Dental Amalgam Pins

By Dr.Swathi Pai on Thursday 1 May 2008 with 0 comments



Types

  1. cemented
  2. friction-lock
  3. self-threading

Advantages

  • more conservative and less time involved than castings

  • enhances retention form (adds walls) and is an economical alternative to castings

Disadvantages

  • can cause dentin crazing

  • microleakage can occur at pin channel

  • pins weaken amalgam alloy



Number of pins

  • one per cusp or marginal ridge may be excessive
  • 3-5 mm between pins
  • 0.05 to 1.0 mm inside dentinoenamel junction
  • sizes of pins in inches

Self threading (TMS) drill size pin diameter

regular 0.027 0.031

minum 0.021 0.024

minikin 0.017 0.019

minutia 0.0135 0.015


  • When pins are placed nearer the occlusal surface, as in cuspal coverage areas, the pins
    should project only minimally into the restorative material.
  • Long pins near an area of occlusal loading will significantly weaken the amalgam.
  • The purpose of the pin in cuspal coverage areas is to bind the cusp to the restoration and to
    resist lateral displacement with occlusal function.
  • Should have 2 mm of amalgam thickness above pin.


Retention vs. resistance form

-retention form resists displacement through tipping or lifting forces

-resistance form enables tooth to withstand stress on restoration and remaining tooth during function

-the effectiveness of pins, slots, box-forms (ledges), or amalgapins can be maximized when used in combination and properly distributed

Cuspal coverage

Cover cusps not because of drying but because of weakness created due to access opening, existing restoration, etc.

1/4 intercuspal distance = to intact tooth

1/3 intercuspal distance 1/3-2/3 as strong

Category: Conservative and Endodontics Notes

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