Durability of Self-Adjusting File (SAF) Used in Canal of Different Curvatures

Abstract

INTRODUCTION This study aimed to evaluate the safety and durability of Self-Adjusting File (SAF) in preparing root canals of different curvatures.

METHODS A total 47 SAFs were tested in 5 groups of mesial canals of extracted lower molars with different angles (α) and radii (r) of curvatures. The file was operated in one canal for a maximum of 4 minutes. The file was removed after every minute of use and examined under magnification to detect any mechanical failures: fracture or deformation. If there was no failure, the operation was resumed with the same file in the same canal. After a total of four minutes, if the file was still intact, the procedure would be continued in a new canal. In any event of failure, the experiment was stopped. A new SAF would be used in a new canal and the experiment repeated. The time when the first mechanical changes occurred was recorded. Then the file was examined in details under a stereo- microscope, followed by Scanning Electron Microscope.

RESULTS SAF operated in relatively straight canals showed the greatest durability of 19 minutes followed by severe-sweeping (7.2 minutes), severe-acute (7.0 minutes), moderate-sweeping (5.7 minutes) and moder- ate-but-acute curvature (4.9 minutes). There was a signif-icant difference between the straight and all other curved canal groups (p < 0.01). Failure of SAF occurred most commonly on the middle portion. Fractographic images revealed the presence of fatigue striations and dimpling patterns.

CONCLUSION There was a significant difference in us-age time of SAF before first failure detection between straight canals and those that were curved.