On the diagnostic cast, path of insertion for the prosthesis is initially determined. The “path of insertion” is defined as the direction in which the restoration is placed onto and removed from the supporting teeth. The direction extends from the first contact point between the rigid parts of the prosthesis and the supporting teeth, all the way to the final seating position, where the rests are fully engaged, and the denture base makes complete contact with the tissues. In the planning of partial dentures, multiple path of insertion often arise. The most significant factor affecting the number of paths of insertion for the prosthesis is whether the edentulous area is tooth-supported or free-end. When the edentulous space is tooth-supported, the prosthesis will have a single path of insertion. In unilateral distal extension cases, since the major connector is rigid, the path of insertion is directed by the tooth-supported side. In bilateral distal extension partial dentures, there are two or more path of insertion, one perpendicular to the occlusal plane and the other forming an arc due to the rotation of the clasps on the abutment teeth (Video 7-2). Partial dentures with edentulous spaces in the anterior region have a single path of insertion, which is parallel to the guiding planes of the adjacent teeth.

Factors affecting the path of insertion

There are four factors that influence the path of insertion for the prosthesis in partially edentulous cases (Figure 7-3):

1. Guide planes

2. Retentive areas (undercut regions)

3. Interferences

4. Esthetics