Considerations For Anterior Teeth

Endodontically treated anterior teeth do not always need complete coverage by placing a complete crown, except when plastic restorative materials have limited prognosis (e.g., if the tooth has large proximal composite restorations and unsupported tooth structure). Many otherwise intact teeth function satisfactorily with a composite resin restoration.

Although commonly believed, it has not been demonstrated experimentally that endodontically treated teeth are weaker or more brittle than vital teeth. Their moisture content, however, may be reduced.' Laboratory testing' has actually revealed a similar resistance to fracture between untreated and endodontically treated anterior teeth. Nevertheless, clinical fracture does occur, and attempts have been made to strengthen the tooth by removing part of the root canal filling and replacing it with a metal post. In reality, placement of a post requires the removal of additional tooth structure (Box 12-1), which is likely to weaken the tooth.

Cementing a post in an endodontically treated tooth is a fairly common clinical procedure despite the paucity of data to support its success. In fact, a laboratory study and two stress analyses"'," have

Stress Lymphocytosis

Fig. 12-5. Experimental stress distributions in an endodontically treated tooth with a cemented post. When the tooth is loaded, the lingual surface is in tension, and the facial surface is in compression. The centrally located cemented post lies in the neutral axis (i.e., not in tension or compression).

(Redrawn from Guzy GE, Nicholls JI: J Prosthet Dent 42:39, 1979.)

Fig. 12-5. Experimental stress distributions in an endodontically treated tooth with a cemented post. When the tooth is loaded, the lingual surface is in tension, and the facial surface is in compression. The centrally located cemented post lies in the neutral axis (i.e., not in tension or compression).

(Redrawn from Guzy GE, Nicholls JI: J Prosthet Dent 42:39, 1979.)

Disadvantages to the Routine Use of a Cemented Post box 12-1

an additional operative

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Placing the post requires procedure.

Preparing a tooth to accommodate the post removes additional tooth structure.

It may be difficult to restore the tooth later, when a complete crown is needed, because the cemented post may have failed to provide adequate retention for the core material.

The post can complicate or prevent future endodontic re-treatment if this becomes necessary.

determined that no significant reinforcement results. This might be explained by the hypothesis that, when the tooth is loaded, stresses are greatest at the facial and lingual surfaces of the root and an internal post, being only minimally stressed, does not help prevent fracture (Fig. 12-5). Other studies, however, contradict this assumption . 8,12 Cemented posts may further limit or complicate endodontic retreatment options if these are necessary. In addition, if coronal destruction occurs, post removal may be necessary to provide adequate support for a future core.

For these reasons, a metal post is not recommended in anterior teeth that do not require complete coverage restorations. This view is supported by a retrospective study that did not show any improvement in prognosis for endodontically treated

Cross Section Central Incisor

Fig. 12-6. Cross section through a central incisor. The dotted line indicates the original tooth contour before preparation for a metal-ceramic restoration. Even with minimum reduction for the extracoronal restoration, note the weakened facial wall, which would not be able to support a prosthesis successfully. The sharp lingual wall complicates pattern fabrication.

Fig. 12-6. Cross section through a central incisor. The dotted line indicates the original tooth contour before preparation for a metal-ceramic restoration. Even with minimum reduction for the extracoronal restoration, note the weakened facial wall, which would not be able to support a prosthesis successfully. The sharp lingual wall complicates pattern fabrication.

anterior teeth restored with a post. In another study, post placement did not influence the position or angle of radicular fracture."

Discoloration in the absence of significant tooth loss may be more effectively treated by bleaching'-' than by the placement of a complete crown, although not all stained teeth can be bleached successfully. Resorption can be an unfortunate side effect of nonvital bleaching. 6 However, when loss of coronal tooth structure is extensive or the tooth will be serving as an FPD or RPD abutment, a complete crown becomes mandatory. Retention and support then must be derived from within the canal because a limited amount of coronal dentin remains once the reduction for complete coverage has been completed. Coupled with the loss of internal tooth structure necessary for endodontic treatment, the remaining walls become thin and fragile (Fig. 12-6), often requiring their reduction in height.

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