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Restorative Dentistry > Post crowns > Flashcards

Post crowns Flashcards

1
Q

When is a post-retained crown used?

A

Used when there is a lack of coronal tissue which prevents a conventional direct restoration

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2
Q

What does a post help aid?

A

Retention

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3
Q

Do posts strengthen teeth?

A

NO, they weaken them

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4
Q

What is the purpose of a post?

A

Provides retention for the core by utilising the root canal

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5
Q

What is the purpose of a core?

A

Replaced dentine and provide retention for the crown

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6
Q

What is the purpose of the crown?

A

To restore morphology and provide function

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7
Q

What are the indications for a post retained crown?

A

Insufficient coronal structure to support a conventional restoration (due to carries/fracture)

Root treated tooth (indicated or elective)

Commonly single rooted anterior teeth

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8
Q

What is ferrule?

A

A band of metal that totally encircles the tooth extending 2, onto sound tooth tissue.

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9
Q

What amount of coronal dentine is needed as a minimum?

A

1.5-2mm coronal dentine needed supragingivally needed as a minimum

Ideally continuously around the tooth

Increases resistance to lateral forces reducing a longitudinal fracture

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10
Q

What happens if there is a lack of ferrule?

A

Stress in post canal - root fracture
Presence of a ferrule means that the forces can be directed along the long axis of the tooth root tissue

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11
Q

What other advantages are there of a ferrule?

A

Increases post length which is important for retention

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12
Q

What is the difference between a passive and an active post?

A

Passive post sits in the tooth whereas an active post actively engages in the tooth

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13
Q

How is an indirect post/core made?

A

Impression of root canal needed

Preserve tooth structure - undercuts must be removed

Must fit the canal well

Less risk of iatrogenic complications during prep

Time consuming

Costly

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14
Q

Describe the active direct posts

A

Threaded screw posts - flutes engage with the tooth

Most retentive type of post

High risk of root fracture as they place stress on the root

Not routinely used

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15
Q

Describe passive direct posts

A

Retention through prep and luting cements

Parallel post retention > tapered post

Tapered post is more likely to cause a root fracture due to a wedging effect

Smooth or serrated

Serrated increases retention by 30-40%

Smooth sided posts create more stress compared to serrated - increased risk of root fracture

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16
Q

What are the advantages of a SS post?

A

easy to use
strong
inexpensive

17
Q

What are the disadvantages of a SS post?

A

Rigidity can cause root fracture
Not aesthetic
Can corrode
Nickel allergy possible

18
Q

What are the advantages of a titanium post?

A

Non allergenic
Does not corrode

19
Q

What are the disadvantages of a titanium post?

A

Rigidity can cause a root fracture
Weaker than steel
Non aesthetic

20
Q

What are the advantages of a carbon fibre post?

A

Bonds to tooth
Flexible
Removable

21
Q

What are the disadvantages of a carbon fibre tooth?

A

Weak - prone to fracture
Non aesthetic - black

22
Q

What are the advantages of a glass fibre post? (quartz>silica)

A

Bonds to tooth
Flexible
High tensile strength
Removable
Aesthetic
Similar elasticity to dentine

23
Q

What are the disadvantages to glass fibre/quartz silica posts?

A

Weaker than metal posts

24
Q

What are the benefits of fibre posts?

A

Glass content allows bonding
Bonding reduces root stress
Allows use of shorter, thinner posts conserving tooth tissue
Shape less important for retention
Depth of cure is same as for metal posts - cement considerations important

25
Q

What are the 4 considerations during post prep?

A

Ferrule
Type of post
Length of post
Width of post

26
Q

How much GP should be left apically?

A

3-5mm
5mm for more curved roots

27
Q

Is retention better for a longer or shorter post

A

Longer post

Shorter post introduce greater stress than longer posts

28
Q

At what length is retention adequate?

A

2/3rds root length

Post:crown
1.5:1

29
Q

What are the properties of the post width?

A

Wider post prep (greater removal) increases the risk of root fracture

Thicker/wider posts introduce more stress. effect is pronounced in shorter posts

Post length is more important in generating stresses

Post diameter no greater than 1/3rd root width at length

30
Q

Why is composite the best core to use?

A

Fractures are not catastrophic - composite fracture before tooth

Avoid amalgam in MOD cavity in root filled teeth

31
Q

Which cements are used in cast posts

A

GIC
ZnP

32
Q

Which cements are used in metal posts

A

GIC
ZNP

33
Q

Which resins are used in fibre posts

A

Self or dual cured panacea/rely X unices

34
Q

Tooth related reasons: post crowns fail?

A

Insufficient tooth
Caries
Root fracture
Endo fails
Perio fails

35
Q

Restoration related post-crown fails?

A

Inadequate post design
Crown/post fracture
Occlusal factors
Cement failure

36
Q

Iatrogenic reasons for failure

A

Perforation during prep

Restorative Dentistry (11 decks)

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