Shaping Ability of XP-Endo Shaper Files With Extended Use Time and R40 Blue in Oval Canals: A Microcomputed Tomography Study in Contralateral Premolars.

Introduction: This study evaluated the shaping ability of the single-file XP-endo Shaper (XP-S) system, employing an extended working time, and the Reciproc Blue number 40/.06 (REC) instrument during the preparation of oval-shaped canals.

Methods: Eleven pairs of contralateral premolars with a single canal were divided into two groups (n = 11) according to the canal preparation protocol: XP-S (with an additional 45 seconds of instrumentation) and REC. Microcomputed tomography images captured before and after preparation were analyzed to assess morphometric measurements (prepared volume/area and unprepared canal walls at 10 mm and 4 mm from the foramen), centroid deviation (at 10 mm), dentin thickness with mesial or distal deviation, and canal-to-root ratio (at 1, 5, and 10 mm from the foramen).

Results: In both groups, root canal preparation significantly altered all tested parameters across all evaluated cross-sections (P ≤ 0.003). No significant differences were observed between the groups in canal centralization, volume or surface area increase at 10 mm or 4 mm, nor in the number of unprepared canal walls at 10 mm. However, the REC system showed a greater reduction in unprepared walls in the critical apical zone (P = 0.047). The XP-S group exhibited greater reductions in mesial (P = 0.007) and distal (P = 0.028) dentin thickness at 1 mm from the foramen.

Conclusions: The REC instrument prepared more root canal walls than the XP-S system and promoted greater dentin preservation in the apical zone.