الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 84 |  |  |
| | | from | 84 | | |
Abstract
This study was to compare between One-shape Ni-Ti rotary system,
Liberator Ni-Ti rotary system, Revo-S Ni-Ti rotary system and K-file hand
system in terms of change in the canal cross sectional area evaluated by using
cone beam computed tomography (CBCT), the ability to remove debris
evaluated by stereo microscope and the presence or absence of smear layer
evaluated by electron microscope.
Preparation of the samples was done by gaining access using round bur,
gaining straight line access of the walls using Endo-Z bur, teeth hemi-sectioning
using diamond disc in a low speed hand piece to remove distal part and leaving
only the mesial parts.
Determination of root canal curvature of each mesiobuccal canal in each
mesial root was done according to Schneider’s technique and the teeth with
angle of curvature ranging between 25-45o were selected , working length
adjusted to be 18 mm and then the samples were inserted into acrylic resin for
standardization of positions and angulations between pre-operative and post
operative scans.
The samples were randomly divided into four equal groups (10 each) and
preparation of each system was done according to the manufacturer’s
instructions.
Evaluation of changes in the canal cross sectional area
The samples were positioned in a custom-made specimen holder and
aligned perpendicular to the beam and scanned before and after instrumentation
by Ondemand3D, version 1.0.9 software. Primary and secondary images were
recorded and their registration was done manually and then automatically by the
software allowing the best possible accuracy.
Changes in the canal cross sectional area were evaluated by subtracting
the pre-operative values from the post-operative values at 3mm (apical), 6mm
(middle) and 9 mm (cervical) levels.
Summary & Conclusion
61
Evaluation of cleaning ability (debris removal and the presence or absence
of smear layer)
Samples were split longitudinally by making two longitudinal grooves in
bucco-lingual direction using double faced diamond disk and then splitting by
using a chisel into two halves.
The cleanliness form debris was evaluated at cervical, middle and apical
regions at standard magnification of 30X and microphotographs were taken and
examined by two trained operators and classified according to of modifications
applied to the numerical evaluation scoring system of Paque et al (76).
Score (0) Clean root canal and only few small debris particles are
present.
Score (1) few small islets of debris covering less than 25% of the root
canal wall.
Score (2) many accumulations of debris covering 25-50% of the root
canal wall.
Score (3) More than 50% of the root canal wall is covered by debris.
Then root canals were gold coated using ion sputtering machine and
examined under electron microscope to evaluate the presence or absence of
smear layer at standard magnification 3500X and rated by two trained operators
and classified according to numerical evaluation scoring system of Rome et
al(77).
Score (0) No smear layer and all dentinal tubules are open.
Score (1) Minimum smear layer and more than 50% of dentinal tubules are
open.
Score (2) Moderate smear layer and less than 50% of dentinal tubules are
open.
Score (3) Heavy smear layer and the outline of dentinal tubules is
obliterated.
Summary & Conclusion
62
The collected data were recorded, tabulated and subjected to statistical
analysis by using Two-way analysis of variance (ANOVA) test of significance
used for comparing variables affecting mean values.One-way analysis of
variance (ANOVA) test of significance followed by pair-wise Tukey’s post-hoc
tests were used for comparing mean values within groups. P values ≤ 0.05 are
considered to be statistically significant in all tests.
Based upon the findings of the present study it could be concluded that :
1) One-shape and Revo-S Ni-Ti rotary systems produced more changes in
the canal cross sectional area at all canal levels than Liberator Ni-Ti rotary
system and K-file hand instruments.
2) The change in canal cross sectional area is directly proportional to the
amount of debris removal from the canal space with the four tested
systems.
3) Regarding smear layer scores, all the tested systems were unable to
produce dentin surface free from smear layer: Revo-S and Liberator Ni-Ti
rotary systems produced less amount of smear layer than One-shape Ni-Ti
rotary system and K-file hand instruments at the apical region.
4) Finally and according to the present study it is promising to use Revo-S or
One-shape Ni-Ti rotary systems for cleaning and shaping of root canals.
Cleaning of root canals can be enhanced when combining the mechanical
preparation using one of those systems with chelating agents and a more
efficient irrigating solution than NaOCl for better debris and smear layer
removal