Which defect is identified as a two or three-sided defect?

A two or three-sided defect refers to the configuration of bone loss that occurs around teeth, typically in relation to periodontal disease. The trench defect specifically describes a situation where there is vertical bone loss that forms a deep, narrow space, usually extending around the tooth. This configuration can have either two or three bony walls depending on the specific area involved, such as its location in the dental arch or the surrounding anatomical structures.

In contrast, a crater is generally a defect that has a circular shape, often affecting the interproximal bone around two adjacent teeth but not fitting the two or three-sided description as accurately as a trench. A moat, typically characterized by a ring-like defect around the tooth, does not conform to the straightforward definition of two or three walls. A Class II furcation defect, while representing some degree of bone loss, is specifically associated with bifurcations and is defined by the horizontal extent of involvement rather than the vertical configuration required to be described as a two or three-sided defect. Thus, the trench defect is correctly identified as having the necessary characteristics to qualify as a two or three-sided defect.