Apex locator in retreatment cases:
- Electronic apex locators may give misread for working length when gutta-percha is initially being removed.
- Due to that file beging covered with chloropercha that may affect its conductivity.
Removal of overextended GP:
- Inserting a new hedstrom 0.5 to 1 mm beyond the apical constriction, using a gentle clockwise rotation then slowly and and firmly withdrawn with no rotation, removing the overextended material.
- Avoid excessive force the instrument.
- Not softened the overextended GP with solvent.
- remove the overextended gutta percha by barbed broach or by H file
- after remove of gutta percha, heat the tip of instrument and insert to catch the gutta percha and removed suddenly.