Coronal root canal morphology of permanent two‐rooted mandibular first molars with novel 3D measurements

Abstract

AimTo measure the coronal root canal morphology of permanent mandibular first molars using 3D coordinates for more precise conservative endodontic cavity preparation.MethodologyIn total, 57 cone beam computed tomography (CBCT) images of sound mandibular molars with fully formed apices without previous endodontic treatment were taken from 33 patients aged 16 to 75 years. The CBCT machine (MCT‐1[EX‐2F], J. Morita Manufacturing Corp, Kyoto, Japan) provided 14‐bit greyscale images with the voxel size of 0.125 mm. All images were taken at 80 kV and 5.0 mA, with a 17‐s exposure time, which were then reconstructed in 3D models and viewed by an endodontist. The gender of the patients and the tooth position, and number of root canals, were recorded. The landmarks of coronal root canals were determined, then the distribution of landmarks, maximum curvature in the axial direction and curvature directions in the horizontal direction of coronal root canals were measured. Distributions of landmarks were analysed using a spatial statistics method. Data about curvature were compared using a t test.ResultsOverall, the distribution of root canal orifices and the centre of the canal primary curve were more centralized than other landmarks. The landmarks were located more mesiobuccally to the centre of the occlusal plane of mandibular first molars. Specifically, the measurements of the maximum curvature of coronal root canals in the axial direction were as follows: in 3‐canal teeth, the average angles of curvatures were 22°,23°,15° for mesiobuccal (MB), mesiolingual (ML) and distobuccal (DB) canals, respectively; in 4‐canal teeth, the average angles of curvatures were 24°,26°,15°,22°for MB, ML, DB and distolingual (DL) canals, respectively. The degrees of coronal root canal curvatures in the horizontal direction were as follows: in 3‐canal teeth, the average angles of curvatures were −8°,47°,−2° for MB, ML and DB canals, respectively; in 4‐canals teeth, the average angles were −11°,50°,−28°,45° for MB, ML, DB and DL canals, respectively. Statistically, there was no reliable side or sex difference in any of the measurements (P > 0.05).ConclusionsIn permanent two‐rooted mandibular first molars, the coronal canals clustered in the direction of the mesiobuccal side of the occlusal surface of the teeth.

Three-dimensional analysis of coronal root canal morphology of 136 permanent mandibular first molars by micro-computed tomography

“…The in vitro 3D measurements collected in this experiment was largely consistent with the in vivo measurements reported in our previous study, 24 with the only major difference being that the equipment for image scanning switched from CBCT to micro-CT. In root canal morphology studies, micro-CT has the advantage of higher imaging resolution compared with CBCT.…”

“… 38 Furthermore, there were greater coronal root canal curvatures in the axial direction in the DL canal of mandibular first molars with radix entomolaris. As we mentioned by Fu et al., 24 the curvature of the coronal part of the root canal may be used to evaluate the additional difficulty in root canal preparation in conservative endodontic cavities compared with that in traditional endodontic access cavities. Greater curvature suggests that there may be additional difficulty.…”

“…To bridge this gap in knowledge, our research group has previously used cone beam computed tomography (CBCT) data in vivo to study coronal root canal morphology of permanent two-rooted mandibular first molars with novel 3D measurement methods. 24 The study provided significant preliminary in vivo results, and these results enabled us to make further in vitro examinations using micro–computed tomographic (micro-CT) imaging.…”

“…In addition, the combination of in vivo results and the current higher-accuracy in vitro results enables us to present our novel protocol for minimally invasive endodontic approach. 24 …”

A novel three‐dimensional morphological analysis of idiopathic condylar resorption following stabilisation splint treatment

“…First, a condylar axis was obtained by principal component analysis, 33,34 based on the condylar contour; a plane (Plane 1) perpendicular to this axis was then set. This plane was moved along the condylar axis to confirm the location where the line between the medial and lateral ends of the condylar section was the longest.…”