Where does apposition of bone primarily occur?

Apposition of bone primarily occurs on the tension side of a bone or bony structure in response to mechanical forces. When a force is applied to bone, it creates tension on one side, leading to the formation of new bone to strengthen that area and adapt to the altered load. This process is crucial for maintaining bone health and integrity, as well as facilitating movement and supporting the alignment of teeth in orthodontics.

In contrast, on the compression side, bone tends to undergo resorption rather than apposition. This is because the mechanical stress compresses the bone, signaling the need for maintaining or reducing the existing bone rather than adding more. The neutral zone refers to an area of minimal stress where forces are neither significantly compressive nor tensile, and generally does not promote apposition. The balanced side is not a recognized zone in the context of bone adaptation and remodeling. Thus, the primary site for apposition is indeed the tension side, where bone responds to the biomechanical loading with new bone formation.