Comparative Evaluation of Pericervical Dentin Preservation and Fracture Resistance of Root Canal-Treated Teeth Prepared Using Instrumentation Systems With Different Tapers: An In Vitro Study

Background and objectivePericervical dentin (PCD) preservation is a crucial consideration in modern endodontics, as excessive removal of dentin during root canal preparation could jeopardize the structural strength of endodontically treated teeth.The objective of this in vitro study was to compare PCD preservation and fracture resistance among various instrumentation systems with different tapers in root canal-treated mandibular premolars. Materials and methodsForty freshly extracted, intact, single-rooted mandibular first premolars were randomly selected and subdivided into four groups (n = 10).Groups I, II, III, and IV were prepared using stainless steel hand files with a 2% taper, TruNatomy rotary files with a 4% taper (Dentsply Sirona, Ballaigues, Switzerland), ProTaper Gold files up to F2 (Dentsply Sirona, Charlotte, United States), and HyFlex rotary files with a 6% taper (Coltène/Whaledent, Langenau, Germany), respectively.The pre-and post-instrumentation thickness of the PCD was assessed at the cementoenamel junction (CEJ) using cone-beam computed tomography (CBCT).After instrumentation, the canals were obturated, and the teeth were restored with composite resin.Statistical analysis was carried out using the paired Student's t-test, one-way ANOVA, and Tukey's post hoc test, with statistical significance set at p < 0.05.Fracture resistance was assessed using a universal testing machine at a crosshead speed of 1 mm/min. ResultsA statistically significant reduction in PCD thickness was observed following instrumentation in all four groups.The mean PCD loss was 0.35 ± 0.10 mm for hand files, 0.23 ± 0.08 mm for TruNatomy, 0.28 ± 0.11 mm for ProTaper Gold, and 0.42 ± 0.09 mm for HyFlex.One-way ANOVA demonstrated a statistically significant difference in PCD reduction among the four instrumentation groups (F(3,36) = 7.50, p = 0.001).Fracture resistance was highest in the ProTaper Gold group (724.91 ± 149.38 N), followed by TruNatomy (706.73 ± 134.52 N), HyFlex (654.68 ± 139.76 N), and hand files (635.42 ± 59.87 N). ConclusionAll four instrumentation systems produced measurable reductions in PCD thickness following root canal preparation.TruNatomy demonstrated the lowest numerical PCD reduction, whereas HyFlex demonstrated the highest numerical reduction.ProTaper Gold showed the highest numerical fracture resistance, followed by TruNatomy, HyFlex, and hand files.The observed numerical differences should be interpreted according to the final validated statistical analysis rather than as evidence of superiority between instrumentation systems.