INTRODUCTION: The purpose of this study was to quantitatively evaluate the wall thickness of C-shaped canals in mandibular first premolars using micro-computed tomographic imaging. The focus was on the relation between the radicular groove and the mesial canal wall thickness. METHODS: A total of 148 mandibular first premolars were scanned by a micro-computed tomographic scanner. After 3-dimensional reconstruction of the teeth, 29 specimens were identified to contain a C-shaped canal, and then they were analyzed in software Mimics 10.01 (Materialise, Leuven, Belgium). The buccal and lingual canal wall thickness, minimum mesial and distal wall thickness, and the depth and angle of radicular grooves were measured at different root levels. Two-way analyses of variance and the post hoc Tukey's honestly significant difference test were used to compare the groups in relation to canal wall thickness. RESULTS: The buccal and lingual canal walls were significantly (P < .005) thicker than the mesial and distal walls. The minimum thickness of the mesial walls was significantly (P < .005) lower than that of the distal walls, and the locations were frequently at lingual sites, with an incidence of 67.3% for the mesial walls and 69.2% for the distal walls. Backward multivariate analysis showed that the root level and groove angle contributed significantly (P < .005) to the minimum mesial wall thickness. CONCLUSIONS: The mesial walls of C-shaped canals in mandibular first premolars are the thinnest zones. The minimum mesial wall thickness decreases with the increased severity of the radicular groove, and it mainly occurs at lingual sites. Care should be taken to avoid perforation at danger zones during shaping and post space preparation procedures.
INTRODUCTION: The purpose of this study was to quantitatively evaluate the wall thickness of C-shaped canals in mandibular first premolars using micro-computed tomographic imaging. The focus was on the relation between the radicular groove and the mesial canal wall thickness. METHODS: A total of 148 mandibular first premolars were scanned by a micro-computed tomographic scanner. After 3-dimensional reconstruction of the teeth, 29 specimens were identified to contain a C-shaped canal, and then they were analyzed in software Mimics 10.01 (Materialise, Leuven, Belgium). The buccal and lingual canal wall thickness, minimum mesial and distal wall thickness, and the depth and angle of radicular grooves were measured at different root levels. Two-way analyses of variance and the post hoc Tukey's honestly significant difference test were used to compare the groups in relation to canal wall thickness. RESULTS: The buccal and lingual canal walls were significantly (P < .005) thicker than the mesial and distal walls. The minimum thickness of the mesial walls was significantly (P < .005) lower than that of the distal walls, and the locations were frequently at lingual sites, with an incidence of 67.3% for the mesial walls and 69.2% for the distal walls. Backward multivariate analysis showed that the root level and groove angle contributed significantly (P < .005) to the minimum mesial wall thickness. CONCLUSIONS: The mesial walls of C-shaped canals in mandibular first premolars are the thinnest zones. The minimum mesial wall thickness decreases with the increased severity of the radicular groove, and it mainly occurs at lingual sites. Care should be taken to avoid perforation at danger zones during shaping and post space preparation procedures.