Hamadan University of Medical Sciences Avicenna Journal of Dental Research 2423-7582 18 1 2026 03 29 Cone Beam Computed Tomography Analysis of TruNatomy, One Curve, and ProTaper Gold in the Canal Preparation of Curved Maxillary First Premolars: An In Vitro Study 29 37 10.34172/ajdr.4402 EN Elham Khoshbin https://orcid.org/0000-0002-5068-8080 Maryam Rasooli https://orcid.org/0009-0005-8727-2686 Abbas Shokri Alireza Hajizadeh https://orcid.org/0009-0005-1885-3962 Hamed Karkehabadi https://orcid.org/0000-0002-1296-7361 Journal Article 10.34172/ajdr.4402 2025 05 24 2025 09 22 Introduction: Root canal preparation is a critical step in endodontic treatment, particularly in curved canals. The palatal groove of the maxillary first premolar is often considered a risk zone, and the amount of remaining dentin plays a significant role in the prognosis and fracture resistance of teeth after treatment. This study compared the canal shaping ability and preservation of the original canal anatomy using TruNatomy, ProTaper Gold, and One Curve in the curved root canals of maxillary first premolars. Methods: Forty-two human maxillary first premolars with mature apices and canal curvatures between 25 and 35 degrees were selected. The teeth were randomly assigned to three groups (14 per group). The canal was prepared using the TruNatomy, ProTaper Gold, and One Curve file systems. Pre-preparation and post-preparation scans were obtained using cone beam computed tomography at 2, 3, 5, and 7 mm from the apex. Canal transportation, centering ability, and residual dentin were evaluated. Statistical analysis was performed using Kruskal-Wallis and one-way ANOVA tests. Results: The TruNatomy system demonstrated less canal transportation in mesiodistal and buccolingual directions. The mean residual dentin thickness in the TruNatomy group was 0.2036±0.1608 mm, which was lower than that in the ProTaper Gold group (0.2700±0.1461 mm) and comparable to that in the One Curve group (0.2057±0.1461 mm). Conclusion: TruNatomy, ProTaper Gold, and One Curve were effective and safe for root canal preparation, with no significant differences in their ability to preserve canal anatomy and residual dentin.