Evaluation of apical root defects during canal instrumentation with two different nickel-titanium (NiTi) systems by optical coherence tomography (OCT) scan

Abstract

Background/purposeCanal instrumentation with rotary nickel-titanium (NiTi) instruments might weaken the dentinal wall. This study aims to investigate the apical root defects during canal instrumentation with two NiTi rotary systems by using optical coherence tomography (OCT) scans. Materials and methodsTwenty mandibular incisors were selected and divided into two groups instrumented using HyFlex CM (HCM) and ProTaper Universal (PTU) systems. OCT scans were taken immediately after canal instrumentation with file #25, #30 and #40. Each cross-sectional reconstructed image of 1, 2 and 3 mm from the apex was examined, root cracks were scored, and dentin thickness was measured at 12 sites. The risk sites with dentin thickness less than 0.30 mm were recorded. ResultsIn HCM group, no cracks were observed after instrumentation with file #30/.06, while in PTU group, root cracks were found in 6 teeth with a total score of 9 after using F3 (#30/.09) (P < 0.05). After file #40, 8 teeth with cracks had a score of 14 in PTU group, while one tooth was observed crack with a score of 1 in HCM group (P < 0.05). The number of risk sites in PTU group was 49 (13.16%), which was significantly more than the 28 (7.78%) in HCM group (P < 0.05) when canals were instrumented with file #30. ConclusionWithin the limitations of this study, when the canals of mandibular incisors were instrumented with size #30 and #40 files, OCT scans showed less root defects in HCM group.