Describe/discuss the major factors that should be taken into consideration when designing metal partial dentures. Include in your answer the functions of the components used.

Describe/discuss the major factors that should be taken into consideration when designing metal partial dentures. Include in your answer the functions of the components used.

1. When evaluating a patient for a removable partial denture, the occlusion should be evaluated to determine if there are any limiting occlusal considerations that may determine which design will work best for the particular patient.

   • An example of this could be a patient with a deep vertical overlap, which would hinder the ability to place a lingual plate along the maxillary anterior teeth. This may lead to either lowering the position of the plate, or selecting a major connector that does not require plating that area; for example; an anteroposterior palatal strap.
   • Some patients have an allergic reaction to Co/Cr alloy used in denture construction. Other alloys or designs should be a consideration in these cases. Stainless steel, Gold etc.

2. Using Kennedy classification system for organisation can simplify the design process. When beginning to design an RPD, the Kennedy classification should be identified first, then once determined, the following questions can be asked:

3. 1. Where are the edentulous modification spaces?

   • The location of edentulous areas helps to determine rest seat location, clasp location, and number of clasps needed for the RPD design. The rest seat is the portion of the tooth that have been selected and prepared to receive a rest. A rest is a rigid extension of partial denture which rest on occlusal , incisal, and lingual surfaces of a tooth and to used to dissipate the forces that applied on the prosthesis.

4. 2. Where are the undercuts for the teeth adjacent to these areas?

   • Typically the teeth adjacent to the edentulous areas will be clasped. The location and depth of the undercuts help in selection of the type of clasp.

5. 3. Where are the soft tissue undercuts located?

   • To determine if they will allow for infrabulge or suprabulge clasps.

6. 4. Do the abutment teeth or residual ridge require ‘protection’ from the external forces acting on the removable partial denture?

   • Abutment teeth and residual ridge must be evaluated with regard to its ability to withstand external forces acting upon it in order to determine the most appropriate clasp design to increase lateral stability.

7. 5. Is additional indirect retention required beyond the direct retainers?

   • Kennedy classification can help determine if additional indirect retention is required. If needed, it is located perpendicular to the fulcrum line, which is determined by a line drawn between the most posterior occlusal rests of the RPD.

8. 6. What type of physical retention is best for the replacement of teeth?

   • Following factors should be evaluated: - Number of teeth to be replaced. - Available vertical and lateral space. - Adjustability of intalingo surface. - Need for ability to reline at later date.
     • In general, latticework is considered to be the physical retention of choice. It may be used for multiple tooth replacements, provides strongest attachment of acrylic, is the easiest to reline, and allows for adjustment of acrylic in regions that have undercuts and might be difficult to fit otherwise.

9. 7. What major connector best connects the RPD components?

   • Once the major components of the RPD have been determined and drawn, the selection of major connector is easily made by selecting the major connector design that links the components on contralateral sides together.
     • The functions of Major connector are: - Forms a framework of the partial denture. - Uniformly distributes the occlusal forces acting on any portion of the prosthesis. - Provides a means of indirect retention.
       • Minor connectors can then be incorporated to connect the major connector to all other units of the RPD. The function is to transfer stresses evenly to all components.

10. 8. What tooth modifications are required for this design?

    • Assessment of tooth contours should include the need for recontouring the tooth to create undercuts, guide planes, rest seat, and alteration of the height of contour.