American Board of Orthodontics (ABO) Practice Exam

An osseous crater defect is characterized by its bowl-shaped morphology, which typically occurs in the interdental alveolar bone. This type of defect signifies a localized area of bone loss that resembles a concave shape or depression, where the bone is essentially missing in a way that creates a cavity or crater-like appearance between adjacent teeth. The term "crater" specifically denotes this round, indent-like feature that can be found adjacent to the roots of teeth, making option B the accurate characterization of such a defect.

In contrast, other options do not accurately reflect the true nature of an osseous crater defect. A pointed defect would not describe the rounded bowl shape typical of these areas of bone loss, while a defect limited to the facial bone would not capture the interdental nature of a crater defect, which occurs primarily between roots of adjacent teeth. Additionally, a smooth defect without bone loss does not align with the defining characteristics of an osseous crater, as the presence of bone loss is fundamental to the description of this type of defect.