post and core Flashcards
What type of post is best for retention?
Active>passive and parallel>tapered
Cast P+C are made from what type of gold?
Type 3 and noble alloys
What materials are prefab P+C made out of?
SS, titanium, ceramic, fiber(carbon, glass, quartz), brass, zirconia
Rate how retrievable posts are from more retrievable to least.
Fiber > Metal > ceramiz/zirconia/titanium
What is a significant weakness of retrospective studies?
It’s probably missing important pieces of info bc dentists don’t record EVERY little detail.
What are KOLs (Key opinion leaders)
recruited and paid to research product/publish results
Gold standard trials must be:
Randomized, controlled (txs are assigned randomly), and blinded (evaluators don’t know which pt received what tx.
Besides for the post, other factors that contribute to the success of P+C?
tooth type, post length, ferrule effect, cement used, DENTIN left
What type of tooth would be good with a 1. Parapost? 2. Cast? 3. Screw post?
- Parapost - long, straight, circular canals in anterior
- Cast= short, curved, ovoid canals in molars
- Screw = very short canals
When do you definitely need a P+C?
loss of 2 cusps<2mm ferrule
KOLs may blame failure on ____ instead of post?
cement or endo
What are the risks with post placement?
Perforation or loss of apical seal, inc risk of root fracture (esp if post is too large)
What makes for a good prognosis?
- Adequate ferrule: Best predictor of success
- Adequate post length
- Cuspal coverage for posteriors
- Use of retrievable posts
Things that make failure more likely?
- Threaded posts
- inadequate dentin/ferrule height
- use of post that are difficult to retrieve
- use of post in multi-rooted molar
Types of failure?
- loss of retention (of crown, core, and/or post)
- PARL or caries
- fractured crown or root
- Iatrogenic: post too short, perforate/weaken root
Options for gutta percha removal?
Risk of perforation or loss of apical seal. Lowest risk is a hot instrument or chemicals
Highest risk approach to remove gutta percha
mechanical removal with end cutting burs; para-post drills; Minimized risk = Gates-Glidden burs
What is the absolute minimum or GP that must remain in canal?
Minimum of 4 mm but 5 is preferred AND 1/2 - 2/3rds the length of root in bone + length equal to length of crown
What is the minimum of denting all around at apex?
1 mm. The post should be equal to about 1/3rd the diameter of root
While paraposts are very popular, ______ types of posts are also needed and fit more canals typically?
Tapered: they require less tooth structure removal.
Tapered posts may have a ____ effect. This is minimized by having ________?
wedging; adequate ferrule and vertical stop on coronal tooth structure
Post length is good for what two things?
retention AND Stress distribution
- _______ portion acts as lever arm
2. _______ portion distrubutes stress over area of post-root contact.
- Coronal 2. Radicular
With inc root length, coronal portion is at mechanical disadvantage so stress is over a larger area
Examples of less rigid/more rigid posts?
Less: carbon, quartz, glass
More: titanium (non-corrosive/weak), SS (corrosive), Cast metals, noble alloys
Rigid advantages/disadvantages?
Resists lateral forces better but has higher incidence of root fracture (1.7%)
Flexible pro/cons
deform during fxn = loss of seal and leakage BUT 0% failure (according to study that seems bias)
How many pins do you need in your buildup?
Fewest possible: 1 per line angle. Molars = 1 per cusp missing and premolars = 2 per missing cusp
Position of pins?
line angles; 3-4 mm between pins, corners are safest area for pin placement.
Rule of 2s
2 mm depth of pin hole; 2X diameter = position inside DEJ; 2mm length above dentin; 2mm of amalgam covering pin
Slots are useful when?
There isn’t enough room for pin and amalgam
