American Board of Dental Examiners (ADEX) Dental Hygiene Licensing Examination 2025 – 400 Free Practice Questions to Pass the Exam

The correct response emphasizes the importance of functional design considerations in the construction of removable partial dentures (RPDs). For Classes I and II, the guide planes should be positioned below the height of contour. This positioning helps ensure that the partial denture can achieve adequate retention and stability, preventing it from dislodging during functional activities such as eating and speaking.

On the other hand, for Classes III and IV, it's acceptable for the guide planes to be located above the height of contour. This adjustment allows these frameworks to provide adequate support while also facilitating the necessary movement of the prosthesis during function. The particular anatomical and biomechanical considerations of these classes dictate that different approaches must be taken for optimal results.

In summary, the positioning of guide planes in relation to the height of contour is crucial and varies depending on the class of the removable partial denture to ensure proper retention, stability, and function.