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. 2022 Sep 1;92(5):606-612.
doi: 10.2319/112021-854.1. Epub 2022 Jul 18.

Mandibular retromolar space in adults with different sagittal skeletal patterns: Cone-beam computed tomography analysis

Zeng Fan  1 , Qi Zhang  1 , Yujun Jiang  1 , Qianyi Qin  1 , Sheng Huang  1 , Jie Guo  2
Affiliations

Mandibular retromolar space in adults with different sagittal skeletal patterns: Cone-beam computed tomography analysis

Zeng Fan et al. Angle Orthod. .

Abstract

Objectives: To analyze the mandibular retromolar space among normal-divergent adult patients with different sagittal skeletal patterns by cone-beam computed tomography (CBCT).

Materials and methods: CBCTs of a total of 120 normal-divergent adult patients were investigated. Patients were categorized into the following three groups according to their ANB angle: skeletal Class I (48 patients), skeletal Class II (36 patients), and skeletal Class III (36 patients). Four different planes parallel to the mandibular occlusal plane were used to measure the retromolar space. The retromolar space was measured by two reference lines and then compared between different sagittal skeletal patterns groups. The incidence of root contact with the inner lingual cortex was compared among the three groups.

Results: The retromolar space of the Class III patients was significantly larger than that of Class I patients and Class II patients. Compared with Class I and Class III patients, Class II patients had a smaller retromolar space and higher incidence of contact with the inner cortex of the mandible.

Conclusions: Class III patients had a larger retromolar space than Class I patients and Class II patients in four different planes. The mandibular retromolar space should be evaluated by CBCT in patients who need mandibular molar distalization.

Keywords: CBCT; Molar distalization; Retromolar space; Sagittal skeletal pattern.

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Conflict of interest statement

The authors declare no competing or financial interests.

Figures

Figure 1.
Figure 1.
Four planes parallel to the mandibular occlusal plane. Four different planes, parallel to the mandibular occlusal plane, were used to measure the mandibular retromolar space. (a) The 0-plane passed through the furcation of the mandibular second molar root and the (b) 2-plane, (c) 4-plane, and (d) 6-plane were at 2, 4, and 6 mm, respectively, apical to the 0-plane.
Figure 2.
Figure 2.
Reference lines. Two reference lines were used in this study. (a) The cuspal line connected the buccal cusps of the mandibular first and second molars and (b) the sagittal line was parallel to the midsagittal reference plane. α indicates the angle between the cuspal and sagittal lines.
Figure 3.
Figure 3.
Measurement of retromolar space. The distances between the most lingual point of the distal root of the second molar and inner and outer cortex of the mandibular body were measured by two reference lines at each plane. (a) The shortest distance to the inner lingual cortex of the mandibular body along the cuspal line. (b) The shortest distance to the inner lingual cortex of the mandibular body along the sagittal line. (c) The shortest distance to the outer lingual cortex of the mandibular body along the cuspal line. (d) The shortest distance to the outer lingual cortex of the mandibular body along the sagittal line.
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