Background/Objectives: To assess the incidence of and risk factors for black triangles between the central incisors after orthodontic treatment; Methods: Ninety-seven post-treatment patients (29 men and 68 women; mean age, 22.7 years) were retrospectively divided into two groups based on the presence or absence of black triangles, using intraoral photographs. Based on the Jemt Index, the black triangle occurrence group was further classified into mild, moderate, and severe groups. Parameters from periapical radio graphs, lateral cephalograms, and study models were compared between the occurrence and the non-occurrence groups by using independent t-tests. Logistic regression analysis was performed to identify the risk factors for black triangles; Results: The incidence of black triangles between the central incisors was 51% and 64% in the maxilla and in the mandible, respectively. The factors significantly associated with the occurrence of black triangles were age, treatment duration, the lingual inclination of the maxillary incisors in the maxilla, and age in the mandible (p < 0.05); Conclusions: This study showed the diverse risk factors associated with black triangles between central incisors after orthodontic treatment and revealed that the formation of black triangles is relatively common. Considering these risk factors during orthodontic diagnosis and treatment planning can help minimize the occurrence of black triangles.

Objective: This study investigated the association between tongue and hyoid position, tongue volume, and pharyngeal airway dimensions with craniofacial growth patterns in the sagittal, vertical, and transverse planes. Methods: Cone beam computed tomography was used to assess 185 non-growing subjects (mean age, 28.7 ± 9.5 years). Multivariate linear regression analyses evaluated relationships between tongue and airway variables, and cephalometric/dental arch measurements. Results: Class III skeletal patterns—reflected by lower ANB and higher APDI—were significantly correlated with anteriorly positioned hyoids (ANB: β = 0.249; APDI: β = –0.291), and lower tongue positions at the tongue tip (ANB: β = –0.231; APDI: β = 0.166) and in the posterior area (ANB: β = –0.186; APDI: β = 0.196), and greater tongue volume (APDI: β = 0.174). Hyperdivergent vertical patterns—indicated by a lower ODI—were significantly correlated with a lower tongue tip position (β = –0.311) and posterior tongue position (β = –0.230). Regarding transverse dimensions, tongue volume showed positive correlations with upper intermolar width (β = 0.349), lower intercanine width (β = 0.130), lower intermolar width (β = 0.311), and a negative correlation with upper intercanine width (β = –0.299). Conclusions: Sagittal and vertical craniofacial patterns are interrelated and show associations with tongue and hyoid position, as well as tongue volume. Transverse dental arch dimensions are correlated not only with tongue position and volume but also with pharyngeal airway volume.

You-Sun Lee, Ji-Yeon Lee. Korean J Orthod 2024;54:185-95. https://doi.org/10.4041/kjod24.004