Where do guide planes run from and to in RPD design?

Guide planes play a crucial role in the design of removable partial dentures (RPDs) as they help in the stability, retention, and proper alignment of the denture framework. The correct answer indicates that guide planes run from line angle to line angle of the tooth. This means they are oriented on the surfaces of the abutment teeth, specifically extending from one line angle—where two surfaces of the tooth meet—to the adjacent line angle.

By positioning the guide planes this way, they create flat, parallel surfaces that enhance the fit of the denture and aid in guiding the placement and removal of the RPD. Properly designed guide planes minimize tipping and provide better support for the denture during function. They are critical for both the aesthetic transition between tooth and denture and the functional aspects of the prosthesis.

The other options describe orientations that do not accurately reflect how guide planes are established in RPD design. For example, running from the occlusal surface to the gingival margin or from the incisal edge to the cervical margin focuses on entirely different dimensions and would not create the necessary parallel orientation that guide planes require for proper denture function. Similarly, describing them as extending from the mesial to distal surfaces of the teeth does not