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Objective <p>To investigate the anatomical characteristics of the apical region of immature mandibular second premolars using CBCT.</p> Method <p>CBCT images of 100 mandibular second premolars at Nolla stage 8 and 100 at Nolla stage 9 were included. Using the CBCT built-in software, the buccolingual (A-B) and mesiodistal (C-D) diameters of the apical foramen, as well as the buccolingual (A1-B1), mesiodistal (C1-D1), and superoinferior (E-F) diameters of the physiologic apical radiolucency, were measured. Data were analyzed using SPSS 26.0.</p> Results <p>The values for Nolla stage 8&#xa0;A-B, C-D, A1-B1, C1-D1, and E-F were 3.32 ± 0.38&#xa0;mm, 2.45 ± 0.28&#xa0;mm, 4.28 ± 0.43&#xa0;mm, 3.29 ± 0.40&#xa0;mm, and 3.04 ± 0.43&#xa0;mm, respectively. The values for Nolla stage 9 were 2.24 ± 0.44&#xa0;mm, 1.37 ± 0.23&#xa0;mm, 3.11 ± 0.52&#xa0;mm, 2.20 ± 0.29&#xa0;mm, and 1.85 ± 0.30&#xa0;mm respectively. The differences were all significant (<i>P</i> &lt; 0.05). In the Nolla stage 8 group, the values of A-B, C-D, A1-B1, C1-D1, and E-F were significantly lower in females than in males (all <i>P</i> &lt; 0.05). At Nolla stage 9, males had slightly higher values than females, the sex difference in C-D was statistically significant (<i>P</i> &lt; 0.05). The values of A-B and C-D were significantly positively correlated with those of A1-B1, C1-D1, and E-F (<i>P</i> &lt; 0.001). In Nolla stage 8, the apical foramen was predominantly flared (85%), thick lamina dura accounted for 62%, lamina dura density was mainly heterogeneous (28%) or moderate (53%), and the lamina dura was mainly rough (67%) or mildly rough (25%). In contrast, Nolla stage 9 predominantly showed parallel apical foramen (91%), thin lamina dura (84%), homogeneous lamina dura density (78%), and smooth lamina dura (72%).</p> Conclusion <p>The apical foramen and physiologic apical radiolucency of the second premolar in the mandible of Nolla stage 9 are smaller than those in Nolla stage 8. During these stages, the apical foramen transforms from a trumpet-shaped to a parallel shape, and the lamina dura becomes more mature.</p> Clinical significance <p>This study provides normative reference data on the apical anatomy of immature mandibular second premolars, which may serve as a baseline for future diagnostic accuracy studies or for comparison with pathological conditions in the same tooth type.</p>

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CBCT analysis of the apical anatomy of immature mandibular second premolars in Chinese individuals

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  • 发表日期：

    2026年7月10日

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  • Jingchao Han,
  • Linlin Wang,
  • Mingru Fan,
  • Xiangyu Ma,
  • Jianli Xie

摘要

Objective

To investigate the anatomical characteristics of the apical region of immature mandibular second premolars using CBCT.

Method

CBCT images of 100 mandibular second premolars at Nolla stage 8 and 100 at Nolla stage 9 were included. Using the CBCT built-in software, the buccolingual (A-B) and mesiodistal (C-D) diameters of the apical foramen, as well as the buccolingual (A1-B1), mesiodistal (C1-D1), and superoinferior (E-F) diameters of the physiologic apical radiolucency, were measured. Data were analyzed using SPSS 26.0.

Results

The values for Nolla stage 8 A-B, C-D, A1-B1, C1-D1, and E-F were 3.32 ± 0.38 mm, 2.45 ± 0.28 mm, 4.28 ± 0.43 mm, 3.29 ± 0.40 mm, and 3.04 ± 0.43 mm, respectively. The values for Nolla stage 9 were 2.24 ± 0.44 mm, 1.37 ± 0.23 mm, 3.11 ± 0.52 mm, 2.20 ± 0.29 mm, and 1.85 ± 0.30 mm respectively. The differences were all significant (P < 0.05). In the Nolla stage 8 group, the values of A-B, C-D, A1-B1, C1-D1, and E-F were significantly lower in females than in males (all P < 0.05). At Nolla stage 9, males had slightly higher values than females, the sex difference in C-D was statistically significant (P < 0.05). The values of A-B and C-D were significantly positively correlated with those of A1-B1, C1-D1, and E-F (P < 0.001). In Nolla stage 8, the apical foramen was predominantly flared (85%), thick lamina dura accounted for 62%, lamina dura density was mainly heterogeneous (28%) or moderate (53%), and the lamina dura was mainly rough (67%) or mildly rough (25%). In contrast, Nolla stage 9 predominantly showed parallel apical foramen (91%), thin lamina dura (84%), homogeneous lamina dura density (78%), and smooth lamina dura (72%).

Conclusion

The apical foramen and physiologic apical radiolucency of the second premolar in the mandible of Nolla stage 9 are smaller than those in Nolla stage 8. During these stages, the apical foramen transforms from a trumpet-shaped to a parallel shape, and the lamina dura becomes more mature.

Clinical significance

This study provides normative reference data on the apical anatomy of immature mandibular second premolars, which may serve as a baseline for future diagnostic accuracy studies or for comparison with pathological conditions in the same tooth type.