Pin Retained Amalgam Preparations
Indicated for:
Too much tooth structure removed for normal retention features to be effective
To build up a badly destroyed tooth
Interim restoration during periodontal or endodontic treatment
Patients who cannot afford to have a crown
Elderly patients not capable of coming in for multiple appointments
Foundation for full coverage restorations
Not For:
Teeth with large pulp chambers
Teeth that are already sensitive
Non-vital teeth (more susceptible to fracture
Teeth inaccessible to pin drill
Anterior teeth
Advantages:
Fine, strong, long term restoration/build-up
Less expensive than a crown
Completed in one appointment
Conservsation of tooth structure
Disadvantages:
Drilling pin holes and placing pins à craze lines or fractures
Pins help retain amalgam, but the amalgam material is not as strong with pin
Remaining tooth structure not protected – fracture risk after placement
Pin may become a pulp irritant depending on placement
Pulp may be penetrated by incorrect angulation/depth of pin placement
Incorrect placement can lead to external tooth perforation
Why not bond amalgams if pins are bad? à Research has not proven that bonding is sufficient for
retention of amalgams. Therefore, retention features are still needed when using bonding agents.
Types of Pins
Cemented Pins à rarely used today
Pin hole usually larger
Cemented with zinc phosphate or polycarboxylate cement
Least retentive
3mm into tooth with 2mm post above tooth
Friction Lock Pins
Hole in tooth is smaller than cemented
Pin is tapped into place
More retentive than cemented
Rarely used
3mm into tooth structure and 3mm post above tooth surface
Self-Threading Pins
Use these in class
Hole in tooth slightly smaller than pin
Retained by threads on pin
More than twice as retentive as others
2mm into tooth, 2mm post above
Sizes (Thread Mate System)
Regular (largest)
Minim ß use this at Pacific (0.021” hole and 0.024” pin diameter)
Minikin
Minuta (smallest)
Placement
At the proximal line angles of molars
At the proximal line angles or cusp tips of premolars
Do not place in interproximals
Do not place in furcation areas
Do not place near root concavities (M of maxillary 1 st premolar)
Do not place in demineralized dentin
At least 0.5mm from DEJ (preferably 1.0mm) in the dentin
If below enamel on tooth, measure 1.0mm from edge of tooth
Drilling and Pin Issues
Use a depth limiting drill to get a depth of 2mm into dentin
2mm of pin should be visible above dentin
May need to bend the pin to get 1.5-2mm clearance for cusp build up (only use the TMS bending tool in
the pin kit)
Must have 3mm from gingival floor to opposing tooth (I have no idea what this means, but you may
want to memorize it anyway!)
Need flat, perpendicular floor for uniform drilling depth
Use one pin per missing cusp and you must have 5 mm between pins
Drill not penetrating:
Dull drill?
Drill flutes clogged?
Handpiece in reverse?
Drilling enamel instead of dentin?
Broken pin drill?!!!!
Dull drills may break
Stop rotating drill before removal à broken drill
Do not attempt drillectomy, leave it and place a new pin at least 1.5mm away from this site
Broken Pin? – Are you done breaking things yet?
Over tightened pin drill?
Aggressive bending = broken pin
Do not remove the pin! Pick a new spot to break something.
Loose Pin?
Pin hole is too large
Overturned pin causes stripping of dentin
If you got lucky and you have stripped dentin à remove the pin with 56 bur in a high speed (lightly
touching top of pin)
And if you can’t remove it, place a new one à the more the merrier, right?
Penetration of the pulp à Run away!!!
Remove pin or pin drill
Control bleeding
Peridex and cover with calcium hydroxide
Pick another location (I don’t know about this?!!!)
Inform patient (obvious)
Endodontic Treatment
Avoid Lawsuit (just kidding)
Penetrating External Tooth surface
Sense by loss of resistance, pin goes beyond 2mm, and blood
Turn out pin if possible
If above gumline, cut off excess and fill with amalgam or place crown margin below perforation
If below gumline, perio surgery and same as above
Pin Alternatives/Assistants
Circumferential Slots
33 ½ bur
Use only where needed
Carefully remove matrix
Amalgapins
330 bur
@ proximal line angles
1.5-2.0mm depth
0.8mm diameter hole
bevel at occlusal
Peripheral Shelves
2mm gingival floor
1mm axial height
Not circumfrential (only in parts where necessary)
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