Characterisation of deformed or separated nickel-titanium retreatment instruments after clinical use - A multicentre experience: Defect profiles of clinically-used retreatment instruments.

Objectives: The present study examined the defect characteristics of clinically-used, discarded nickel titanium rotary retreatment instruments and analysed the impact of clinical use on their metallurgical properties.

Methods: 92 XP-endo Shaper (XPS; FKG Dentaire) and 20 XP-endo Finisher (XPFR; FKG Dentaire) instruments with structural deformation or separation were collected after retreatment from four endodontic clinics over a 20-month period. The types of defects and their relative locations were recorded.