Mandibular third molar protraction using a segmented arch and mini-implant anchorage: A case report

The absence of the mandibular second molar (M2) significantly compromises oral function and quality of life. Conventional prosthetic rehabilitation or autotransplantation presents notable limitations. Under the premise of efficiency and precision, orthodontic mesialization of the third molar (M3) using a localized appliance offers a promising, noninvasive alternative for tooth replacement.

A 20-year-old male patient with severe caries in the right mandibular M2 was referred by the Department of Endodontics and admitted to the Orthodontics Department at the Hospital of Stomatology, Jilin University, Changchun, Jilin, China, with the chief complaint of functional rehabilitation in the right mandibular region.

After conducting routine orthodontic examinations and analyses, the patient was diagnosed with skeletal Class III malocclusion and Angle Class I malocclusion. Additionally, the right mandibular M2 exhibited severe caries with pulp involvement and subgingival extension.

This case involved mesialization of the mandibular right M3 to substitute for the compromised M2, utilizing a segmental arch combined with a temporary anchorage device. Over 20 months, the M3 was mesialized by 11.7 mm, followed by 10 months of occlusal adjustment and 36 months of natural retention.

The treatment successfully restored occlusal function on the right side. The M3 exhibited favorable root parallelism, preservation of the original occlusal plane, and maintenance of the facial profile.

The use of a segmental arch in combination with temporary anchorage devices enables effective mesialization of vertically positioned, two-rooted mandibular M3s. This approach offers a minimally invasive and low-risk alternative for the replacement of prematurely lost M2s in young adults.