The preparation diameter is directly proportional to which factor?

The preparation diameter being directly proportional to resistance is based on the fundamental principles of dental prosthetics. A larger preparation diameter can provide a greater surface area for the retention of crowns or other prosthetic devices. This increased surface area helps to distribute forces more evenly, enhancing the resistance to dislodgment from lateral and axial forces that can occur during functional use.

In essence, as the diameter of the preparation increases, the stability and retention of the final restoration improve, making it less likely to come loose over time due to chewing and other dynamics in the oral environment. This understanding is crucial in prosthodontics, where the goal is to provide durable and functional restorations that can withstand daily wear and maintain their position against various forces.