Prior to each preparation, pre-flaring was performed with
Gates Glidden burs (Komet, Lemgo, Germany)
in the
crown-down technique in the upper-third of the canal.
Figure 1 Purpose-designed stand for standardised photograph.
Preparation for testing
Serial numbers from one to 20 were engraved into the
acrylic blocks with the simulated root canals.
A 0.1%
aqueous methylene blue solution (Pharmacy of Philipps
University) was injected into the canals to enhance the
image contrast for the subsequent photographic documentation
and to verify that the canals were suitable for
instrumentation.
If the solution failed to emerge through
the apical foramen, the block was discarded and replaced
Determination of Root Canal Curvatures
After each change of instrument the root canals were irrigated
with water to remove debris.
The working length of the industrially produced blocks
was set at 18 mm, corresponding to a distance of 1 mm
from the apical foramen.
The working length of each
instrument was set by the students themselves with rubber
stoppers prior to the start of treatment and was
checked in the course of treatment.
Preparations were
performed with a new set of instruments for each preparation
system.
The conicity was 2% (taper 0.02) with
manual preparation, and 4% (taper 0.04) with rotary
preparation.
Manual preparation was performed with stainless steel
or Ni-Ti K-files with a working length of 25 mm.
For optimised
canal preparation, the stainless steel instruments
were pre-bent by the students and applied with slight apically
directed pressure with a 1/8 turn clockwise and
counterclockwise direction (14).
Rotary preparation was done with 25 mm long Ni-Ti
FlexMaster® files and Profile® instruments, which were
lightly coated with Glyde® (Dentsply De Trey, Konstanz,
Germany) before being inserted into the canal.
Both systems
were driven at 250 rpm by a torque-controlled lowspeed
motor (Endo IT control; VDW, Munich, Germany)
adapted to the individual instruments. Between each
change of instruments the canals were irrigated with
water.
If necessary, the canals could be recapitulated with
a previously used, smaller file.
The instrument application sequence is shown in
Tables 2 and 3.
All prepared root canals were photographed once again
with a digital camera in standardised position and the
image data were stored in the PC.
In contrast to the first
photo, however, the canals were not dye-penetrated and
the blocks were photographed against a black background.
