Indications of RPD

Although a removable partial denture should be considered only when a fixed restoration is contraindicated, there are several specific indications for the use of a removable restoration.

Distal Extension Situations

Replacement of missing posterior teeth is often best accomplished with a removable partial denture (see Figure 13-22, B), especially when implant treatment is not feasible for the patient. The exception to this includes situations in which the replacement of missing second (and third) molars is inadvisable or unnecessary, or in which unilateral replacement of a missing first molar can be accomplished by means of a multiple-abutment cantilevered fixed restoration or an implant-supported prosthesis. The most common partially edentulous situations are the Kennedy Class I and Class II. With the latter, an edentulous space on the opposite side of the arch is often conveniently present to aid in required retention and stabilization of the removable partial denture. If no space is present, selected abutment teeth can be modified to accommodate appropriate clasp assemblies, or intracoronal retainers can be used. As stated previously, all other edentulous areas are best replaced with fixed partial dentures.

After Recent Extractions

The replacement of teeth after recent extractions often cannot be accomplished satisfactorily with a fixed restoration. When relining will be required later or when a fixed restoration using natural teeth or implants will be constructed later, a temporary removable partial denture can be used. If an allresin denture is used rather than a cast framework removable partial denture, the immediate cost to the patient is much less, and the resin denture lends itself best to future temporary modifications, including those required after implant placement and before restoration. Tissue changes are inevitable following extractions. Tooth-bounded edentulous areas (as a result of extractions) are best initially restored with removable partial dentures. Relining of a tooth-supported resin denture base is then possible. This is usually done to improve esthetics, oral cleanliness, or patient comfort. Support for such a restoration is supplied by occlusal rests on the abutment teeth at each end of the edentulous space.

Long Span

A long span may be totally tooth-supported if the abutments and the means of transferring the support to the denture are adequate and if the denture framework is rigid. There is little if any difference between the support afforded a removable partial denture and that afforded a fixed restoration by the adjacent abutment teeth. However, in the absence cross-arch stabilization, the torque and leverage on the two abutment teeth would be excessive. Instead, a removable denture that derives retention, support, and stabilization from abutment teeth on the opposite side of the arch is indicated as the logical means of replacing the missing teeth.

Need for Effect of Bilateral Stabilization

In a mouth weakened by periodontal disease, a fixed restoration may jeopardize the future of the involved abutment teeth unless the splinting effect of multiple abutments is used. The removable partial denture, on the other hand, may act as a periodontal splint through its effective cross-arch stabilizing of teeth weakened by periodontal disease. When abutment teeth throughout the arch are properly prepared and restored, the beneficial effect of a removable partial denture can be far greater than that of a unilateral fixed partial denture.

Excessive Loss of Residual Bone

The pontic of a fixed partial denture must be correctly related to the residual ridge and in such a manner that the contact with the mucosa is minimal. Whenever excessive resorption has occurred, teeth supported by a denture base may be arranged in a more acceptable buccolingual position than is possible with a fixed partial denture (Figure 13-22). Unlike a fixed partial denture, the artificial teeth supported by a denture base can be located without regard for the crest of the residual ridge and more nearly in the position of the natural dentition for normal tongue and cheek contacts. This is particularly true of a maxillary denture. Anteriorly, loss of residual bone occurs from the labial aspect. Often the incisive papilla lies at the crest of the residual ridge. Because the central incisors are normally located anterior to this landmark, any other location of artificial central incisors is unnatural. An anterior fixed partial denture made for such a mouth will have pontics contacting the labial aspect of this resorbed ridge and will be too far lingual to provide desirable lip support. Often the only way the incisal edges of the pontics can be made to occlude with the opposing lower anterior teeth is to use a labial inclination that is excessive and unnatural, and both esthetics and lip support suffer. Because the same condition exists with a removable partial denture in which the anterior teeth are abutted on the residual ridge, a labial flange must be used to permit the teeth to be located closer to their natural position. The same method of treatment applies to the replacement of missing mandibular anterior teeth. Sometimes a mandibular anterior fixed partial denture is made six or more units in length, in which the remaining space necessitates leaving out one anterior tooth or using the original number of teeth but with all of them too narrow for esthetics. In either instance, the denture is nearly in a straight line because the pontics follow the form of the resorbed ridge. A removable partial denture will permit the location of the replaced teeth in a favorable relation to the lip and opposing dentition regardless of the shape of the residual ridge. When such a removable prosthesis is made, however, positive support must be obtained from the adjacent abutments.

Unusually Sound Abutment Teeth

Sometimes the reasoning for making a removable restoration is the desire to see sound teeth preserved in their natural state and not prepared for restorations. As mentioned previously, if this decision is made because it is felt that no tooth modification is necessary for removable partial dentures, then the prosthesis will lack tooth-derived stability and support. When this condition exists, the dentist should not hesitate to reshape and modify existing enamel surfaces to provide proximal guiding planes, occlusal rest areas, optimum retentive areas, and surfaces on which nonretentive stabilizing components may be placed. Continued durability of the natural teeth is best ensured if the modifications that optimize prosthesis function are provided. This is due to the fact that such modifications also ensure the most harmonious use of the natural dentition.

Abutments with Guarded Prognoses

If the prognosis of an abutment tooth is questionable or if it becomes unfavorable while under treatment, it might be possible to compensate for its impending loss by a change in denture design. The questionable or condemned tooth or teeth may then be included in the original design and, if subsequently lost, the removable partial denture can be modified or remade (Figure 13-23). Most removable partial denture designs do not lend themselves well to later additions, although this eventuality should be considered in the design of the denture. When the tooth in question will be used as an abutment, every diagnostic aid should be used to determine its prognosis as a prospective abutment. It is usually not as difficult to add a tooth or teeth to a removable partial denture as it is to add a retaining unit when the original abutment is lost and the next adjacent tooth must be used for that purpose. It is sometimes possible to design a removable partial denture so that a single posterior abutment, about which there is some doubt, can be retained and used at one end of the tooth-supported base. Then if the posterior abutment is lost, it could be replaced by adding an extension base to the existing denture framework. Such an original design must include provisions for future indirect retention, flexible clasping of the future abutment, and provisions for establishing tissue support. Anterior abutments that are considered poor risks may not be so freely used because of the problems involved in adding a new abutment retainer when the original one is lost. It is rational that such questionable teeth should be condemned in favor of more suitable abutments, even though the original treatment plan must be modified accordingly.