Accessory Retention Flashcards
When is accessory retention used with?
LARGE restorations and less than ideal supporting tooth structure
What material are pins commonly used with?
amalgam (because it relies on mechanical retention)
What are indications for pins?
- Improve retention as a last resort
- Large restorative that are missing cusp(s)
- Prognosis of tooth is uncertain (unstable perio)
- Unable to access pulp canals (sclerosed tooth) for needed
additional retention
What are contraindications for pins?
- Severe loss of tooth structure
- Endodontically treated teeth (11)
o Teeth are too brittle
o Alternatively use post or amalgam core - Large pulp canals (children)
- Difficult access for placement
- Tooth serves as abutment for RPD
How big is the pin hole in a self threading pin?
Pin hole is 0.002” smaller than pin
How does a self-threading pin work?
Self-threads into dentin (with hand wrench or latch grip on slow speed)
Where is a self-threading pin located?
2mm in dentin
2mm outside of dentin
Self threading pins are _________ times more retentive as cemented pin
5-6x
Do self-threading pins create stress?
Yes; high crestal and apical stresses; crazing and microleakage
Where do self-threading pins give the most stress to?
Dentin
What is a cool feature of self-threading pins?
Self-shearing
- break off on their own as you turn them
Where should pins be placed?
In dentin
- should be at least 1mm of dentin around pin hole
How far apart should pins be placed from eachother?
5mm apart (minimum of 3mm)
How far should a pin be placed from the wall of a prep?
1mm (minimum of 0.5mm)
Where should a pin be placed relative to the DEJ?
1mm inside DEJ (minimum of 0.5mm)
Why could you increase the pin placement from 1mm inside DEJ to 1.5mm inside DEJ?
If planning to crow tooth to avoid exposure upon crown prep
How far should a pin be placed from any wall?
0.5mm to allow room for condensation of amalgam around pin
Where exactly should a pin be placed relative to the tooth itself?
In line angle
How deep should a pin be placed into dentin?
2mm deep
What axis should a pin be placed in relation to?
Long axis of tooth
If using multiple, angle in slightly different directions
Should you bend pins?
AVOID
What are the different twist drill sizes?
Regular 0.027 (gold)
Minim 0.021 (silver)- Most frequently used
Minikin 0.017 (red)
Minutia 0.0135 (pink)
What are the types of twist drills?
- Standard
- Self limiting (drill stops itself from drilling too deep of a pilot hole)
What part of the drill acts as a heat absorber?
Aluminum shank
What kind of size drill has a built in wobble?
Minuta and Minikin
What is the function of the wobble that a minuta or minikin size drill have?
Minimize dentin crazing and drill breakage
When should you discard a drill?
After 20 uses
How do you know if the pin is the correct height?
2mm of amalgam must be over top of the pin
What do you do if the pin is too tall?
educe with handpiece stabilized by forceps to cut perpendicular to pin or bend slightly with pin bender
Where should you not place a pin?
Near the pulp
Concavities of the tooth
Where should you not place a pin to avoid a concavity?
- Mesial concavity over maxillary 1st premolar
- Distal mand molars and max lingual of molars
- Mid-F, Mid-M, and Mid-D furcations of Max 1st/2nd molars
Where should you not place a pin to avoid a concavity?
- mesial concavity over max 1st premolar
- lingual and facial of mandibular molars
- facial, mesial, and distal fucation of maxillary molars
What stress can pins introduce?
Introduces stress into dentin which can lead to fracture
What strength do pins reduce?
Pins reduce the compressive and transverse strength of amalgam
What exposures are preferred in terms of pins?
Pulp exposure preferred to PDL exposure
How to deal with pulp exposure from a pin?
Direct pulp cap with calcium hydroxide or RCT
What does a PDL exposure result in?
Abscess
How to deal with a PDL exposure from a pin?
Treated by removing pin that is perforating tooth and plugging with amalgam
Does a pulpal or PDL exposure have a less predictable prognosis?
PDL
Where can there be microleakage with a pin?
Around it
Does adding a pin make it more or less difficult to restore and carve anatomy?
More
