الفهرس 
One Shape Rotary FileOnly 14 pages are availabe for public view
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Abstract
The present study aimed to evaluate types of surface defects and incidence of fracture after root canal preparation using different single file systems at different torque settings.
Forty eight lower first permanent molar were collected and stored in purified filtered water. Facial and proximal radiographic views were taken to determine root curvature, average (mild, moderate and sever). By Schneider method using mage J software.
Proper access cavity was done for all teeth; the crowns were flattened with steel wheel until the required length 16mm was obtained. Patency of the canals was established and the WL was determined using stainless steel k-file #10, measured by digital caliper.
A sequential crown down technique was carried where the coronal portion of the tooth was pre enlarged by orifice opener C1 then each tooth the mesiobuccal canal is done by One shape file but the mesiolingual by Neoniti file. EDTA used as a lubricant during the mechanical preparation and the canals were irrigated by 2.6% NAOCL. Constant rotation speed was adjusted 350 rpm for all subgroups. A total number of 26 samples were used, 2 controlled files (one from each system) and 24 experimental files, were divided into groups according to the file used in canal preparation, then each group was subdivided into 2 subgroups according to torque applied:-
group I (One shape files) (size 25 and taper 0.06) :- (n=12)
Subgroup A: Low Torque. 2 N/cm.
Subgroup B: High Torque. 4 N/cm,
group II (Neoniti files) (size 25 and taper 0.08) :- (n=12)
Subgroup A: Low Torque. 2 N/cm.
Subgroup B: High Torque. 4 N/cm,
Scan electron microscope with a magnification 400X was used for evaluation the surface of the new and used files, for the presence or absence of the certain defects (pitting, fretting, blunt edge, disruption of cutting edge, metal flash, debris, unwinding and fracture).
After examination of all files, data were recorded and the mean value for the incidence of each surface defect was calculated for each file after use in single tooth (four canals).Data were presented as frequency percentage values; the chi square test was used to compare the two groups. The significant level was set at P ≤ 0.05.
Scanning the files before use showed that files suffered from surface defects and this proved that manufacturing procedure is always far from ideal.
Examination of each system after use under low and high torque showed that there was no statistical significant difference between them in terms of all defects.
When comparing One shape to Neoniti files under low torque, there was no statistical significant difference between them in terms of all defects, except disruption of cutting edge. Also when comparing them under high torque there was no statistical significant difference in terms of all defects except metal flash.