For the wide zirconia post space preparation (subgroup ZW)
Using the shaping drills of Contec-HAHNENKRATT glass-fiber post kit, no. 3 blue calibration drill of 1.75 mm diameter was used to prepare a wide post space for the ZW subgroup, in respect of adjusting the drill’s length to 10 mm [Periapical radiograph was taken for each specimen to insure complete removal of root canal filling material as well as the fitting of the corresponding glass-fiber post in both subgroups ZN and ZW [