The screw shears! What's up?

Possible reasons

  1. The screw is in soft dentine
  2. The screw thread is blunt

As to 1: the screw needs positioning in firm dentine

Mill the core of the root deep down into the apical third of the root with a round bur.

Open the visible root channel with the trephine and prepare with the Benex drill (often using the shaft extender).


Drilling should penetrate the root; this is clearly noticeable (the drilling resistance diminishes). 
This enables the screw to be well and securely anchored in the apical, firm root fragment.

As to 2: the screw thread is blunt