An in vitro study to determine fracture resistance of tooth roots after different instrumentation techniques

Abstract

Aim: The aim was to study the influence of rotary and hand instruments techniques on the susceptibility of the root to fracture. Materials and Methods: Forty extracted human maxillary permanent first and second molars without any defects were selected as sample. Teeth were randomly divided into four groups of ten teeth in each group. Palatal canals were instrumented depending on the instrumentation techniques used in the groups. Group 1: 0.02 taper K-files and Gates Glidden drills (Mani Inc., Japan); group 2: Hand ProTaper (Dentsply-Maillefer, France); group 3: Rotary ProTaper (Dentsply-Maillefer, France); and group 4: Endowave (J. Morita, Japan). After instrumentation, palatal roots were resected and apical 7 mm sectionally obturated. Obturated roots were embedded in putty impression material and mounted on Universal testing machine (Lloyd instruments, UK). Vertical load was applied by means of a spreader inserted into the canal and load at fracture was recorded for each tooth. Fractured roots were embedded in self-cure resin, sectioned horizontally, and viewed under operating microscope to determine the direction of fracture line: Maximum and minimum remaining dentin thickness was measured at coronal, middle, and apical thirds. Statistical analysis of data was accomplished by one-way ANOVA and post-hoc tests with Tukey honest significant difference. Results: Mean fracture loads was 20.6 ± 3.8 kg (group 1), 9.5 ± 2.4 kg (group 2), 8.4 ± 1.4 kg (group 3), and 13.4 ± 3.1 kg (group 4). There was statistical significance in the values between group 1 and groups 2, 3, and 4 (P Conclusion: Preparation of canals with a conventional hand instrumentation technique using 0.02 taper K-files showed highest fracture resistance with least amount of dentin removed at all levels followed by Endowave, ProTaper Hand, and Rotary files.