Evaluation of Remaining Dentine Thickness in Mandibular Incisors After Shaping With Varied Tapered Instruments: A...

This study evaluated by cone beam computed tomography (CBCT) the impact of canal enlargement using ProGresShape (REKITA, Zouk Mikael, Lebanon) rotary files with 5% and 7% tapers on remaining dentine thickness (RDT) in mandibular incisors with different root canal configurations.

Twenty-four mandibular incisors with two root canal configurations (n=12) were selected and scanned using CBCT. Canal shaping was performed in two steps: first with ProGresShape up to #25.05, followed by #25.07. After each step, a new CBCT scan was taken. RDT was measured at the coronal, middle, and apical thirds of the root, considering both mesial and distal walls. Statistical analyses were performed using repeated measures analysis of variance (ANOVA) (p<0.05).

A statistically significant difference in RDT was observed after preparation with 5% and 7% taper files (p<0.05). The 5% taper preserved more dentine than the 7%. In both groups, the number of root surfaces measuring less than 0.5 mm increased significantly after shaping, particularly in the apical third. The 25.07 file resulted in more slices under 0.5 mm compared to the 25.05 file. Overall, shaping led to a notable reduction in dentine, raising concerns about the risks of perforation and fracture, especially apically.

Instruments with a smaller taper (<5%) are preferable for shaping mandibular incisors to preserve dentine thickness. However, clinicians must ensure effective disinfection protocols. Future research should explore irrigation activation protocols in conservative approaches for mandibular incisors with different configurations.