This retrospective study of roots with C-shaped canals investigated their prevalence, configuration type, and lingual wall thickness, as well as the panoramic radiographic features of roots in permanent mandibular second molars confirmed to have C-shaped canals on cone-beam computed tomography (CBCT) in a Korean population. In total, 1884 CBCT images of mandibular second molars were examined by two endodontists to analyze the presence of C-shaped canals according to age and sex. The bilateral occurrence of C-shaped roots and their morphology on panoramic radiography were assessed and statistically analyzed using the chi-square test. The classification of Fan et al. was applied to categorize the configurations of C-shaped canals. The lingual wall thickness was calculated in the mesial, middle, and distal areas at the orifice and at 5 mm from the apex. The Mann–Whitney test was used to analyze the mean difference of lingual wall thickness between the apex and orifice level. A value of 0.05 was considered to indicate statistical significance in the statistical analyses. Of 2508 mandibular second molars, 924 (36.8%) had C-shaped root canals. The prevalence was significantly lower in the over 61 age group (24.08%) than in the 21–30-year age group (40.02%) and was higher in women (42.32%). Most cases were bilateral (85.9%). The C1 type was the most common (35.3%). The prevalence of C1 type canals decreased, while that of C3b type canals increased with age. In 75.2% of teeth having C-shaped root canals on CBCT, fused roots were observed on panoramic views. The difference in the lingual wall thickness at the orifice and 5 mm from the apex was significant in the middle area in all configurations of C-shaped root canals. When performing nonsurgical or surgical endodontic procedures of the mandibular second molars, clinicians should consider age, sex, ethnicity, and anatomical variations.

中文翻译：

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C 形运河的患病率和形态：韩国人群的 CBCT 分析

这项对 C 形根管的回顾性研究调查了其患病率、配置类型和舌壁厚度，以及在锥形束计算机断层扫描上证实具有 C 形根管的下颌第二恒磨牙根部的全景影像学特征。 CBCT）在韩国人群中。总共有 1884 张下颌第二磨牙的 CBCT 图像由两名牙髓科医生检查，以根据年龄和性别分析 C 形根管的存在。采用卡方检验对C形根的双侧发生情况及其全景X线形态进行评估和统计分析。Fan等人的分类。用于对 C 形运河的配置进行分类。舌壁厚度按近中、中、孔口和距顶点 5 毫米处的远端区域。曼-惠特尼采用检验法分析舌尖与孔口水平舌壁厚度的平均差值。一种0.05的值被认为表明统计分析中的统计显着性。2508颗下颌第二磨牙中，924颗（36.8%）有C形根管。61岁以上年龄组（24.08%）的患病率显着低于21-30岁年龄组（40.02%），女性更高（42.32%）。大多数病例是双侧的（85.9%）。C1 型最常见（35.3%）。随着年龄的增长，C1型根管的患病率下降，而C3b型根管的患病率增加。在 CBCT 上 75.2% 的 C 形根管牙齿中，在全景视图中观察到融合的牙根。在 C 形根管的所有配置中，在孔口和距根尖 5 mm 处的舌壁厚度差异在中间区域是显着的。在对下颌第二磨牙进行非手术或手术根管治疗时，