平坦形状根管におけるSAF Infinitumシステムの時間依存的デブリ除去能

To evaluate the shaping ability, debris removal efficiency and morphological alterations induced by the SAF Infinitum system during progressive instrumentation of flat-shaped root canals of mandibular incisors.

Twelve extracted mandibular incisors with flat-shaped canals were selected using micro-CT and instrumented with 1.5-mm Self-Adjusting File (SAF) Infinitum instruments under continuous NaOCl-HEDP irrigation for 2, 4 and 6 min. Micro-CT scans were performed before and after each step to evaluate changes in canal volume, surface area, debris removal, unprepared canal walls and dentine thickness. Following the preparation procedures, all instruments were examined under a microscope for defects. Data were analysed using GLM for repeated measures and the Related-Samples Friedman test (α = 0.05).

Root canal preparation with the SAF Infinitum significantly increased canal volume and surface area (p = 0.000), while progressively reducing unprepared canal wall areas and hard tissue debris (p = 0.000). Unprepared surfaces decreased by 77.8% and debris volume by 77.2% from 2 to 6 min, with improved cleaning efficiency over time. Dentine thickness also declined significantly (p < 0.001), particularly on the lingual surface at the pericervical area and the mesial surface at midroot. Buccolingual walls consistently remained above 1.0 mm, whereas only two mesiodistal cross-sections at the midroot level exhibited dentine thickness below 0.5 mm. After 6 min, all instruments showed structural deformations, and one specimen exhibited a minor intracanal fragment.

This is the first study to evaluate the progressive, time-dependent effects of the SAF Infinitum system in challenging flat-shaped root canals. The system exhibited a time-dependent shaping effect, with most morphological changes occurring within the first 2 min, followed by continued, although more gradual, improvements up to 6 min. Cleaning efficacy increased steadily over time, while remaining dentine thickness generally stayed above critical safety thresholds. All instruments showed structural deformations after 6-min preparation.