In our sample, the frequency of single apical foramen
was highest in the distal root (76.76%) followed by two foramina (23.24%).
Apical patency was maintained at each change of instrument by inserting #10 K-file up to the apical foramen
. The groups were divided according to the final irrigation protocol.
The ARCL was measured by inserting a size 10 K-file into the root canal until its tip was visible at the apical foramen
under a stereomicroscope (Leica WILD M3Z; Leica Mikrosysteme Vertrieb, Wetzlar, Germany).
For that calculation, each tooth was divided into thirds: apical (0 to 4 mm from the apical foramen
), middle (4 to 8 mm from the apical foramen
), and coronal (8 to 12 mm from the apical foramen
Furthermore, during the regenerative endodontic treatment, a #15 K-file was used to probe the apical foramen
and an obvious sense of friction was found, so we judged the tooth in this case belongs to mature permanent tooth.
The working length was estimated by advancing this file passively into the root canal until the tip of the file was seen at the apical foramen
. This was done by using the Heine HR 2.5x High Resolution Binocular Loupes with LED, working length was determined by subtracting 0.5 mm from this measurement (Fig 1).
The working length (WL) of each canal was determined to be 1 mm short of the length of a size 10 K-file (Dentsply Maillefer) that was visible through the apical foramen
. According to the manufacturer instruction, preparation of the root canal was carried out with the Mtwo rotary instrument system (VDW, Munich, Germany) using #10.04, #15.05, #20.06, #25.06, #30.05 and #35.04 files sequentially with a torque-controlled endodontic motor (X-Smart; Dentsply Maillefer, Ballaigues, Switzerland).
Microcomputed tomography analysis of mesiobuccal orifices and major apical foramen
in first maxillary molars.
All teeth were examined for morphology of roots, root canals and apical foramen
by Cone Beam Computed Tomography (CBCT).
Number 15 K files (Dentsply-Maillefer, Ballaigues, Switzerland) were introduced further into the root canals until their tips were visible at the apical foramen
. The working length was determined as 1 mm shorter than this length.
As the apical foramen
was surrounded by air, the presence of periapical tissues that could act as a natural barrier and exert some resistance to irrigant extrusion was not simulated .