الفهرس 
. INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 121 |  |  |
| | | from | 121 | | |
Abstract
To compare the incidence of dentinal defects produced by four heat-treated motor-driven Ni-Ti files; Hyflex EDM(coltene), Reciproc Blue(VDW),One Curve(MicroMega) and M-Pro(IMD) using stereomicroscope analysis.
This study was conducted on 50 mesio-buccal root canals of human mandibular molars. All teeth were examined under the stereomicroscope to exclude any pre-existing dentinal defects. All the specimens were decoronated and the distal roots were sectioned and discarded. Roots were embedded in impression material and acrylic resin to simulate periodontal ligament. The root canals were randomly divided into five equal groups according to file system used for canal preparation. group I: Hyflex EDM files with continuous rotation motion. group II: Reciproc Blue files with reciprocating motion. group III: One Curve files with continuous rotation motion. group IV: M-Pro files with continuous rotation motion. Roots were prepared till tip size 25 for groups I-IV. While in group V: unprepared canals (negative control). All roots were sectioned at 3, 6, and 9 mm from the apex using a precision cutter (Metkon). Examiners calibration and reliability tests were achieved prior to images evaluation. Stereomicroscopic examination (Olympus) was performed to all sections after their cleaning with an ultrasonic cleanser (L&R Company).A cracked sample was considered when a line was originating from the inner wall of the prepared canal, all other varying forms of defects were not considered as cracks. A crack is either incomplete or complete, according to the extent of propagation toward the outer surface. Roots were classified as cracked if at least one of the 3 sections of each root showed a crack.
Data were statistically analyzed using Fisher Exact test, and results showed that, in all the study groups (including the control group) only one section at the 6mm level (middle third) showed an incomplete crack and this section belonged to the Reciproc Blue file group. Accordingly, no statistical significant differences were found among all experimental groups or in relation to the control group, regardless the section level; apical/ middle/ coronal.
During microscopic examination, a number of sections at different levels showed dentinal defects and cracks that were not extending from inner canal wall, and thus were not considered as cracked samples.
It was concluded that,newly heat-treated engine-driven files could yield root canal preparation with less dentinal defects owing to their enhanced mechanical and physical properties.