Treatment Planning

Extensive caries or periodontal disease may make removal of a tooth more sensible than endodonti-cally treating it, although a severely damaged tooth occasionally can be restored after orthodontic repositioning or root resection (Fig. 12-1). This should be done if its loss will significantly jeopardize the pa tient's occlusal function or the total treatment plan, particularly if dental implants are not an option. When the decision is made to treat the tooth en-dodontically, consideration must have been given to its subsequent restoration. Before restoration, existing endodontically treated teeth need to be assessed carefully for the following': Good apical seal i No sensitivity to pressure 3 No exudate No fistula

No apical sensitivity No active inflammation Inadequate root fillings should be retreated. If doubt remains, the tooth should be observed until there is definite evidence of success or failure.

If the coronal structures are largely intact and loading is favorable as on anterior teeth that are farther removed from the fulcrum, a simple filling can be placed in the access cavity (Fig. 12-2, A). However, if a substantial amount of coronal structure is missing, a cast post-and-core is indicated instead (Fig. 12-2, B). Molars are often restored with amalgam or a combination of one or more cemented posts and amalgam or composite resin (Fig. 12-2, C and D).

Although one-piece post-crowns were once made, such prostheses are of historical interest only. Superior results can now be obtained with a two-step technique (Fig. 12-3) consisting of a post-and-core foundation and a separate crown. Most often a metal post is used, which provides the necessary retention for the core. This replaces any lost coronal tooth structure of the tooth preparation. The shape of the residual coronal tooth structure, combined with the core, should result in an ideal shape for the preparation (Fig. 12-4).

Prefabricated metal, carbon fiber, ceramic, and glass fiber posts are available. These last two options provide esthetic alternatives to metal posts. 2-3 They are used in conjunction with a plastic material such as composite resin, amalgam, or glass ionomer.

With the two-step approach of fabricating a separate crown over a cast post-and-core, achieving a

Post And Core Failure
Fig. 12-1. A to C, A severely damaged tooth can sometimes be retained after orthodontic extrusion (see Chapter 6). D and E, Plaque control around periodontally compromised teeth may be improved after hemisectioning (see Chapter 5). (D and E courtesy Dr. H. Kahn.)
Pinledge Dental Restoration

Fig. 12-2. A, An anterior tooth with intact clinical crown can be predictably restored with a composite restoration in the access cavity. B, When most coronal tissue is missing, a cast post-and-core is indicated to obtain optimal tooth preparation form. C, In mandibular molars an amalgam foundation is supported by a cemented prefabricated post in the distal canal. D, In maxillary molars the palatal canal is most often used.

Fig. 12-2. A, An anterior tooth with intact clinical crown can be predictably restored with a composite restoration in the access cavity. B, When most coronal tissue is missing, a cast post-and-core is indicated to obtain optimal tooth preparation form. C, In mandibular molars an amalgam foundation is supported by a cemented prefabricated post in the distal canal. D, In maxillary molars the palatal canal is most often used.

satisfactory marginal fit is easier because the expansion rate of the two castings can be controlled individually. A cast post-and-core needs to be slightly smaller than the canal to achieve optimal internal seating, whereas the crown needs to be slightly larger to achieve optimal seating (see Chapter 7). The two-step approach further permits fabrication of a replacement crown, if necessary, without the

Lower Partial With Molars
Fig. 12-3. A, The first molar and second premolar have been restored with post-and-cores. Note the margins, optimally located on sound tooth structure, cervical to the castings. B, Extracoronal restorations in place.
Post Core And Crown One Piece

Fig. 12-4. The second premolar has been restored with a cast post-and-core, before a metal-ceramic crown. (Courtesy Dr. R. Webber.)

incisors and molars. Failure rate under fixed partial dentures was significantly lower than under single crowns. The latter may be due to load reduction resulting from bracing by the FPD. No correlation was apparent between failure and reduced marginal height of the encasing bone. Custom cast post-and-cores exhibited slightly higher failure rates than amalgam foundations. This observation was also made by Sorensen and Martinoff. However, Torbjorner et a14 suggest that custom cast post-and-cores tend to be used more often in teeth that already have considerably weakened root structure. Thus, regardless of the technique selected for subsequent restoration, the teeth themselves are already more prone to failure. Distal cantilevers appear to contribute to post-and-core failure in endodontically treated abutment teeth that support the cantilever.

Most of the failures just discussed are influenced by load. In general, as loading increases, failure rates appear to increase concomitantly. Failure loads have been shown to increase as the load angle approaches parallelism to the long axes of the teeth . 6 This suggests that failure will occur more readily under lateral loading. When planning the restoration of en-dodontically treated teeth, the practitioner's prognosis must consider the strength of the remaining tooth structure weighed carefully against the load to which the restored tooth will be subjected.

Fig. 12-4. The second premolar has been restored with a cast post-and-core, before a metal-ceramic crown. (Courtesy Dr. R. Webber.)

need for post removal. Finally, a different path of placement than the one selected for the post-and-core may be selected for the crown. This is often helpful when the tooth is restored to serve as an abutment for a fixed partial denture (FPD).

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