Pin Retention
What is an acceptable alternative to pin placement if there is enough tooth structure?
coves, slots, troughs placed in dentin (put in areas furthest away from pulp!) (use pins only when there isn't enough tooth structure to place retentive grooves or slots)
Align twist drill to the __________ in the ____________ 1/3 near the _________________
external surface of the tooth; gingival; transitional line angle (near transitional line angle; NOT the long axis of the tooth)
True or false: you should place pins in the anticipated area of the smallest bulk of amalgam and avoid areas of occlusal contact
false (largest bulk of amalgam)
True or false; you should aline the twist drill in the long axis of the tooth
false (run the risk of perforating the tissue; like with external surface of tooth)
When drilling the pinhole, the area that will receive the pinhole should be ________ and ________ to the direction of the pin hole
flat; 90 degrees (when the area to receive pin is sloped, the drill may not achieve full 2mm depth)
In general: pins are placed in the _______ 1/3 of the tooth near the line angles
gingival
Pins are (good/bad) for amalgam retention and (good/bad) for tooth strength
good; bad
Retention of restoration generally increases with (increase/decrease) in pin diameter
increase
Generally we like to use as (small/large) of a pin as we can
large
The (smaller/larger) the pin diameter, the greater the retention
larger
For a cemented pin, the pin channel diameter is (smaller/larger) than the pin diameter
larger (this makes it easy to us)
Why might a patient choose to have a pin/amalagam large restoration over a crown?
more conservative and costs less
Should you place pins in areas of heavy occlusal loading?
no
Can a sensitive tooth have pins?
no (will make it more sensitive)
you should use (slow speed/fast speed) to drill a pin hole
slow speed (too fast = too big)
For self-threading pins, the pin channel diameter is (smaller/larger) than the pin diameter
smaller
For a friction-locked pin, the pin channel diameter is (smaller/larger) than the pin diameter
smaller (this creates a little bit of stress)
True or false: twist drill only cuts while rotating in one direction
true (so make sure the motor is in the forward position) (make sure the twist drill is sharp or you may get a crack/oversized hole)
What can you do to prevent the twist drill from slipping?
use a 1/2 round bu to make an indention where you intend to place the pin
The more pins used, the (stronger/weaker) the restoration becomes
weaker
True or false: retention of the large amalgam significantly improved with pin when other means of retention are not possible
true
True or false: you should place pins at the line angles of the tooth
true
When placing pin holes, which 3 locations should you especially avoid?
- mid-mesial of maxillary 1st premolar (prominent concavity) (mesial developmental depression) - MF corner of maxillary 1st molar (tall pulp horn) - MF corner of mandibular first molar (tall pulp horns)
What are the 2 types of perforations that can happen with pins?
- pin drilled into the pulp - pin perforates surrounding tissue (both are bad)
What are disadvantages of pins?
- produces stresses within the dentin
Pinholes should be located ___ mm inside of the DEJ
1
You should use ___ pin(s) for missing cusp in molars
1
You should use ___ pin(s) per missing line angle
1
There should be ____ mm to any axial wall so alloy will be completely condensed around the pin
1-1.5
A pin hole should be ___ mm away from the external surface of the tooth
1.5-2 (2mm is preferable; puts us about 1mm inside the the DEJ)
We would like to have at least ___ mm of amalgam covering a pin
2
You should use ___ pin(s) for missing cusp in premolars
2 (extra retention in smaller teeth is necessary)
What is the optimal depth into dentin for a pin?
2-3 mm
There should be ___ mm amalgam occlusal to pin; __ mm height of pin above the shoulder stop; and ___ mm depth of pin into dentin
2; 2; 2
When multiple pins are used, there should be a space of > or equal to ___ mm between pins
4 (this helps avoid cracking)
As the number of pins used increases, dentinal crazing and risk of fracture A. increases B. decreases
A
As the number of pins used increases, the risk of perforating the pulp or external tooth surface A. increases B. decreases
A
When external perforations occur occlusal to the gingival attachment: A. the pin may be cut off flush and then the casting preparation extended below perforation B. periodontal surgery is required for crown lengthening
A
When using a twist drill you should make sure the drill is running in a _______________ direction A. clockwise B. counterclockwise
A
Which is the least retentive? A. cemented pins B. friction-locked pins C. self-threading pins
A
Which places the least stress on dentin? A. cemented pins B. friction-locked pins C. self-threading pins
A
Which of the following materials works best for pins? A. amalgam B. composite
A (but composite works too; just not as well as amalgam)
Which pin is the easiest to use? A. cemented pins B. friction-locked pins C. self-threading pins
A (doesn't take a lot of work to insert pin in there)
Which of the following has to go deep into the dentin? A. cemented pins B. friction-locked pins C. self-threading pins
A, B (3mm) (self-threaded pins only 2mm into dentin)
As the number of pins used increases, amount of available dentin between pins A. increases B. decreases
B
As the number of pins used increases, the strength of the amalgam restoration A. increases B. decreases
B
When external perforations occurs below the gingival attachment: A. the pin may be cut off flush and then the casting preparation extended below perforation B. periodontal surgery is required for crown lengthening
B
Which pin is held in place by the elasticity of the dentin? A. cemented pins B. friction-locked pins C. self-threading pins
B
Which places the most stress on dentin? A. cemented pins B. friction-locked pins C. self-threading pins
B
Pins must be placed in A. enamel B. dentin
B (2-3 mm into dentin; need elasticity from dentin and enamel is too brittle)
Retention form is best in: A. enamel B. dentin
B (enamel is too brittle) (don't place retentive grooves too close to DEJ or in enamel)
Which of the following will likely produce stress in the dentin? A. cemented pins B. friction-locked pins C. self-threading pins
B, C (because the pin channel diameter is smaller than the pin diameter)
What is the ideal pin? A. cemented pins B. friction-locked pins C. self-threading pins
C
Which is the most retentive? A. cemented pins B. friction-locked pins C. self-threading pins
C
Which pin has a shoulder stop to prevent the end of the pin from putting stress on the dentin in the bottom of the channel? A. cemented pins B. friction-locked pins C. self-threading pins
C
Which pin is screwed into place? A. cemented pins B. friction-locked pins C. self-threading pins
C
Which pin has a low chance of bottoming out? A. cemented pins B. friction-locked pins C. self-threading pins
C (due to shoulder stop)
Pin retention restorations are often used for (simple/complex) restorations
complex (replacing one or more cusps) (last resort option when there is no other way to hold a large amalgam in a tooth)
If you drill a pinhole and you see blood, what does this mean? What should you do?
You have perforated the pulp -- take radiograph to verify (if tooth has been asymptomatic you can probably put a direct pulp cap and place another pin hole 2mm away from exposure; however, generally this calls for the need of root canal/crown)
What does a cove allow for?
allows to condense amalgam around a pin (if there is a pin too close to an axial wall there would be no way to do this) (also allows twist drill to completely reach 2mm into dentin without hitting any other tooth structure to stop it)
True or false: We want to start the twist drill before entering the tooth and keep it running the whole time as we move in and out once
true (don't go in and out more than one time or it will be too big for pin)
