Replacement Of A Single Missing Tooth

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Unless bone support has been weakened by advanced periodontal disease, a single missing tooth can almost always be replaced by a three-unit FPD having one mesial and one distal abutment tooth. An exception is when the FPD is replacing a maxillary or mandibular canine. Under these circumstances, the small anterior abutment tooth needs to be splinted to the central incisor to prevent lateral drift of the FPD.

Cantilever Fixed Partial Dentures. FPDs in which only one side of the pontic is attached to a retainer are referred to as cantilevered. An example would be a lateral incisor pontic attached only to an extracoronal metal-ceramic retainer on a canine. Their use remains popular because some of the difficulties encountered in making a three-unit FPD are lessened. Also, many clinicians are reluctant to prepare an intact central incisor, preferring instead to use a cantilever.

However, the long-term prognosis of the single-abutment cantilever is poor.16 Forces are best tolerated by the periodontal supporting structures when directed in the long axes of the teeth.17 This is the case when a simple three-unit FPD is used. A cantilever will induce lateral forces on the supporting tissues, which may be harmful and lead to tipping,

Replace Lateral Incisor With Canine
Fig. 3-15. A to C, Congenitally missing lateral incisors replaced with two simple three-unit FPDs. D to F, This patient had a missing canine as well as two congenitally missing laterals. Here, there is a much greater restorative challenge than in A, requiring an eight-unit prosthesis.

rotation, or drifting of the abutment (Fig. 3-16). Laboratory analysis's" has confirmed the potential harmful nature of such fixed partial dentures. However, clinical experience with resin-retained FPDs has suggested that cantilever designs may be preferred, especially since readhesion after failure is greatly facilitated and often leads to predictable long-term success20 (see Chapter 26).

When multiple missing teeth are replaced, cantilever FPDs have considerable application (see p. 70). The harmful tipping forces are resisted by multiple abutment teeth, and movement of the abutments is unlikely. Cantilevers are also successfully used with implant-supported prostheses (see Chapter 13).

Assessment of Abutment Teeth. Considerable time and expense are spared, and loss of a patient's confidence can be avoided, by thoroughly investigating each abutment tooth before proceeding with tooth preparation. Radiographs are made, and pulpal health is assessed by evaluating the response to thermal and electrical stimulation. Existing restorations, cavity liners, and residual caries are removed21 (preferably under a rubber dam), and a careful check is made for possible pulpal exposure. Teeth in which pulpal health is doubtful should be endodontically treated before the initiation of fixed prosthodontics. Although a direct pulp cap may be an acceptable risk for a simple amalgam or composite resin, conventional en-dodontic treatment is normally preferred for cast restorations, especially where the later need for en-dodontic treatment would jeopardize the overall success of treatment.

Cantilever FpdForces Cantilever Fpd

Fig. 3-16. A, Forces applied to a cantilever FPD are resisted on only one side, leading to imbalance. Vertical forces can cause tipping, and horizontal forces, rotation, of abutment teeth. B, By including both adjacent teeth in the prosthesis, it is possible to resist forces much better since the teeth have to be moved bodily rather than merely rotated or tipped.

(Redrawn from Rosenstiel SF: In Rayne J, editor: General dental treatment, London, 1983, Kluwer Publishing.)

Fig. 3-16. A, Forces applied to a cantilever FPD are resisted on only one side, leading to imbalance. Vertical forces can cause tipping, and horizontal forces, rotation, of abutment teeth. B, By including both adjacent teeth in the prosthesis, it is possible to resist forces much better since the teeth have to be moved bodily rather than merely rotated or tipped.

(Redrawn from Rosenstiel SF: In Rayne J, editor: General dental treatment, London, 1983, Kluwer Publishing.)

Endodontically Treated Abutments. If a tooth is properly treated endodontically, it can serve well as an abutment with a post and core foundation for retention and strength (see Chapter 12). Failures occur, however, particularly on teeth with short roots or little remaining coronal tooth structure. Care is needed to obtain maximum retention for the post and core. Sometimes it is better to recommend removal of a badly damaged tooth rather than to attempt endodontic treatment.

Unrestored Abutments. An unrestored, caries-free tooth is an ideal abutment. It can be prepared conservatively for a strong retentive restoration with optimum esthetics (Fig. 3-17). The margin of the retainer can be placed without modifications to accommodate existing restorations or caries. In an adult patient, an unrestored tooth can be safely prepared without jeopardizing the pulp as long as the design and technique of tooth preparation are wisely chosen. Certain patients are reluctant to have a perfectly sound tooth cut down to provide anchorage for a fixed partial denture. In these cases, the overall dental health of the patient should be emphasized rather than looking at each tooth individually.

Mesially Tilted Second Molar. Loss of a permanent mandibular first molar to caries early in life is still relatively common (Fig. 3-18). If the space is ignored, the second molar will tilt mesially, espe-

Fpd Maxilla
Fig. 3-17. A, Unrestored abutment teeth can be prepared for conservative retainers. B, An esthetic FPD replacing a maxillary incisor.
Tilted Abutment FpdUprighting Tilted Teeth

Fig. 3-18. A, Early loss of a mandibular first molar with mesial tilting and drifting of the second and third molars. B, A conventional three-unit FPD will fail because its seating is prevented by the third molar. C, A modified preparation design can be used on the distal abutment. D, A better treatment plan would be to remove the third molar and upright the second molar orthodontically before fabricating an FPD. (Redrawn front Rosenstiel SF: In Rayne J, editor: General dental treatment, London, 1983, Kluwer Publishing.)

Fig. 3-18. A, Early loss of a mandibular first molar with mesial tilting and drifting of the second and third molars. B, A conventional three-unit FPD will fail because its seating is prevented by the third molar. C, A modified preparation design can be used on the distal abutment. D, A better treatment plan would be to remove the third molar and upright the second molar orthodontically before fabricating an FPD. (Redrawn front Rosenstiel SF: In Rayne J, editor: General dental treatment, London, 1983, Kluwer Publishing.)

cially with eruption of the third molar. It then becomes difficult or impossible to make a satisfactory fixed partial denture, because the positional relationship no longer allows for parallel paths of insertion without interference from the adjacent teeth. In such circumstances, an FPD is sometimes made with modified preparation designs or with a nonrigid connector, or a straightforward solution 22 may be considered: uprighting the tilted abutment or-thodontically with a simple fixed appliance. However, the problem can be avoided altogether if a space-maintainer appliance (Fig. 3-19) is fabricated when the first molar is removed. This device may be as simple as a square section of orthodontic wire bent to follow the edentulous ridge and anchored with small restorations in adjacent teeth.

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  • Asmarina
    How to do radiograph tracing for single tooth replacement in fpd?
    8 years ago
  • julia
    Is a core also need when replacing a abutment?
    8 years ago
  • anna-liisa jokela
    How to upright a tilted molar orthodontics?
    7 years ago

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