of function and aesthetics using the most appropriate materials and techniques

30
Q

Failure mechanisms of RF teeth?

A

Fatigue disintegration of labial margins
Opening of palatal margins
Bending of post, rotation, dislodgement, fracture of post
Fracture of root

31
Q

Biological failure?

A

Periapical abscess
Periodontal disease
Recurrent caries

32
Q

Mechanical failure?

A

Inappropriate coronal retention
Unfavourable displacing forces
Loss of structural integrity of tooth
Inappropriate use of materials and techniques

33
Q

Success with post core crowns?

A

Lateral/vertical condensation with GP and bland root sealer
Leave 3-5mm GP at apical root terminus
Use a passive, adhesively retained custom post
Ferrule design for crown prep

ACS (23 decks)

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