Fundamentals of Fixed Prosthodontics. James C. Kessler
and frequent recall, but it cannot be eliminated.
Resin-bonded tooth-supported fixed partial denture
The resin-bonded fixed partial denture is a conservative restoration that is reserved for use on defect-free abutments in situations where there is a single missing tooth, usually an incisor or premolar. A single molar can be replaced by this type of prosthesis if the patient’s muscles of mastication are not too well developed, thus assuring that a minimum load will be placed on the retainers. The resin-bonded fixed partial denture requires an abutment both mesial and distal to the edentulous space.
This prosthesis utilizes a standard pontic form, accommodating an edentulous ridge with moderate resorption and no gross soft tissue defects. Because it requires a shallow preparation that is restricted to enamel, the resin-bonded fixed partial denture is especially useful in younger patients whose immature teeth with large pulps are poor candidates for endodonticfree abutment preparations.
Tilted abutments can be accommodated only if there is enough tooth structure to allow a change in the normal alignment of axial reduction. This is limited by the need to restrict most of the reduction to enamel. Rarely can a mesiodistal difference in abutment inclination greater than 15 degrees be accommodated. There can be little or no difference in the inclination of the abutments faciolingually.
The resin-bonded prosthesis cannot be used for replacing missing anterior teeth where there is a deep vertical overlap. Reduction deep into the underlying dentin of the abutment teeth will be required in this situation, so a conventional fixed partial denture should be employed.
Although this type of prosthesis has been described for periodontal splints, it should be used with extreme care in those situations. Preparations will demand additional resistance features, such as long, well-defined grooves. Abutment mobility has been shown to be a serious hazard in the successful use of this type of restoration.
Implant-supported fixed partial denture
Fixed partial dentures supported by implants are ideally suited for use where there are insufficient numbers of abutment teeth or inadequate strength in the abutments to support a conventional fixed partial denture and when patient attitude and/or a combination of intraoral factors make a removable partial denture a poor choice. Implant-supported fixed partial dentures can be employed in the replacement of teeth when there is no distal abutment. Span length is limited only by the availability of alveolar bone with satisfactory density and thickness in a broad, flat ridge configuration that will permit implant placement.
A single tooth can be replaced by a single implant, saving defect-free adjacent teeth from the destructive effects of retainer crown preparations. A span length of two to six teeth can be replaced by multiple implants, either as singleunit restorations or as implant-supported fixed partial dentures. In fact, an entire arch can be replaced by an implant-supported complete prosthesis, but that type of restoration lies outside the realm of this discussion.
The retainers used for most implant systems require a great degree of abutment alignment precision, as do the retainers for a tooth-supported fixed partial denture. If implants are placed by someone other than the restorative dentist, implant/abutment alignment demands close coordination between surgeon and restorative dentist. The abutments should be positioned so that the occlusal forces will be as nearly vertical to the implants as possible to prevent destructive lateral forces.
Implants should be better able than natural teeth to survive in a dry mouth. Implants may be a better choice for fixed partial denture abutments if prospective tooth abutments would require endodontic therapy with or without dowel cores, periodontal surgery, and possibly root resections to support a long-span, complex, and expensive prosthesis.
No prosthetic treatment
If a patient presents with a long-standing edentulous space into which there has been little or no drifting or elongation of the adjacent or opposing teeth, the question of replacement should be left to the patient’s wishes. If the patient perceives no functional, occlusal, or esthetic impairment, it would be a dubious service to place a prosthesis. This in no way contradicts the recommendation that a missing tooth routinely should be replaced. The teeth adjoining an edentulous space usually move, but they do not always move. When meeting the occasional patient who has beaten the odds, the dentist should recognize it for what it is, congratulate the patient for being fortunate, and tend to his or her other needs.
Case presentation
In cases in which the choice between a fixed partial denture and a removable partial denture is not clear cut, two or more treatment options should be presented to the patient along with their advantages and disadvantages. The dentist is in the best position to evaluate the physical and biologic factors present, while the patient’s feelings should carry considerable weight on matters of esthetics and finances.
Both dentist and patient must agree on the definitive treatment plan. If the patient understands and is willing to accept the risks associated with the dentist’s second-choice treatment, it is prudent to make a notation to that effect and have it signed by the patient. If the restorative dentist is convinced that a particular type of treatment desired by the patient is absolutely wrong for a given situation, an attempt should be made to educate the patient by explaining the reasons behind this opinion. If the patient remains unconvinced, the patient should be referred to someone else. Life is too short for the aggravation that may otherwise follow.
Abutment Evaluation
Every restoration must be able to withstand the constant occlusal forces to which it is subjected. This is of particular significance when designing and fabricating a fixed partial denture because the forces that would normally be absorbed by the missing tooth are transmitted, through the pontic, connectors, and retainers, to the abutment teeth. Abutment teeth are therefore called upon to withstand the forces normally directed to the missing teeth in addition to those usually applied to the abutments.
If a tooth adjacent to an edentulous space needs a crown because of damage to the tooth, the restoration usually can double as a fixed partial denture retainer. If several abutments in one arch require crowns, there is a strong argument for the selection of a fixed partial denture rather than a removable partial denture.
Whenever possible, an abutment should be a vital tooth. However, a tooth that has been endodontically treated and is asymptomatic, with radiographic evidence of a good seal and complete obturation of the canal, can be used as an abutment. However, the tooth must have some sound, surviving coronal tooth structure to ensure longevity. Even then, some compensation must be made for the coronal tooth structure that has been lost. This can be accomplished through the use of a dowel core or a pin-retained amalgam or composite resin core.
Teeth that have been pulp capped in the process of preparation should not be used as fixed partial denture abutments unless they are endodontically treated. There is too great a risk that they will require endodontic treatment later, with the resultant destruction of retentive tooth structure and of the retainer itself. This is a situation that is better handled before the fixed partial denture is made.
The supporting tissues surrounding the abutment teeth must be healthy and free from inflammation before any prosthesis can be contemplated. Normally, abutment teeth should not exhibit mobility because they will be carrying an extra load. The roots and their supporting tissues should be evaluated for three factors:
1 Crown-root ratio
2 Root configuration
3 Periodontal ligament area
Crown-root ratio
The crown-root ratio is a measure of the length of tooth occlusal to the alveolar crest of bone compared with the length of root embedded in the bone. As the level of the alveolar bone moves apically, the lever arm of the portion out of bone increases, and the chance for harmful lateral