Ji-Hyun Lee

Objective: To compare ClinCheck‐predicted and achieved maxillary occlusal contact areas immediately after an initial 14‐aligner anterior segmental sequence without programmed posterior movement. Materials and Methods: This retrospective study included 31 adult women treated with 14 maxillary and mandibular clear aligners. Bilateral first premolars through second molars were digitally locked. Predicted stage‐14 models and intraoral scans obtained immediately after aligner 14 and before refinement were assessed at maximum intercuspation. Contact regions at 0.00‐mm clearance were quantified with ImageJ. The primary outcome was the patient‐level total posterior achieved‐minus‐predicted difference. Tooth‐type differences were analysed using patient‐clustered generalized estimating equations with Holm adjustment; bite‐ramp comparisons were exploratory. Results: Predicted and achieved total posterior areas were 63.71 ± 36.56 and 30.30 ± 18.26 mm ² , respectively (mean difference, −33.41 mm ² ; 95% CI, −44.42 to −22.40; p < 0.001). After Holm adjustment, the achieved central‐incisor area was 0.49 mm ² greater than predicted ( p = 0.003), whereas areas were smaller at the first premolars, second premolars, first molars, and second molars by 3.09, 5.44, 11.46, and 13.42 mm ² , respectively (adjusted p ≤ 0.016). Lateral‐incisor and canine differences were not significant. Bite‐ramp groups did not differ significantly. Conclusion: After 14 aligners, the achieved posterior contact area was substantially smaller than predicted despite no programmed posterior movement. This early discrepancy supports direct evaluation of posterior contacts before refinement.

Jinsuk Lee, Jung-Yul Cha, Hyung Seog Yu, Ji-Hyun Lee, Kyung-Ho Kim, Chooryung Judi Chung. Korean J Orthod 2026;56:221-30. https://doi.org/10.4041/kjod26.002

Background/Objectives: This retrospective longitudinal study analyzed height growth velocity (GV) across skeletal maturity indicator (SMI) intervals in Korean adolescents with skeletal Class II malocclusion to identify the timing and duration of peak height velocity (PHV) and to define a PHV window relevant to growth-modification treatment. Methods: Sixty patients (30 males, 30 females) were followed for at least six years with serial hand-wrist radiographs and height records. GV was calculated for each SMI interval, defined as the period between adjacent SMI stages. In females, the timing of menarche by SMI stage was also recorded. Results: GV increased with skeletal maturation and was greatest at the SMI 5–6 interval in both sexes. In males, GV was already high at SMI 4–5 and did not differ significantly from that at SMI 5–6, whereas in females GV remained high at SMI 6–7 and did not differ significantly from that at SMI 5–6. In all female subjects, menarche occurred after PHV and coincided with growth deceleration. GV declined markedly after SMI 7–8, with minimal growth beyond SMI 11. Conclusions: These findings indicate that the PHV window spans SMI 4–6 in males and SMI 5–7 in females, suggesting that growth-modification therapy may achieve optimal outcomes when initiated within these stages. Because this study evaluated height rather than maxillomandibular growth and individual variation persists, SMI stage alone cannot define PHV, and additional assessments of growth are required when determining the timing of orthopedic intervention.

Extraction of the mandibular second molar (L7) and substitution by the mandibular third molar (L8) is an effective treatment option. This study aimed to evaluate spontaneously erupted L8 occlusion after L7 extraction, and identify the influencing factors. This study assessed 46 L8 from 28 patients using dental study models, panoramic radiographs, and lateral cephalograms obtained during L7 extraction (T1) and completion of L8 eruption (T2). At T2, samples were categorized as acceptable (A-group) or unacceptable (U-group) based on the American Board of Orthodontics index. L8 angulation and position, retromolar space, distance between the Xi point and mandibular first molar (L6), and Nolla stage were compared between the groups to identify the predictive factors for successful eruption. At T2, 58.7% of L8 exhibited acceptable occlusion. Age at T1 was significantly higher in the U-group than that in the A-group. Angles ∟6-MnP and ∟8-MnP differed significantly between the groups at T2. Xi-L6 distance was considerably longer in the A-group than that in the U-group at T1 and T2. Younger age at extraction and Xi-L6 distance at T1 affected the acceptable occlusion. Younger age at L7 extraction and adequate eruption space (Xi-L6 distance) appear to be the key factors for achieving acceptable L8 occlusion.