In-vitro Comparison of Hero 642 Protaper Ni-Ti Rotary Systems and K-Files in Primary Teeth Root Canal Preparation Regarding Preparation Safety and Time

The aim of this study was to compare two Ni-Ti rotary instrument systems (ProTaper-Hero 642) with K-files, regarding preparation safety and time. Fifty four (27 maxillary and 27 mandibular) primary molars were randomly divided into three groups each having 18 teeth (9 maxillary and 9 mandibular). In Group H the root canals were prepared using Hero 642 system, In Group P the root canals were prepared using ProTaper system and in Group K the root canals were prepared manually with K-files. The groups were compared regarding perforation, file fracture and preparation time. Perforation and instrument fracture were assessed with t-test for two independent proportions, and the Kruskall-Wallis test was used to assess differences in preparation time. There were no statistically significant differences according to perforations and instrument fractures between groups according to total number of prepared canals and canal types (MB, ML, DB, DL, M, D, P). The number of perforations in Group P was statistically higher than Group H when the groups were compared according to the total number of teeth (p 0.05). The shortest preparation time was spent for Group H while Group K required the longest preparation time and the difference between the groups was statistically significant (p 0.05). Differences among groups were statistically significant when the groups were compared according to the preparation times. According to the results of this study Hero 642 showed best results and can be recommended as an alternative to K-files for the root canal preparations of primary teeth.