Indications for fixed prosthesis

Indications of Fixed Restorations

Tooth-Bounded Edentulous

Regions Generally any unilateral edentulous space bounded by teeth suitable for use as abutments should be restored with a fixed partial denture cemented to one or more abutment teeth at either end. The length of the span and the periodontal support of the abutment teeth will determine the number of abutments required. As mentioned earlier, such a span could be managed with the use of dental implants if deemed feasible and elected by the patient. The fact that implant support does not place additional functional demands on adjacent teeth likely contributes to their preservation, although this has not been universally demonstrated. For conventional fixed prostheses, lack of parallelism of the abutment teeth may be counteracted with copings or locking connectors to provide parallel sectional placement. Sound abutment teeth make possible the use of more conservative retainers, such as partial-veneer crowns, or resinbonded-to-metal restorations, rather than full crowns. The age of the patient, evidence of caries activity, oral hygiene habits, and the soundness of remaining tooth structure must be considered in any decision to use less than full coverage for abutment teeth. Two specific contraindications for the use of unilateral fixed restorations are known. One is a long edentulous span with abutment teeth that would not be able to withstand the trauma of nonaxial occlusal forces. The other is abutment teeth, which exhibit reduced periodontal support due to periodontal disease, which would benefit from cross-arch stabilization. In either situation, a bilateral removable restoration can be used more effectively to replace the missing teeth.

Modification Spaces

A removable partial denture for a Class III arch is better supported and stabilized when a modification area on the opposite side of the arch is present. A fixed partial denture need not be used to restore such an edentulous area because its inclusion may simplify the design of the removable partial denture. However, when a modification space is bound by a lone-standing single-rooted abutment, it is better restored by means of a fixed partial denture. This acts to stabilize the at-risk tooth, and the denture is made less complicated by not having to include other abutment teeth for the support and retention of an additional edentulous space or spaces. When an edentulous space that is a modification of a Class I or Class II arch exists anterior to a lone-standing abutment tooth, this tooth is subjected to trauma by the movements of a distal extension removable partial denture far in excess of its ability to withstand such stresses. The splinting of the lone abutment to the nearest tooth is mandatory. The abutment crowns should be contoured for support and retention of the removable partial denture; in addition, a means of supporting a stabilizing component on the anterior abutment of the fixed partial denture or on the occlusal surface of the pontic usually should be provided.

Anterior Modification Spaces

Usually any missing anterior teeth in a partially edentulous arch, except in a Kennedy Class IV arch in which only anterior teeth are missing, are best replaced by means of a fixed restoration. There are exceptions. Sometimes a better esthetic result is obtainable when the anterior replacements are supplied by a removable partial denture, at other times treatment is simplified by inclusion of an anterior modification space into the removable partial denture (Figure 13-20). This is also true when excessive tissue and bone resorption necessitates placement of the pontics in a fixed partial denture too far palatally for good esthetics or for an acceptable relation with the opposing teeth. However, in most instances, from mechanical and biological standpoints, anterior replacements are best accomplished with fixed restorations. The replacement of missing posterior teeth with a removable partial denture is then made much less complicated and gives more satisfactory results.

Replacement of Unilaterally Missing Molars (Shortened Dental Arch)

Often the decision must be made to replace unilaterally missing molars (Figure 13-21). The decision must balance the impact of the treatment on the remaining oral structures with the potential benefit to the patient long term. To restore the missing molars with a fixed partial denture would require a cantilever prosthesis or the use of dental implants. A cantilever-fixed prosthesis is most applicable if the second molar is to be ignored, then only first molar occlusion need be supplied with the use of a cantilever-type fixed partial denture. Occlusion need be only minimal to maintain occlusal relations between the natural first molar in the one arch and the prosthetic molar in the opposite arch. The cantilevered pontic should be narrow buccolingually and need not occlude with more than one half to two thirds of the opposing tooth. Often such a restoration is the preferred method of treatment. However, at least two abutments should be used to support a cantilevered molar opposed by a natural molar. To replace unilaterally missing molars with a removable partial denture necessitates the use of a distal extension prosthesis. This involves the major connector joining the edentulous side to retentive and stabilizing components located on the non-edentulous side of the arch. Leverage factors are frequently unfavorable, and the retainers used on the non-edentulous side are often unsatisfactory. Two factors important to consider in making the decision to provide a unilateral, distal extension removable partial denture include the opposing teeth and the future effect of the maxillary tuberosity. First, the opposing teeth must be considered if it is considered important to prevent extrusion and migration. This influences replacement of the missing molars far more than any improvement in masticating efficiency that might result. Replacement of missing molars on one side is seldom necessary for reasons of mastication alone. Second, the future effect of a maxillary tuberosity must be considered if concern exists for tuberosity enlargement. Often when left uncovered, the tuberosity increases in size, making future occlusal treatment difficult. However, covering the tuberosity with a removable partial denture base, in combination with the stimulating effect of the intermittent occlusion, helps maintain tuberosity size and position. In such an instance, it may be better to make a removable partial denture with cross-arch stabilization and retention than to leave a maxillary tuberosity uncovered.