10 - Posts Flashcards Preview

DENTAL MATERIALS > 10 - Posts > Flashcards

Flashcards in 10 - Posts Deck (18):
1

posts - indications for use?

- root filled teeth
- severely broken down coronal tooth structure: inadequate retention for restoration or core
- weakened remaining tooth structure

2

posts: can be? what is each made of?

- cast (indirect): metal
- prefabricated (direct): metal, non-metal

3

posts: 2 types? describe each

- active posts: threaded
- are tapered or parallel

- passive posts: smooth sided or serrated
- are tapered or parallel

4

cast (indirect) post and cores: how is GP root filling removed?
how does this allow the cast post system to be used?

- using non end cutting burs e.g. gates glidden
- the size is gradually increased and transferred to the appropriate size twist drill for the cast post system to be used

5

how does the cast post cool down?
what are the implications of this?
what could result?

- it cools from the outside. it contracts while solidifying, sucks molten gold from the core.
- this could create porosities at the junction of the post
- could lead to increased likelihood of fracture

6

coring: if the alloy cast is cooled quickly, how does the composition of the alloy change?
- what does this change lead to?
- how to improve the mechanical properties of the cast alloy?

- it varies at different sites due to premature precipitation of some components of the alloy
- different areas richer in one material to another, sets up electrolytic cells -> corrosion leading to a weaker structure
- it should be cooled slowly

7

which class of alloy is used for cast post and core?

- usually type IV (extra hard)

8

prefabricated (direct) metal posts: what materials can they be made of?
which one is stronger? but what does it have risk of?

- platinum-gold-palladium
- brass
- nickel chromium (stainless steel)
- pure titanium
- titanium alloys
- chromium alloys

- stainless steel. risk of adverse tissue response to nickel (for technician, unlikely for patient).

9

prefabricated metal posts: what has stimulated concerns about the use of these posts?

- excessive stiffness (modulus of elasticity)
- corrosion of the post
- post & root fracture?

10

prefabricated metal posts - active threaded posts:
- possible materials they are made of?
- reamers?
- square cross cut head - how is it beneficial?
- examples of other active posts?

- titanium, stainless steel, goldplated SS versions
- reamers screw post into root
- helps with retention of core
- self-threading posts: parapost XT (titanium alloy parallel), radix anchor (titanium alloy parallel)

11

prefabricated metal posts - passive: most are in what form?
interconnecting serrations help with?

- parallel
- parapost XH:
serrated pattern
titanium alloy
parallel
vented via interconnecting serrations - help luting cements set into pattern, provides mechanical retention

12

luting cements for metal posts: choice based upon?
ideal cements are?
what not to use?

- choice is based upon retrievability; metal posts are removed using ultrasonics meaning that the cements should be relatively brittle
- zinc phosphate, zinc polycarboxylate, GI, RMGI
- no adhesive resin luting cements e.g. panavia

13

prefabricated non-metal posts: name 3

- zirconia
- ceramic
- fibre reinforced resins: carbon fibre, glass fibre, woven polyethylene reinforced composite

14

prefabricated non-metal posts: zirconia and ceramic - issues with use?

- brittle
- high modulus of elasticity, may lead to fracture
- zirconia difficult to remove with USS

15

prefabricated non-metal posts - fibre reinforced posts:
advantage?
disadvantage?

- strong, but can flex
- absorbs and transfers forces similar to dentine

- dark color - cannot transmit light, not suitable for aesthetic restorations

16

prefabricated non-metal posts: glass (quartz) fibre posts - embedded where? made out of?

- embedded longitudinally in an epoxy resin (die?)
- 60% fibre 40% resin

17

advantages of fibre based posts?

- good flexural str
- less rigid than metal
- cement with adhesive resin cements
- white or transparent quartz fibre posts - translucent
- all ceramic bonded crowns
- easier to remove if required
- must be covered, will delaminate in moist environment

18

luting cements for non-metal fibre posts: choice based on?

- based on retrievability
- fibre posts drilled out, bond to post and dentine walls beneficial
- therefore luting cements needs to be resin based
- ideally self etching resin luting cements e.g. RelyX Unicem