American Board of Orthodontics (ABO) Practice Exam

The ideal canine morphology for U2 substitution according to Kokich emphasizes the importance of the shape and dimensions of the tooth, particularly at the cervical enamel junction (CEJ) and midcrown area. A narrow CEJ allows for easier alignment and helps in creating a natural-looking transition when the canine is used to substitute for the upper lateral incisors (U2s). When the CEJ is narrow, it can more closely mimic the profile of lateral incisors, which tend to have a smaller width at the CEJ compared to the canines.

Additionally, having a midcrown that is balanced in its buccolingual (B/L) dimensions is essential. A narrow CEJ combined with a midcrown that is not excessively broad helps in achieving a more aesthetically pleasing appearance when the canine takes on the role of the U2, creating a smoother contour and better integration with adjacent teeth.

This aspect of canine morphology is especially significant in orthodontic treatment and esthetics, as it impacts how well the substitute canines blend with the overall dental arch and facial aesthetics, particularly in the smile zone. The characteristics mentioned prevent an overly bulky appearance, which could detract from the desired esthetic outcome in treatment.