Why may a partial-coverage restoration have less resistance than a complete crown?

A partial-coverage restoration typically has less resistance compared to a complete crown due to the preparation diameter. When a tooth is prepared for a partial coverage, only a portion of the tooth structure is removed, resulting in a smaller surface area that adheres to the restoration. This limited surface area provides less resistance to occlusal (biting) forces and may increase the risk of dislodgement or failure under function.

In contrast, a complete crown encompasses the entire surface of the tooth, offering a larger bonding area that enhances retention and stability. This full coverage allows the crown to better distribute forces across the tooth structure, increasing the resistance against dislodging or fracture.

The other options do not adequately address the main reason for the difference in resistance. While opposing wall convergence and flexibility in margins can play roles in the performance of restorations, they do not directly influence the fundamental difference in resistance due to the extent of tooth coverage provided by partial versus complete restorations.