Osteoblasts trapped in the matrix become:

1. The cell stops secreting and changes role. 2. It ends up sealed inside the bone. 3. When osteoblasts get trapped within the calcified matrix they become osteocytes. 4. So the answer is osteocytes. _Source: OpenStax 'Anatomy and Physiology 2e', Ch 6 'Bone Tissue and the Skeletal System'_