Dr. M. Raghavalli
BACKGROUNDCanal preparation is adversely influenced by the highly variable anatomy and relative inability to visualise canal anatomy from radiograph.1The causes of endodontic failure include coronal leakage, radicular fracture, post error due to diameter, length and direction, missed canal, short files, over extension, internal under fillings, ledges perforations, transportation, separated instruments surgical failures.2 MATERIALS AND METHODSNinety freshly extracted human mandibular premolars were collected and stored in Hank’s balanced salt solution. Length was standardised at 16mm. The roots were covered by aluminium foil and inserted in acrylic resin. After setting, the root was removed from set acrylic tube and aluminium foil suspended from root surface. A light body silicon-based material was used to fill the space created by the foil to simulate periodontal ligament.Ninety samples collected were divided into six groups with fifteen teeth in each group. Group 1- Unprepared Root Canal Shaping Group (Control Group). Group 2- prepared by Hand File. Group 3- prepared by Protaper Next. Group 4- prepared by Twisted File. Group 5- prepared by Reciproc. Group 6- prepared by Self Adjusting File.Statistical analysis was performed with SPSS 20.0 Software by using Kruskal Wallis ANOVA and Mann-Whitney U test. p-value of less than 0.05 was considered statistically significant for all tests. RESULTSAll the file systems showed formation of dentinal microcracks in root canals.The present study showed that there is significant difference between study groups in number of crack formation at 2 mm (p=0.0023) between control group and twisted group p=0.029, between hand file and twisted file p=0.048 and between twisted file and SAF p= 0.05 and 6 mm (p=0.0213) between control group and twisted file (p= 0.05) and between twisted and SAF (p=0.05) and there was no significant difference between groups at 4 mm (p=0.07) and 8 mm (p= 0.1367). CONCLUSIONWithin the limitations of present study, it was concluded that-1. All the instruments used, produced cracks with twisted file showing highest number of cracks followed by Reciproc, ProTaper Next, hand files and self adjusting file.2. There were considerably more cracks produced at apical 2 mm level due to less dentine thickness to counteract the lateral stresses generated by instrumentation.
