Final answer:
The primary reason the base of a distal extension partial denture should cover the maximum support area is to reduce the force per unit area, ensuring even distribution of pressure and minimizing stress on the oral tissues.
Step-by-step explanation:
The base of a distal extension partial denture should cover the maximum support area primarily because the force transmitted per unit area will be kept to a minimum. This ensures that the pressure exerted on the supporting tissues is distributed over a larger surface area, thereby reducing the stress on any given point. This concept is crucial for the long-term health of the oral tissues and the stability of the denture.
While having the maximum number of artificial teeth might be a secondary benefit, and while phonetics may potentially be influenced by the extension of the base, these are not the primary reasons for the design criterion. Similarly, the strength of the denture base is related more to the material used and the design rather than the coverage area.