Adult Orthodontics Adult patients present a challenge to orthodontists because they have high esthetic demands and often have dental conditions that complicate treatment. In many adults, “black triangular” spaces develop between both maxillary and mandibular incisors with the orthodontic treatment. This is seen particularly in patients with pretreatment overlapping of incisors, or triangularly shaped incisor crowns. The loss of the interdental papillae associated with the treatment may be of concern to the patients, particularly when the gingival papillae were intact at the start of treatment. The size of the dark spaces seems to be largely dependent on the extent of pretreatment incisor overlap, and patients with wide-open gingival embrasures posttreatment may consider these spaces to be unattractive. What is the present research knowledge regarding the underlying causes of the development of “black triangles,” and how can the practitioner modify these factors to prevent, reduce, or eliminate their development and thus enhance the esthetic outcome of orthodontic therapy?