The function of the posterior palatal seal (PPS) is to ensure a complete seal thus helping in retention of a denture.

A patient with a -4mm overbite can be classified to have an open bite.

Explanation: Implant-supported prostheses have the advantage of maintaining alveolar bone due to osseointegration. This helps preserve the natural bone structure and reduces the risk of bone resorption that is common with traditional complete dentures, which can lead to changes in the patient's facial profile over time.

Occlusal rims are also called dummy dentures.

Explanation: In bilateral balanced occlusion, if the incisal guidance is steep, it is necessary to create a compensating curve that is also steep to maintain balanced occlusion during lateral movements. This helps to ensure that the occlusal contacts remain balanced and stable, preventing tipping or dislodgment of the denture during function. The other options do not adequately address the need for balance in occlusion.