question: Buccal shelf area is the primary stress bearing area in mandibular edentulous ridge because:
opa: It is covered with cortical bone which is usually at right angles to occlusal forces.
opb: It is covered with spongy bone which is usually at right angles to occlusal forces.
opc: Least forces are there.
opd: Keratinized mucosa over the ridge makes it resistant to occlusal forces.