Fig. 1

a Morphological reconstruction of one maxillary first molar; b & c size 25/.06 NiTi instrument with 3 mm apical segment assumed to be fractured in the mesiobuccal canal with 3 mm and 5 mm away from the canal orifice; d using modified Gates Glidden burs to create a staging platform and CPR ultrasonic tip to trephine dentin a 1.5 mm distance apically from the coronal part of the fragment around the fragment; e access to the fragment at 3 mm; f access to the fragment at 5 mm