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.
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|
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.
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.
Tom M. Limoli, Jr
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.
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.
- Freedman G. A look at post and cores. Dent Today. 2002;7:118-119.
- Duke ES. New directions for posts in restoring endodontically treated teeth. Compend Contin Educ Dent. 2002;23:116-122.
- Hew YS, Purton DG, Love RM. Evaluation of pre-fabricated root canal posts. J Oral Rehabil. 2001;28:207-211.
- 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.
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.