The Occurrence and Risk Factors of Black Triangles Between Central Incisors After Orthodontic Treatment

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 <i>t</i>-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 (<i>p</i> < 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.