Cores for Teeth with Vital Pulps Flashcards
What are the indications to make cores for teeth with vital pulps
- Teeth that are vital and have lost a lot of tooth tissue and where RCT is unnecessary and need for it in the near future is unlikely
- Periodontal condition and hard tissues are stable
- You can never place an indirect restoration (crown) without a core being constructed first
What materials can benefit the most from additional retention methods when making a core
- Amalgam
- Composite
What additional retention features can be added to a prep
- Slots
- Grooves
- Amalgapins
What problems can occur with the pulp after a crown has been prepared and fitted
- Teeth can become non-vital
- ## Stressed pulp syndrome can lead to pulp death and necrosis
How close can you go to the pulp when you start to cause irreversible symptoms
If you go nearer than 1mm its likely to cause irreversible symptoms
How far from the pulp can you be until changes start to occur in the pulp
2mm.
Name some materials that can be used to protect a thin wall of dentine
- Setting calcium hydroxide cement
- Dentine bonding agents
- Glass ionomer
What advantages of using setting calcium hydroxide cement to protect a thin wall of dentine are there
- High pH stimulates tertiary dentine and walls of the pulp chamber to protect the nerve
- Toxic to carious bacteria
What disadvantages of using setting calcium hydroxide cement to protect a thin wall of dentine are there
- V brittle so should only be applied thinly and only in discrete areas of thin dentine
- V voluble and micro leakage can cause it to be leached away
- Doesnt bond to tooth structure
What is the aim of dentine bonding agents when trying to protect a thin wall of dentin
- Aim is to seal the cut dentine tubules after removal of the smear layer
What is a disadvantage of using dentine bonding agents to protect a thin wall of dentine
- They are readily hydrolysed
Why is using Glass ionomers to protect a thin wall of dentine not suitable
- Low bond strength of 3-5MPa compared to 20MPa with resins
- Its brittle
- Easily leaches away
- Etch and bond to composite is not comprehensive
What are the advantages of using Amalgam as a core (this is usually the first choice)
- Strong af
- Easy to mix
- Relatively cheap
- Good longevity
What are the disadvantages of using Amalgam as a core (this is usually the first choice)
- Colour
- Not chemically adhesive
- Environmental issues
What are the disadvantages of using composite resin cores
- Composite is improving but still has a problem of water inclusion over time (expansion of 8%)
- Initial polymerisation shrinkage
- Bonds to tooth but how long for, saline is the weakest link
- If trying to remove it can be hard to distinguish between tooth or composite
- Doesnt bond to metal pins or posts
What can be used to increase the retention of your core
- Undercuts in the remaining tooth tissue
- Pins
- Slots, grooves and amalgapins
- Adhesives
What are the 3 main types of dentine pins
- Cemented
- Friction
- Self Tapping
List the 3 main dentine pins in terms of amount of retention
- Friction = high stress/high retention
- Self Tapping = Medium stress/medium retention
- Cemented = Least stress/Least retention
What are the problems with using dentine pins
- Cause stress in dentine leading to micro cracks, which can lead to micro leakage and then caries
- Pins don’t bond with amalgam alloys or composite
- Hole prep is 2mm deep so is near the pulp
- Only go in about 50-70% of hole prep depth so a space is left where bacteria can build up
What are amalgapins
- These are small holes that are large enough to an instrument to place and pack amalgam, this must be in a safe position and 2mm deep
What bur is often used to cut slots and grooves
- A small pear shaped diamond bur
Why are adhesives for amalgam not successful long term
- They leak and can cause catastrophic failure
SUMMARY POINTS FOR THE CORES OF TEETH WITH VITAL PULPS LECTURE
- Avoid use of the dentine pins
- Remove as little tooth tissue as possible
- Use amalgam if possible
- Remember poor cores are the biggest cause of mechanical crown failure
