[Effect of mandibular third molar tooth germ extraction on mandibular development: a retrospective study].

Objective: To investigatethe effect of extraction of mandibular third molar (M3) tooth germon the development of the mandible in orthodontic patients, with a view to providing a reference for clinical M3 tooth germ extraction. Methods: One hundred and twenty-nine Angel class Ⅰ patients aged 10-16 years who attended the Department of Orthodontics Division 1, School & Hospital of Stomatology, Wuhan University from 1 January 2013 to 30 December 2021 and fulfilled the criteria for nativity were included. Those who had their M3 extracted in the Department of Oral and Maxillofacial Surgery were included in the study group, with a total of 66 cases; and those who did not have their M3 extracted were included in the control group, with a total of 63 cases. The average annual growth was calculated by tracing point measurements on cephalometric films before and after orthodontic treatment according to the Jarabak and McNamara methods, with measurements of the mandibular ramus height (Ar-Go'), mandibular body length (Go'-Me), and overall mandibular length (Co-Gn) values, respectively. The average annual growth of Ar-Go', Go'-Me, and Co-Gn were compared between the two groups for the overall sample of patients, patients of the same sex (male/female), patients of the same age group (A, B, and C), and patients of the same cervical vertebral maturation stage (stages Ⅱ, Ⅲ, and Ⅳ), respectively, to see if there was any difference in the average annual growth of Ar-Go', Go'-Me, and Co-Gn. Results: There was no statistically significant difference in the average annual growth of Ar-Go', Go'-Me, and Co-Gn between the study group [0.88 (0.40, 1.80), 0.67 (0.15, 1.18), and 0.86 (0.40, 1.90) mm, respectively] and the control group [1.08 (0.45, 1.60), 0.53 (0.25, 1.13), and 1.20 (0.46, 2.28) mm, respectively] (P>0.05). In addition, there was no significant difference in the average annual growth in the Ar-Go', Go'-Me, and Co-Gn between the groups for patients of the same sex group (male/female), patients of the same age group (A, B, and C), and patients of the same cervical vertebral maturation stage group (stages Ⅱ, Ⅲ, and Ⅳ) (P>0.05). Conclusions: Extraction of the mandibular third molar tooth germ has no significant effect on the development of the mandible in Angle class Ⅰ orthodontic patients.