| Abstract|| |
This clinical report describes an alternative prosthodontic treatment of a patient who had severely damaged endodontically-treated first molar teeth in all quadrants of her mouth. The young patient's severely damaged permanent molar teeth were treated with a restoration combining the advantage of the esthetics of dental porcelain, reinforced with the underlying cast gold dowel crown. Using this technique, the remaining sound tooth structure was preserved with function and esthetics accomplished. The described metal-ceramic one piece dowel crown restoration seemed to perform without any problems for the 12 month evaluation time.
Keywords: Dowel core, dowel crown, endodontic therapy, esthetics, onlay restoration
|How to cite this article:|
Yuzugullu B, Canay S. Metal-ceramic dowel crown restorations for severely damaged teeth: A clinical report. Indian J Dent Res 2009;20:110-3
The probable survival rate of an endodontically treated tooth is directly related to the quantity and quality of the remaining dental tissue.  The roof of the pulp chamber provides much of the necessary support for the natural tooth and its loss leaves the facial and lingual walls severely weakened and without sufficient support.  Dowel-core restorations are used in the reconstruction of coronal structure lost due to caries, fracture, endodontic access, abscess, or prior restorations. ,,,,,,,, The post size and shape, the final preparation design of the tooth, and the kind of luting agent used influence tooth resistance.  Dowel posts mainly provide protection from horizontal as well as vertical fracture and retention and stabilization to the core. , Because their insertion and retention in the prepared canal is independent of dentin elasticity, they produce no lateral stress that can crack or fracture the root if they have a positive seat and can not move apically beyond this seat.  A tooth with more than one canal requires a dowel of optimal length in the most desirable canal and a shorter key-type lock post in a second canal. The key aids in seating the dowel and prevents rotation. ,,
|How to cite this URL:|
Yuzugullu B, Canay S. Metal-ceramic dowel crown restorations for severely damaged teeth: A clinical report. Indian J Dent Res [serial online] 2009 [cited 2021 Oct 23];20:110-3. Available from: https://www.ijdr.in/text.asp?2009/20/1/110/49063
Of the various dowel-core designs available, the most widely used can be classified into two basic types: metal posts and cores that are custom cast as a single piece and two-element designs comprising a commercial prefabricated post to which a silver amalgam, resin composite, or glass-ionomer cement core is subsequently adapted. Cast dowel-cores are commonly advocated for teeth with little remaining coronal structure. In such situations, the use of an alloy with high gold content, and thus high biocompatibility, high corrosion resistance, and low rigidity appear to be most appropriate. 
Even in the situation of minimal coronal destruction, cuspal coverage is mandatory. The restoration can be an onlay design instead of a complete coverage restoration.  Ceramic onlays have become an important treatment modality in modern dental practice because of the increased demand for esthetic posterior restorations.  This clinical report presents a young patient whose severely damaged permanent molar teeth were treated with a modality combining the advantage of esthetics of porcelain reinforced with an underlying cast gold dowel crown.
| Case Report|| |
A 21-year-old young female reported for an evaluation of her permanent first molar teeth. She had a dental history of caries in all first molars, which were consecutively treated with amalgam fillings [Figure 1]. Six months before her treatment in the prosthodontic department, the patient had an endodontic emergency procedure in the maxillar right first molar tooth. A clinical evaluation revealed an anterior open articulator and posterior premature contacts while the radiographic evaluation revealed unsuccessful fillings. The patient also stated that she was "not fond of the black fillings" on her teeth. Therefore, endodontic treatment was applied to all of her first molar teeth prior to prosthetic treatment. Since the molar teeth were extremely damaged and esthetics was an important factor, a metal-ceramic dowel crown, which is a combination of a cast gold dowel-core with coronal porcelain structure, was planned in this case.
All first molar teeth canals were obturated with gutta percha and were asymptomatic. Isolation of the severely damaged molar teeth were achieved by cotton rolls, suction, and a tongue guard (HiandDri-Drident, Microplus Inc., Clinton, MA) because a rubber dam would have interfered with frequent checks for occlusal clearance and alignment with adjacent teeth. After the existing provisional restorations were removed, all unsupported dentin and enamel were removed using a horizontally approaching rotary cutting instrument (Diatech Dental AG, Heerbrugg, Switzerland) so that sound residual tooth structure had a minimum wall thickness of 1 mm. With a bur, the pulp chamber was rendered free of luting cement, gutta percha, and provisional restorative material. The gingival margins were left supragingivally for easier access. The preparation was made with a 1 mm wide chamfer and a counterbevel to achieve the ferrule effect. Dowel spaces were prepared in the distal canals of the mandibular molar teeth and the palatinal canals of the maxillar molar teeth. Before the enlargement of the canals, the Peeso reamer's (Dentsply, Ballalgues, Switzerland) length was chosen by measuring against the radiographs so that at least 3-4 mm in length of the gutta percha was left in the apex to prevent dislodgement and leakage. After the dowel spaces were prepared, orifices of the mesial canals of the mandibular molar teeth and mesial-distal canals of the maxillar molar teeth were prepared as the key-locks using a bur (Diatech Dental AG, Heerbrugg, Switzerland). The length of each key-lock was 3-4 mm [Figure 2a],[Figure 2b], and [Figure 3]. The preparations were washed, dried, and lubricated with a water-soluble lubricant (Panavia™ F Oxyguard II, Kuraray Medical Inc., Okayama, Japan).
The cast dowel crowns were fabricated using the direct impression technique. Solid plastic sprues (Williams Dental, Buffalo, NY) were trimmed to fit loosely in the canals. Hard inlay wax (Almore International Inc., Portland, OR) was softened and applied on the sprue and was seated in the canals. When the wax had achieved an initial set, the pattern was moved in and out of the canal to ensure that it would not be locked into any undercuts. The core and the key-lock preparations were waxed around the dowel impression. The dowel crown was then sprued and cast from a gold alloy (Degudent G; DeguDent GmbH, Hanau, Germany). After casting, removal, and cleansing, the dowel crowns were adapted and seated to the teeth [Figure 4]. With four cast dowel crowns in place, a new complete-arch impression was made using a vinyl polysiloxane impression paste (Speedex; Coltene Whaledent, Mahwah, NJ). The new casts, with the cast dowel crowns in place, were transferred to an articulator (Whip Mix Corp; Louisville, KY) for the fabrication of the porcelain (Ceramco 3; Dentsply Ceramco, PA) part of the restoration. After the completion of the porcelain superstructure on the cast dowel crowns, the restorations were tried and checked for marginal integrity, proximal and occlusal relations, and color [Figure 5],[Figure 6]. Between the tooth margins and the porcelain part, there was a 1-1.5 mm cast collar. The cast part of the restorations was airborne-particle abraded with 50 µ aluminum oxide abrasive (Microetcher Model Er Precision Sandblaster; Danville Engineering, Inc., U.S.A.). Dual-cure resin cement (Panavia F; Kuraray Medical, Inc.) was used as a luting agent [Figure 7]. After applying the alloy primer (Alloy Primer; Kuraray Medical, Inc.) on the cast dowel parts, ED Primer II A and B (ED Primer II A, B; Kuraray Medical, Inc.) were mixed and applied to the coronal and dowel parts on the tooth structure. Thirty seconds later, the tooth was air dried and the excess primer was removed with paper points. Panavia F pastes A and B (Panavia F; Kuraray Medical, Inc.) were dispensed in equal amounts, then the mixed cement was applied to coat the cast dowel parts of the restoration. The manufacturer's instructions were followed for all aspects of the seating procedure. The excess cement on the margins was cleaned. The restoration margins were light cured for 20 seconds on each surface and the restoration was left for self cure by applying Oxyguard II (Oxyguard II, Kuraray Medical, Inc.) for 3 minutes. The margins were burnished so that the gold alloy and tooth were on the same plane. The panoramic radiograph of the patient was made after 12 months [Figure 8]. The described metal-ceramic one-piece dowel crown restoration seemed to perform without any problems for the 12-month evaluation time.
| Discussion|| |
As alternatives to cast dowel-cores, the use of prefabricated posts and custom-made buildups with amalgam, resin composites, and glass-ionomer cements simplifies the restorative procedures.  Composite cores are more prone to recurrent caries and bacterial adhesion. Amalgam core's main disadvantage is that even the fastest setting amalgam requires 20 to 30 minutes before sufficient strength is achieved for preparation. Other disadvantages are concerns about mercury, discoloration of gingival tissues, and esthetic problems when certain all-ceramic crowns are used. 
The cast gold dowel-core has been regarded as the "gold standard" in post and core restorations due to its superior success rates.  Cast post and core assemblies were reported to yield higher fracture strengths than direct buildups with prefabricated posts and amalgam.  According to the research by Reagan, et al.,  two different prefabricated posts used with either amalgam or composite core material and a cast post and core performed equally well. Sorensen and Martinoff  concluded that 94% of endodontically treated molars and premolars that subsequently received coronal coverage were successful, while only 56% of occlusally unprotected endodontically treated posterior teeth survived.
Porcelain is most satisfying for the patient's quest for natural color and esthetics. The stable metal base concept with overlying porcelain has been widely recognized for inlays and onlays. ,,, Using a high gold content metal as a base allows easier burnishing for the sealing of the margins and adaptation of the dowel to the preparation. 
The restoration described in this article meets the requirements of esthetics with the porcelain veneer and at the same time the cast substructure provides the strength needed to withstand occlusal loading. Also, conventionally there is a need for complete occlusal coverage for severely damaged and endodontically treated teeth. With the described method, there has been no more necessity for the fabrication of a crown.
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Department of Prosthodontics Faculty of Dentistry, University of Hacettepe 06100, Ankara
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2a], [Figure 2b], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]