Functional Unit‐Based Analysis Unveils the Skeletal Mandibular Effects of Class <scp>II</scp> Elastics Therapy in Adolescents

BACKGROUND: This study sought to thoroughly assess the skeletal impacts of Class II elastics therapy on the developing mandible, highlighting three-dimensional changes in its functional units. METHODS: Treatment records of 140 CBCT scans from 70 adolescent patients were retrospectively collected and assigned to one of two groups: the Class II elastics group (n = 35), in which class II elastics were performed on the stainless steel archwires for more than 12 months, and the control group (n = 35). Pre- and post-treatment cone beam computed tomography (CBCT) images were used to assess changes related to the skeletal facial pattern, functional units, and transverse parameters. An independent t-test was used to compare between the two groups. RESULTS: In the Class II elastics group, the mandibular body unit length (IAF-MF) increased by 3.09 ± 3.16 mm from pre- to post-treatment, significantly larger than that in the control group (1.37 ± 3.14 mm). No other mandibular functional unit or transverse parameters demonstrated significant differences between the two groups. CONCLUSIONS: Based on the single-center sample included in this study, the adolescent group receiving prolonged Class II elastics may have exhibited a greater increase in mandibular body unit length compared to the group with minimal elastic use. However, these findings cannot be generalized without further validation.