Aesthetic Efficiency in a Post-and-Core System

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INTRODUCTION
The objective of a post-and-core buildup is primarily to replace missing coronal tooth structure sufficiently to provide adequate retention and resistance for the crown that will eventually restore the function and the aesthetics of the tooth in question.1 The use of posts is still an area of great debate within dentistry. This debate ranges from dentists who only do cast posts, to dentists who use any of a variety of prefabricated systems, to clinicians who do not believe that posts are clinically effective. Within the literature, there are wide ranging studies that could be used to support any of the above beliefs. In the end, clinical experience, common sense, and evidence-based decisions should be the practitioner’s guide as to whether to use a post or not.

Figure 1. Tooth No. 12 had recently undergone root canal therapy. Figure 2. Removal of the temporary material, carious tooth structure, and exposure of the distal-apical margin of tooth No. 12.
Figure 3. Post spaces were created and a matrix was placed. Figure 4. The posts were cemented into place using the composite resin build-up material as the cement.
Figure 5. The composite resin build-up material (LuxaCore Z [DMG America]) was used to create the buildup or core. Figure 6. The completed post-and-core restoration ready for crown preparation.
Figure 7. The final preparation for an all-ceramic crown. Figure 8a. All-ceramic crown (e.Max [Ivoclar Vivadent]) fabricated on a digitally created (iTero [Cadent]) model.

Figure 8b. All-ceramic crown (e.Max) 2 weeks after delivery.

In the last decade, the use of prefabricated fiber posts has gained a lot of popularity with dentists. These new systems have demonstrated a modulus of elasticity that closely matches dentin, a reduction of stresses concentrated within the root canal, and reduced incidence of fracture.2-4
The purpose of a post is to retain a core that is needed because of extensive loss of coronal tooth structure; a post is not intended to provide any increase in the strength of the tooth. A post is the anchor to which the core gains additional retention. Fiber posts are able to provide additional retention because they are bonded into place. A fiber post is adhesively bonded into place using a bonding agent in combination with a dual cure resin cement. This combination allows for the resin cement to bond to the dentin of the tooth and the resin reinforced fibers of the posts. The post is then adhesively retained to the core when a composite resin build-up material is used. The synergistic nature of the use of these materials has the potential to create the strongest possible replacement of missing tooth structure.

CASE REPORT
A 22-year-old female presented with a recently completed root canal on tooth No. 12 (Figure 1). Upon discussion with the patient, it was agreed to restore the tooth with a post-and-core and an all-ceramic crown.

Table. Universal Principles to Consider When Placing Posts
  • Preserve as much healthy tooth structure as possible
  • Avoid contamination of the root canal system
  • Restore the tooth as soon as possible after completion of the root canal
  • Use posts only when necessary to retain a core buildup
  • The post preparation should leave a minimum of 4 mm of gutta-percha at the apical end
  • The minimum length of the post below the crest of bone should be equal to the height of the tooth above the crest of bone.

Removal of the Temporary and Pre-Preparation Steps
First, the temporary material was removed to visualize the remaining tooth structure. A caries detection dye (Seek [Ultradent Products]) was used to ensure that all decay had been removed. The apical extent of the decay required the use of a laser to perform a gingivectomy to allow for the exposure of healthy tooth structure. Probing determined that we were not in violation of biological width; therefore, no osseous removal was required. Figure 2 shows tooth No. 12 with the removal of all temporary material and carious tooth structure, as well as the exposure of the distoapical aspect of the tooth.
Next, a heated instrument was used to remove the gutta-percha. Radiographs were used to determine and ensure that there was a minimum of 4 mm of gutta-percha left in place to protect the apical seal.

Post Preparation
Next, the smallest diameter of post drills was used to finalize the post space. In an effort to minimize the removal of healthy tooth structure, it is important to start with the smallest drill size available. With the post spaces created in both buccal and lingual canals, the tooth was then isolated with a disposable matrix (OmniMatrix [Ultradent Products]) (Figure 3). Note that the post spaces are barely wider than the gutta-percha seen in the previous photo.
For this tooth, a tapered, prefabricated, resin reinforced fiber post system (LuxaPost [DMG America]) was selected. This system is tooth-colored, will bond to the resin cement that will be used (which will bond to the tooth), comes in a small diameter size, and has a modulus of elasticity that virtually matches that of dentin.

Post-and-Core

Tom M. Limoli, Jr
The doctor must provide a date of completion for any root canal therapy on a particular tooth if a core buildup on that tooth is to be supported by either a cast or prefabricated post. (Third-party payers may request a dated radiograph of the completed root canal treatment.)
A post is simply a dowel that is placed in the instrumented canal to retain the core buildup. The CDT does not furnish a coded procedure for the individual post, per se. Therefore, using a post without a buildup of the anatomical core does not justify the use of either code D2952 or D2954.
Because of the duplication of both purpose and function, the post in addition to the individual buildup is generally reimbursed only once per tooth. The standard exception would be if documentation indicated that the tooth was broken down to the extent that a buildup was necessary to perform the completed endodontic procedure. In such cases, both a core buildup (D2950) before the root canal and a post-and-core buildup after the root canal should be benefited.
Building up the anatomical core attached to a post is not a core buildup as identified by code D2950. When the third-party payer reimburses for a post-and-core on an endodontically treated tooth, the benefit administrator considers the core a completed entity that was payable with the attached post. It would appear inappropriate for the dental office to charge the patient (and/or third-party payer) to recontour or otherwise supplement the size and shape of the core with further build-up material.
When a practitioner simply prepares an endodontically treated canal and delivers a prefabricated post, the appropriate code to identify the procedure code would be D3950-canal preparation and fitting of preformed dowel or post. It is imperative that the same provider does not submit D3950 with either D2952 or D2954 for the same tooth.

2010 Clinical Oral Evaluations
Code Lower Low Medium High Higher National Average National
RV
D2952 $226 $271 $307 $487 $647 $385.00 8.56
D2954 $197 $200 $242 $359 $440 $299.00 4.33

CDT-2009/2010. Copyright American Dental Association. All rights reserved. Fee Data. Copyright Limoli and Associates/Atlanta Dental Consultants. This data represents 100% of the 90th percentile. The relative value is based upon the national average and not the individual columns of broad-based data. The abbreviated code numbers and descriptors are not intended to be a comprehensive listing. Customized fee schedule analysis for your individual office is available for a charge from Limoli and Associates/Atlanta Dental Consultants at (800) 344-2633 or visit the Web site limoli.com.

Post Placement Technique
A total-etch technique was used to bond the post-and-core. First the entire preparation was acid etched for 20 seconds, then thoroughly rinsed, and lightly air-dried. Next, a fourth generation bonding agent was used (OptiBond FL [Kerr]), including the use of a dual-cured activator for the resin. For the cement, an automix, dual-cured composite resin build-up material (LuxaCore Z [DMG America]) was used. Use of a single material will allow for the entire procedure to be more efficient. The material, when initially extruded from the “gun,” is highly flowable and has a sufficiently low film thickness to be used as a resin cement. As it is a dual cure product, it will completely set in the canals. As a core material, it has excellent compressive strength and cuts with a hardness that duplicates that of dentin.
For post placement, a small amount of LuxaCoreZ was injected directly into the canals. Extrusion was stopped when the material just filled the canals. Then the LuxaPosts were put into place with a reciprocating motion. The reciprocating motion allows the cement to cover the entire canal’s space. Then the posts were held to place and light-cured for 10 seconds (Figure 4). This tack curing ensured that the posts were fully seated and also allowed for the rest of the LuxaCoreZ to be extruded to fill the matrix, creating the core of the restoration (Figure 5). The entire core was then light-cured (Demi [Kerr]) for 30 seconds with the matrix on. Next, the matrix was removed and the core was cured for another 30 seconds. Figure 6 shows final post-and-core before being prepared for the crown. From the beginning of etching to matrix removal, should take less than 4 minutes.
The crown preparation was then completed (Figure 7) and readied for the final impression, bite registration, and temporization.

CONCLUSION
In contemporary dentistry, there is still a place for post-and-core restorations. Modern materials and techniques provide the opportunity to take advantage of our material technology to create a post-and-core complex that is strong, minimizes stresses to the endodontically treated tooth, is tooth-colored, and utilizes adhesive principles to create a post that is well-retained to both the tooth and the core material. The technique demonstrated in the case report presented herein exemplifies all the above advantages. In addition, the entire process can be completed in an extremely time efficient manner.


References

  1. Freedman G. A look at post and cores. Dent Today. 2002;7:118-119.
  2. Duke ES. New directions for posts in restoring endodontically treated teeth. Compend Contin Educ Dent. 2002;23:116-122.
  3. Hew YS, Purton DG, Love RM. Evaluation of pre-fabricated root canal posts. J Oral Rehabil. 2001;28:207-211.
  4. Rosentritt M, Furer C, Behr M, et al. Comparison of in vitro fracture strength of metallic and tooth-coloured posts and cores. J Oral Rehabil. 2000;27:595-601.

Dr. Radz is a graduate of the University of North Carolina School of Dentistry. His private practice is located in downtown Denver, Colo. He is an associate clinical professor at the University of Colorado School of Dentistry. He serves on the editorial board of 7 different dental journals and has published more than 100 articles related to the materials and techniques used in cosmetic dentistry. Additionally, he lectures internationally on subjects related to aesthetic dentistry and the development of cosmetic-based dental practices. Visit the Web site garyradz.com for more information. Dr. Radz can be reached at (303) 298-1414, or via e-mail at radzds@aol.com.

Disclosure: The author developed LuxaCore, LuxaCore Dual, and LuxaCoreZ with the chemists at DMG America. He receives a royalty on the sales of this product.



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