additional retention on amalgam

[Janeausten]

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haaaaaalp! I'm having trouble determining when to use different additional retention methods on complex amalgam restorations. And I have an exam after break. :/ For practice I have this question.

Patient is an adolescent and requires an amalgam restoration on a molar which will replace the mesio buccal cusp. What would be preferred for additional retention: a buccal finger (box preparation at the mesio - buccal groove) or threaded pin placement or an amalgam pin ? Select the preferred retention.

I am torn between 2, but my doctor says there is one correct answer. Thoughts? Please and thank you 🙂

 

[THS]

I prefer to use a pin when replacing a cusp. A threaded pin, not an amalgam pin

 

[Janeausten]

Thank you! I was torn between the buccal box and the amalgam pin because threaded pins create stress in dentin. Why do you prefer threaded pins if you do not mind me asking?

 

[THS]

Thank you! I was torn between the buccal box and the amalgam pin because threaded pins create stress in dentin. Why do you prefer threaded pins if you do not mind me asking?

The buccal box would not have provided enough retention to prevent dislodgement in the buccal direction. A mesial box would have helped somewhat.
I prefer the threaded pins over amalgam pins because they do not remove as much tooth structure, and I am convinced that having a pin to build up amalgam around further increases retention of the restoration. As for stressing the dentin, the Max pins (which i prefer over Minikin or other pins) have a little collar that prevents them from sinking to the depth of the pilot hole, leaving a little bit of space between the end of the pin and the floor of the hole. Therefore, the dentin does not experience the same compressive stress as it would with other pins.

 

[Janeausten]

This makes a lot of sense. Thank you very much!