Journal of Jilin University(Medicine Edition) ›› 2023, Vol. 49 ›› Issue (6): 1561-1568.doi: 10.13481/j.1671-587X.20230620

• Research in clinical medicine • Previous Articles     Next Articles

Structural characteristics of mandible in patients with different osteofacial types measured by CBCT and influencing factors of mandibular retromolar space

Yunyun SUN1,Yuguang YAO2,Han ZHANG1,Hanyi LI1,Xianchun ZHU1()   

  1. 1.Department of Orthodontics,Stomatology Hospital,Jilin University,Changchun 130021,China
    2.Department of Stomatology,Hospital of Caofeidian District,Tangshan City,Hebei Province,Tangshan 063299,China
  • Received:2022-12-08 Online:2023-11-28 Published:2023-12-22
  • Contact: Xianchun ZHU E-mail:zhuxc@jlu.edu.cn

Abstract:

Objective To discuss the influence factors of retromolar space in the patients with different osteofacial types, and to analyze the correlation between the mandibular bone structure and retromolar space and craniofacial structure. Methods A total of 200 adult orthodontic patients with fully erupted dentition except the third molars and crowding less than 5 mm were chosen and divided into skeletal type Ⅰ low angle group, skeletal type Ⅰ average angle group, skeletal type Ⅰ high angle group, skeletal type Ⅱ average angle group, and skeletal type Ⅲ average angle group. The sella nasion A point angle(SNA), sella nasion B point angle(SNB), AB plane angle(ANB), skull base anterior-mandibular plane angle(SN-MP),facial height index(FHI),mandibular ramus length(Go-Co),and mandibular body length(Go-Gn) of all the patients were detected. Cone-beam computed tomography (CBCT) technology was used to detect the shortest distances C0 and C2 from the mandibular second molar to the anterior border of the ramus at the planes parallel to the cuspid line with a depth of 0 and 2 mm form the occlusal plane, and the shortest distances R2, R4, R6, R8, and R10 from the tooth root to the lingual cortical bone of the mandible at the enamel-bone junction in the root direction 2, 4, 6, 8, and 10 mm planes.The correlation was analyzed by using Spearman correlation analysis. Results Compared with skeletal type Ⅰ low angle group, the SN-MP of the patients in skeletal type Ⅰ average angle group and skeletal type Ⅰ high angle group was increased significantly (P<0.01), and the FHI was decreased significantly (P<0.01). Compared with skeletal type Ⅰ average angle group, the SN-MP of the patients in skeletal type I high angle group was increased significantly (P<0.01),FHI was decreased significantly (P<0.01). Compared with skeletal type Ⅰ average angle group, the ANB of patients in skeletal type Ⅱaverage angle group was significantly increased (P<0.01), while the ANB of the patients in skeletal type Ⅲ average angle group were significantly decreased (P<0.01). Compared with skeletal type Ⅱ average angle group, the ANB of the patients in skeletal type Ⅲ average angle group was significantly decreased (P<0.01). Under the C2, R2, R4, R6, R8, R10 planes and in the Go-Co and Go-Gn, compared with skeletal type Ⅰ low angle group, the retromolar spaces of the patients in skeletal type Ⅰ average angle group and the skeletal type Ⅰ high angle group were significantly decreased (P<0.01); compared with skeletal type Ⅰ average angle group, the retromolar space of the patients in skeletal type Ⅰ high angle group was significantly decreased (P<0.01). Under the C0 plane, compared with skeletal type Ⅰ low angle group and the skeletal type Ⅰ average angle group, the retromolar space of the patients in skeletal type Ⅰ high angle group was decreased (P<0.01). Under the C0, R2, R4, R6, R8, and R10 planes, compared with skeletal type Ⅰ average angle group, the retromolar space of the patients in skeletal type Ⅱ average angle group was significantly decreased (P<0.01), the retromolar space of the patients in skeletal type Ⅲ average angle group was increased (P<0.01); compared with skeletal type Ⅱ average angle group, the retromolar space of the patients in skeletal type Ⅲ average angle group was increased (P<0.01).Under the C2 plane and in the Go-Co and Go-Gn, compared with skeletal type Ⅰ average angle group and skeletal type Ⅱ average angle group, the retromolar space of the patients in skeletal type Ⅲ average angle group was increased (P<0.01). The retromolar space,Go-Co and Go-Gn of the patients in skeletal type Ⅰ low angle group, skeletal type Ⅰ average angle group, and skeletal type Ⅰ high angle group under all planes had positive correlations with the SNB and FHI (P<0.01), and a negative correlation with SN-MP (P<0.01);the retromolar space at all levels had a positive correlation with Go-Co (P<0.01); except for the C2 plane, the remaining retromolar space under all planes had positive correlations with Go-Gn (P<0.01);there was a positive correlation between Go-Co and Go-Gn (P<0.01);there was a negative correlation between Go-Gn and ANB((P<0.01).The retromolar space and Go-Co and Go-Gn of the patients in skeletal type Ⅰ average angle group, skeletal type Ⅱ average angle group, and skeletal type Ⅲ average angle group under all planes had positive correlations with SNB (P<0.01),and the retromolar space had positive correlations with Go-Co and Go-Gn (P<0.01); there was a positive correlation between Go-Co and Go-Gn (P<0.01);there was a positive correlation between Go-Co and FHI(P<0.01). Conclusion The skeletal type is an important influence factor of the retromolar space of mandible, when the molar distalization plan is formulated, the skeletal type of the patient should be considered; CBCT should be used to evaluate the available space for mandibular molar distalization.

Key words: Retromolar space, Molar distalization, Vertical osteofacial type, Sagittal osteofacial type, Cone-beam computed tomography

CLC Number: 

  • R783.5