An alternative post-and-core method for patients with limited interarch space
Bahadir Ersu, DDS, PhD and
enay Canay, DDS, PhD
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ABSTRACT
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Background. The authors describe a technique for placement of a three-unit posterior fixed partial denture where one abutment lacked sufficient interarch space.
Case Description. This method involves the use of a cast post and core with a precision attachment soldered into the core to provide the necessary retention and resistance. The prosthesis is retained by a combination of cement and screw retention.
Clinical Implications. This method is desirable when there is insufficient interarch space for a conventional post-and-core restoration. Achieving internal reinforcement by connecting the precision attachment to the residual root should provide the prosthesis with retention and added stability.
Key Words: Dental abutments; cavity preparation; endodontics; post-and-core technique; restorative dentistry; root canalAbbreviations: FPD: Fixed partial denture • PFM: Porcelain-fused-to-metal
A post-and-core assembly is placed in a badly broken-down tooth to restore the bulk of the coronal portion of the tooth to facilitate the subsequent restoration of the tooth by means of an indirect extracoronal restoration.1–3 The literature describes numerous techniques for fabricating the cast post and core.4,5 Failures of these systems include loss of retention of posts and fracture of the root or root perforation. In this case report, we describe an alternative technique for fabricating post-and-core restorations for teeth with extensive loss of hard tissue.
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REPORT OF A CASE
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A 25-year-old woman was referred to the prosthodontics clinic, Hacettepe University Faculty of Dentistry, Ankara, Turkey, with a missing first molar on the right side of the mandible. Because of extensive damage to the coronal portion of the second molar on the same segment and insufficient interarch space, we felt it was inappropriate to use this tooth as the abutment for a fixed partial denture (FPD). A radiographic and clinical examination revealed the need for endodontic therapy and a cast post-and-core buildup for the right mandibular second molar (Figure 1
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An endodontist from the endodontics clinic performed root canal therapy. The endodontist used a lateral compaction technique to fill the root canals to the level of the canal orifices. At the next visit, the endodontist removed gutta-percha from the pulp chamber and distal root, leaving 4 millimeters of gutta-percha in the apical portion of the canal to create a space for the post-and-core assembly. The endodontist shaped the canal with Peeso reamers (Moyco Union Broach, York, Pa.) to a final diameter of 1.25 mm and a depth of 8 mm from the prepared coronal surface.
We then trimmed the unsupported tooth structure and adapted a resin pattern (Palavit G, Heraeus Kulzer GmbH, Hanau, Germany) to the prepared canal and pulp chamber. A dental technician fabricated the core buildup outside the oral cavity by using the same resin material. The dental technician invested the post-and-core pattern and cast it in gold alloy (Metalor Technologies, Neuchâtel, Switzerland).
We prepared the right second premolar abutment as the anterior retainer for the FPD. After adjusting the post-and-core assembly and seating it into the tooth, we took an impression (President, Coltène/Whaledent AG, Alstätten, Switzerland). We made the working model from Type IV dental stone (Fujirock, GC, Tokyo).
We created a threaded hole with a metric no. 2 guide drill (internal screw threads) in the post and core using a milling machine (Figure 2). We inserted into this hole the female component of the Ceka anchor (Alphadent NV, Antwerp, Belgium) (special Irax base ring M3) by using a parallelometer, and soldered it using silver solder (3M Unitek, Monrovia, Calif.). Placing the nut of the Ceka anchor with a parallelometer allowed for proper alignment with the path of insertion of the prepared anterior abutment. Because the base ring’s thickness of 3 mm might not have provided sufficient retention, we drilled the hole through both the core and the post assembly to increase the retention capability.
We then seated the post-and-core assembly into the drilled hole and screwed in a titanium occlusal screw (SCS occlusal screw 048.350, Straumann, Institut Straumann AG, Basel, Switzerland) using an implant key (Straumann) on the model (Figures 3 through 5).
We prepared the wax pattern as a full-cast crown on the second molar core, a porcelain-fused-to-metal (PFM) retainer on the second premolar and a PFM pontic for the first molar. Before clinical insertion, we seated the metal framework on the stone die. We fused the porcelain to the metal framework and, after the trial seating, a dental technician glazed the three-unit FPD in the laboratory. For cementation, we used a dental adhesive (Scotchbond Multi-Purpose Plus, 3M ESPE, St. Paul, Minn.) along with cement (RelyX ARC Adhesive Resin Cement, 3M ESPE). We used a no. 40 Lentulo spiral filler (Dentsply Maillefer, Ballaigues, Switzerland) to introduce the cement into the canal space. We coated the post-and-core assembly with cement and seated it slowly by using finger pressure maintained for eight minutes. We then removed the excess cement. We cemented the three-unit FPD onto the abutments using the same resin cement. During cementation, we screwed in the bridge using a Straumann implant key (Institut Straumann AG) (Figures 6 and 7).
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CONCLUSION
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The technique described above seems to be effective for extensively damaged teeth that lack sufficient tooth structure to create an adequate ferrule of 1.5 to 2 mm for the final crown, particularly when combined with insufficient interarch space for a conventional post-and-core restoration. When insufficient tooth structure exists to prepare a tooth for coronal coverage, the clinician must use a technique that restores lost dentin. Lengthening the clinical crown by removing supporting alveolar bone to expose more sound tooth structure may be effective, but typically it produces other problems.6,7 Because the crown-lengthening procedure may compromise the supporting bone, we decided to extrude the tooth; however, the patient refused to have orthodontic brackets placed. In addition, the insufficient interarch space limited the amount of forced eruption. As a result, we decided to treat the patient with this alternative technique.
Achieving internal reinforcement by connecting a precision attachment to the residual root provides retention and adds stability to the prosthesis. At the one-year clinical examination, the prosthesis exhibited no evidence of failure and the patient was satisfied with its function and esthetics.
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FOOTNOTES
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Dr. Ersu is an assistant professor, Department of Prosthodontics, Faculty of Dentistry, Hacettepe University, Ankara, Turkey.
Dr. Canay is a professor, Department of Prosthodontics, Faculty of Dentistry, Hacettepe University, 06100, Ankara, Turkey, e-mail "canaysenay{at}yahoo.com". Address reprint requests to Dr. Canay.
This study was presented at the 29th Annual Conference of European Prosthodontic Association, Poznan, Poland, Sept. 1–3, 2005.
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REFERENCES
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- Paul SJ, Werder P. Clinical success of zirconium oxide posts with resin composite or glass-ceramic cores in endodontically treated teeth: a 4-year retrospective study. Int J Prosthodont 2004;17(5):524–8.[Medline]
- Akkayan B, Gülmez T. Resistance to fracture of endodontically treated teeth restored with different post systems. J Prosthet Dent 2002;87(4):431–7.[Medline]
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- Assif D, Pilo R, Marshak B. Restoring teeth following crown lengthening procedures. J Prosthet Dent 1991;65(1):62–4.[Medline]
- Jorgensen MG, Nowzari H. Aesthetic crown lengthening. Periodontol 2000 2001;27:45–58.
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