Aim This prospective study on teeth with necrotic pulps evaluated the clinical outcome of root canal treatments performed with two full-length Ni-Ti rotary file systems with different cross-sectional design and canal-cleaning ability. Methodology Ninety-four patients with necrotic pulps, and periapical lesions needing root canal treatment were included and randomly divided into two groups. At baseline, a preliminary periapical radiograph was taken and the presence of pain was registered according to the Verbal Rating Scale. A single operator performed all single-visit root canal treatments under rubber dam isolation; when necessary, pre-endodontic restorations were provided. Canals were instrumented with Mtwo (Sweden & Martina, Italy) (Group 1, n = 55) or Alpha Kite (Komet, Germany) (Group 2, n = 39), irrigated with 2.5% NaOCl and filled by the continuous wave of condensation technique (System B; SybronEndo, USA). No chelating agents were used during irrigation. Coronal seal was assured by immediate direct composite restorations. Patients were recalled after 6 months to repeat clinical and radiographic evaluations. Statistical analysis was performed using chi-square, McNemar, Mann–Whitney, Wilcoxon tests (SPSS Inc., USA) (P < 0.05). Results Complete periapical healing was observed in 55% and 51% of cases in Group 1 and Group 2 respectively. Subtotal reduction of periapical radiolucencies occurred in 40% of patients in Group 1 and 49% in Group 2. Almost all symptoms disappeared at 6-month follow-up in both groups. No significant differences were found between the groups in any of the parameters considered (P > 0.05). Conclusions Within the limits of the present study, the use of M two and Alpha Kite instruments produced similar success rates at 6-month follow-up.
