| Autor: |
Spanaki‐Voreadi, A. P., Kerezoudis, N. P., Zinelis, S. |
| Předmět: |
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| Zdroj: |
International Endodontic Journal; Mar2006, Vol. 39 Issue 3, p171-178, 8p, 5 Black and White Photographs, 1 Graph |
| Abstrakt: |
Aim To evaluate the failure mechanism of ProTaper Ni-Ti rotary instruments fractured under clinical conditions. Methodology A total of 46 ProTaper instruments that failed (fractured and/or plastically deformed) during the clinical use were collected from various dental clinics, whereas a new set of ProTaper instruments served as control. After inspection under stereomicroscopy the instruments were classified into three categories: (i) plastically deformed but not fractured, (ii) fractured with plastic deformation and (iii) fractured without plastic deformation. Three instruments from each group were analysed with computerized X-ray microtomography (micro-XCT) to detect surface and internal defects, whilst all the fracture surfaces were investigated under SEM. Results Stereomicroscopic inspection showed that 17.4% of the discarded instruments were only plastically deformed, 8.7% were fractured with plastic deformation and 73.9% were fractured without plastic deformation. Micro-XCT revealed instruments without any surface or bulk defects along with a few files with crack development below the fracture surface. No defects were identified in the unused instruments. SEM examination of fractured surfaces demonstrated the presence of dimples and cones, a typical pattern of dimple rupture developed because of ductile failure. Conclusions The results suggest that a single overloading event causing ductile fracture of ProTaper instruments is the most common fracture mechanism encountered under the clinical conditions. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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